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The Keimoes Suite redefined: The geochronological and geochemical characteristics of the ferroan granites of the eastern Namaqua Sector, Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa
Accepted Manuscript The Keimoes Suite redefined: The geochronological and geochemical characteristics of the ferroan granites of the eastern Namaqua Sector, Mesoproterozoic NamaquaNatal Metamorphic Province, southern Africa Russell Bailie, Paul Hugh Macey, Sedzani Nethenzheni, Dirk Frei, Petrus le Roux PII:
S1464-343X(17)30303-5
DOI:
10.1016/j.jafrearsci.2017.07.017
Reference:
AES 2969
To appear in:
Journal of African Earth Sciences
Received Date: 14 February 2017 Revised Date:
2 June 2017
Accepted Date: 17 July 2017
Please cite this article as: Bailie, R., Macey, P.H., Nethenzheni, S., Frei, D., le Roux, P., The Keimoes Suite redefined: The geochronological and geochemical characteristics of the ferroan granites of the eastern Namaqua Sector, Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa, Journal of African Earth Sciences (2017), doi: 10.1016/j.jafrearsci.2017.07.017. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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The Keimoes Suite redefined: The geochronological and geochemical
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characteristics of the ferroan granites of the eastern Namaqua Sector,
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Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa
4 Russell Bailie a, *, Paul Hugh Macey b, Sedzani Nethenzheni a, Dirk Frei a, c, Petrus le Roux d
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a
Department of Earth Sciences, University of the Western Cape, South Africa
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b
Council for Geoscience, Western Cape Regional Office, South Africa
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c
Central Analytical Facility, Stellenbosch University, South Africa
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d
Department of Geological Sciences, University of Cape Town, South Africa
*Corresponding author
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E-mail address: [email protected]
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12 ABSTRACT
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Voluminous granite gneisses and granites straddle the boundary between the Kakamas and Areachap
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Terranes in the eastern Namaqua Sector (NS) of the Mesoproterozoic Namaqua-Natal Metamorphic
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Province (NNMP). These rocks have been previously poorly defined and loosely grouped into the
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Keimoes Suite, but a recent U-Pb age study has suggested the suite be subdivided into syn-tectonic
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and post-tectonic groups relative to the main phase of the Namaqua Orogeny. This study adds new
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whole rock geochemical, isotopic and age data for these granites that confirms the subdivision is
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appropriate. The older group of syn-tectonic granite gneisses, dated between 1175 and 1146 Ma, have
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penetrative foliations and are largely derived from fractionated, leucogranitic metaluminous to
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peraluminous magmas with low maficity, low Ti, Mn and Ca. They were derived from mildly
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depleted sources (εNd(t): -1.47 to 1.78), with Meso- to Paleoproterozoic Nd model ages (1.57-1.91 Ga),
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and high initial Sr ratios (0.71970-0.75567) suggesting mixing between younger depleted and older,
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arc-like sources imparting an arc-like signature to the magmas. High initial Sr ratios appear to be an
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intrinsic character of these granites reflecting those of granites in the region and the highly radiogenic
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nature of the NS.
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The weakly to unfoliated late- to post-tectonic megacrystic granodiorites and monzogranites,
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including charnockites, intruded between 1110 and 1078 Ma and constitute the Keimoes Suite proper.
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They have I-type characteristics, being strongly metaluminous and locally hornblende- and
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orthopyroxene-bearing with moderate SiO2 and with arc-type affinities (LILE enrichment relative to
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the HFSE, Ta-Nb, Ti and P anomalies). However, the granitoids also have high Fe/Mg ratios, along
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with high HFSE, LILE and REE contents more indicative of A-type granites. They show an
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increasing maficity, metaluminous character, and general decreasing degree of fractionation with
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decreasing age. They are similar to the syn-tectonic granites in having εNd(t) values close to zero (-2.95
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ACCEPTED MANUSCRIPT to 2.83) and Meso- to Paleoproterozoic model ages (TDM: 1.38-1.99 Ga) but lower initial Sr ratios
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(<0.723 in general) suggesting derivation from relatively depleted sources with a variable enriched
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and/or crustal component.
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The timing of emplacement of the syn-tectonic granites places peak D2 deformation in the eastern NS
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predominantly at ∼1.16-1.15, varying from ∼1.18-1.13 Ga. There was more voluminous granitic
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magmatism in the Areachap Terrane to the east during the late- to post-tectonic magmatic episode,
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whereas the earlier, ∼1.18-1.14 Ga syn-tectonic magmatic episode is more concentrated to the west in
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the Kakamas Terrane. The broad, protracted period of magmatism in the eastern NS attests to a long-
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lived duration of high-heat flow in this portion of the southern African crust at this time. Nd model
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ages of Meso- to Paleoproterozoic age reflect those in other granites throughout the NS suggesting
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extensive reworking of Paleoproterozoic crust during the 1.2-1.0 Ga Namaquan Orogeny.
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47 Keywords:
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Eastern Namaqua Sector; post-tectonic felsic magmatism; ferroan, metaluminous megacrystic
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granitoids; variably enriched sources; mixed model ages
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1. Introduction
The Namaqua-Natal Metamorphic Province (NNMP) developed as a Mesoproterozoic mobile belt
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along the southern and western margin of the Archean-Paleoproterozoic Kaapvaal Craton during the
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Rodinian supercontinent assembly (Hartnady et al., 1985; Cornell et al., 2006; Li et al., 2008, Fig. 1).
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The Namaqua Sector (NS), forming the western portion of the NNMP, is dominated by granitic
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gneisses and granites aged between ~1.3 and 1.0 Ga (e.g. Eglington, 2006 and references therein;
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Bailie et al., 2011a; Cornell et al., 2012; Bial et al., 2015a; Colliston et al., 2015; Macey et al., 2015).
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The granitic melts intruded almost continuously over this period but the most significant and
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voluminous magmatic events occurred during several pulses linked to specific tectono-metamorphic
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episodes and associated with major developing structures. The timing and location of these major
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intrusive events varies across the NS and reflect the shift in the tectonic and thermal axis during the
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long duration, high-T, low-P Namaqua Orogeny (Eglington, 2006; Miller, 2012). Clearly an
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understanding of the characteristics, age and source of the various granite suites and the tectonics
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controlling their emplacement is critical to unravelling the complex evolution of the NS and its heat
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source.
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The granites, granodiorites and charnockites of the Keimoes Suite intruded the eastern parts of the NS
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of the NNMP (Fig. 1). A suite is defined as an assemblage of temporally and spatially related
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magmatic rocks having chemical, mineralogical and textural features or characteristics that together
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exhibit a continuous variation from one extremity to the other (Bates and Jackson, 1987). The original
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acknowledged by the authors, was loosely defined as a collection of intrusive rocks in the Keimoes-
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Kakamas area, possibly not belonging to a single intrusive rock series and therefore subject to
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redefinition and reclassification. It was differentiated from the older basement granites of the
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Kaapvaal Craton to the east and an augen gneiss-dominated domain to the west based on the apparent
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lack or weakness of the penetrative gneissic foliation (disregarding the localised shear zones). Several
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refinements of the original definition have been proposed following geological surveys (e.g. Moen,
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1988, 2007; Slabbert, 1998; Slabbert et al., 1999) and geochemical studies (Geringer et al. 1988) of
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which the subdivision of Moen (2007) is most widely accepted. More recently, Cornell et al. (2012)
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proposed subdividing the Keimoes Suite (sensu Moen, 2007) on the basis of new U-Pb ages
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(Pettersson, 2008; Bailie et al., 2011a; Cornell et al., 2012) and intensity of gneissic fabric into an
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older syn-tectonic group of foliated rocks (1203 to 1146 Ga), which they term the Augrabies Suite,
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and a post-tectonic group of granites and charnockites (1113 to 1078 Ga) which remain in the
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Keimoes Suite.
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In light of the issues associated with this poorly defined suite, this study contributes new age, whole
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rock major, trace, rare earth element (REE) geochemical and isotope data combined with a review of
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the existing map information (intensity of regional gneissic foliation, texture, mineralogy and
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distribution of granitoids) which can be used to further characterise these granites, their age of
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emplacement relative to the main tectonothermal events of the eastern Namaqua Sector, as well as the
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source characteristics. The main objective is to test whether the subdivision of these granitoids into
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two suites relative to the main Namaquan deformation event, as proposed by Cornell et al. (2012), is
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valid. The age of emplacement, whole rock geochemical and isotopic characteristics can also
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contribute to a greater understanding of the role of voluminous granitic magmatism in not only the
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eastern Namaqua Sector but also throughout the NNMP during the 1.2-1.0 Ga Namaquan Orogeny.
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2. Geological Setting
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The granites of the Keimoes Suite intrude the Kakamas and Areachap Terranes in the eastern parts of
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the NS of the NNMP. The NS covers an area of over 100 000 km2 in the lower Orange River region
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of the Northern Cape Province of South Africa and the Karas Region of southern Namibia (Hartnady
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et al., 1985; Cornell et al., 2006; Fig. 1) and consists of Paleoproterozoic (~2.05-1.83 Ga) and
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Mesoproterozoic (~1.3-1.0 Ga) igneous and metamorphic rocks that were deformed during various
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phases of the low-P - high T ∼1.2-1.0 Ga Namaquan Orogeny (e.g. Cornell et al., 2006; Eglington,
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2006; Bial et al., 2015a, b; Thomas et al., 2016; Macey et al., 2017). The NS is subdivided into five
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terranes/domains defined by differences in lithostratigraphy, radiometric ages, structural trends and
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intensities and metamorphic histories (e.g. Hartnady et al., 1985; Joubert, 1986; Cornell et al., 2006;
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ACCEPTED MANUSCRIPT Eglington, 2006; Miller, 2008, 2012; Thomas et al., 2016; Macey et al., 2017; Fig. 1). The tectonic
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domains are separated by major structural discontinuities and were juxtaposed during several regional
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thrusting events.
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The Richtersveld Subprovince forms the westernmost tectonic domain and consists of belts of calc-
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alkaline, arc-derived volcanic rocks intruded by coeval granodiorite-dominated plutonites at ca. 2.02
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Ga and ca. 1.88 Ga, respectively. The eastern parts of the subprovince were strongly deformed under
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amphibolite-facies conditions during the Mesoproterozoic Namaquan Orogeny associated with minor
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~1.2 Ga granite, leucogranite and gabbroic intrusions (Reid, 1997; Thomas et al., 2016; Macey et al.,
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2017). The Bushmanland Subprovince is more complex with ∼1.85 Ga granitic gneisses and
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migmatites dominating the northern parts, whereas in the south belts of high-grade supracrustal
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gneisses of various ages (∼1.60-1.15 Ga) occur as rafts within voluminous intrusions of pre- to syn-
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tectonic ~1.20-1.12 Ga granitic augen gneisses and quartzo-feldspathic gneisses and 1.10-1.035 Ga
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late- to post-tectonic granites (e.g. Robb et al., 1999; Clifford et al., 2004; Eglington, 2006; McClung,
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2006; Bailie et al., 2007). The Kaaien Terrane is the easternmost tectonic domain of the NS
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representing a tectonic transition zone between the Kaapvaal Craton and Kheis Province and the NS
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and is composed of ∼1.77 Ga metaquartzites, ∼1.37 and 1.17-1.10 Ga bimodal volcano-sedimentary
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rocks and 1.10 Ga granitic intrusions (Van Niekerk, 2006; Bailie et al., 2011a, 2012).
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The Kakamas Terrane (Fig. 1) is dominated by late Mesoproterozoic granulite-facies meta-
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sedimentary rocks (~1220-1150 Ma) intruded by various 1.21-1.08 Ga granites, anatectic
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leucogranites and minor gabbroic rocks (Pettersson et al., 2009; Bial et al., 2015a, b, 2016; Macey et
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al., 2017). The Kakamas Terrane is regarded as a low-angle imbricate mega-nappe stack separated
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from the Bushmanland and Richtersveld Subprovinces by major thrust structures (Onseepkans,
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Hartebeest, Lower Fish River, Kerelbad thrusts; e.g. Praekelt, 1984; Colliston et al., 2015; Macey et
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al., 2017).
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The Areachap Terrane, to the east thereof (Fig. 1), is marked by numerous younger Nd model ages, of
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Mesoproterozoic age (Pettersson et al., 2009) suggesting a juvenile component compared to the
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dominant Paleoproterozoic model ages in the Bushmanland Subprovince to the west (Yuhara et al.
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2002, Reid, 1997; Macey et al., 2017). The NW-trending Areachap Terrane is dominated by 1.30-1.22
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Ga volcaniclastic, volcanic and sedimentary rocks (Areachap Group) representing a metamorphosed
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juvenile Mesoproterozoic volcanic arc succession (Geringer et al., 1986, 1994; Cornell et al., 1990;
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Pettersson et al., 2007; Cornell and Pettersson, 2007; Bailie et al., 2010) that was intruded by younger
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∼1.20 to ∼1.10 Ga granitoids (Pettersson et al., 2007; Bailie et al., 2011a; Cornell et al., 2012). The
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eastern boundary of the terrane is marked by the Trooilapspan shear zone (TLSZ) and the Brakbosch
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fault (Fig. 1), whereas the boundary with the Kakamas Terrane is considered to be the Boven Rugzeer
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Shear Zone (BRSZ) (Fig. 1). The Areachap Group was subjected to upper amphibolite facies
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of the Areachap Terrane, in particular, is characterised by a greater dominance of Paleoproterozoic
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model ages (Geringer et al., 1986; Pettersson et al., 2007; Cornell and Pettersson, 2007) suggesting
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that an older crustal component was present in the magmatic arc(s) which gave rise to the Areachap
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Group (Pettersson et al., 2009).
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The eastern Namaqua Sector was subjected to extensive polyphase low pressure, high temperature
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metamorphism and deformation during the ∼1.2-1.0 Ga Namaquan Orogeny with four main high
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grade deformation events recognized in the Kakamas and Areachap Terranes (Cornell et al., 1992,
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2006; Pettersson et al., 2007; Bailie et al., 2011a; Bachmann et al., 2015). Intense fold and thrust
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tectonics during the D2 deformation gave rise to large scale tight to isoclinal sub-vertical NW-trending
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F2 folds and the regional penetrative foliation (e.g. Praekelt, 1984; Macey et al., 2015). Peak
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metamorphic grade varies from lower granulite facies in the Kakamas Terrane to upper amphibolite
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facies in the Areachap Terrane diminishing eastward to greenschist facies into the Kaaien Terrane
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(Stowe, 1983; Cornell et al., 1992, 2006; Bial et al., 2015b, 2016). The main deformation and
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metamorphism appears to have occurred over a protracted period dated between ~1.20 and 1.15 Ga
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(Pettersson et al., 2007; Miller, 2012; Bachmann et al., 2015; Bial et al., 2015b). Subsequent D3
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deformation, associated with M3 metamorphism gave rise to open east-west trending F3 folds at
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amphibolite facies conditions (∼640oC and 4.8 kbar; Cornell et al., 1992) and was associated with
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magmatism at around 1.10 Ga (Pettersson et al., 2007; Bailie et al., 2011a). D4 deformation involved
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later reactivation and dextral strike-slip faulting along major regional shear zones and faults, including
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the BRSZ, TLSZ, and Brakbosch shear zones (Geringer et al., 1994).Whilst many of the shear zones
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are likely to have formed during D2 fold and thrust tectonics, they show evidence for extensive
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reactivation, retrograde M4 metamorphism and vertical and lateral movement (e.g. van Bever Donker,
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1980, 1991), with many showing a dextral shear sense, e.g. the BRSZ (van Bever Donker, 1991;
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Miller, 2012), TLSZ and Brakbosch shear zones (Moen, 1999).
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Regional lithological mapping by the geological survey of South Africa (Moen, 2007; Slabbert, 1998;
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Slabbert et al., 1999) identified 29 biotite, biotite-hornblende and orthopyroxene-bearing granitoid
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units in the Upington-Kakamas-Kenhardt region considered to constitute the Keimoes Suite. The
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subdivision included two subsuites (further subdivided into 7 lithodemes) and was based on the
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distribution, composition, texture and structural fabric of individual granite bodies (Geringer et al.,
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1988; Stowe, 1983). Moen (2007) excluded the gabbroic members previously included in the
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Keimoes Suite and limited it to the granitic units distributed between the Brakbosch fault and
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Neusspruit-Wolf Kop shear zone (Fig. 1). Moen (2007) suggested a subdivision into syn-tectonic and
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late-tectonic granites but cautioned that strain intensity is not only dependent on age relative to
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deformation but the size and mineral composition of the granite.
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range from ~1264 to 1020 Ma with some granites giving widely different ages and thus early
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geochronology (e.g. Geringer and Botha, 1977; Linstrom, 1977; Smit, 1977; Barton and Burger, 1983;
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Jankowitz, 1987; summarised in Geringer et al. (1988) and Moen (2007)) did not really help to
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subdivide or determine relative timing of emplacement and the role of the Keimoes Suite in the
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tectonothermal evolution of the eastern NS. Recent U-Pb zircon dating yielded a range of ages for the
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Keimoes Suite (as defined by Moen, 2007) between 1.2 and 1.08 Ga (Pettersson, 2008; Bailie et al.,
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2011a; Cornell et al., 2012).
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Based on these new ages, Cornell et al. (2012) suggest the Keimoes Suite be subdivided into an older
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1.2-1.15 Ga syn-tectonic group, and a younger 1.11-1.08 Ga late- to post-tectonic suite, named the
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Augrabies and Keimoes Suite, respectively. Cornell et al. (2012) proposed grouping the syn-tectonic
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Vaalputs Granite (1146 ± 14 Ma), formerly included in the Keimoes Suite of Moen (2007), with the
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similarly-aged Riemvasmaak augen gneiss dated at 1156 ± 8 Ma and 1151 ± 14 Ma (Pettersson,
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2008). The Augrabies Gneiss, which occurs in close association with the Riemvasmaak Gneiss, has
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been dated at 1168 ± 6 Ma (Colliston et al., 2015) and presumably would also fall into the Augrabies
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Suite of Cornell et al. (2012).
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3. Methodology
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Fourteen plutons were sampled during the course of this study. Typically five geochemical samples
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per pluton were collected depending on the size and accessibility of the outcrops and exposed pluton.
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Petrographic thin section and geochemical sample preparation were undertaken at the Department of
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Earth Sciences, University of the Western Cape (UWC), Bellville, South Africa and at the Council for
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Geoscience (CGS), Pretoria, South Africa. Fifty-four samples were analysed for trace elements,
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including the rare earth elements (REE), by Inductively Coupled Plasma - Mass Spectrometry (ICP-
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MS) analysis at the Central Analytical Facility (CAF), Stellenbosch University, with major element
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contents determined by X-ray fluorescent (XRF) spectrometry at the CGS. Rb-Sr and Sm-Nd isotope
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analysis was undertaken at the Department of Geological Sciences, University of Cape Town. U-Pb
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age data were obtained at CAF, Stellenbosch University by laser ablation - single collector - magnetic
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sector field - inductively coupled plasma - mass spectrometry (LA-SF-ICP-MS). Details of the
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analytical techniques are given in the Appendix.
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4. Lithological Description
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The medium- to coarse-grained porphyritic monzogranites, granodiorites and charnockites of the
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Keimoes Suite (sensu Moen, 2007) intrude the Kakamas and Areachap terranes in the eastern NS of
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ACCEPTED MANUSCRIPT the NNMP. The granitoids are most voluminous along and immediately adjacent to the Boven
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Rugzeer Shear Zone (BRSZ) which separates the terranes, diminishing in volume and aerial extent
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both eastward and westward (Fig. 1). The two most voluminous members of the suite, the Vaalputs
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Granite and Friersdale Charnockite are concentrated along the BRSZ.
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Moen (1988; 2007), Slabbert (1998), Slabbert et al. (1999); Geringer et al. (1988); Bailie et al.
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(2011a) and Cornell et al. (2012) provide detailed descriptions of the various members of the Keimoes
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Suite and these, along with the observations of the 14 plutons studied during this study, are
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summarized in Table 1.
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The outcrop extents of the granites vary from small, isolated outcrops, to large, voluminous plutons.
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Various granites, such as the Colston Granite, comprise two or more members which differ in terms
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of mineral abundances, colour and texture. The Cnydas Subsuite is a genetically coherent group of
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syn-tectonic, epizonal granitoids (Fig. 1; Jankowitz, 1987; Moen, 2007; Bailie et al., 2011a). The
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Kleinbegin Subsuite refers to numerous outcrops of granite that intrude to the west of the Brakbosch
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fault and is not a genetic grouping as such (Moen, 2007).
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The Keimoes Suite (sensu Moen, 2007) is characterised by medium- to coarse-grained porphyritic
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biotite granites varying from monzogranites to granodiorites. K-feldspar (Kfs) is typically more
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abundant than plagioclase, with biotite being the dominant mafic mineral in most cases (10-15%
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typically), which helps define a foliation, where developed. Rounded phenocrysts of Kfs are present
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in some granites, but elsewhere, and more typically, randomly oriented euhedral-subhedral Kfs
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phenocrysts are present. These vary in abundance from abundant to sparsely distributed. Some
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younger granites, as defined by poorly developed to unfoliated characteristics, are non-porphyritic.
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Hornblende is present in some cases (e.g. the Straussburg Granite). Muscovite is present in minor
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amounts (6% and less) and is more prevalent in those granites which are cross-cut by, or have been
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subjected to shearing, particularly the Vaalputs and Louisvale granites. Some granites contain
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pyroxene in variable amounts thus forming charnockites. The most notable are the voluminous,
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unfoliated Friersdale Charnockite and the Gous Charnockite, a member of the Cyndas Subsuite,
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exposed in the far northern extent of the eastern NS granites. Both orthopyroxene and clinopyroxene,
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in the form of augite, are present in these rocks. Garnet is sporadically present in some granites.
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The granites exhibit variable degrees of foliation development. Foliation can also intensify toward the
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margins of the pluton or exhibit a magmatic flow structure. As such, some of the foliation, particularly
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along the margins, may be of magmatic origin rather than tectonic. Where developed the foliation is
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defined by the mafic minerals, notably biotite, along with muscovite, which envelope or wrap around
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glomeroporphyritic clusters of the felsic minerals, notably the feldspars (variable amounts of
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plagioclase, microcline, perthite and orthoclase) as well as quartz, which also occurs in the
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proximity to major crosscutting transcurrent shear zones.
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Most of the granites contain numerous inclusions, with xenoliths largely reflecting the composition of
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the intruded country rock. Inclusions also tend to be largely both mafic and leucocratic, with the
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former typically biotite-rich to amphibolitic. Some granites, however, also contain inclusions of
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tonalitic composition which are likely magmatic enclaves compositionally related to the host granite
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representing relics of an earlier magma (e.g. Geringer et al., 1987). Crosscutting granitic and
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pegmatitic veins are common features. Certain granites, such as the Friersdale Charnockite, crosscut
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other granites as dykes.
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Moen (2007) included the Josling Granite within the Keimoes Suite, although, based on an age of
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1275 ± 7 Ma by Pettersson (2008), acknowledged that it likely does not form part of the Keimoes
255
Suite. The Josling Granite is characterised by a well-developed gneissic fabric, which contrasts with
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the largely weakly foliated to unfoliated nature of many of the Keimoes Suite granitoids.
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5. Geochronology
The results of the eight granite samples dated during the course of this study are described
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alphabetically and are summarised in Table 2. Age data from previous studies (Pettersson, 2008;
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Bailie et al., 2011a; Cornell et al., 2012) are summarized separately below the new age data. The
262
tabulated analytical data may be found in Appendix Tables A1-A8. The uncertainties are expressed as
263
s (sample standard deviation) as opposed to σ, following the recommendations of Horstwood et al.
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(2016), since only a representative sample of the entire population was taken. Given that the
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ratios are used. Weighted mean ages are calculated, with 2% added to the uncertainty in quadrature to
267
account for systematic uncertainty following the recommendations of Hortwood et al. (2016) and
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Spencer et al. (2016). All data with greater than 10% discordance is not considered in determining the
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weighted mean age of the sample following a general recommendation by Gehrels et al. (2008).
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Analyses which show a clear inherited component, as determined from CL imaging and their age, e.g.
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spots Me1-12 and 13 of the Elsie se Gorra Granite (sample Me1 – Table A3) are also not included in
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the weighted mean age.
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Pb/238U ratio gives higher precision for ages younger than ∼1.5 Ga (Spencer et al., 2016), these
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5.1. Cnydas Subsuite – Smalvisch Granite
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Most of the euhedral to subhedral zircons (100 - 250 µm; Fig. 2a) exhibit oscillatory zoning with
276
relatively bright cores. All 24 zircons analysed provided concordant data (99-102%; Table A1) with
277
overlapping core and rim ages and no evidence for older inheritance. These data provide a weighted
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mean U-Pb age of 1159 ± 28 Ma which is considered to be the crystallisation age of this granite (Fig.
279
3a).
280 281
5.2. Colston Granite The zircons from the Colston Granite are mostly elongate, ranging in size from 100 to 250 µm (Fig.
283
2b). Most of the larger (>150 µm) euhedral grains have bright cores and show oscillatory zoning, with
284
the smaller zircons (<100 µm) having mostly dark cores. Twenty five spots were analysed (Table A2).
285
The upper intercept age of 1161 ± 16 Ma obtained from all 25 spots is within error of the weighted
286
mean U-Pb age of 1151 ± 28 Ma (Fig. 3b). The latter is taken as the timing of intrusion of the granite.
287
Core and rim ages cannot be distinguished and no zircon inheritance or metamorphic overprinting
288
ages are evident in the data.
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The zircon grains in the Elsie se Gorra Granite range in size from 100 µm to 200 µm (Fig. 2c). Of the
292
21 spots analysed only twelve were less than 10% discordant (Table A3). Of these, a dark, weakly
293
zoned core yielded 206Pb/238U inheritance ages of 1335 ± 35 and 1344 ± 35 Ma (Fig. 2c). The
294
remainder provide a weighted mean U-Pb age of 1175 ± 18 Ma which is considered to be the
295
crystallisation age (Fig. 3c; Table 2). Some cores are discordant having ages of > 1075 Ma possibly
296
reflecting metamorphism.
297 5.4. Josling Granite
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The zircons examined during this study are mostly prismatic (50 - 150 µm). Mostly bright oscillatory
300
zoned cores yield mostly concordant ages, whereas dark weakly zoned to unzoned rims are generally
301
characterised by high U contents (411 - 582 ppm) yielding mostly discordant ages (Fig. 2d). Of the 23
302
spots analysed only 12 yielded concordant data with the rest highly discordant (<61% concordant;
303
Table A4). The remaining concordant data from 12 zircons have a weighted mean U-Pb granite
304
crystallization age of 1217 ± 20 Ma (Fig. 3d), within error of the upper intercept age of 1222 ± 16 Ma.
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5.5. Kanoneiland Granite
307
The zircons of the Kanoneiland Granite are dark, mostly unzoned and form subhedral to anhedral
308
grains 100 - 200 µm in size with moderately to well zoned cores (Fig. 2e). Twenty-two concordant
309
(98-101%; Table A5) analyses provide a weighted mean U-Pb age of 1098 ± 26 Ma which is regarded
310
as the crystallisation age (Fig. 3e). No inherited or metamorphic zircons were found. 9
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5.6. Keboes Granite The zircons of this granite exhibit oscillatory zoning with bright cores and dark rims and range in size
314
from 80 - 250 µm in size (Fig. 2f). Twenty-five spots were analysed, of which only one spot (spot 16
315
– Table A6) is strongly discordant. One concordant analysis (spot 3 – Table A6) of a dark, strongly
316
oscillatory zoned inherited zircon core provides a 206Pb/238U age of 1346 ± 35 Ma. The remaining 23
317
spots provide a weighted mean U-Pb age of 1105 ± 27 Ma (Fig. 3f) within error of the upper intercept
318
age of 1111 ± 10 Ma. The former is taken as the crystallisation age of the Keboes Granite. No
319
metamorphic ages were obtained from the zircons.
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5.7. Klipkraal Granite
The zircons from the Klipkraal Granite are mostly subhedral, elongated sector zoned grains (80 µm to
323
150 µm, Fig. 2g). Only 8 spots were analyzed which yield only discordant data (≤90% concordant;
324
Table A7) from which an upper intercept age of 1270 ± 26 Ma (Fig. 3g) was determined. Since the
325
Klipkraal Granite is only weakly deformed and is unlikely to be older than 1.2 Ga this age is regarded
326
as representing inheritance from the Jannelsepan Formation (Areachap Group) country rocks into
327
which the Klipkraal Granite intrudes (Fig. 2) and which has an extrusion age of 1275 ± 7 Ma (Cornell
328
and Pettersson, 2007; Table 2). A weighted mean U-Pb age from two grains with 90% concordance
329
yields an age of ∼1111 Ma. The Klipkraal Granite is considered to be post-tectonic given its weakly
330
deformed nature and likely to have an age of ∼1110 Ma. This granite requires dating again in order to
331
determine its age of emplacement.
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Zircons of this granite range in size from 100 µm to 200 µm, with most having bright, well zoned
335
cores. The rest have dark, moderately to poorly zoned cores (Fig. 2h). Fourteen spots were analysed
336
(Table A8), of which one (spot 26) was badly discordant, and two (spots 11 and 33) each have 89%
337
concordance. The remaining 11 spots provide a weighted mean U-Pb age of 1125 ± 16 Ma which is
338
taken to be the crystallisation age of this granite (Fig. 3h). This is within error of the upper intercept
339
age of 1134 ± 16 Ma of a line fitted through all of the data. There are no inherited ages for this
340
granite.
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5. Geochemistry 5.1. Whole rock major, trace element (TE) and rare earth element (REE) geochemistry 10
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345
as Figures 5 to 8 along with fields, in Fig. 5, representing the datasets of Jankowitz (1987) (Cyndas
346
Subsuite – Figs. 4a, b, 5) and Geringer et al. (1988) (Keimoes Suite - Fig. 4a) along with the
347
geochemistry of the Riemvasmaak Gneiss (Geringer, 1973; Saad, 1987) (Figs. 4a, b, 5). In the
348
following section, the data are described for the Keimoes Suite (sensu Moen, 2007) as a whole and as
349
comparisons between the syn-tectonic and post-tectonic granitoid groups (sensu Cornell et al., 2012).
350
The Josling Granite, clearly older than the Keimoes Suite, is included for completeness.
351
The Keimoes Suite granitoids classify mostly as monzogranite and, to a lesser degree, granodiorite on
352
the normative modal Q-A-P Streckeisen (1976) diagram (Fig. 4a). The granites are predominantly
353
ferroan (Fig. 4d), potassic and metaluminous (Fig. 4f). Most of the granites combine to define
354
coherent major element trends on the Harker plots with negative correlations between SiO2 and TiO2,
355
FeO(t), MgO, CaO, MnO and P2O5 (Fig. 5; the last not shown), and weakly positive correlations for
356
Na2O and K2O; Al2O3 does not show a definitive trend (Fig. 5). There are also broadly negative
357
correlations of SiO2 with V, Sc, Co, Zr and Hf.
358
Plots of maficity (defined as moles of Fe and Mg per 100 g of rock or magma – Clemens et al., 2011)
359
against other major and trace elemental concentrations (after Clemens et al., 2011; Clemens and
360
Stevens, 2012) do not define any significant differences in terms of both the major or trace elements
361
between the older ∼1.18-1.15 Ga syn-tectonic granites and the younger ∼1.11-1.08 Ga late- to post-
362
tectonic granites (Fig. 6). Maficity is used rather than traditional indices such as wt.% SiO2 as it is far
363
easier to relate mineralogical and chemical influences on magma composition, and hence potential
364
source differences (Clemens et al., 2011). It relates to the concentration of mafic minerals in the
365
granitic magma, with higher maficities implying a greater mafic mineral content. Such plots (Fig. 6)
366
indicate strong positive correlations between maficity and Ti, Fe, Mg, Mn, Zr and Hf, and less well
367
defined positive trends for Ca, P, and Eu. Na and K define fairly flat, to slightly negative trends
368
against maficity, with Al displaying a flat trend. The large ion lithophile (LIL) elements (Rb and Sr)
369
show flat trends, with Ba showing a very poorly define weakly positive slope.
370
With few exceptions, the trace elements show consistent saw-tooth trace element patterns on primitive
371
mantle-normalised (McDonough et al., 1992) spider diagrams (Fig. 7) with enrichment of Th, U and
372
Pb, and the large ion lithophile elements (LILE) over the high field strength elements (HFSE), and
373
depletions in Cs, Ba, Sr, P, Eu and Ti. All the granites show a prominent negative Nb-Ta ‘trough’
374
usually taken to indicate a subduction-related or crustal signature. The chondrite-normalised
375
(McDonough and Sun, 1995) REE plots are also mostly consistent, with moderate to strong light REE
376
enrichment (Fig. 7; (La/Lu)N: 3.6-20.9). The pattern is concave up with moderate fractionation in the
377
LREE [(La/Sm)N = 2.17-6.28] and moderately flat HREE traces [(Gd/Lu)N = 0.92-2.45]. For almost
378
all the granites Eu shows relatively moderate to strongly negative anomalies [(Eu/Eu*)N = 0.19-0.76]
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380
4-7) having anomalous concentrations in most of the major and trace elements (Figs. 5 to 7), distinctly
381
low concentration REE patterns and positive Eu anomalies and probably should be excluded from the
382
suite. The samples from the Kleinbegin Subsuite have low K2O and higher CaO (Figs. 5, 6) than the
383
remainder of the suite whereas the Elsie se Gorra leucogranite and Keboes Granite show distinctive
384
low maficities (Fig. 6), TE and REE patterns on the trace element spider and REE plots (Fig. 7). The
385
high MgO values for the Cyndas Subsuite in the Jankowitz dataset (Fig. 5) is likely due to analytical
386
error.
387
When comparing the geochemistry of the syn- and post-tectonic granites (sensu Cornell et al., 2012),
388
there is significant overlap in major and trace element compositions with general consistencies in
389
elemental trends, enrichments and depletions. The main distinguishing factors are that the syn-
390
tectonic intrusive rocks are generally more felsic (SiO2 mostly between ~69 and 78 wt.%; Colston
391
Granite is the main exception) and are mildly metaluminous to peraluminous as opposed to the post-
392
tectonic group being strongly metaluminous and having SiO2 values between 60 and ∼70 wt.%. The
393
post-tectonic group has a higher overall, and a narrower range of REE and trace element
394
concentrations relative to the syn-tectonic group (Fig. 7; Tables 3, 4).
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5.2. Radiogenic isotope geochemistry
397
The Sr-Nd isotopic data for the granites is given in Table 5 and shown in Fig. 8. Sm/Nd ratios vary
398
between 0.14 and 0.22, but are mostly between 0.18 and 0.21. Initial 143Nd/144Nd ratios vary between
399
0.51107 and 0.51136. Excluding the pre-tectonic ∼1.22 Ga Josling Granite, the εNd(t) values of the
400
granites are close to 0, varying from -2.95 to +2.83 (with a much lower value of -7.51 for the
401
Kleinbegin Granite) (Table 5). Sm-Nd model ages (TDM) vary from Meso- to Paleoproterozoic (TDM =
402
1.38 – 1.99 Ga), apart from older, >2.3 Ga model ages for the Kleinbegin Granite (Fig. 8c; Table 5).
403
Rb/Sr ratios are highly variable, ranging from 0.18 to 5.26, but mostly range between 0.59 and 1.63.
404
Initial Sr ratios [(87Sr/86Sr)I] range between 0.70630 and 0.77130 (Fig. 8a).
405
When comparing the isotopic geochemistry of the syn- and post-tectonic granites (sensu Cornell et al.,
406
2012) both have similar initial Nd ratios, with the syn-tectonic granites having a slightly narrower
407
range (0.51107-0.51128) compared to those of the post-tectonic group (0.51083-0.51136). The model
408
ages of both age groups are essentially the same (Table 5). The syn-tectonic group shows a wider
409
variability in terms of Rb/Sr ratio (0.18 to 5.26) compared to the post-tectonic group (Rb/Sr = 0.24-
410
1.63). Apart from the Keboes Granite, the syn-tectonic granites have higher initial Sr ratios, in general
411
(>0.720), compared to the post-tectonic group (Fig. 8a; Table 5).
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414
6.1. Recommendations for a new stratigraphy for the granitoids of the eastern Namaqua Sector
415
The Keimoes Suite (sensu Moen, 1988, 2007) yielded a wide range of modern U-Pb ages
416
between1275 Ma and 1078 Ma (Pettersson, 2008; Bailie et al., 2011a; Cornell et al., 2012; this study).
417
Based on new age and geochemical data we recommend excluding the much older Josling Granite
418
from the Keimoes Suite. The intrusive rocks can be subdivided on the basis of the intensity of the
419
gneissic fabric (as described by Moen, 2007). The granitoids having moderate to strong penetrative
420
gneissic fabrics (syn-tectonic) have ages between ~1175 and 1125 Ma, whereas the weakly deformed
421
granites and charnockites (late- to post-tectonic) intruded between ~1110 and 1078 Ma. On the basis
422
of age and strain intensity alone, the new age data presented in this paper are in agreement with the
423
subdivision proposed by Cornell et al. (2012). Foliation intensity is, however, not a reliable guide to
424
time of emplacement as various factors may influence this, such as size of the pluton, method of
425
emplacement, extent of magma flow, and the presence or absence of a persisting or waning regional
426
stress field amongst other factors (e.g. Paterson and Tobisch, 1988).
427
Based on its age and geochemistry we recommend excluding the more tonalitic Louisvale Granite
428
from the Keimoes Suite and renaming it the Louisvale Tonalite or Louisvale Gneiss. In agreement
429
with Cornell et al. (2012), we also recommend excluding the pre- to syn-tectonic granites previously
430
included in the Keimoes Suite, restricting it to the post-tectonic granites and charnockites. The newly
431
defined Keimoes Suite is therefore limited to unfoliated ferroan, metaluminous, largely feldspar
432
porphyritic, biotite ± hornblende ± orthopyroxene granites and charnockites with a restricted age of
433
between 1110 and 1078 Ma (Fig. 9) and confined spatially to between the Neusspruit shear zone and
434
Brakbosch fault (Moen, 2007; Fig. 1; Table 6). In this definition, most of the Keimoes Suite granites
435
are situated within the Areachap Terrane, and only the Friersdale Charnockite within the Kakamas
436
Terrane. Slabbert et al. (1999) recognised a number of small, isolated plutons to the south of
437
Kleinbegin that are thought to be associated with or part of the Keimoes Suite. These were not
438
examined as part of this study and require further work in the form of whole rock major, minor, trace
439
element and isotope geochemistry as well as single zircon U-Pb dating in order to clarify their age and
440
association in the eastern NS.
441
Cornell et al. (2012) also proposed grouping the foliated granites (pre- to syn-tectonic Elsie se Gorra,
442
Vaalputs and Colston Granites) with the augen gneisses (Riemvasmaak and Augrabies gneisses) in the
443
“Augrabies Suite”. Based on our new data, we confirm that the grouping of granitic and leucogranitic
444
gneisses aged between 1175 and 1146 Ma may be valid but the term “Augrabies” is already used for
445
the Augrabies Gneiss (Moen, 1988, 2007) and cannot be used for the suite name. Whilst we support
446
the possibility of grouping the pre- and syn-tectonic granite orthogneisses, the paucity of modern
447
geochemical data for these rocks makes it difficult to demonstrate they are co-genetic and therefore
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449
additional work has been completed. We also suggest renaming the Elsie se Gorra and Vaalputs
450
Granites as “gneisses”.
451
The spatially restricted Cyndas Subsuite represent a series of granitoid types (monzogranites to
452
granodiorites) and a range of ages and composition from syn- to post-tectonic times (Jankowitz,
453
1987). As such it constitutes its own separate suite and should possibly be upgraded from a subsuite
454
of the Keimoes Suite, as previously defined (Moen, 2007), to its own separate suite. This study only
455
sampled the Smalvisch Granite of this subsuite and so cannot draw any interpretations or conclusions
456
based on the very limited data. The subsuite requires more extensive research, whole rock
457
geochemical analysis of all the different granites, and more intensive modern U-Pb zircon
458
geochronology than currently available from the work of Jankowitz (1987).
459
The generally unfoliated Colston Granite has an age of 1151 ± 28 Ma (this study) and thus is grouped
460
with the syn-tectonic granites. A similar thermal ionization mass spectrometer (TIMS) zircon age of
461
1156 ± 20 Ma was reported in the summary of Bailie et al. (2011a). Its unfoliated nature may be due
462
to its composition or mode of emplacement. Foliation intensity increases near the pluton margins
463
(Moen, 2007), a feature which does correlate with a syn-tectonic timing of emplacement (Paterson
464
and Tobisch, 1988).
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6.2. General textural, mineralogical and geochemical characteristics of the syn-tectonic granitic
467
gneisses
468
The well-foliated syn-tectonic Elsie se Gorra and Vaalputs granitoids are mostly medium-grained and
469
equigranular, locally with scattered rounded feldspar megacrysts. These grey coloured leucogneisses
470
are dominated by feldspar and quartz with only minor biotite and rare muscovite (Moen, 1988; 2007;
471
Slabbert, 1998). Hornblende is largely absent.
472
The syn-tectonic granites are ferroan monzogranites and granodiorites (Fig. 4; Table 6). Whilst the
473
geochemical characteristics of the syn- and post-tectonic groups show significant overlap, the
474
majority of the syn-tectonic group is more felsic than the post-tectonic granites. The generally high
475
SiO2 content (mostly between ~69 and 78 wt.%,), alkali-rich nature, low maficity, and low Ti, Mg, Fe,
476
Ca and Mn contents (Figs. 6, 7) of these syn-tectonic granite gneisses (the Colston Granite is the
477
exception in all cases) supports possible correlation with the near coeval, similarly acidic, but more
478
strongly deformed Riemvasmaak leucogranite augen gneiss and Augrabies granite gneiss (Fig. 4a, b),
479
although this would need to be tested more rigorously. In the past, these leucogranitic gneisses were
480
distinguished from the large bodies of syn-tectonic Riemvasmaak and Augrabies granite gneisses
481
dominating the western Kakamas Terrane on the basis that the latter are commonly augen-textured
482
(SACS, 1980), despite having similar compositions (Figs. 4, 5) and mineralogies (low biotite contents
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and minor primary muscovite (Moen, 2007)). As such the syn-tectonic granites show similarities to
484
the augen gneisses apart from a well-developed augen texture.
485 6.3. Textural, mineralogical and geochemical characteristics of the late- to post-tectonic Keimoes
487
Suite
488
Mineralogically, many of the post-tectonic granites are typically feldspar porphyritic and have
489
significant amounts of biotite together with, or without, hornblende and/or orthopyroxene (Table 6).
490
Primary muscovite is not identified. In addition, the post-tectonic intrusions become more
491
granodioritic with decreasing age concomitant with an increase in mafic minerals and decreasing K-
492
feldspar content.
493
In terms of whole rock geochemistry, most of the Keimoes Suite granites, excluding the Louisvale
494
Tonalite, show consistent major element trends and classify as ferroan, mostly metaluminous
495
monzogranites (including charnockite) and granodiorites (Fig. 4). The post-tectonic granites show a
496
trend towards more intermediate, aluminous and less alkali compositions with decreasing age (Figs. 5,
497
6), a trend not observed in the syn-tectonic group. They have higher maficities and are less
498
fractionated than the syn-tectonic granites (Figs. 5, 6).
499
The Louisvale Granite differs in being dominantly tonalitic (Fig. 5), and has a major and trace
500
element geochemistry (Figs. 6-8) inconsistent with the other granites and granite gneisses. The
501
Louisvale Granite also has a higher initial 143Nd/144Nd ratio (0.51128), εNd(t) value (1.89) and a
502
younger model age (TDM = 1.49 Ga) than most of the other granites (Fig. 8), and, with a low initial Sr
503
ratio of 0.70630 (Fig. 8a), appears to have been derived from a relatively depleted mantle source with
504
minor crustal contribution. This compositional difference, along with the gneissic nature and age of
505
this granitoid, forms the basis for the exclusion of the Louisvale Granite from the Keimoes Suite.
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6.4. Origins of the granites in the eastern Namaqua Sector
508
6.4.1. Origins of the post-tectonic Keimoes Suite
509
The post-tectonic Keimoes Suite, as defined in this study, has geochemical compositions reflecting
510
mixed or hybrid sources. On one hand, the granites have characteristics suggestive of I-type granites,
511
having more granodioritic compositions, with arc-like affinities (Ta-Nb, Ti and P anomalies – Fig. 7).
512
However, the high Fe/Mg ratios [0.82-3.84, avg. 1.66], and high HFSE, LILE and REE contents, are
513
more suggestive of A-type granites, particularly fractionated A2-type granites (Eby, 1992; Fig. 4e,
514
Loiselle and Wones, 1979).
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516
orthopyroxene as the predominant mafic minerals in these post-tectonic granites and charnockites,
517
argues for the melting of igneous sources with little to no sedimentary source material present giving
518
rise to dry parental magmas. Significant enrichments in Pb, Th, U, LREE relative to the HREE, and
519
the LILE relative to the HFSE, with depletions in Ba, Nb, Ta, Sr, Eu, Ti, Al2O3, V and Sc (Fig. 7)
520
indicate significant crustal contributions to the source magmas. A general geochemical trend to more
521
intermediate compositions with time and decreasing age of emplacement suggests that the initial
522
crustal component was initially greater and was reduced over time giving rise to a greater mantle
523
contribution (e.g. Fig. 8a, c, d).
524
εNd(t) values varying around, and close to zero (Fig. 8) suggest a variably depleted component, being
525
potentially mantle and/or juvenile lower crust. The Nd model ages range from relatively juvenile (as
526
young as 1.38 Ga (Fig. 8c; Table 5)) to Paleoproterozoic (TDM to 1.99 Ga) with potentially Archean
527
crustal contributions (the Kleinbegin Granite - εNd(t): -7.51; TDM: 2.34 Ga). These, combined with arc
528
signatures (Fig. 7), suggest the involvement of both juvenile, Mesoproterozoic crust as well as older,
529
∼1.85-2.0 Ga Paleoproterozoic crust (e.g. the Sperrgebiet and Richtersveld arcs; Reid, 1997; Thomas
530
et al., 2016; Macey et al., 2017). The ∼1.3-1.24 Ga Areachap arc (Pettersson et al., 2007) potentially
531
contributed juvenile Mesoproterozoic material. Mixing between juvenile material, of likely mantle
532
origin, and older Paleoproterozoic material, occurred. The Paleoproterozoic material was reworked at
533
this time. Initial Sr ratios [(87Sr/86Sr)I]] for the eastern NS granitoids, in general, are both high and
534
highly variable (0.70628-0.77130, and generally >0.707 – Table 5]. Such high SrI ratios are typical of
535
the NNMP (e.g. Fig. 12 of Eglington, 2006). Eglington (2006) interpreted these patterns as suggesting
536
reworking of material not older than 2.2 Ga. This is seen in the (87Sr/86Sr)I vs. age plot (Fig. 8d) where
537
the (87Sr/86Sr)I ratios vary along a general mixing trend between the depleted mantle (DM) curve and
538
Paleoproterozoic crust of ∼2.0 Ga age. The Keimoes Suite granites are characterized by high
539
maficities and low SrI ratios, which, in combination with low εNd(t) values, suggest that the older,
540
Paleoproterozoic material may not have been highly radiogenic and the mantle contribution was
541
significantly large.
542
Varying contributions of Meso- to Paleoproterozoic-ages sources to the parental magmas to the
543
Keimoes Suite granites is recorded by the presence of inherited zircons in these granites, e.g. Bailie et
544
al. (2011a). The intercept age determined for the Klipkraal Granite (1270 ± 26 Ma; this study) clearly
545
reflects inheritance and the age of the Areachap arc (Pettersson et al., 2007). Inherited zircons of older
546
Mesoproterozoic age (1346 Ma) are found in the Keboes Granite (this study; Table A1). These
547
inherited zircons thus likely reflect the influence of juvenile material of Mesoproterozoic age in the
548
source area to these granites. Cornell et al. (2012) reported xenocrysts with older ages of 1725 ± 25
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550
clear but may reflect mixing.
551
The tectonic setting of the Keimoes Suite granites, using the Pearce et al. (1984) plots, is dominantly
552
of within-plate granites (WPG) (Fig. 9). The WPG field corresponds to a continental intra-plate to
553
continental back-arc as well as rifting settings and/or post-collision magmatism (Förster et al., 1997).
554
Such settings highlight a period of transcurrent shearing and extension at ∼1100 Ma (Jacobs et al.,
555
1993; Gutzmer et al., 2000; Pettersson et al., 2007; Bailie et al., 2012). It also correlates with the A-
556
type signature and mantle component of these granites related to crustal thinning and resultant mantle
557
upwelling at this time.
558
Cornell et al. (2012) proposed that the Keimoes Suite represents a mixed/hybrid melt generated during
559
late-Namaqua tectonics related to the ~1100 Ma subcontinental scale Umkondo plume (Hanson et al.,
560
2004). Further geochemical and isotopic studies are required in order to test this proposed hypothesis.
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6.4.2. Origins of the syn-tectonic granites and granitic gneisses
563
The pre- to syn-tectonic granites are characterized by fractionated leucogranitic melts that intruded
564
during peak metamorphism and the main deformation in the Kakamas and Areachap terranes
565
(Pettersson et al., 2007; Fig. 10). The syn-tectonic granites are more dominantly leucogranitic, being
566
mafic mineral-poor, and have a more S-type character compared to the late- to post-tectonic Keimoes
567
Suite granites. They exhibit similar enrichments and depletions as the post-tectonic Keimoes Suite
568
granites, particularly with regard to LILE enrichment (Fig. 7). The syn-tectonic granites have εNd(t)
569
values close to 0 (-1.47 to 1.78) (Fig. 9; Table 5) suggesting a mantle component to these melts. A
570
crustal signature is suggested by their leucogranitic compositions, enrichment in Rb, K, Th and U
571
(Fig. 7), and metaluminous to peraluminous characteristics (Fig. 4f). Nd model ages (TDM = 1.57-1.91
572
Ga) (Table 5) suggest variable degrees of mixing between sources of Meso- and Paleoproterozoic age
573
of likely arc derivation as denoted by arc-like signatures (LILE enrichment relative to the HFSE,
574
depletions in Nb, Ta and Ti). As for the Keimoes Suite, inherited zircons of Mesoproterozoic age
575
(1335-1344 Ma) are found in the Elsie se Gorra Granite (this study; Table A9). The syn-tectonic
576
granites are, however, characterized by lower maficities than the post-tectonic granites (Fig. 6)
577
suggesting a lower mafic mineral content and a more fractionated nature (correlating with high SiO2
578
content in general). They are also characterized by higher initial Sr ratios (Fig. 8c) and so likely
579
represent a greater degree of crustal melting, and incorporation of older, ∼2.0 Ga, radiogenic crust
580
relative to the post-tectonic Keimoes Suite. Mixing of radiogenic crust characterized by low εNd(t)
581
values, e.g. those of the Richtersveld Magmatic Arc (RMA) with low εNd(t) values of near 0 (0.53 to -
582
3.19 for the RMA - Macey et al., 2017), may explain the low εNd(t) values of the eastern NS granites.
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585
The period of arc magmatism associated with development of the 1.30-1.24 Ga Areachap arc
586
(Pettersson et al., 2007) due to eastward-directed subduction (Pettersson et al., 2007) was dominated
587
by extensive juvenile magmatism with dominantly Mesoproterozoic Nd model ages (Bailie et al.,
588
2010). A period of peak magmatism between ∼1.23 and 1.18 Ga is seen in the western Kakamas
589
Terrane (Fig. 10; Bial et al., 2015a), corresponding to extensive magmatism within the Bushmanland
590
Subprovince further west (Bailie et al., 2007; Cornell et al., 2009). This is taken to be amalgamation
591
of the Bushmanland Subprovince and Kakamas Terrane at this time. Extensive magmatism is not seen
592
during this period in the Areachap Terrane. Extensive magmatism, however, occurred between ∼1.18
593
Ga and 1.13 Ga in both the Kakamas and Areachap terranes (Fig. 10) associated with closure of the
594
Areachap ocean (Pettersson et al., 2007) leading to reworking of Paleoproterozoic material, and,
595
potentially, of the Areachap arc as well. Mixing of crustal melts with mantle material affected or
596
enriched by subduction processes is likely. Ocean basin closure resulted in peak metamorphic
597
conditions at ∼1.15 Ga. Accretion processes are likely given the low-P, high-T nature of the NS more
598
akin to a continental back-arc scenario compared to a continental collision scenario (Bial et al., 2015a,
599
b). Current interpretations, such as Cornell et al. (2011), interpret the Kakamas Terrane as a separate
600
crustal block that collided, or was juxtaposed with the Areachap Terrane prior to ∼1.12 Ga although
601
current age data do not support a collisional or amalgamation event between the two prior to ∼1.18 Ga
602
(Fig. 10).
603
Late- to post-tectonic magmatism is more voluminous, particularly in the Areachap Terrane (Fig. 10)
604
and is characterized by a substantial juvenile component. Potential slab breakoff, mantle upwelling or
605
collapse, and potential transcurrent shearing (Gutzmer et al., 2000; Bailie et al., 2012), likely resulted
606
in the late- to post-orogenic magmatism at ∼1.12-1.07 Ga characterized by variable mixing between
607
juvenile and older (reworked?) Paleoproterozoic sources. The overall proportion of the older,
608
radiogenic crust is less given the generally lower SrI ratios of the Keimoes Suite granites relative to
609
the more radiogenic, older syn-tectonic granites (Fig. 8), implying a greater non-radiogenic
610
component to the melts.
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6.6. Implications for timing of tectonics in the eastern Namaqua Sector of the NNMP
613
Pettersson et al. (2007) reported an age of 1165 Ma for migmatization and deformation in the
614
Areachap Group which corresponds well with the dating of intrusion of the syn-tectonic granite
615
gneisses between 1175 and 1146 Ma. The emplacement of the syn-tectonic Vaalputs Granite Gneiss
18
ACCEPTED MANUSCRIPT (1146 Ma) and Riemvasmaak Gneisses (1156 Ma) across the boundary between the Areachap and
617
Kakamas terranes (Fig. 10) indicates that they were juxtaposed prior to ~1.16 Ga (Table 2).
618
The Louisvale Tonalite that intruded at ∼1125 Ma, is also strongly foliated and provides the
619
maximum age for the peak D2 Namaquan deformation. The minimum age for the D2/Namaquan
620
deformation in the eastern NS is constrained by the post-tectonic Keimoes Suite (sensu Cornell et al.,
621
2012; this study) for which the oldest reliably dated member, the weakly foliated Keboes Granite, has
622
been dated at 1105 Ma. The weak magmatic fabric observed in the margins of some of the post-
623
tectonic granites is considered the result of intrusion into a waning regional stress field (van Zyl,
624
1981).
625
Subsequent open E-W-trending F3 folds, associated with weaker D3 deformation, developed at ∼1.10
626
Ga (Pettersson et al., 2007). The post-tectonic Keimoes Suite is synchronous with this deformation
627
event although these granites are largely weakly foliated to unfoliated. The syn-tectonic Vaalputs
628
Granite and the weakly to unfoliated late- to post-tectonic Keimoes Suite granites are concentrated
629
along the BRSZ (Fig. 1), the boundary between the Kakamas and Areachap terranes, suggesting that
630
this major crustal feature played an important, long-lived role in the emplacement of the granites of
631
the eastern NS.
632
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6.7. Origins and age of Namaquan crust
634
Paleoproterozoic TDM ages are typical for most of the western Namaqua Sector (Reid, 1997; Clifford
635
et al., 1981, 1995, 2004; Yuhara et al., 2001; Bailie et al., 2007; Pettersson et al., 2009; Macey et al.,
636
2017) suggesting that large portions of the NS were derived from the magmatic reworking of
637
Paleoproterozoic crust (e.g. Clifford et al., 2004; Eglington, 2006; Pettersson et al., 2009; Bial et al.
638
2015a, b; Macey et al., 2017) carrying a subduction related arc signature based on geochemical
639
characteristics. εNd(t) values of rocks in the Bushmanland Subprovince to the west show a similar
640
pattern of being all near zero, whereas the SrI values give a large range of highly radiogenic values
641
(Clifford et al., 1981, 1995; Yuhara et al., 2001, 2002) which appears to be another characteristic
642
feature of the NS in general (Eglington, 2006). The subcontinental lithospheric mantle (SCLM) of
643
southern Africa is highly enriched in general having 87Sr/86Sr ratios varying between 0.7114 and
644
0.7550 (concentrates from kimberlite pipes – Richardson et al., 1984). Small variations in εNd(t) values
645
which vary around 0 have been used to suggest derivation from a mantle wedge metasomatised by
646
slab-derived melts (e.g. Wang et al., 2013). In the case of the NS it likely represents reworking of
647
Proterozoic arc-related crust and variable degrees of mixing with juvenile Mesoproterozoic material
648
(Eglington, 2006). Given the limited amount of isotopic data for the eastern NS in general (e.g.
649
Eglington, 2006; Pettersson et al., 2009) more extensive isotopic determinations are required in order
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ACCEPTED MANUSCRIPT 650
to more fully assess the origin of the highly radiogenic initial Sr isotopic signatures coupled to low
651
εNd(t) values of the NS.
652 6.8. The pre- to early syn-tectonic Josling Granite
654
The Josling Granite, with a well-developed, gneissic fabric is pre-tectonic with regards to the peak D2
655
deformation (Fig. 10). Pettersson (2008) determined an age of 1275 ± 7 Ma for this granite, whereas
656
the present study determined a younger age of 1217 ± 20 Ma. Based on its age it should be removed
657
from the Keimoes Suite. The Josling Granite may be related to an older cluster of pre-D2 intrusions
658
(1371 to 1220 Ma; Cornell et al., 2012) related to the development of the Areachap arc.
659
The Josling Granite is a feldspathic leucogranite characterized by low maficity (Fig. 6) and a
660
relatively high SiO2 content (Fig. 5) and is relatively fractionated. With a high initial 143Nd/144Nd ratio
661
(0.511158-0.511260), mildly positive εNd(t) values (1.79-3.77), and low initial Sr ratios (0.70674-
662
0.70821; Fig. 8; Table 5) it was derived from a relatively depleted source with a minor crustal
663
component. With model ages varying between 1.45 and 1.63 Ga it also shows mixing of Meso- and
664
Paleoproterozoic aged sources, with the former more dominant. Given its depleted source signature
665
and low initial Sr ratio it likely is related to juvenile magmatism related to development of the
666
Areachap arc, but, with a spread of model ages toward Paleoproterozoic ages, also reflects a generally
667
older Paleoproterozoic aged crustal source component to the magmas in the northern Areachap
668
Terrane (Pettersson et al., 2009; Bailie et al., 2010).
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669 7. Conclusions
671
New U-Pb zircon age data and whole rock geochemistry presented in this study support the new
672
definition of the Keimoes Suite as proposed by Cornell et al. (2012) in which the 1175-1146 Ma syn-
673
tectonic leucogranite and granite gneisses are removed from the suite. The Keimoes Suite (sensu
674
Cornell et al., 2012; this study) is now defined as a group of foliated to unfoliated late- to post-
675
tectonic, largely megacrystic granites and charnockites emplaced during a relatively narrow period
676
between 1110 and 1078 Ma.
677
The 1.11-1.08 Ga post-tectonic Keimoes Suite granites have geochemical compositions reflecting
678
mixed or hybrid sources with both fractionated I-type characteristics (metaluminous, hornblende- and
679
orthopyroxene-bearing and arc-like affinities) as well as fractionated A-type characteristics (high
680
Fe/Mg ratios, high HFSE, LILE and LREE contents). They exhibit an overall trend of increasing
681
maficity (elemental Fe + Mg), Ti, Ca and Mn, and decreasing Si, Na and K with decreasing age
682
becoming increasingly less fractionated and more metaluminous. Isotopic systematics suggest
683
derivation from a mildly depleted source with variable degrees of an enriched and/or crustal
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ACCEPTED MANUSCRIPT component, as denoted by εNd(t) values close to 0 and relatively low initial Sr isotope ratios (<0.725).
685
Variable mixing between juvenile Mesoproterozoic and older Paleoproterozoic arc material, the latter
686
likely represented by the Richtersveld arc, contributed to the parental melts and an arc-like signature
687
(LILE enrichment relative to the HFSE, negative Ta-Nb, P and Ti anomalies, enrichment in Pb, K, Th
688
and U). The Keimoes Suite granites were emplaced mostly within the Areachap Terrane of the eastern
689
NS, but the youngest member, the Friersdale Charnockite, intruded both the Kakamas and Areachap
690
Terranes and the tectonic boundary between them. The granites were emplaced during a period of
691
transcurrent shearing and extension at ∼1.11 Ga which was associated with crustal thinning and
692
mantle upwelling, as denoted by their A-type characteristics. The suite is concentrated along the
693
BRSZ suggesting this structure may have played a role in the migration of magmas into the upper
694
crust.
695
By contrast the ∼1.18-1.15 Ga syn-tectonic granites are fractionated metaluminous to peraluminous
696
moderately to strongly foliated leucogranites and gneisses with low maficity, Ti, Ca and Mn, and high
697
Si, Na and K contents suggesting largely pure melts. Isotopic ratios (εNd(t) values close to 0 (-1.47 to
698
1.78)) support a juvenile lower crustal source, but with a likely greater radiogenic crustal component
699
relative to the Keimoes Suite, as denoted by highly variable and high initial Sr isotope ratios likely
700
suggesting reworking of initially radiogenic crust. Nd model ages also suggest mixing between Meso-
701
and Paleoproterozoic aged sources. These granitic gneisses are also more voluminous toward the west
702
compared to the late- to post-tectonic Keimoes Suite granites possibly indicating a potential shift in
703
magmatism with time. The main penetrative fabric forming event in the eastern Namaqua Sector is
704
constrained to between ∼1125 and ∼1110 Ma, the ages of the youngest granite gneiss and the oldest
705
weakly foliated granite, respectively. The juxtapositioning of the Areachap and Kakamas terranes
706
occurred prior to 1.15 Ga.
707
The variable Nd model ages varying to Paleoproterozoic age confirm a dominant Paleoproterozoic arc
708
source in the Namaqua Sector, as also found by previous workers. This Paleoproterozoic aged arc was
709
extensively reworked during the Namaquan Orogeny. Granites in the eastern Namaqua Sector also
710
carry signatures of a more juvenile Mesoproterozoic source, as denoted by Nd model ages and
711
inherited zircons.
712
Further detailed geochemical and structural studies of the eastern Namaqua Sector granites are
713
required. The former is required to determine the more detailed petrogenesis of the syn-tectonic
714
granitic gneisses as well as the Keimoes Suite, with the latter to investigate their means of
715
emplacement. In addition, the relationship between the syn-tectonic granites straddling the boundary
716
between the Kakamas and Areachap terranes and the voluminous granitic gneisses of the central to
717
western Kakamas Terrane is of future research interest.
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ACCEPTED MANUSCRIPT Acknowledgements
720
This project was done in conjunction with the Council for Geoscience (CGS) who funded some of the
721
analyses. The project was also funded by an NRF Y-rated researcher incentive funding grant awarded
722
to RB as well as a CGS bursary to SN. Whole rock geochemical analyses were undertaken by H.
723
Cloete and Melissa Crowley of the CGS (major elements) and Riana Rossouw of the Central
724
Analytical Facility, Stellenbosch University (trace elements). Many thanks to Dr. Luc Chevallier and
725
Dr. Hendrik Minnaar (CGS) for their logistical assistance during the field work phase of the study.
726
Peter Meyer and Janine Becorney of the Department of Earth Sciences, UWC are thanked for
727
technical support. Stefan Büttner and David Cornell are thanked for providing helpful and insightful
728
reviews of an earlier version of this manuscript. Jodie Miller and an anonymous reviewer are thanked
729
for helpful comments that substantially improve this version of the manuscript.
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730 Appendix - Analytical techniques
732
Whole rock geochemistry
733
Major element contents for all representative samples were determined by X-ray fluorescent (XRF)
734
spectrometry at the CGS, Pretoria, on glass beads prepared from a 0.2 g sample following a lithium
735
metaborate/tetraborate fusion and dilute nitric acid digestion. Loss on ignition (LOI) was calculated
736
by the weight difference after ignition to 1000oC. Powdered whole-rock samples were mixed with
737
flux for a sample-to-flux (lithium tetraborate) ratio of 1:10. Thirty-two USGS and GSJ standard
738
reference samples were used for calibration of the instrument.
739
The trace and rare earth element (REE) abundances were determined using inductively coupled
740
plasma mass spectrometry (ICP-MS) at CAF following the same procedure as for the whole rock
741
analyses but with a separate 0.5 g split digested in Aqua Regia and analysed by ICP-MS. Fusion disks
742
prepared for XRF analysis by an automatic Claisse M4 Gas Fusion instrument and ultrapure Claisse
743
Flux, using a ratio of 1:10 sample : flux, were coarsely crushed and a chip of sample mounted along
744
with up to 12 other samples in a 2.4cm round resin disk. The mount was mapped, and then polished
745
for analysis.
746
A Resonetics 193nm Excimer laser connected to an Agilent 7500ce ICP-MS is used in the analysis of
747
trace elements in bulk rock samples at CAF, Stellenbosch University. Ablation is performed in He gas
748
at a flow rate of 0.35l/min, then mixed with argon (0.9l/min) and Nitrogen (0.004l/min) just before
749
introduction into the ICP plasma. For traces in fusions, 2 spots of 173µm are ablated on each sample
750
using a frequency of 10Hz and 100mJ energy.
751
Trace elements are quantified using NIST 612 for calibration and the % SiO2 from XRF measurement
752
as internal standard, using standard – sample bracketing. Two replicate measurements are made on
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22
ACCEPTED MANUSCRIPT each sample. The calibration standard was run every 12 samples. A quality control standard is run in
754
the beginning of the sequence as well as with the calibration standards throughout. BCR-2 or BHVO
755
2G, both basaltic glass certified reference standards produced by the USGS (Dr Steve Wilson,
756
Denver, CO 80225), is used for this purpose. A fusion control standard from certified basaltic
757
reference material (BCR-2, also from the USGS) is also analysed in the beginning of a sequence to
758
verify the effective ablation of fused material. The precision and accuracy of the results are 2–5%
759
(1σ) for most elements. Detection limits of most trace elements are 0.1 ppm, except for Th and Co
760
(0.2 ppm), Sr (0.5 ppm), Sc and Zn (1 ppm), and V (8 ppm). Most REE have detection limits less than
761
or equal to 0.05 ppm, the exceptions being La and Ce (0.1 ppm), and Nd (0.3 ppm).
RI PT
753
762 Whole rock Rb-Sr and Sm-Nd isotope analysis
764
Rb-Sr and Sm-Nd isotope analysis, for the same eight samples that were analysed for geochronology,
765
was done at the Department of Geological Sciences, University of Cape Town (UCT). Following
766
concentration analysis, separation of Sr and Nd fractions in the same sample dissolutions were
767
undertaken by chromatographic techniques as described by Miková and Denková (2007), after that
768
described by Pin and Zaldegui (1997) and Pin et al. (1994). The Sr fractions were separated using
769
Eichrome Sr resin beds, and the aqueous solution was diluted in 2 ml 0.2% HNO3, ready for Sr
770
isotope ratio determination. The remaining portions were converted to salts, dried down and further
771
dissolved to extract the REEs using AG50W cation resin columns. The REE portions were converted
772
to nitrate, dried down and then diluted in 0.05M HNO3 to collect Nd using Eichrome Ln resin
773
columns. These portions were dried down and diluted in 1.5 ml 2% HNO3 for Nd isotope ratios
774
determination.
775
The determination of Rb, Sr, Sm and Nd concentrations in each sample was performed on a Thermo
776
XSeries II ICP-MS at UCT following dissolution with concentrated HF and HNO3, and dilution with
777
5% HNO3 containing an internal standard. Concentrations were determined in duplicate for each
778
sample. The international standard BHVO-2 was analysed with every batch of samples as a measure
779
to assess accuracy and precision.
780
Sr is analysed as a 200ppb 0.2% HNO3 solution. All Sr isotope analyses of unknowns are referenced
781
to bracketing analyses of the NIST SRM987 reference standard, using a reference value for 87Sr/86Sr
782
of 0.710255. The international reference material BHVO-2 gave a value of 0.703490 ± 15 relative to a
783
value of 0.703479 ± 20 reported by Weis et al. (2006). The long-term UCT average is 0.703479 ± 22
784
(n = 47). All Sr isotope data are corrected for Rb interference using the measured signal for 85Rb and
785
the natural 85Rb/87Rb ratio. Instrumental mass fractionation is corrected using the exponential law and
786
a 86Sr/88Sr value of 0.1194.
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23
ACCEPTED MANUSCRIPT Nd isotopes are analysed as 50 ppb 2% HNO3 solutions using a Nu Instruments DSN-100 desolvating
788
nebuliser. JNdi-1 is used as a reference standard, with a 143Nd/144Nd reference value of 0.512115,
789
corresponding to the La Jolla standard (Tanaka et al., 2000). The BHVO-2 reference material gave
790
values of 0.512981 ± 10, relative to a value of 0.512984 ± 11 reported by Weis et al. (2006). All Nd
791
isotope data are corrected for Sm and Ce interference using the measured signals for 147Sm and 140Ce,
792
and the natural Sm and Ce isotope abundances. Instrumental mass fractionation is corrected using the
793
exponential law and a 146Nd/144Nd value of 0.7219. The initial 87Sr/86Sr and 143Nd/144Nd ratios were
794
calculated using decay constants of 1.42 x 10-11 y-1 (Steiger and Jäger, 1977) and 6.54 x 10-12 y-1
795
(Begemann et al., 2001), respectively.
796
Measurements of standards BHVO-2 (Weis et al., 2006) and JNdi-1 (Tanaka et al., 2000) for samples
797
S188, 367 and 815 of the Friersdale Charnockite yielded 143Nd/144Nd values of 0.512987 ± 9 and
798
0.512115 ± 7 respectively. The long-term UCT average for BHVO-2 (n = 44) is 0.512985 ± 15
799
relative to the value of 0.512984 ± 11 (Weis et al., 2006). Sr isotope measurements of BHVO-2 and
800
reference material NIST987 for the same samples yielded 87Sr/86Sr values of 0.704375 ± 13 and
801
0.710255, respectively. Measurements of standards BHVO-2 and JNdi-1 for samples Me1, Mcol3,
802
Mkn4, Ml5, Mkb6, Mc8, Mkl3 and Mka6 yielded 143Nd/144Nd values of 0.512981 ± 10 and 0.512115
803
± 7 respectively. Sr isotope measurements of BHVO-2 and reference material NIST987 for the same
804
samples yielded 87Sr/86Sr values of 0.704390 ± 15 and 0.710255, respectively.
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805 U-Pb zircon LA-SF-ICP-MS age dating
807
Zircon crystals were extracted from samples by traditional methods of crushing and grinding,
808
followed by separation with a Wilfley table, heavy liquids, and a Frantz magnetic separator. Samples
809
are processed such that all zircons are retained in the final heavy mineral fraction. A split of these
810
grains (generally 50-100 grains) are selected from the grains available and incorporated into a 1 inch
811
resin mount together with fragments of Plešovice (Sláma et al., 2008) and 91500 (Wiedenbeck et al.,
812
1995) reference materials. The mounts are sanded down to a depth of ~20 µm, polished, imaged, and
813
cleaned prior to isotopic analysis.
814
All U-Pb age data of zircons was conducted by laser ablation - single collector – magnetic sector field
815
- inductively coupled plasma - mass spectrometry (LA-SF-ICP-MS) employing a Thermo Finnigan
816
Element2 mass spectrometer coupled to a Resonetics Resolution HR-S155 excimer laser ablation
817
system at the Central Analytical Facility (CAF), Stellenbosch University. The analyses involve
818
ablation of zircon using a spot diameter of 30 µm and a crater depth of approximately 10-15 µm. A
819
sampling pattern of 30 µm single spot analyses was used. The use of the LA-ICP-MS dating
820
technique does not allow spots of <30 µm to be analysed so that metamorphic rims on zircons could,
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ACCEPTED MANUSCRIPT unfortunately, not be analysed. The methods employed for analysis and data processing are those
822
described by Frei and Gerdes (2009) with the modifications described in Cornell et al. (2016).
823
For quality control, the 91500 (Wiedenbeck et al., 1995), Plešovice (Sláma et al., 2008) and M127
824
(Nasdala et al., 2008; Mattinson, 2010) zircon reference materials were analysed, and the results were
825
consistently in excellent agreement with published ID-TIMS ages. 91500 has a concordia age of 1067
826
± 6 Ma (2s, MSWD = 0.34), M127 a concordia age of 527 ± 3 Ma (2s, MSWD = 0.29) and Plešovice
827
a concordia age of 339 ± 2 Ma (2s, MSWD = 0.47).
828
An in-house spreadsheet using the intercept method for laser induced elemental fractionation (LIEF)
829
correction is used for data processing. Mass discrimination is undertaken by standard-sample
830
bracketing with 207Pb/206Pb and 206Pb/238U normalized to reference material GJ-1 (Jackson et al.,
831
2004). Common Pb correction is accomplished by using the Hg-corrected 204Pb and assuming an
832
initial Pb composition from Stacey and Kramers (1975) at the projected age of the mineral with a 5%
833
uncertainty assigned. Ages are quoted at 2 sigma absolute, with propagation by quadratic addition.
834
Reproducibility and age uncertainty of reference material and common-Pb composition are
835
propagated. Uncertainties of 1.5 for 206Pb/204Pb and 0.3 for 206Pb/207Pb are applied to these
836
compositional values based on the variation in Pb isotopic composition in modern crystalline rocks.
837
For each analysis, the errors in determining 206Pb/238U and 206Pb/204Pb result in a measurement error of
838
~1-2% (at 2-sigma level) in the 206Pb/238U age. The errors in measurement of 206Pb/207Pb and
839
206
840
are substantially larger for younger grains due to low intensity of the 207Pb signal. For most analyses,
841
the cross-over in precision of 206Pb/238U and 206Pb/207Pb ages occurs at ~1.20 Ga (Gehrels et al., 2008),
842
although compilations of LA-ICP-MS and scanning ion mass spectrometer (SIMS) data suggests an
843
older crossover at ∼1.5 Ga (Spencer et al., 2016).
844
Inter-element fractionation of Pb/U is generally ~5%, whereas apparent fractionation of Pb isotopes is
845
generally <0.2%. In-run analysis of fragments of GJ-1 (generally every fifth measurement) with
846
known age of 608.5 ± 0.4 Ma (2-sigma error) (Jackson et al., 2004) is used to correct for this
847
fractionation. The uncertainty resulting from the calibration correction is generally 1-2% (2-sigma) for
848
both 206Pb/207Pb and 206Pb/238U ages. Concentrations of U and Pb and Th/U ratios are calculated
849
relative to the GJ-1 reference zircon.
850
Full analytical and data reduction details for the LA-SF-ICP-MS U-Pb dating undertaken at CAF,
851
Stellenbosch University, including operating procedures, sample preparation, instrument set up, as
852
advocated by Horstwood et al. (2016), are given in electronic supplementary material Table A11, with
853
the results for all quality control materials analysed reported in Table A12 in the electronic
854
supplementary material. Measurements of standards and reference materials are reported in Appendix
855
Tables A1 to A8. Uncertainties shown in these tables are at the 2-sigma level, and include only
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Pb/204Pb also result in ~1-2% (at 2-sigma level) uncertainty in age for grains that are >1.0 Ga, but
25
ACCEPTED MANUSCRIPT measurement errors. Analyses that are >10% discordant (by comparison of 206Pb/238U and 206Pb/207Pb
857
ages) or >5% reverse discordant (both in italics in Tables A1 - A8) are not considered when
858
determining weighted mean U-Pb ages (Gehrels et al., 2008 recommended >20%). Inherited cores are
859
highlighted in bold in the data tables.
860
The resulting interpreted ages are shown on Pb*/U concordia diagrams and weighted mean diagrams
861
using the plots generated by Isoplot/Ex 3.0 (Ludwig, 2003). The weighted mean diagrams show the
862
weighted mean (weighting according to the square of the internal uncertainties), the final uncertainty
863
of the age (determined by quadratic addition of the weighted mean and external uncertainties), and the
864
MSWD of the data set. Ages are reported on the basis of 206Pb/238U following the recommendations of
865
Gehrels et al. (2008) as the zircons analysed are all less than ∼1.2 Ga. Spencer et al. (2016), based on
866
previous compilations of LA-ICP-MS zircon analyses, and SIMS zircon analyses, noted that an ∼1.5
867
Ga cross over point from 207Pb/206Pb ages to 206Pb/238U is preferable. The analytical data analysis, data
868
validation and reporting methodologies, as advocated by Horstwood et al. (2016), and the
869
international network of practitioners (LA-ICP-MS U-(Th-)Pb Network, given at the website:
870
http://www.PlasmAge.org/recommendations), have been followed as far as possible.
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Slabbert, M.J., Moen, H.F.G., Boelema, R., 1999. Die geologie van die gebied Kenhardt. Explanation,
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sheet 2920. Council for Geoscience, South Africa, 123 pp.
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Sláma J., Košler, J., Condon, D.J., Crowley, J.L, Gerdes, A., Hanchar, J.M., Horstwood, M.S.A.,
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Morris, G.A., Nasdala, L., Norberg, N., Schaltegger, U., Schoene, B., Tubrett, M.N., Whitehouse,
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M.J., 2008. Plešovice zircon—a new natural reference material for U–Pb and Hf isotopic
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microanalysis. Chem. Geol. 249, 1–35.
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Smit, C.A., 1977. Die geologie rondom Groblershoop met spesiale verwysing na die verband tussen
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die Namakwalandse Mobiele Gordel en die Matsap-Kheisgesteentes. PhD thesis (unpubl.) (in
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Afrikaans), University of the Orange Free State, South Africa.
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Spencer, C.J., Thomas, R.J., Roberts, N.M.W., Cawood, P.A., Millar, I., Tapster, S., 2015. Crustal
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growth during island arc accretion and transcurrent deformation, Natal Metamorphic Province, South
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Africa: New isotopic constraints. Precambr. Res. 265, 203-217.
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interpretations of in situ U-Pb zircon geochronology. Geosci. Front. 7, 581-589.
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Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotopic evolution by a two-stage
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model. Earth Planet. Sci. Lett. 26, 207-221.
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Steiger, R.H., Jäger, E., 1977. Subcommission on geochronology: Convention on use of decay
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constants in geo- and cosmochronology: Earth Planet. Sci. Lett. 126, 359-362.
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Streckeisen, A., 1976. To each plutonic rock its proper name. Earth-Sci. Rev. 12, 1-33.
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Stowe, C.W., 1983. The Upington geotraverse and its implications for craton margin tectonics. In:
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Botha, B.J.V. (Ed.), The Namaqualand Metamorphic Complex, Spec. Publ. Geol. Soc. S. Afr. 10, pp.
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147–171.
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Tanaka, T., Togashi, S., Kamioka, H., Amakawa, H., Kagami, H., Hamamoto, T., Yuhara, M.,
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Orihashi, Y., Yoneda, S., Shimizu, H., Kunimaru, T., Takahashi. K., Yanagi, T., Nakano, T.,
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Fujimaki, H., Shinjo, R., Asahara, Y., Tanimizu, M., Dragusanu, C., 2000. JNdi-1: a neodymium
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Thomas, R.J., Macey, P.H., Spencer, C., Dhansay, T., Diener, J.F.A., Lambert, C.W., Frei, D. Nguno,
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Van Bever Donker, J.M., 1980. Structural and metamorphic evolution of an area around Kakamas and
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Van Bever Donker, J.M., 1991. A synthesis of the structural geology of a major tectonic boundary
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Van Niekerk, H.S., 2006. The origin of the Kheis Terrane and its relationship with the Archean
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Kaapvaal Craton and the Grenvillian Namaqua Province in southern Africa. PhD thesis, University of
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Johannesburg, Johannesburg, 260 pp.
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Van Zyl, C.Z., 1981. Structural and metamorphic evolution in the transitional zone between craton
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Wang, Y.J., Zhang, A.M., Cawood, P.A., Fan, W.M., Xu, J.F., Zhang, G.W., Zhang, Y.Z., 2013.
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Geochronological, geochemical and Nd–Hf–Os isotopic fingerprinting of an early Neoproterozoic
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Weis, D., Kieffer, B., Maerschalk, C., Barling, J., de Jong, J., Williams, G.A., Hanano, D., Pretorius,
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Geophys. Geosys. 7(8), 30 pp. Q08006, doi:10.1029/2006GC001283.
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Whalen, J.B., Currie, K.L., Chappell, B.W., 1987. A-type granites: geochemical characteristics,
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Wiedenbeck, M., Allé, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., von Quadt, A., Roddick,
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Yuhara, M., Kagami, H., Tsuchiya, N., 2001. Rb-Sr and Sm-Nd systematics of granitic and
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1156
evolution of marginal part of Kaapvaal craton. Natl. Instit. Polar Res., Spec. Issue Mem. 55, 127-144.
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Yuhara, M., Miyazaki, T., Ishioka, J., Suzuki, S., Kagami, H., Tsuchiya, N., 2002. Rb-Sr and Sm-Nd
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Africa. Gondwana Res. 5, 771-779.
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Zindler, A., Hart, S.R., 1986. Chemical geodynamics. Ann. Rev. Earth Planet. Sci. 14, 493-571.
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List of figures
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Fig. 1. Distribution of granites and geochronological sample localities, eastern Namaqua Sector (NS).
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Compiled from the 1:250 000 scale map data of Moen (1988) and Slabbert (1998). Inset of the NNMP
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in southern Africa (after Cornell et al., 2006).
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Fig. 2. Zircon CL images for the dated eastern NS granites. Ages reported next to representations of
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analysed spots are 206Pb/238U ages. a. Smalvis Granite, Cyndas Subsuite, b. Colston Granite, c.
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Kanoneiland Granite, d. Keboes Granite, e. Louisvale Granite, f. Klipkraal Granite, g. Josling Granite,
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h. Elsie se Gorra Granite.
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Fig. 3. U-Pb isochron diagrams for the dated eastern NS granites. Plots are generated by Isoplot 3.0
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(Ludwig, 2003) but weighted mean ages are given rather than concordia ages. a. Smalvis Granite,
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Cyndas Subsuite, b. Colston Granite, c. Elsie se Gorra Granite, d. Josling Granite, e. Kanoneiland
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Granite, f. Keboes Granite, g. Klipkraal Granite, h. Louisvale Granite.
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Fig. 4. General geochemical characteristics and classification of the eastern NS granites. (a) QAP
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classification for granitoids, after Le Maitre et al. (2005), (b) The An-Ab-Or ternary plot to determine
1177
the composition of granite (after O’Connor, 1965), (c) The Na2O + K2O - CaO vs. SiO2 plot (after
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Frost et al., 2001), (d) Fe*/Fe*+ MgO vs. SiO2 plot used to determine if the rocks are ferroan or
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magnesian (after Frost et al., 2001), (e) The K2O+Na2O/CaO vs. Zr + Nb + Ce + Y plot indicating the
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vs. molar Al2O3/Na2O+K2O+CaO plot to differentiate between peralkaline, metaluminous and
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peraluminous granites (after Maniar and Piccoli, 1989). The fields for the compositions of the Cyndas
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Subsuite (after Jankowitz, 1987) and the Riemvasmaak Gneiss (after Geringer, 1973; Saad, 1987) are
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shown for (a) and (b).
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Fig. 5. Binary Harker diagrams for major and minor elements for the eastern NS granites. The fields
1186
for the Cyndas Subsuite (after Jankowitz, 1987) and the Riemvaasmaak Gneiss (after Geringer, 1973;
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Saad, 1987) are shown for reference.
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Fig. 6. Select major and minor element maficity (Mg + Fe) plots for the eastern NS granites.
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Fig. 6. (cont.) Select trace element maficity (Mg + Fe) plots for the eastern NS granites.
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Fig. 7. Spider diagrams and rare earth element (REE) plots for the syn-tectonic and late- to post-
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tectonic granites of the eastern NS granites. The colours and symbols are as for Figs. 5 and 6.
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Fig. 8. Isotopic diagrams for the eastern NS granites. a. εNd(t) vs. initial Sr showing major crustal and
1193
mantle sources, b. εNd(t) vs. 147Sm/144Nd, c. εNd(t) vs. age (in Ma), d. Initial Sr [SrI = (87Sr/86Sr)t], where t
1194
is the time of emplacement, vs. age, e. εNd(t) vs. maficity (elemental Fe + Mg), f. Initial Sr [SrI =
1195
(87Sr/86Sr)t] vs. maficity. The upper crust curve (Harris et al., 1986) and a theoretical lower crustal
1196
curve (Ben Othman et al., 1984) are indicated for reference in (a). The positions of the main oceanic
1197
mantle reservoirs identified by Zindler and Hart (1986) shown in (a) are: DM = depleted mantle, BSE
1198
= bulk silicate earth, EMI and EMII = enriched mantle I and II, HIMU = high mantle U/Pb ratio,
1199
PREMA = frequently observed prevalent mantle composition. The mantle source of MORB and the
1200
mantle end-members DMM, PREMA, HIMU, BSE, EMI and EMII are from Zindler and Hart (1986).
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The evolution curves for Paleoproterozoic crust of ∼2.4 Ga (c) and ∼2.0 Ga crust (d) is after Eglington
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(2006). The data used to plot d) and e) can be found in Appendix Table A10.
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Fig. 9. Tectonic setting discrimination diagrams for the late- to post-tectonic Keimoes Suite. a. The
1204
Rb vs. Y + Nb plot of Pearce et al. (1984). b. The Nb vs. Y plot of Pearce et al. (1984) is used because
1205
of the potential mobility of Rb during metamorphism.
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Fig. 10. Compilation of magmatic and metamorphic data for the Kakamas, Areachap and Kaaien
1207
terranes of the eastern NS (adapted after Spencer et al., 2015).
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potassic monzogranite
fine-grained, porphyritic
euhedral – subhedral K-fsp phenocrysts (up to 12 mm), qtz, K-fsp, plag, bt, msc
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Table 1 Features of the eastern Namaqua Sector granites (sensu Moen, 2007) (after Stowe, 1983; Geringer et al., 1987, 1988; Moen, 2007; Bailie et al., 2011a; Cornell et al., 2012) Granite Composition Grain Mineralogy Presence Host rocks Contacts Inclusions Age or relative Size of foliation age (in Ma) + ref. Josling leucogranite fine-grained qtz, K-fsp > plag, gneissic, well- Areachap Grp gradational 1275 ± 7b bt-poor, msc developed not part of Keimoese Elsie se Gorra leucogranite coarse-grained qtz, K-fsp, plag, bt moderate to no contacts, msc well-developed isolated outcrops Colston potassic, medium qtz, mcl, plag, bt, minor weakly Korannaland foliation numerous, 1156 ± 20 Ma peraluminous, equigranular, msc developed Group stronger toward mafic (can TIMS – zircon granodiorite porphyritic in central part contacts, no be up to 1 m) Geringer and Botha metam. effects (1977) Cyndas monzogranites variable, qtz, K-fsp, plag, bt ± hbl variable, mostly Korannaland mafic (cognate variable 1155Subsuite medium-coarse, ± msc, pyx (locally) unfoliated Group xenoliths) and 1061 Maa medium-fine metased xenoliths Vaalputs monzogranite, medium rounded phenocrysts of well-developed Korannaland sharp, generally numerous 1146 ± 14 b unevolved equigranular K-feldspar (up to 15 mm), Group concordant, qtz, feldspars, biotite, cross-cutting plag phenocrysts locally Louisvale heterogeneous, medium mafic – variable amts of strong / gneissic Bethesda Fm, concordant, during peak mesocratic to fsp phenocrysts, disharmonic Areachap Grp lit-par-lit, very metamorphism; leucocratic, opalescent blue qtz, flow pattern foliated; deep crustal tonalite to cordierite; leucocratic – gradational with monzogranite elongate mcl phenocrysts Klipkraal and Vaalputs Granites Gouskop medium qtz, K-fsp, plag, no bt moderate semi-pelites poor, subvertical lineation
Bethesda Fm, Areachap Grp, Louisvale Grn
sharp with Areachap Grp, Friersdale Charnockite
very few mafic lenticles
approx. same age as Kanoneiland Granite
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Table 1 (cont.) Features of the eastern Namaqua Sector granites (sensu Moen, 2007) (after Stowe, 1983; Geringer et al., 1987, 1988; Moen, 2007; Bailie et al., 2011a; Cornell et al., 2012) Granite Composition Grain Mineralogy Presence Host rocks Contacts Inclusions Age or relative Size of foliation age (in Ma) + ref. Kanoneiland biotite-rich medium to qtz, K-fsp, plag, bt poor gradational with sharp, crossnumerous late-tectonic monzogranite coarse, nonKeboes, sharp cutting; metam. mafic and porphyritic with Vaalputs aureole present felsic inclusions and Louisvale Gemsbokbult monzogranite medium to qtz, K-fsp, plag, bt, weak Klip Koppies concordant and 1104 ± 11c coarse, staur Granite sheared, foliated equigranular Kleinbegin leucocratic medium to qtz, K-fsp, plag, bt, poor to Dagbreek Fm, clots of mafic 1101 ± 10c Subsuite granodiorite coarse, nonhbl, mgt, hmt unfoliated Jannelsepan Fm, mineral porphyritic Areachap Grp aggregates Klip Koppies monzogranites fine to K-fsp phenocrysts (5poor not exposed, small mafic 1096 ± 10c medium 30 mm), qtz, K-fsp, foliated nearing inclusions intrudes porphyritic plag, bt, msc contacts Gemsbokbult Straussburg bt-rich, medium-coarse, blue opaline qtz, K-fsp moderate to feldspathic sharp, metam. numerous 1089 ± 9d monzogranitic porphyritic (as large phenocrysts), poor quartzite, aureole lensoid granodioritic to locally plag (An20-35), bt, Dagbreek Fm developed mafic granitic minor hbl inclusions Klipkraal variable, commonly non-porph: plag, K-fsp, unfoliated Jannelsepan intrusive into young granodioriticporphyritic, hbl, hyp; porph: qtz, fsps Fm, Areachap Louisvale Granite monzogranite medium-coarse plag phenocrysts, bt, hbl Grp Gif Berg fine to medium, fsp phenocrysts (10 mm), unfoliated sharp, fineyoung porphyritic, qtz, K-fsp, plag, bt, gnt grained, chilled granophyric margin Neilers Drift biotite-rich coarse, nonbt-rich unfoliated intruded by none post-tectonic porphyritic Friersdale Friersdale monzogranite- fine- to opalescent blue qtz, unfoliated Korannaland concordant ellipsoidal 1080 ± 13b Charnockite granodiorite medium-grained, K-fsp, minor plag, Grp, Vaalputs to sharply (3-15 cm) of 1078 ± 12d porphyritic bt – groundmass; and Keboes discordant; mafic + bt, qtz, hyp, aug, Granites contact aureoles quartzitic plag – phenocrysts developed composition Abbreviations: mineralogy: aug – augite, bt – biotite, gnt – garnet, hbl – hornblende, hmt – hematite, hyp – hypersthene, K-fsp – K-feldspar, mgt – magnetite, msc- muscovite, plag – plagioclase, pyx – pyroxene, qtz – quartz; porph – porphyritic; References: a Jankowitz (1987), b Pettersson (2008), c Bailie et al. (2011a), d Cornell et al. (2012), e Moen (2007)
ACCEPTED MANUSCRIPT Table 2 Summary of geochronological data obtained in this study (top) and that from previous studies for the magmatic rocks of the eastern Namaqua Sector (in chronological order)
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Reference this study this study this study this study this study this study this study this study Pettersson et al. (2007) Moen & Armstrong (2008) Moen & Armstrong (2008) Bailie et al. (2011b) Pettersson (2008) Cornell & Pettersson (2007) Bailie (2008) Pettersson et al. (2007) Fransson (2008) Bial et al. (2015a) Bial et al. (2015a) Pettersson (2008) Pettersson (2008) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Pettersson (2008) Gutzmer et al. (2000) Colliston et al. (2015) Pettersson (2008) Jankowitz (1987) Pettersson (2008) Pettersson (2008) Jankowitz (1987) Colliston et al. (2015) Bailie et al. (2011a) Pettersson et al. (2007) Bailie et al. (2012) Bailie et al. (2011a) Bial et al. (2015a) Jankowitz (1987) Bailie et al. (2012) Bailie et al. (2012) Bailie et al. (2011a) Pettersson et al. (2007) Jankowitz (1987) Pettersson et al. (2007) Pettersson et al. (2007) Pettersson et al. (2007) Cornell et al. (2012) Jankowitz (1987) Pettersson (2008) Cornell et al. (2012)
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Age of metamorphism
1142 ± 11 Ma 1165 ± 10 Ma
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Age of emplacement 1217 ± 20 Ma 1175 ± 18 Ma 1151 ± 28 Ma 1159 ± 28 Ma 1125 ± 16 Ma 1105 ± 27 Ma ∼1110 Ma1 1098 ± 26 Ma 1371 ± 9 Ma 1293 ± 9 Ma 1290 ± 8 Ma 1289 ± 9 Ma 1275 ± 7 Ma 1275 ± 7 Ma 1261 ± 18 Ma 1241 ± 12 Ma 1190 ± 27 Ma 1229 ± 16 Ma (lc) 1222 ± 13 Ma (lc) 1220 ± 10 Ma 1203 ± 11 Ma 1201 ± 10 Ma (mg) 1198 ± 46 Ma (mg) 1197 ± 10 Ma (mg) 1197 ± 11 Ma (lc) 1195 ± 16 Ma (mg) 1191 ± 7 Ma (mg) 1189 ± 18 Ma (lc) 1189 ± 6 Ma (mg) 1173 ± 12 Ma 1171 ± 7 Ma 1168 ± 6 Ma (ip) 1156 ± 8 Ma 1155 ± 62 Ma 1151 ± 14 Ma 1146 ± 14 Ma 1120 ± 22 Ma 1107 ± 11 Ma (la) 1104 ± 11 Ma 1104 ± 8 Ma 1101 ± 2 Ma 1101 ± 10 Ma 1101 ± 6 Ma 1100 ± 14 Ma 1100 ± 8 Ma 1098 ± 10 Ma 1096 ± 10 Ma 1095 ± 10 Ma 1094± 11 Ma 1093 ± 11 Ma 1093 ± 10 Ma 1092 ± 9 Ma 1089 ± 9 Ma 1087 ± 17 Ma 1080 ± 13 Ma 1078 ± 12 Ma
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Terrane Areachap Kakamas Areachap Areachap Areachap Areachap Areachap Areachap Kaaien Kaaien Kaaien Kaaien Areachap Areachap Areachap Areachap Areachap Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kaaien Kaaien Kakamas Areachap Areachap Kakamas Kakamas Areachap Kakamas Areachap Kaaien Kaaien Areachap Kakamas Areachap Kaaien Kaaien Areachap Kaaien Areachap Kaaien Kaaien Kaaien Areachap Areachap Kakamas Areachap
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Granite Josling Granite Elsie se Gorra Granite Colston Granite Smalvisch Granite, CS Louisvale Granite Keboes Granite Klipkraal Granite Kanoneiland Granite Swanartz Gneiss Kalkwerf Gneiss Wilgenhoutsdrif Group Wilgenhoutsdrif Group Josling Granite Areachap Group Areachap Group Areachap Group Areachap Group ZA-93-1 ZA-81-2 Dyasons Klip Gneiss Polisiehoek Granite ZA-68-1 ZA-70-1 ZA-82-2 ZA-80-1 ZA-49-2 ZA-62-1 ZA-103-1 ZA-61-2 Lower Koras Group Lower Koras Group Augrabies Granite Riemvasmaak Gneiss Cyndas E Granodiorite, CS Riemvasmaak Gneiss Vaalputs Granite Smalvisch Granite, CS Karama’am augen gneiss Gemsbokbult Granite Upper Koras Group Upper Koras Group Kleinbegin Granite Naros Granite (957/967) Gous Charnockite, CS Upper Koras Group Upper Koras Group Klip Koppies Granite Upper Koras Group Cyndas E Granodiorite, CS Rooiputs Granophyre Bloubos Granite Upper Koras Grp Straussburg Granite Enna Granite, CS Friersdale Charnockite Friersdale Charnockite
1156 ± 14 Ma
1108 ± 9 Ma 1108 ± 12 Ma (metam.?) 1098 ± 10 Ma 1091 ± 8 Ma 1125 ± 5 Ma 1088 ± 10 Ma
1090 ± 16 Ma
1062 ± 27 Ma 1014 ± 36 Ma
Abbreviations: CS – Cyndas Subsuite; la – LAICPMS, ip – ion probe; lc – leucogranite, mg – mesocratic granite; 1 assumed age based on field relationships and lack of foliation, inherited age of 1270 ± 26 Ma determined
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Table 3 Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Metamorphic Province granites
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Sample Mkl2 Mkl4 Mkl5 Mkl6 Mkl3 Ml1 Ml2 Ml4 Ml5 Mka1 Mka3 Mka6 Mka7 Mkb1 Mkb2 Mkb4 Mkb6 Mv2 SiO2 66.09 66.74 65.49 65.67 65.52 65.00 66.34 65.48 71.15 69.96 69.31 68.23 69.10 70.24 70.00 73.62 69.70 73.62 TiO2 0.90 0.94 1.11 1.14 0.95 0.58 0.89 0.58 0.29 0.75 0.70 0.73 0.76 0.48 0.50 0.18 0.49 0.32 Al2O3 13.11 12.97 13.85 13.71 13.11 17.18 13.19 16.77 15.23 12.68 13.12 13.73 13.06 13.64 14.07 14.30 14.27 13.26 8.87 8.73 7.24 7.47 8.92 4.82 8.24 4.95 2.23 5.40 5.10 5.45 5.37 3.77 3.71 1.64 3.70 2.69 Fe2O3 MnO 0.20 0.18 0.15 0.15 0.18 0.08 0.17 0.08 0.05 0.12 0.11 0.11 0.11 0.08 0.08 0.03 0.08 0.05 MgO 0.47 0.48 0.97 1.00 0.49 0.99 0.46 1.00 0.61 0.66 0.61 0.72 0.65 0.68 0.69 0.25 0.69 0.28 CaO 2.54 2.48 3.19 3.20 2.55 3.63 2.61 3.51 2.02 2.21 2.32 2.50 2.35 2.10 2.23 0.79 2.27 1.00 Na2O 1.51 2.19 2.26 2.20 2.42 4.90 2.38 4.81 4.88 2.46 2.70 2.80 2.66 2.93 2.98 2.97 3.06 2.69 K2O 5.09 4.33 4.74 4.44 4.52 1.93 4.61 1.95 2.63 4.72 4.75 4.68 4.73 4.82 4.82 5.14 4.81 5.48 P2O5 0.48 0.47 0.45 0.47 0.48 0.35 0.45 0.34 0.10 0.25 0.24 0.26 0.26 0.18 0.18 0.22 0.18 0.18 Cr2O3 0.001 0.001 0.001 0.001 0.003 0.001 0.001 0.003 0.002 0.001 0.005 0.002 0.002 0.005 0.005 0.003 0.002 0.005 L.O.I. 0.13 0.12 0.15 0.13 0.08 0.13 0.16 0.10 0.12 0.14 0.10 0.13 0.08 0.13 0.09 0.09 0.09 0.10 Total 99.39 99.63 99.59 99.58 99.23 99.58 99.50 99.58 99.31 99.34 99.05 99.34 99.14 99.06 99.35 99.24 99.33 99.32 Sc 23.3 25.3 20.9 21.5 26.7 11.5 22.9 11.8 7.5 17.5 16.3 20.1 14.3 12.3 12.1 6.9 11.8 10.0 Ti 5421 5620 6637 6845 5701 3457 5364 3474 1755 4509 4175 4368 4545 2880 2981 1093 2938 1941 V 30.0 26.2 72.9 80.0 35.1 78.2 30.5 51.4 47.6 61.1 52.6 60.3 58.2 50.4 47.4 21.8 79.1 38.9 101.8 72.3 50.7 84.1 149.6 124.4 92.4 134.8 184.4 154.6 66.5 81.9 116.0 131.2 79.4 74.4 102.1 208.9 Cra Co 7.8 7.9 11.7 11.4 9.1 7.7 7.8 5.7 4.4 7.5 7.0 8.0 7.1 5.9 6.0 3.0 8.2 4.0 Ni 7.1 7.4 11.1 11.5 11.7 10.7 8.8 12.2 12.0 9.8 12.4 9.7 10.1 11.5 11.7 8.6 10.3 11.3 Cu 20.2 18.5 25.1 26.7 27.6 47.3 14.9 14.5 33.9 11.7 21.5 14.6 12.2 14.0 20.6 17.8 43.2 29.2 Zn 122.6 124.8 113.9 107.1 146.1 112.0 115.2 71.2 57.8 97.3 93.2 98.7 90.7 71.7 77.8 113.1 129.5 52.9 Rb 174.2 204.1 199.6 186.2 220.2 172.8 189.8 233.6 89.0 245.9 234.5 233.2 227.8 255.7 242.9 335.9 185.6 404.5 Sr 151.1 146.7 165.3 171.2 165.1 292.6 151.9 124.7 501.6 159.6 148.3 142.9 155.3 131.0 130.7 43.1 294.3 63.1 Y 92.5 92.6 69.2 69.0 99.7 19.0 84.5 36.6 5.1 56.2 73.1 69.6 46.7 41.0 40.9 6.2 21.1 60.0 Zr 482.8 419.4 515.3 524.4 534.8 298.9 444.3 225.0 135.5 349.8 298.3 331.9 337.4 229.1 234.6 51.6 307.5 192.6 Nb 24.4 23.6 27.3 28.5 29.6 15.5 24.2 16.0 3.1 22.4 22.7 21.2 21.2 17.3 16.4 12.2 16.4 23.0 Cs 2.5 4.6 2.5 2.1 7.2 11.4 3.8 10.0 1.6 14.3 12.6 11.6 11.3 11.0 10.7 6.1 12.3 13.4 Ba 1443 1467 1198 1186 1588 253 1351 681 1364 874 882 824 870 715 714 174 255 451 Hf 13.7 12.2 14.4 14.2 14.6 7.0 12.3 6.3 3.3 10.0 8.4 9.5 9.5 6.6 6.8 2.0 7.3 6.4 Ta 2.5 2.9 1.5 3.1 3.8 1.6 1.6 3.2 1.0 2.1 2.6 1.9 1.6 3.0 1.5 1.3 1.7 2.8 Pb 41.3 40.9 41.7 39.3 38.6 17.6 36.1 30.3 33.7 32.6 32.0 34.8 31.0 32.5 30.9 37.0 18.0 35.2 Th 36.0 41.8 54.6 51.1 38.3 16.1 38.4 31.9 7.5 22.4 21.5 34.7 22.6 34.4 34.5 6.4 14.5 44.2 U 3.6 3.5 4.5 4.4 4.1 3.9 3.6 3.8 1.7 3.8 2.5 4.0 4.5 7.2 7.6 3.6 3.5 9.8 Note: Mkl – Klipkraal Granite, Ml – Louisvale Granite, Mka – Kanoneiland Granite, Mkb – Keboes Granite, Mv – Vaalputs Granite. All REE normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
ACCEPTED MANUSCRIPT
Table 3 (cont.) Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Sector granites
AC C
EP
TE D
M AN U
SC
RI PT
Sample Mv3 Mv5 Mv9 Ms1 Ms2 Ms6 Ms7 Mf1 Mf4 Mf6 Mf7 Mc2 Mc6 Mc8 Mc9 Mcol1 Mcol2 Mcol3 SiO2 72.81 69.75 72.71 67.66 68.18 68.29 67.87 66.46 65.40 65.36 65.91 64.18 70.42 71.25 65.78 66.80 65.19 65.51 TiO2 0.29 0.83 0.30 0.96 0.95 0.91 0.99 1.24 1.27 1.30 1.28 1.34 0.66 0.50 1.19 0.86 1.07 1.15 Al2O3 13.35 11.89 13.32 13.37 13.00 13.14 12.92 12.85 13.00 13.15 12.77 13.75 13.42 13.25 13.53 14.04 13.90 13.51 2.74 5.52 2.73 5.52 5.40 5.43 5.45 7.09 7.28 7.37 7.41 7.45 3.99 3.16 6.97 6.06 7.13 7.36 Fe2O3 MnO 0.05 0.12 0.05 0.12 0.11 0.11 0.12 0.15 0.16 0.16 0.16 0.15 0.10 0.06 0.14 0.11 0.13 0.141 MgO 0.26 0.91 0.28 0.95 0.92 0.97 0.93 1.36 1.45 1.35 1.40 1.54 0.62 0.55 1.33 0.96 1.25 1.29 CaO 1.38 2.43 1.43 3.03 2.96 3.01 2.89 3.86 4.16 4.06 3.96 3.71 1.98 1.52 3.43 2.32 2.84 2.91 Na2O 3.03 2.48 3.03 2.77 2.59 2.73 2.61 2.50 2.59 2.62 2.53 2.64 2.93 3.13 2.64 2.27 2.10 2.22 K2O 5.30 4.21 5.34 4.53 4.81 4.39 4.84 3.90 3.81 3.75 3.91 3.87 5.08 5.38 4.11 5.01 4.52 4.39 P2O5 0.11 0.32 0.11 0.30 0.28 0.29 0.27 0.48 0.50 0.51 0.48 0.41 0.21 0.15 0.35 0.31 0.30 0.34 Cr2O3 n.d. 0.004 0.001 0.005 0.004 0.005 0.004 0.002 0.001 0.002 0.003 0.004 0001 0.005 0.02 0.002 0.002 0.001 L.O.I. 0.05 0.12 0.11 0.12 0.13 0.22 0.08 0.11 0.07 0.07 0.06 0.10 0.09 0.10 0.08 0.11 0.11 0.10 Total 99.38 98.59 99.43 99.33 99.34 99.50 98.96 99.99 99.68 99.69 99.87 99.15 99.49 99.05 99.58 98.84 98.56 98.92 Sc 10.7 16.3 10.6 16.6 16.1 19.0 11.9 22.8 21.9 21.3 20.9 10.5 10.7 23.1 15.2 19.0 19.2 15.3 Ti 1766 4991 1787 5736 5689 5453 5928 7422 7588 7774 7683 8012 3959 3013 7123 5130 6416 6892 V 25.6 72.8 22.6 87.5 90.5 91.6 66.8 115.3 115.0 125.9 117.0 50.4 40.2 116.2 68.7 90.8 96.4 89.4 76.3 164.3 60.2 142.6 162.7 68.9 182.2 52.6 79.9 162.4 74.1 107.4 56.5 69.9 104.5 63.8 109.5 142.0 Cra Co 3.3 7.6 3.1 9.4 9.2 10.9 6.8 13.6 12.8 13.3 15.6 5.9 5.2 16.6 10.6 13.3 13.2 9.0 Ni 9.4 14.5 7.5 12.9 14.8 18.1 13.9 16.1 15.1 18.8 18.6 11.0 8.8 20.7 17.4 17.4 15.3 14.4 Cu 29.5 11.9 25.4 14.5 26.3 31.4 13.4 67.7 16.0 100.3 28.9 23.8 17.2 35.8 36.6 29.5 19.2 25.4 Zn 36.5 85.8 39.1 75.6 77.9 90.2 76.7 110.5 99.7 104.8 108.8 112.3 60.8 130.4 83.5 97.4 86.7 70.5 Rb 510.9 196.3 489.6 195.9 224.5 199.2 278.6 156.6 161.4 159.4 167.8 226.7 265.1 193.1 246.5 218.1 217.6 196.3 Sr 67.0 182.2 65.3 188.0 171.5 197.3 126.6 279.4 277.3 264.3 240.0 159.3 162.6 220.1 110.0 118.9 149.1 180.3 Y 116.3 53.4 129.5 48.2 50.3 53.2 50.9 63.1 59.7 59.1 59.9 43.3 49.7 62.8 46.4 56.2 54.2 46.7 Zr 219.5 309.5 266.3 413.2 432.1 410.6 334.3 395.0 422.0 387.0 504.4 351.5 333.0 570.6 351.0 415.6 396.6 420.9 Nb 38.2 21.4 49.5 20.6 22.3 22.9 19.0 22.2 24.9 24.4 27.6 17.1 19.2 26.8 19.8 21.3 22.2 21.3 Cs 26.7 6.1 26.0 6.3 5.6 5.3 13.2 5.3 5.3 5.9 6.8 9.3 3.6 9.6 6.1 7.2 8.3 5.0 Ba 333 883 332 1104 1076 1193 884 1134 1130 1070 1105 753 756 1136 739 856 833 1069 Hf 7.6 8.5 8.8 11.2 12.0 11.0 9.8 10.3 11.1 10.3 13.5 10.0 9.7 15.0 10.3 11.8 10.9 11.1 Ta 4.2 1.7 4.8 1.5 2.7 1.6 2.0 1.5 1.8 2.4 2.6 1.6 1.4 1.8 2.8 1.3 1.5 2.6 Pb 34.0 26.8 33.4 30.8 32.4 37.1 40.6 29.3 27.3 28.8 28.0 22.7 31.7 32.2 34.7 31.8 29.6 32.2 Th 88.4 20.8 89.5 25.0 34.1 57.8 53.8 17.1 17.1 20.1 17.5 24.4 49.2 26.1 32.4 32.1 28.7 19.2 U 23.7 3.9 31.1 4.0 4.4 4.9 6.6 3.7 3.2 4.3 5.9 4.1 6.4 5.5 4.9 4.6 3.9 5.8 Note: Mv – Vaalputs Granite, Ms – Straussburg Granite, Mf – Friersdale Charnockite, Mc – Cyndas Subsuite, Mcol – Colston Granite. All REE are normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
ACCEPTED MANUSCRIPT
Table 3 (cont.) Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Metamorphic Province granites
AC C
EP
TE D
M AN U
SC
RI PT
Sample Mcol4 Mcol6 Mge1 Mge2 Mge3 Mge5 Mkle1 Mkle2 Mkle3 Me1 Me2 Mks1 Mks2 Mks3 Mks4 Mkn2 Mkn4 Mkn7 SiO2 66.88 65.90 69.64 68.92 68.96 65.70 70.87 70.22 70.52 76.02 75.12 69.14 69.19 68.92 69.00 72.49 71.38 71.31 TiO2 0.97 1.02 0.71 0.82 0.76 1.02 0.47 0.55 0.53 0.28 0.29 0.75 0.74 0.80 0.79 0.30 0.34 0.34 Al2O3 13.79 13.76 13.41 13.05 12.95 12.81 13.66 13.64 13.68 12.07 12.36 12.95 12.97 13.11 13.02 13.84 13.96 14.14 6.19 6.45 4.52 6.07 5.99 8.54 3.49 3.97 3.80 1.77 1.92 5.91 5.73 5.89 5.65 3.09 3.17 3.34 Fe2O3 MnO 0.13 0.14 0.09 0.13 0.12 0.19 0.08 0.08 0.08 0.03 0.03 0.12 0.12 0.12 0.12 0.07 0.08 0.08 MgO 1.61 1.70 0.65 0.60 0.64 0.60 0.80 0.95 0.93 0.22 0.21 0.58 0.56 0.60 0.56 0.34 0.51 0.41 CaO 2.49 2.58 1.84 2.14 2.20 3.16 3.08 3.41 3.26 0.97 0.98 2.11 2.11 2.24 2.20 2.36 2.35 2.62 Na2O 2.26 2.23 2.48 2.26 2.27 2.11 3.47 3.38 3.50 2.72 2.66 2.25 2.32 2.36 2.46 3.54 3.36 3.66 K2O 3.95 4.18 5.51 5.07 5.02 4.97 3.30 2.93 2.87 5.25 5.65 5.21 5.16 4.95 4.97 3.09 3.80 3.12 P2O5 0.27 0.27 0.29 0.32 0.31 0.42 0.11 0.13 0.12 0.05 0.06 0.30 0.30 0.32 0.30 0.09 0.09 0.11 Cr2O3 0.004 0.006 n.d. 0.003 0.001 0.003 0.009 0.009 0.012 0.010 0.006 0.001 0.003 0.005 0.001 0.002 0.009 0.005 L.O.I. 0.16 0.12 0.16 0.09 0.09 0.10 0.08 0.09 0.10 0.09 0.09 0.08 0.05 0.11 0.09 0.08 0.10 0.07 Total 98.71 98.38 99.29 99.48 99.31 99.62 99.40 99.37 99.40 99.47 99.39 99.41 99.25 99.42 99.16 99.29 99.15 99.20 Sc 18.4 19.3 12.2 19.2 19.7 24.5 10.0 12.6 10.8 7.8 7.4 17.8 18.1 18.1 18.1 8.5 8.6 8.9 Ti 5822 6144 4252 4910 4576 6116 2839 3308 3191 1661 1747 4520 4429 4814 4762 1773 2017 2019 V 110.4 110.0 71.8 47.4 53.0 37.6 61.1 77.4 73.6 29.9 38.4 46.1 42.4 49.6 45.8 33.9 39.0 45.9 169.1 67.4 242.6 91.2 161.0 133.2 98.9 167.2 184.0 83.8 225.7 113.3 72.5 147.4 93.2 104.8 96.9 171.3 Cra Co 13.8 14.7 6.9 6.7 7.1 8.2 8.1 9.6 9.0 3.8 3.3 6.5 6.7 6.8 6.5 4.0 4.5 4.6 Ni 21.8 18.9 14.4 10.5 12.0 11.4 15.8 22.9 21.2 11.5 13.3 11.4 22.9 12.2 9.0 11.9 11.3 10.7 Cu 45.5 62.0 21.4 14.3 17.2 32.6 37.6 76.5 43.2 24.5 32.8 17.7 38.8 17.9 13.5 27.1 12.4 13.4 Zn 82.6 85.9 74.8 102.4 103.5 139.0 45.8 53.3 47.5 52.3 31.0 97.6 101.5 96.1 100.8 60.8 65.5 69.4 Rb 188.8 194.0 292.2 209.7 193.1 189.1 107.0 99.1 106.5 276.0 296.1 197.2 206.1 200.3 197.5 98.1 103.0 95.5 Sr 118.4 110.1 133.2 165.5 151.1 167.4 153.5 156.7 156.2 60.0 50.5 142.1 142.9 148.2 145.0 221.4 240.0 249.5 Y 57.8 60.6 54.1 52.7 50.3 77.3 59.6 56.7 44.0 10.4 8.6 49.7 52.3 51.3 50.4 25.2 21.7 22.3 Zr 364.6 387.8 341.5 369.5 351.4 510.2 275.3 307.3 307.7 224.2 171.2 323.9 325.6 340.1 344.0 263.9 205.9 227.3 Nb 18.3 18.6 20.1 20.9 21.6 28.8 11.4 13.3 10.9 9.4 9.7 20.4 19.9 21.3 21.2 12.5 11.5 12.2 Cs 6.8 6.9 13.9 3.5 3.4 2.4 1.8 2.0 2.6 1.7 1.6 5.7 6.5 6.0 6.0 3.0 2.6 2.5 Ba 770 805 931 1115 1102 1369 1135 982 959 523 520 1043 1084 1050 1061 1257 1534 1205 Hf 10.4 11.1 10.1 10.3 9.9 14.1 7.9 8.0 8.4 6.8 5.1 9.2 9.3 9.5 9.6 6.6 5.5 5.9 Ta 1.9 1.3 2.0 1.4 2.9 3.5 0.8 3.0 3.0 0.4 1.6 1.9 1.3 2.2 1.3 1.7 0.7 2.0 Pb 38.6 41.0 39.3 36.9 35.3 39.4 18.9 17.7 16.2 43.2 22.6 34.2 37.5 35.0 34.4 18.0 18.4 17.0 Th 56.4 83.3 55.5 29.0 28.9 37.5 16.9 13.1 5.9 68.7 3.8 27.3 29.1 28.9 28.1 15.7 11.5 12.2 U 6.0 7.6 6.6 3.0 2.3 3.6 2.0 1.6 1.5 3.6 0.8 3.2 3.2 3.2 2.7 2.1 1.9 1.6 Note: Mcol – Colston Granite, Mge – Gemsbokbult Granite, Mkle – Kleinbegin Granite, Me – Elsie se Gorra Granite, Mks – Klip Koppies Granite, Mkn – Josling Granite. All REE are normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
ACCEPTED MANUSCRIPT
Table 4 Whole rock rare earth element (REE) geochemistry of the eastern Namaqua Metamorphic Province granites Ml2 103.52 222.03 26.35 103.69 19.48 2.87 17.13 2.59 15.70 3.15 9.10 1.25 8.80 1.21 0.48 3.33 7.98 1.76 8.93 Ms7 85.65 189.44 20.80 76.07 13.74 1.60 10.54 1.55 8.91 1.75 5.24 0.77 5.56 0.79 0.41 3.91 10.45 1.66 11.35
Ml4 53.35 117.58 13.78 52.96 10.30 1.23 7.93 1.12 7.03 1.31 3.83 0.55 3.89 0.52 0.42 3.25 9.31 1.89 10.71 Mf1 85.38 180.22 21.25 82.44 15.58 3.11 13.73 2.02 12.16 2.40 6.59 0.95 6.60 0.96 0.65 3.44 8.77 1.77 9.25
Ml5 19.56 35.34 3.66 12.65 1.92 0.64 1.49 0.18 0.92 0.16 0.58 0.08 0.50 0.10 1.16 6.40 26.28 1.91 21.09 Mf4 82.24 174.74 20.65 81.01 15.48 3.05 12.62 1.86 11.09 2.36 6.67 0.88 6.02 0.88 0.67 3.33 9.27 1.77 9.70
Mka1 65.37 139.13 16.45 62.91 12.69 2.04 10.83 1.69 10.54 2.06 6.09 0.83 6.09 0.85 0.53 3.23 7.28 1.58 8.00 Mf6 81.60 174.21 20.38 79.82 14.47 2.86 12.22 1.86 11.15 2.25 6.51 0.94 6.21 0.87 0.66 3.54 8.92 1.74 9.74
Mka3 62.96 131.12 15.54 57.83 12.40 2.12 10.88 1.92 12.89 2.67 7.99 1.27 8.62 1.15 0.56 3.19 4.95 1.17 5.71 Mf7 75.10 160.26 19.41 74.52 14.81 2.81 12.45 1.82 11.23 2.31 6.19 0.95 6.24 0.86 0.63 3.18 8.16 1.79 9.07
Mka6 98.31 215.51 25.19 95.24 18.05 2.05 14.47 2.23 13.61 2.63 7.59 1.09 7.29 1.02 0.39 3.42 9.15 1.75 10.00 Mc2 49.27 106.61 12.93 51.03 10.56 1.58 9.12 1.39 8.15 1.58 4.35 0.60 4.39 0.61 0.49 2.93 7.61 1.85 8.42
Mka7 67.66 142.45 16.53 63.29 12.04 2.02 9.46 1.44 8.76 1.72 4.89 0.73 4.91 0.65 0.58 3.52 9.34 1.81 10.87 Mc6 90.58 199.36 23.06 85.25 15.66 1.47 11.75 1.69 9.51 1.89 5.16 0.74 5.05 0.77 0.33 3.63 12.16 1.89 12.25
RI PT
Ml1 35.74 62.61 6.34 23.07 4.48 0.84 3.66 0.51 3.16 0.65 1.86 0.26 1.94 0.27 0.64 5.00 12.52 1.65 13.55 Ms6 120.02 249.90 27.59 96.30 15.76 2.35 11.92 1.72 10.23 1.95 5.43 0.92 5.57 0.86 0.52 4.78 14.61 1.72 14.54
SC
Mkl3 113.05 241.53 29.09 115.35 21.73 3.49 19.64 3.06 18.93 3.72 10.81 1.66 10.57 1.55 0.52 3.26 7.25 1.57 7.60 Ms2 67.71 144.36 17.08 64.72 12.09 2.05 9.56 1.54 9.58 1.92 5.56 0.77 5.46 0.80 0.58 3.51 8.41 1.49 8.87
M AN U
Mkl6 115.41 260.89 31.96 128.49 22.72 2.71 16.34 2.26 13.25 2.67 7.39 0.95 6.82 0.98 0.43 3.19 11.48 2.07 12.27 Ms1 73.18 148.55 16.90 61.83 11.34 2.04 9.14 1.42 8.87 1.80 5.12 0.79 5.10 0.75 0.61 4.05 9.73 1.52 10.21
TE D
Mkl5 119.13 270.33 33.12 129.45 23.56 2.79 16.88 2.24 13.41 2.66 7.24 1.06 6.83 0.85 0.43 3.17 11.82 2.46 14.61 Mv9 112.63 238.91 25.60 89.71 17.65 1.11 16.03 2.99 20.33 4.34 14.11 2.14 14.72 2.14 0.20 4.00 5.19 0.93 5.48
EP
Mkl4 120.82 255.03 30.50 118.87 23.20 3.37 19.40 2.91 17.69 3.61 9.94 1.46 9.32 1.32 0.49 3.27 8.79 1.82 9.54 Mv5 66.64 142.83 16.81 64.49 12.55 2.11 11.01 1.67 10.24 2.08 5.73 0.78 5.69 0.79 0.55 3.33 7.95 1.73 8.79
AC C
Sample Mkl2 La 103.83 Ce 223.32 Pr 26.61 Nd 104.60 Sm 20.62 Eu 3.07 Gd 17.96 Tb 2.74 Dy 16.71 Ho 3.49 Er 10.26 Tm 1.40 Yb 9.85 Lu 1.40 Eu/Eu* 0.49 (La/Sm)N 3.16 (La/Yb)N 7.15 (Gd/Lu)N 1.59 (La/Lu)N 7.70 Sample Mv3 La 118.57 Ce 250.73 Pr 27.17 Nd 93.04 Sm 18.88 Eu 1.08 Gd 16.65 Tb 3.05 Dy 18.48 Ho 4.08 Er 11.86 Tm 1.94 Yb 13.03 Lu 1.96 Eu/Eu* 0.19 (La/Yb)N 3.94 (La/Sm)N6.17 (Gd/Lu)N1.05 (La/Lu)N 6.30
Mkb1 57.27 124.67 14.96 56.94 10.99 1.40 8.43 1.30 7.63 1.56 4.22 0.62 4.25 0.63 0.44 3.27 9.14 1.67 9.53 Mc8 89.12 186.30 21.56 82.17 15.08 2.59 12.87 1.85 11.71 2.30 6.77 0.96 6.53 0.98 0.57 3.71 9.25 1.63 9.49
Mkb2 56.39 122.74 14.40 56.07 10.90 1.28 8.36 1.25 7.46 1.48 4.52 0.60 4.31 0.59 0.41 3.25 8.87 1.77 10.03 Mc9 69.85 157.29 18.94 75.11 15.22 1.68 11.96 1.68 9.58 1.74 4.68 0.67 4.41 0.62 0.38 2.88 10.75 2.40 11.80
Mkb4 14.42 31.79 3.66 14.74 3.78 0.51 3.00 0.35 1.52 0.18 0.50 0.08 0.47 0.08 0.46 2.39 20.67 4.61 18.65 Mcol1 79.73 178.27 21.39 85.87 17.20 1.88 13.84 1.96 11.34 2.06 5.84 0.84 5.28 0.79 0.37 2.91 10.25 2.17 10.51
Mkb6 32.64 57.10 5.93 21.09 4.33 0.88 3.41 0.57 3.35 0.71 2.25 0.34 2.11 0.25 0.70 4.73 10.51 1.68 13.51 Mcol2 77.56 170.32 20.31 80.20 15.95 2.09 12.67 1.78 10.75 2.07 5.58 0.74 5.38 0.75 0.45 3.05 9.77 2.10 10.82
Mv2 65.69 148.41 17.34 66.56 13.65 0.94 10.85 1.68 10.58 2.19 6.30 0.97 6.35 0.98 0.24 3.02 7.02 1.37 6.95 Mcol3 37.60 91.58 12.07 50.80 10.22 2.00 8.81 1.34 8.39 1.68 5.21 0.70 4.92 0.73 0.65 2.31 5.18 1.49 5.35
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Table 4 (cont.) Whole rock rare earth element (REE) geochemistry of the eastern Namaqua Metamorphic Province granites
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Sample Mcol4 Mcol6 Mge1 Mge2 Mge3 Mge5 Mkle1 Mkle2 Mkle3 Me1 Me2 Mks1 Mks2 Mks3 Mks4 Mkn2 Mkn4 Mkn7 La 92.78 113.28 90.99 78.42 77.15 99.25 40.73 43.85 24.68 65.99 27.59 73.65 73.85 76.40 73.30 55.38 41.62 43.64 Ce 205.12 258.90 198.85 168.21 165.08 221.45 96.18 98.12 56.56 147.24 53.75 157.39 154.36 162.46 156.94 103.80 76.42 82.31 Pr 24.49 30.53 21.91 19.78 19.41 26.62 11.97 12.10 7.39 16.03 5.38 18.72 18.55 19.20 18.37 11.23 8.39 8.75 Nd 93.73 113.78 80.82 77.13 75.62 107.31 46.45 46.17 31.63 57.14 19.16 71.41 73.00 75.16 71.77 40.20 29.83 32.26 Sm 17.46 19.78 14.42 14.98 14.71 20.26 9.78 9.05 6.99 8.96 3.33 14.17 14.49 14.95 14.12 7.59 5.37 5.66 Eu 1.74 1.97 1.79 2.40 2.23 3.08 1.33 1.48 1.24 1.17 1.07 2.11 2.20 2.25 2.22 1.49 1.27 1.40 Gd 12.91 15.17 10.82 12.44 11.49 16.51 9.28 8.70 6.68 6.11 2.99 11.54 11.89 11.89 11.97 6.40 4.60 4.72 Tb 1.89 2.08 1.62 1.77 1.64 2.44 1.60 1.47 1.16 0.65 0.36 1.71 1.65 1.68 1.65 0.90 0.70 0.72 Dy 11.10 11.84 9.54 10.05 9.68 14.73 10.35 9.20 7.31 2.78 1.94 9.32 9.96 9.57 9.79 5.11 4.00 4.24 Ho 2.18 2.29 1.98 1.93 1.94 2.96 2.22 1.94 1.57 0.46 0.36 1.87 1.97 1.87 1.90 0.91 0.80 0.84 Er 6.12 6.20 5.56 5.61 5.27 8.53 6.18 5.77 4.59 1.08 0.76 5.17 5.49 5.43 5.54 2.61 2.22 2.20 Tm 0.86 0.90 0.80 0.77 0.77 1.18 0.85 0.90 0.66 0.12 0.12 0.73 0.75 0.73 0.78 0.37 0.33 0.32 Yb 5.69 5.93 5.72 5.42 5.18 8.05 5.59 5.86 4.61 0.78 0.71 4.99 5.13 4.87 5.12 2.40 1.99 2.07 Lu 0.80 0.83 0.88 0.77 0.74 1.16 0.76 0.88 0.71 0.13 0.11 0.70 0.72 0.70 0.75 0.35 0.29 0.29 Eu/Eu* 0.35 0.35 0.44 0.54 0.52 0.52 0.43 0.51 0.55 0.49 1.04 0.50 0.51 0.52 0.52 0.65 0.78 0.83 (La/Yb)N 3.33 3.59 3.96 3.28 3.29 3.07 2.61 3.04 2.22 4.62 5.20 3.26 3.20 3.20 3.26 4.58 4.86 4.84 (La/Sm)N11.06 12.95 10.78 9.82 10.11 8.36 4.94 5.08 3.63 57.14 26.36 10.01 9.76 10.65 9.72 15.64 14.21 14.33 (Gd/Lu)N1.99 2.26 1.52 1.99 1.94 1.76 1.51 1.23 1.17 5.71 3.23 2.06 2.06 2.10 1.97 2.23 2.00 2.00 14.19 10.74 10.55 10.92 8.88 5.56 5.22 3.62 51.84 25.08 11.03 10.73 11.35 10.13 16.26 15.20 15.56 (La/Lu)N 12.02 Note: Mv – Vaalputs Granite, Ms – Straussburg Granite, Mf – Friersdale Charnockite, Mc – Cyndas Subsuite, Mcol – Colston Granite, Mkl – Klipkraal Granite, Ml – Louisvale Granite, Mka – Kanoneiland Granite, Mkb – Keboes Granite, Mv – Vaalputs Granite Mcol – Colston Granite, Mge – Gemsbokbult Granite, Mkle – Kleinbegin Granite, Me – Elsie se Gorra Granite, Mks – Klip Koppies Granite, Mkn – Josling Granite. All REE are normalized relative to Boynton (1984). The REE are measured in parts per million (ppm).
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Table 5 Isotopic data for the granites of the eastern Namaqua Sector for this study, and those from literature data, arranged from oldest to youngest according to emplacement age
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143 87 Granite Sm Nd Sm/ Nd/ 2σ σ 147Sm/ (143Nd/ Age εNd(t) εNd(o) TCHUR TDM Rb Sr Rb/ (87Sr/ Rb/ SrI Ref.a 144 144 144 86 86 (ppm) (ppm) Nd Nd Nd Nd)o (Ma) (Ma) (Ma) Sr Sr)o Sr Josling 5.4 29.8 0.18 0.51203 9 0.1089 0.51116 1217 1.79 -11.90 1059 1630 103.0 240.0 0.43 0.72662 1.1406 0.70674 1 Josling 4.2 27.3 0.15 0.51200 6 0.0928 0.51126 1217 3.77 -12.41 934 1447 114.4 207.6 0.55 0.73373 1.4638 0.70821 1 Elsie se 9.0 57.1 0.16 0.51192 10 0.0949 0.51119 1175 1.40 -13.93 1068 1571 276.0 60.0 4.60 0.95515 12.227 0.74944 1 Cyndas 15.1 82.2 0.18 0.51205 10 0.1110 0.51120 1159 1.17 -11.55 1053 1637 193.1 220.1 0.88 0.79434 2.3304 0.75567 1 Cyndas 11.8 65.0 0.18 0.51205 7 0.1094 0.51122 1159 1.56 -11.38 1019 1600 221.8 174.1 1.27 0.77653 3.3840 0.72038 1 Colston 10.2 50.8 0.20 0.51200 8 0.1217 0.51107 1151 -1.47 -12.52 1303 1908 196.3 180.0 1.09 0.78169 2.8965 0.73396 1 Colston 10.3 47.8 0.22 0.51215 7 0.1307 0.51116 1151 0.24 -9.48 1121 1829 221.3 42.1 5.26 0.95662 13.963 0.72653 1 Vaalputs 11.0 55.7 0.20 0.51215 7 0.1196 0.51125 1146 1.78 -9.53 966 1619 187.2 180.5 1.04 0.76491 2.7556 0.71970 1 Louis 1.9 12.7 0.15 0.51196 12 0.0918 0.51128 1125 1.89 -13.23 985 1487 89.0 501.6 0.18 0.71389 0.4715 0.70630 1 Klipkr 108.6 576.8 0.19 0.51197 10 0.1139 0.51114 1110b -1.25 -13.01 1227 1798 1101 825.7 1.33 0.77235 3.5419 0.71608 1 -2.50 -13.94 1349 1910 175.2 161.2 1.09 0.76482 2.8869 0.71896 1 Klipkr 20.8 108.6 0.19 0.51192 8 0.1160 0.51108 1110b Keboes 4.3 21.1 0.21 0.51198 14 0.1242 0.51107 1105 -2.64 -12.89 1388 1993 185.6 294.3 0.63 0.79779 1.6753 0.77130 1 Kleinbe 7.4 37.4 0.20 0.51170 7 0.1196 0.51083 1101 -7.51 -18.34 1853 2344 221 179 1.23 0.76380 3.2795 0.71212 1 Kanon 18.1 95.2 0.19 0.51208 10 0.1146 0.51125 1098 0.57 -10.96 1044 1651 233.2 142.9 1.63 0.79110 4.3332 0.72300 1 Kanon 1.7 12.1 0.14 0.51197 5 0.0835 0.51136 1098 2.83 -13.08 903 1383 129.6 533.1 0.24 0.71753 0.6458 0.70738 1 Klip Ko 9.7 53.1 0.18 0.51195 7 0.1105 0.51115 1096 -1.44 -13.52 1224 1777 209 149 1.40 0.72387 3.7259 1 Strauss 15.4 98.1 0.16 0.51176 10 0.0949 0.51108 1089 -2.95 -17.12 1313 1780 157.9 228.0 0.69 0.74612 1.8398 0.71744 1 Friers 14.2 79.4 0.18 0.51203 8 0.1082 0.51127 1078 0.41 -11.81 1042 1612 164.8 262.2 0.63 0.73666 1.6695 0.71090 1 Friers 14.4 78.8 0.18 0.51201 9 0.1105 0.51123 1078 -0.35 -12.24 1110 1682 164.9 277.1 0.60 0.73434 1.5807 0.70995 1 Friers 14.3 76.6 0.19 0.51201 10 0.1129 0.51121 1078 -0.67 -12.23 1140 1720 160.1 271.0 0.59 0.73407 1.5692 0.70987 1 Josling 6.9 30.8 0.22 0.51227 20 0.1359 0.51119 1217 2.36 -7.12 915 1716 2 Vaalputs 10.5 53.9 0.19 0.51202 20 0.1174 0.51113 1146 -0.50 -12.13 1195 1792 2 Gemsbok 14.0 77.9 0.18 0.51198 12 0.0930 0.51131 1104 1.91 -12.76 961 1471 3 Kleinbe 13.7 88.7 0.15 0.51164 8 0.1187 0.51079 1101 -8.44 -19.41 1938 2409 3 Klip Ko 14.6 74.6 0.20 0.51202 10 0.1257 0.51112 1096 -2.06 -12.02 1321 1950 3 Strauss 11.6 58.0 0.20 0.51197 10 0.1206 0.51111 1089 -2.49 -13.09 1342 1933 2 Friers 14.9 78.7 0.19 0.51200 20 0.1143 0.51119 1078 -1.08 -12.45 1179 1761 2 Friers 14.7 77.4 0.19 0.51198 20 0.1144 0.51117 1078 -1.42 -12.78 1212 1788 2 a References: 1 – this study, 2 – Pettersson et al. (2009), 3 – Bailie et al. (2011a) b Presumed as no U-Pb zircon emplacement age determined; age estimated based on field relationships Abbreviations: Elsie se – Elsie se Gorra, Friers – Friersdale Charnockite, Gemsbok – Gemsbokbult, Kanon – Kanoneiland, Kleinbe – Kleinbegin, Klip Ko – Klip Koppies, Klipkra – Klipkraal, Louis – Louisvale, Strauss - Straussburg
Sample No. Mkn4 Mkn Me1 Mc8 Cyn1 Mcol3 Col1 Vaal Ml5 Mkl3 Klp Mkb6 Kle1 Mka6 Kan1 Klip Str1 S188 S815 S367
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Late- to post-tectonic granites (Keimoes Suite) c Monzogranite to variable, Granodiorite; mostlybt-rich for mediumsome, ferroan, grained, metaluminous most porphyritic/ megacrystic
εNd(t) range
Host rocks + contacts
SrI range
TDM model ages (Ma)
gneissic, welldeveloped
Areachap Grp, gradational
moderate to well-developed
Korannaland -1.47 to 0.71970- 1571-1908 Grp, foliation 1.78 0.74944 stronger toward contacts, concordant
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Presence of foliation
1217
1175-1146
M AN U
SC
1.79 to 0.70674- 1447-1716 3.77 0.70821
Emplacement age (in Ma)
strong / gneissic Bethesda Fm, 1.89 disharmonic Areachap Grp, flow pattern concordant, lit-par-lit, foliated, gradational with syn-tectonic granites
0.70630
1487
1125
TE D
Table 6 Summary of proposed subdivision of the eastern Namaqua Sector granites Granite Composition Grain Mineralogy Size Early syn-tectonic granite Josling leucogranite fine-grained qtz, K-fsp > plag, metaluminous bt-poor, msc Syn-tectonic granites a, b leucogranite coarse- to qtz, K-fsp, plag, bt, to granodiorite, mediumminor msc ferroan, grained, metaluminous typically to peraluminous medium, equigranular Louisvale heterogeneous, medium mafic – variable amts of mesocratic to fsp phenocrysts, leucocratic, opalescent blue qtz, tonalite to cordierite; leucocratic – monzogranite, elongate mcl phenocrysts ferroan, metaluminous
Areachap Grp, -2.95 to 0.70738- 1383-1993 d 1110-1078 older granites; 2.83 c 0.77130 country rocks Dagbreek Fm, Korannaland Grp; sharp, cross-cutting; metam. aureole a The Cyndas Subsuite is excluded from this table due to showing a range of different granite varieties within the subsuite. Generalizations with regard to element contents and petrogenesis cannot not, therefore, be made. b The summary is generalized for the overall age grouping. c Generalized summary for the Keimoes Suite as each granite can show variable and differing aspects relative to the other Keimoes Suite granites. c excluding the Kleinbegin Granite (εnd(t) = -7.51 to -8.44), d Excluding the Kleinbegin Granite (TDM = 2344-2409 Ma)
AC C
EP
qtz, K-fsp, plag, bt ± hbl weak/poor to ± opx (in some); K-fsp unfoliated phenocrysts
Abbreviations: mineralogy: bt – biotite, fsp – feldspar, hbl – hornblende, K-fsp – K-feldspar, mcl – microcline, msc- muscovite, opx – orthopyroxene, plag – plagioclase, pyx – pyroxene, qtz – quartz; porph – porphyritic; Fm – Formation, Grp – Group, metam. – metamorphic, amts - amounts
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Mc8-01 Mc8-02 Mc8-03 Mc8-04 Mc8-05 Mc8-06 Mc8-07 Mc8-08 Mc8-09 Mc8-10 Mc8-11 Mc8-12 Mc8-13 Mc8-14 Mc8-15 Mc8-16 Mc8-17 Mc8-18 Mc8-19 Mc8-20 Mc8-22 Mc8-23 Mc8-24 Mc8-25
Dark core Dark core Dark core Dark core Bright core Dark core Bright core Dark core Bright core Dark rim Dark core Bright core Bright core Bright core Dark core Bright core Bright core Bright core Dark core Bright core Bright core Bright core Dark core Dark rim
Mc8
Mc8-21 irregular signal
Pb/235Ub
2 σd
206
Pb/238Ub
2 σd
rhoc
2σ
43 47 50 43 58 48 49 44 52 47 49 48 46 48 57 45 50 59 49 51 44 45 43 49 avg.
0.080 0.085 0.092 0.080 0.107 0.087 0.091 0.081 0.095 0.087 0.090 0.088 0.084 0.087 0.106 0.083 0.093 0.108 0.090 0.095 0.080 0.081 0.079 0.089
0.1957 0.1961 0.1973 0.1953 0.1988 0.1966 0.1998 0.1976 0.1979 0.1987 0.1952 0.1963 0.1969 0.1966 0.1990 0.1948 0.1985 0.1967 0.1990 0.2003 0.1942 0.1937 0.1956 0.1956
0.0056 0.0057 0.0058 0.0056 0.0058 0.0057 0.0058 0.0057 0.0059 0.0057 0.0057 0.0057 0.0057 0.0057 0.0059 0.0056 0.0058 0.0058 0.0058 0.0059 0.0056 0.0056 0.0056 0.0056
0.76 0.72 0.68 0.76 0.59 0.70 0.69 0.76 0.67 0.72 0.68 0.71 0.74 0.71 0.60 0.72 0.67 0.57 0.69 0.67 0.75 0.74 0.76 0.68
0.0786 0.0780 0.0786 0.0783 0.0791 0.0777 0.0786 0.0781 0.0781 0.0787 0.0781 0.0785 0.0791 0.0783 0.0786 0.0771 0.0781 0.0775 0.0780 0.0789 0.0778 0.0779 0.0774 0.0786
0.0019 0.0022 0.0025 0.0019 0.0032 0.0023 0.0024 0.0019 0.0026 0.0022 0.0024 0.0023 0.0021 0.0023 0.0031 0.0021 0.0025 0.0033 0.0024 0.0026 0.0020 0.0021 0.0019 0.0024
1156 1152 1161 1152 1170 1151 1170 1158 1158 1167 1149 1156 1164 1156 1167 1139 1161 1150 1162 1174 1143 1142 1144 1155
0
0
#DIV/0!
0.00
#VALUE!
-0.002
0.018
#VALUE!
0.0000
#VALUE!
0
U [ppm]a Pb [ppm]a Th/U meas
716 547 71 70 70
39 30 13 13 13
0.10 0.08 0.33 0.34 0.34
207
Pb/235Ub
0.40 0.40 1.84 1.87 1.88
2 σd
206
Pb/238Ub
0.02 0.02 0.08 0.08 0.08
0.054 0.054 0.179 0.181 0.181
2 σd
0.002 0.002 0.005 0.005 0.005
rhoc
0.71 0.72 0.70 0.70 0.70
Conc.
Pb/235U
207
2.121 2.109 2.138 2.108 2.167 2.106 2.165 2.129 2.129 2.156 2.102 2.123 2.147 2.123 2.156 2.070 2.137 2.102 2.139 2.179 2.082 2.079 2.086 2.120
207
Pb/206Pbe
EP
PL-06 PL-07 91500-06 91500-07 91500-08
Dates [Ma]
1.14 2.56 1.95 1.13 1.69 1.83 1.75 1.25 1.51 1.40 2.07 1.78 1.46 1.66 2.57 2.25 1.99 2.07 1.57 1.83 0.78 0.68 2.12 1.13
Pb/238U
2σ
1152 1155 1161 1150 1169 1157 1174 1163 1164 1168 1150 1155 1159 1157 1170 1147 1167 1158 1170 1177 1144 1141 1152 1152 1159
30 31 31 30 31 31 31 31 32 31 31 31 31 31 32 30 31 31 31 31 30 30 30 30
-10
115
206
0.0534 0.0532 0.0746 0.0751 0.0751
2 σd
0.0015 0.0015 0.0023 0.0023 0.0023
2σ
%
1162 1146 1161 1155 1173 1139 1161 1151 1149 1165 1149 1159 1175 1155 1161 1123 1149 1134 1147 1169 1141 1143 1130 1162
48 56 62 48 78 58 59 49 65 55 62 58 52 57 77 54 63 83 60 64 51 52 49 60
99 101 100 100 100 102 101 101 101 100 100 100 99 100 101 102 102 102 102 101 100 100 102 99
0
4000
-10200
207
Pb/206Pb
#VALUE!
Dates [Ma]
Conc.
Pb/235U
2σ
340 339 1061 1071 1072
14 14 45 45 45
207
Pb/238U
2σ
339 339 1063 1071 1073
10 10 29 29 29
206
207
Pb/206Pb
344 338 1057 1071 1071
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207 d
Pb/235U calculated using (207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the 206Pb/238U and the 207Pb/235U ratio.
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).e Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
a
PL PL 91500 91500 91500
2 σd
31 12 9 29 8 11 9 28 6 13 12 11 19 11 15 19 10 10 9 9 28 22 43 23
RATIOS Analysis
Pb/206Pbe
160 61 45 148 40 57 46 144 33 66 61 54 95 57 76 97 53 53 48 44 142 113 220 116
Reference Materials Sample
207
M AN U
Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8
207
RI PT
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas
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Sample
SC
Table A1 LA-ICP-MS U-Pb geochronological data for zircons from the Smalvisch Granite, Cyndas Subsuite, eastern Namaqua Sector Mc8 RATIOS
2σ
%
64 62 61 60 60
98 100 101 100 100
weighted Uncertainty mean age variance
1159.0
27
88.85
weighted uncertainty variance mean 339.1 4.36 1069.15
9.31
17
MSWD 1.000
MSWD
1.535
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Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mcol-01 Dark core 66 13 0.82 Mcol-02 Dark rim 62 12 0.57 Mcol-03 Bright rim 66 13 0.60 Mcol-04 Dark core 194 38 0.72 Mcol-05 Bright core 55 11 0.88 Mcol-06 Bright core 113 21 0.83 Mcol-07 Bright core 99 18 0.42 Mcol-08 Bright core 35 7 0.73 Mcol-09 Bright core 100 20 0.57 Mcol-10 Dark core 59 12 0.79 Mcol-11 Dark rim 96 19 0.40 Mcol-12 Dark core 121 24 0.46 Mcol-13 Dark core 61 12 0.87 Mcol-14 Dark core 112 22 0.56 Mcol-15 Bright core 89 18 0.99 Mcol-16 Dark core 187 36 0.37 Mcol-17 Bright core 46 9 0.68 Mcol-18 Dark core 134 26 0.64 Mcol-19 Dark core 181 36 0.98 Mcol-20 Bright rim 104 20 0.41 Mcol-21 Dark core 149 29 0.83 Mcol-22 Bright core 42 8 0.70 Mcol-23 Dark rim 125 25 0.33 Mcol-24 Bright core 95 18 0.99 Mcol-25 Bright core 65 13 0.71
207
Pb/235Ub 2.152 2.104 2.150 2.117 2.141 2.046 2.012 2.150 2.098 2.120 2.079 2.138 2.127 2.137 2.144 2.098 2.129 2.123 2.128 2.124 2.119 2.135 2.168 2.025 2.128
2σ 0.086 0.093 0.086 0.078 0.094 0.109 0.083 0.104 0.096 0.088 0.086 0.088 0.117 0.129 0.084 0.101 0.093 0.091 0.081 0.088 0.088 0.109 0.100 0.087 0.103 d
206
Pb/238Ub 0.1981 0.1964 0.1972 0.1950 0.1971 0.1887 0.1866 0.1983 0.1955 0.1963 0.1938 0.1966 0.1981 0.1967 0.1974 0.1936 0.1975 0.1961 0.1967 0.1950 0.1971 0.1978 0.1977 0.1879 0.1969
Dates [Ma] 2 σd 0.0057 0.0056 0.0057 0.0055 0.0057 0.0054 0.0053 0.0058 0.0056 0.0057 0.0056 0.0056 0.0057 0.0056 0.0057 0.0055 0.0058 0.0056 0.0056 0.0056 0.0056 0.0058 0.0057 0.0054 0.0058
rhoc 0.72 0.65 0.72 0.77 0.66 0.53 0.70 0.60 0.63 0.69 0.70 0.69 0.53 0.48 0.73 0.59 0.67 0.67 0.75 0.69 0.69 0.57 0.62 0.67 0.60
207
Pb/206Pbe 0.0788 0.0777 0.0791 0.0787 0.0788 0.0786 0.0782 0.0786 0.0778 0.0784 0.0778 0.0789 0.0779 0.0788 0.0788 0.0786 0.0782 0.0786 0.0785 0.0790 0.0780 0.0783 0.0795 0.0782 0.0784
2 σd 0.0022 0.0026 0.0022 0.0019 0.0026 0.0035 0.0023 0.0030 0.0028 0.0023 0.0023 0.0024 0.0036 0.0042 0.0021 0.0031 0.0026 0.0025 0.0020 0.0024 0.0023 0.0033 0.0029 0.0025 0.0030
Conc. 2σ 47 51 46 43 51 60 46 56 53 48 47 48 64 70 46 55 51 49 44 48 48 59 54 49 56
207
Pb/235U 1166 1150 1165 1154 1162 1131 1120 1165 1148 1155 1142 1161 1158 1161 1163 1148 1158 1156 1158 1156 1155 1160 1171 1124 1158
Reference Materials
RATIOS Sample
Analysis
PL PL 91500 91500 91500
PL-04 PL-05 91500-03 91500-04 91500-05
U [ppm]a Pb [ppm]a Th [ppm] Th/U meas Th/U calc
547 579 82 81 79
30 31 15 15 14
43 46 27 27 26
0.08 0.08 0.33 0.33 0.33
0.03 0.03 0.09 0.09 0.09
207
Pb/235Ub
0.40 0.40 1.93 1.87 1.87
2 σd
1s%
0.02 0.02 0.10 0.08 0.08
2.07 2.45 2.50 2.14 2.08
206
Pb/238Ub
0.054 0.054 0.180 0.181 0.180
1 σd
2 σd
1s%
rhoc
0.001 0.001 0.003 0.003 0.003
0.002 0.002 0.005 0.005 0.005
1.44 1.44 1.46 1.46 1.45
0.69 0.59 0.58 0.68 0.70
207
Pb/206Pbe
0.0536 0.0538 0.0778 0.0749 0.0752
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
2σ 31 30 31 30 31 29 29 31 30 31 30 30 31 30 31 30 31 30 30 30 30 31 31 29 31
2σ 55 66 54 46 65 88 58 76 70 59 58 59 92 104 52 76 64 62 49 59 59 82 70 63 76
207
Pb/206Pb 1167 1140 1174 1165 1167 1163 1152 1163 1143 1156 1142 1169 1144 1167 1167 1162 1152 1161 1158 1172 1146 1154 1185 1152 1157
Pb/235 U calculated using ( 207 Pb/206 Pb)/(238 U/206 Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the 206 Pb/238 U and the 207 Pb/235 U ratio.
1 σd
2 σd
1s%
0.0008 0.0011 0.0016 0.0012 0.0011
0.0016 0.0021 0.0032 0.0023 0.0022
1.4925 1.9892 2.0306 1.5629 1.4902
EP
TE D
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD). e Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
d
Pb/238U 1165 1156 1160 1149 1160 1114 1103 1166 1151 1155 1142 1157 1165 1158 1161 1141 1162 1154 1158 1149 1160 1163 1163 1110 1159
weighted uncertainty mean variance
% 100 101 99 99 99 96 96 100 101 100 100 99 102 99 100 98 101 99 100 98 101 101 98 96 100
1151.4
27.54
285.31
MSWD 1.042
Dates [Ma]
1 σd
0.01 0.01 0.05 0.04 0.04
a
207
206
SC
Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3
M AN U
Sample
RI PT
Table A2 LA-ICP-MS U-Pb geochronological data for zircons from the Colston Granite, eastern Namaqua Sector Mcol3 RATIOS
Pb/235U
2σ
342 344 1091 1071 1069
14 17 55 46 45
207
Conc. Pb/238U
2σ
340 341 1066 1073 1068
9 10 29 29 29
206
Pb/206Pb
2σ
%
354 362 1142 1065 1073
67 88 80 62 59
96 94 93 101 100
207
Age Display analysis 207Pb/206Pb 2.8 2.8 2.7 2.7 2.7
PL PL 91500 91500 91500
340 341 1142 1065 1073
weighted 1σ
2σ
conc %
5 5 40 31 30
9 10 80 62 59
96 94 93 101 100
mean
340.45 1068.95
uncertainty variance 4.36 0.305 9.28
10.41
MSWD 1.984 1.499
ACCEPTED MANUSCRIPT
Table A3 LA-ICP-MS U-Pb geochronological data for zircons from the Elsie se Gorra Granite, eastern Namaqua Sector Me1 RATIOS Pb/235Ub 1.40 1.14 2.01 2.23 2.22 2.23 2.73 2.75 0.96 1.04 0.93 1.60 2.26 2.22 2.01 2.21 1.85 2.20 2.21 1.89 2.21
2 σd 0.05 0.04 0.10 0.10 0.08 0.09 0.10 0.10 0.03 0.04 0.03 0.06 0.08 0.08 0.09 0.08 0.07 0.08 0.08 0.12 0.09
Pb/238Ub 0.134 0.109 0.183 0.203 0.203 0.202 0.230 0.232 0.087 0.096 0.088 0.147 0.198 0.202 0.181 0.202 0.169 0.201 0.201 0.170 0.201
2 σd 0.004 0.003 0.005 0.006 0.006 0.006 0.007 0.007 0.003 0.003 0.003 0.004 0.006 0.006 0.005 0.006 0.005 0.006 0.006 0.005 0.006
rhoc 0.81 0.80 0.59 0.67 0.76 0.74 0.77 0.78 0.80 0.74 0.80 0.79 0.78 0.77 0.67 0.78 0.78 0.77 0.78 0.47 0.74
0.012 -0.006 -0.010 -0.017 0.039 0.009 0.025 -0.114 -0.008
0.023 0.005 0.037 0.057 0.071 0.023 0.014 0.473 0.013
#VALUE! -0.48 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
206
Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1
Me1-07 metamict - irregular signal 0 Me1-08 metamict - irregular signal 0 Me1-09 metamict - irregular signal 0 Me1-10 metamict - irregular signal 0 Me1-11 metamict - irregular signal 0 Me1-17 metamict - irregular signal 1 Me1-20 metamict - irregular signal 0 Me1-25 metamict - irregular signal 0 Me1-29 metamict - irregular signal 0
0 0 0 0 0 0 0 0 0
0.00 #DIV/0! #DIV/0! #DIV/0! #DIV/0! 0.02 #DIV/0! 0.37 #DIV/0!
0.00 0.26 0.00 0.00 0.00 0.00 0.00 0.00 0.00
#VALUE! 0.46 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
a
Pb/206Pbe 0.0758 0.0763 0.0795 0.0797 0.0794 0.0800 0.0860 0.0862 0.0798 0.0789 0.0770 0.0793 0.0827 0.0795 0.0805 0.0793 0.0796 0.0795 0.0794 0.0806 0.0795
0.0000 -0.3152 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
#VALUE! 0.4827 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
TE D
Not used
Dates [Ma] 2 σd 0.0016 0.0016 0.0031 0.0026 0.0019 0.0021 0.0020 0.0020 0.0017 0.0020 0.0017 0.0017 0.0019 0.0019 0.0026 0.0018 0.0018 0.0019 0.0018 0.0044 0.0021
207
Conc. 2σ
207
Pb/235U 889 774 1118 1190 1188 1189 1336 1343 684 725 668 972 1200 1187 1118 1186 1065 1181 1183 1079 1183
32 28 54 51 45 46 50 50 25 28 24 35 44 44 48 44 39 44 43 67 46
206
Pb/238U 810 665 1085 1191 1192 1185 1335 1344 540 589 542 882 1167 1187 1071 1189 1007 1180 1183 1014 1183
0 237 0 0 0 0 0 0 0
#VALUE! 415 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
78 -39 -67 -110 249 57 160 -782 -49
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value); Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
EP
d
AC C
207
2σ 22 18 29 31 31 31 35 35 15 16 15 24 31 31 28 31 27 31 31 27 31
RI PT
207
SC
Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Me1-01 Dark core 2110 283 0.29 Me1-02 Dark core 2214 241 0.26 Me1-03 Bright rim 325 60 0.67 Me1-04 Dark core 519 105 0.14 Me1-05 Bright core 526 107 0.12 Me1-06 Bright core 549 111 0.12 Me1-12 inherited core (dark) 353 81 0.21 Me1-13 inherited core (dark) 330 76 0.20 Me1-14 Bright rim 3748 327 0.05 Me1-15 Bright rim 3470 332 0.06 Me1-16 Bright core 2462 216 0.10 Me1-18 Bright core 1913 281 0.34 Me1-19 Bright core 438 87 0.15 Me1-21 Bright core 270 55 0.21 Me1-22 Dark core 861 156 0.34 Me1-23 Bright rim 515 104 0.24 Me1-24 Bright core 1024 173 0.21 Me1-26 Bright core 338 68 0.15 Me1-27 Dark rim 965 194 0.28 Me1-28 Bright core 353 60 0.22 Me1-30 Bright core 223 45 0.21
M AN U
Sample
148 33 239 375 437 147 91 3440 84
207
Pb/206Pb 1090 1102 1184 1190 1181 1197 1337 1342 1193 1170 1121 1180 1262 1186 1210 1180 1186 1184 1182 1212 1184 0 0 0 0 0 0 0 0 0
weighted uncertainty variance
2σ
%
mean
42 43 77 63 47 50 45 44 42 51 43 43 44 46 63 45 45 46 45 105 52
74 60 92 100 101 99 100 100 45 50 48 75 92 100 89 101 85 100 100 84 100
1174.74
4000 0 4000 4000 4000 4000 4000 4000 4000
78200 -39200 -67100 -110000 248500 56700 159700 -782000 -49300
17.57
931.01
MSWD 1.104
ACCEPTED MANUSCRIPT
Table A4 LA-ICP-MS U-Pb geochronological data for zircons from the Josling Granite, eastern Namaqua Sector Mkn4 RATIOS Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4
Mkn5-01 Mkn5-02 Mkn5-03 Mkn5-04 Mkn5-07 Mkn5-08 Mkn5-09 Mkn5-10 Mkn5-11 Mkn5-12 Mkn5-13 Mkn5-14 Mkn5-15 Mkn5-16 Mkn5-17 Mkn5-18 Mkn5-19 Mkn5-20 Mkn5-21 Mkn5-22 Mkn5-23 Mkn5-24 Mkn5-25
Dark rim Bright core Bright core Dark rim Bright core Dark rim Dark rim CL bright core CL dark rim Bright core Bright core Dark rim Dark rim CL bright core CL dark rim Dark core Dark core CL dark core CL bright rim Bright core Bright core CL bright core CL dark rim
Mkn5-05 Mkn5-06
not zircon not zircon
U [ppm]a Pb [ppm]a Th/U meas 1923 188 0.02 76 16 0.52 54 11 0.47 1283 124 0.08 46 9 0.59 582 121 0.60 411 86 0.62 51 11 0.60 3411 149 0.02 303 22 0.10 42 5 0.64 1858 191 0.02 2572 115 0.01 92 19 0.65 1335 130 0.03 337 70 0.58 113 23 0.87 2632 172 0.07 968 106 0.05 297 61 0.30 182 38 0.52 140 29 0.30 1609 141 0.04
207
Pb/235Ub 1.088 2.350 2.329 1.023 2.309 2.310 2.330 2.345 0.396 0.839 1.445 1.146 0.401 2.325 1.089 2.315 2.298 0.741 1.231 2.288 2.331 2.272 0.970
2 σd 0.040 0.100 0.111 0.038 0.106 0.084 0.085 0.103 0.015 0.044 0.140 0.042 0.015 0.091 0.041 0.086 0.092 0.033 0.049 0.101 0.149 0.088 0.038
206
Pb/238Ub 0.0977 0.2097 0.2082 0.0967 0.2068 0.2082 0.2094 0.2084 0.0438 0.0740 0.1270 0.1030 0.0449 0.2079 0.0977 0.2084 0.2083 0.0652 0.1096 0.2057 0.2073 0.2060 0.0878
Dates [Ma] 2 σd 0.0028 0.0061 0.0063 0.0028 0.0061 0.0060 0.0060 0.0062 0.0013 0.0021 0.0037 0.0030 0.0013 0.0061 0.0028 0.0060 0.0061 0.0019 0.0032 0.0061 0.0062 0.0060 0.0025
rhoc 0.80 0.69 0.64 0.78 0.64 0.79 0.79 0.68 0.77 0.56 0.30 0.79 0.79 0.74 0.78 0.78 0.72 0.66 0.72 0.67 0.47 0.75 0.74
0.005 0.020
#VALUE! #VALUE!
Not used Mkn4 Mkn4
2 1
0 0
0.00 0.00
0.00 0.00
#VALUE! #VALUE!
0.002 0.026
RATIOS Sample
Analysis
PL PL PL PL PL
A_135 A_136 A_137 A_138 A_139
U [ppm]a Pb [ppm]a Th/U meas
500 496 500 494 405
27 27 27 27 22
0.08 0.08 0.08 0.08 0.08
207
Pb/235Ub
0.40 0.40 0.40 0.39 0.40
2 σd
0.02 0.02 0.02 0.02 0.02
206
Pb/238Ub
0.054 0.055 0.054 0.054 0.054
2 σd
rhoc
0.002 0.002 0.002 0.002 0.002
0.73 0.73 0.72 0.72 0.66
2 σd 0.0018 0.0025 0.0030 0.0018 0.0029 0.0018 0.0018 0.0026 0.0016 0.0036 0.0076 0.0018 0.0015 0.0021 0.0019 0.0019 0.0022 0.0027 0.0023 0.0026 0.0046 0.0021 0.0021
0.0000 0.0000
207
Pb/206Pbe
0.0528 0.0533 0.0534 0.0528 0.0531
Conc. 2σ
207
Pb/235U 748 1228 1221 715 1215 1215 1221 1226 339 619 908 775 342 1220 748 1217 1212 563 815 1209 1222 1204 689
27 52 58 27 56 44 45 54 13 32 88 28 13 48 28 45 49 25 33 53 78 47 27
Pb/238U 601 1227 1219 595 1212 1219 1226 1220 276 461 770 632 283 1218 601 1221 1220 407 670 1206 1214 1208 542
2σ
12 164
30 128
Pb/238U
2σ
341 343 340 338 340
10 10 10 10 10
206
#VALUE! #VALUE!
0 0
#VALUE! #VALUE!
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
Pb/206Pb 1217 1228 1225 1113 1222 1208 1214 1236 794 1250 1258 1213 768 1224 1216 1210 1197 1258 1233 1214 1235 1196 1202 0 0
2σ
%
43 60 71 47 69 44 44 62 50 84 176 44 48 51 45 46 54 64 54 63 109 51 52
49 100 100 53 99 101 101 99 35 37 61 52 37 99 49 101 102 32 54 99 98 101 45
4000 4000
11900 163800
0.0014 0.0015 0.0015 0.0015 0.0018
Conc.
Pb/235U
2σ
338 343 340 336 339
13 14 14 13 15
207
206
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
d
17 33 34 16 33 32 32 33 8 13 21 17 8 32 17 32 32 11 18 33 33 32 15
207
Dates [Ma] 2 σd
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
EP
a
Pb/206Pbe 0.0808 0.0813 0.0811 0.0767 0.0810 0.0805 0.0807 0.0816 0.0656 0.0822 0.0825 0.0807 0.0648 0.0811 0.0808 0.0806 0.0800 0.0825 0.0815 0.0807 0.0816 0.0800 0.0802
TE D
Reference Materials
207
RI PT
Comment
SC
Analysis
M AN U
Sample
207
Pb/206Pb
321 342 344 320 335
2σ
%
62 62 62 63 74
106 100 99 105 101
weighted mean uncertainty variance 1217.43 19.78 38.43
MSWD 1.091
weighted mean uncertainty variance 340.15 6.95 2.53
MSWD 1.250
ACCEPTED MANUSCRIPT
Table A5 LA-ICP-MS U-Pb geochronological data for zircons from the Kanoneiland Granite, eastern Namaqua Sector Mka6 RATIOS
Mka6 Mka6 Mka6
Mka6-06 Mka6-07 Mka6-08 Mka6-09 Mka6-10 Mka6-11 Mka6-12 Mka6-13 Mka6-16 Mka6-17 Mka6-18 Mka6-20 Mka6-21 Mka6-22 Mka6-23 Mka6-24 Mka6-25
Bright core Dark core Bright core Dark core Dark core Bright core Dark core Bright core Bright core Bright core Bright core Bright core
Mka6-14 irregular cPb Mka6-15 irregular cPb Mka6-19 metamict
2 σd 0.075 0.075 0.076 0.077 0.095
Dates [Ma]
Pb/238Ub 0.1803 0.1811 0.1791 0.1785 0.1803
2 σd 0.0053 0.0053 0.0053 0.0052 0.0053
rhoc 0.73 0.73 0.72 0.71 0.58
206
Pb/206Pbe 0.0752 0.0752 0.0748 0.0750 0.0752
2 σd 0.0021 0.0021 0.0021 0.0022 0.0031
207
393 219 300 365 267 255 700 339 194 422 156 339 267 219 265 128 229
73 41 56 69 50 48 131 64 36 79 29 64 49 41 50 24 42
0.44 0.40 0.33 0.48 0.40 0.36 0.13 0.42 0.50 0.34 0.43 0.27 0.41 0.36 0.34 0.46 0.48
1.961 1.958 1.965 1.977 1.974 1.959 1.970 1.973 1.944 1.976 1.988 1.981 1.950 1.945 1.993 2.013 1.938
0.072 0.073 0.072 0.073 0.073 0.073 0.072 0.073 0.073 0.073 0.107 0.074 0.075 0.074 0.075 0.084 0.075
0.1854 0.1872 0.1873 0.1879 0.1880 0.1869 0.1867 0.1881 0.1857 0.1875 0.1888 0.1883 0.1850 0.1862 0.1892 0.1901 0.1853
0.0053 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0055 0.0054 0.0053 0.0054 0.0055 0.0056 0.0055
0.78 0.77 0.78 0.78 0.78 0.77 0.79 0.78 0.77 0.78 0.54 0.78 0.75 0.76 0.77 0.70 0.76
0.0767 0.0759 0.0761 0.0763 0.0761 0.0760 0.0766 0.0761 0.0760 0.0764 0.0764 0.0763 0.0764 0.0758 0.0764 0.0768 0.0759
0.0018 0.0018 0.0017 0.0017 0.0018 0.0018 0.0017 0.0018 0.0018 0.0017 0.0035 0.0018 0.0019 0.0019 0.0018 0.0023 0.0019
0 2 1
0 0 0
0.00 0.00 0.00
0.00 0.00 0.00
#VALUE! #VALUE! #VALUE!
-0.020 0.007 -0.006
0.041 0.006 0.009
#VALUE! #VALUE! #VALUE!
0.0000 0.0000 0.0000
#VALUE! #VALUE! #VALUE!
RATIOS Sample
Analysis
PL PL PL PL PL
PL-01 PL-02 PL-03 PL-04 PL-05
U [ppm]a Pb [ppm]a Th/U meas
501 493 488 493 521
27 26 26 27 28
207
Pb/235Ub
0.08 0.13 0.08 0.08 0.08
0.39 0.39 0.40 0.40 0.40
2 σd
0.02 0.03 0.02 0.02 0.02
206
Pb/238Ub
0.054 0.053 0.054 0.054 0.054
2 σd
TE D
Reference Materials rhoc
0.002 0.002 0.002 0.002 0.002
Pb/206Pbe
0.72 0.37 0.73 0.65 0.70
0.0528 0.0535 0.0531 0.0533 0.0532
2σ
0.0015 0.0040 0.0015 0.0018 0.0016
2σ
43 43 44 44 54
Pb/238U 1069 1073 1062 1059 1068
1102 1101 1104 1108 1107 1101 1105 1106 1096 1107 1112 1109 1098 1097 1113 1120 1094
41 41 41 41 41 41 40 41 41 41 60 41 42 42 42 47 43
1096 1106 1107 1110 1111 1104 1103 1111 1098 1108 1115 1112 1094 1101 1117 1122 1096
29 29 29 29 29 29 29 29 29 29 30 30 29 29 30 30 30
0 0 0
#VALUE! #VALUE! #VALUE!
-129 46 -40
271 38 57
Pb/238U
2σ
340 335 340 340 340 339.0
10 10 10 10 10
207
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
29 29 29 29 29
2σ
338 337 339 340 339
14 27 14 15 14
206
206
Pb/238U and the 207Pb/235U ratio.
AC C
1110
1100
1090
1080
1070
1060 0
200
400
U [ppm]
600
800
2σ
%
55 55 57 58 81
100 100 100 99 100
1114 1092 1098 1103 1099 1096 1110 1097 1094 1106 1106 1104 1107 1089 1106 1116 1092
46 47 46 45 46 47 44 46 48 45 90 46 50 49 48 59 50
98 101 101 101 101 101 99 101 100 100 101 101 99 101 101 101 100
0 0 0
4000 4000 4000
-129400 46000 -39600
207
Pb/206Pb 1073 1074 1063 1069 1073
Conc.
Pb/235U
207
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975). 1120
Date [Ma]
d
206
Dates [Ma]
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
EP
a
2 σd
207
Conc.
Pb/235U 1070 1073 1062 1062 1070
207
RI PT
Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Not used
Pb/235Ub 1.869 1.878 1.847 1.846 1.868
207
SC
Mka6 Mka6 Mka6 Mka6 Mka6
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mka6-01 low U! - bright core 78 14 0.33 Mka6-02 low U! - dark core 77 14 0.33 low U! - bright core 81 14 0.33 Mka6-03 Mka6-04 low U! - bright core 82 15 0.33 Mka6-05 low U! - bright core 80 14 0.33
M AN U
Sample
207
Pb/206Pb
322 348 331 343 336
2σ
%
63 163 62 75 67
106 96 103 99 101
weighted uncertainty variance mean 1097.51 25.37 336.21
MSWD
weighted uncertainty variance mean 339.03 6.93 3.57
MSWD
1.048
1.248
ACCEPTED MANUSCRIPT
Table A6 LA-ICP-MS U-Pb geochronological data for zircons from the Keboes Granite, eastern Namaqua Sector Mkb6 RATIOS Pb/235Ub 1.973 2.002 2.763 1.999 1.842 2.022 1.967 1.977 1.984 2.013 2.033 1.985 1.970 2.046 1.965 1.095 1.939 2.000 1.957 1.928 1.962 1.955 2.009 1.991 1.877
2 σd 0.078 0.077 0.104 0.073 0.067 0.081 0.076 0.075 0.073 0.077 0.080 0.075 0.073 0.076 0.073 0.040 0.073 0.073 0.081 0.074 0.080 0.077 0.078 0.077 0.070
206
2 σd
206
Pb/238Ub 0.1873 0.1878 0.2323 0.1893 0.1737 0.1895 0.1871 0.1872 0.1881 0.1901 0.1901 0.1875 0.1871 0.1923 0.1872 0.1044 0.1854 0.1898 0.1865 0.1839 0.1877 0.1862 0.1896 0.1881 0.1773
Dates [Ma]
2 σd 0.0055 0.0055 0.0067 0.0054 0.0050 0.0055 0.0054 0.0054 0.0054 0.0056 0.0055 0.0054 0.0054 0.0056 0.0054 0.0030 0.0054 0.0055 0.0054 0.0053 0.0054 0.0054 0.0055 0.0055 0.0051
rhoc 0.75 0.75 0.77 0.79 0.79 0.72 0.75 0.77 0.78 0.77 0.73 0.77 0.78 0.78 0.77 0.78 0.76 0.79 0.70 0.75 0.71 0.74 0.75 0.75 0.78
207
2 σd
rhoc
207
0.005 0.005 0.005 0.005 0.005
0.71 0.71 0.71 0.65 0.70
Pb/206Pbe 0.0764 0.0773 0.0863 0.0766 0.0769 0.0774 0.0763 0.0766 0.0765 0.0768 0.0776 0.0768 0.0764 0.0772 0.0761 0.0761 0.0758 0.0764 0.0761 0.0761 0.0758 0.0761 0.0769 0.0767 0.0768
Reference materials
RATIOS Analysis
91500 91500 91500 91500 91500
A_101 A_102 A_103 A_104 A_105
U [ppm]a Pb [ppm]a Th/U meas
80 81 82 84 84
14 15 15 15 15
207
Pb/235Ub
0.34 0.33 0.34 0.34 0.34
1.87 1.88 1.88 1.87 1.83
207
Pb/235U 1106 1116 1346 1115 1061 1123 1104 1108 1110 1120 1127 1111 1105 1131 1103 751 1095 1116 1101 1091 1103 1100 1118 1112 1073
Conc. weighted uncertainty variance 2σ 44 43 50 41 38 45 43 42 41 43 44 42 41 42 41 28 41 41 46 42 45 44 43 43 40
206
Pb/238U 1107 1110 1346 1117 1033 1119 1105 1106 1111 1122 1122 1108 1106 1134 1106 640 1097 1120 1103 1088 1109 1101 1119 1111 1052
0.08 0.08 0.08 0.09 0.08
0.180 0.181 0.181 0.180 0.178
a
Pb/206Pbe
0.0751 0.0756 0.0751 0.0753 0.0746
2 σd
e
0.0022 0.0022 0.0022 0.0026 0.0023
2σ
1069 1074 1074 1069 1058
44 45 44 49 45
Pb/238U
2σ
1069 1070 1075 1065 1058
29 29 29 29 29
206
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
EP
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
d
30 30 35 30 27 30 30 29 29 30 30 29 29 30 29 18 29 30 29 29 30 30 30 30 28
207
Pb/206Pb 1106 1129 1345 1111 1119 1132 1102 1110 1108 1116 1137 1116 1105 1126 1098 1097 1090 1106 1098 1097 1091 1099 1117 1114 1115
2σ
%
52 50 46 44 44 55 51 48 45 48 53 48 46 47 47 45 49 45 58 50 57 53 50 51 47
100 98 100 101 92 99 100 100 100 100 99 99 100 101 101 58 101 101 100 99 102 100 100 100 94
mean 1104.94
27
465
Conc. weighted uncertainty variance
Pb/235U
207
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
2σ
Dates [Ma]
Pb/238Ub
TE D
Sample
2 σd 0.0020 0.0020 0.0021 0.0017 0.0017 0.0022 0.0020 0.0018 0.0017 0.0019 0.0021 0.0019 0.0018 0.0018 0.0018 0.0017 0.0019 0.0017 0.0022 0.0019 0.0022 0.0020 0.0020 0.0020 0.0018
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207
SC
Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mkb6-01 Bright core 107 20 0.55 Mkb6-02 Bright core 157 29 0.52 37 0.40 Mkb6-03Inherited core 161 Mkb6-04 Dark core 401 76 0.35 Mkb6-05 Dark rim 559 97 0.28 Mkb6-06 Bright rim 137 26 0.39 Mkb6-07 Bright core 133 25 0.30 Mkb6-08 Dark core 184 34 0.49 Mkb6-09 Dark rim 328 62 0.40 Mkb6-10 Bright core 153 29 0.30 Mkb6-11 Dark core 167 32 0.46 Mkb6-12 Bright rim 215 40 0.29 Mkb6-13 Bright core 275 51 0.39 Mkb6-14 Bright core 251 48 0.55 Mkb6-15 Bright core 237 44 0.51 Mkb6-16 Dark core 1447 151 0.28 Mkb6-17 Dark core 308 57 0.51 Mkb6-18 Dark rim 1068 203 0.31 Mkb6-19 Bright core 111 21 0.35 Mkb6-20 Bright core 156 29 0.26 Mkb6-21 Bright core 163 31 0.40 Mkb6-22 Bright core 116 22 0.37 Mkb6-23 Bright core 204 39 0.29 Mkb6-24 Bright core 169 32 0.41 Mkb6-25 Dark core 703 125 0.29
M AN U
Sample
207
Pb/206Pb
1070 1084 1071 1078 1057
2σ
%
58 58 58 70 61
100 99 100 99 100
mean 1067.3
12.05
31.37
MSWD 1.045
MSWD 1.250
ACCEPTED MANUSCRIPT
Table A7 LA-ICP-MS U-Pb geochronological data for zircons from the Klipkraal Granite, eastern Namaqua Sector MKl3 RATIOS
MK MK
A_044 cPb inclusions A_050 cPb inclusions
192 460 422 943 1058 139 763 932
36 82 80 166 112 26 92 150
0.84 0.33 1.77 0.11 0.12 0.70 0.20 0.11
0 1
0 0
#DIV/0! 0.00
Pb/235Ub
2 σd
2.10 2.02 2.14 2.03 1.12 2.13 1.36 1.82
0.07 0.06 0.07 0.07 0.03 0.07 0.04 0.06
0.00 0.00
#VALUE! #VALUE!
Dates [Ma]
2 σd
rhoc
0.187 0.178 0.189 0.176 0.105 0.189 0.121 0.161
0.004 0.004 0.004 0.004 0.002 0.004 0.003 0.003
0.69 0.71 0.70 0.67 0.71 0.68 0.70 0.70
0.0812 0.0823 0.0823 0.0834 0.0773 0.0817 0.0818 0.0820
-0.028 -0.013
0.032 0.012
#VALUE! #VALUE!
0.0000 0.0000
206
Pb/238Ub
207
Pb/206Pbe
Conc.
Pb/235U
2σ
0.0018 0.0018 0.0018 0.0020 0.0017 0.0019 0.0018 0.0018
1147 1122 1163 1124 764 1158 873 1051
#VALUE! #VALUE!
0 0
2 σd
b
207
Pb/238U
2σ
36 35 36 36 23 37 27 33
1106 1057 1117 1046 646 1116 735 961
#VALUE! #VALUE!
-181 -84
206
Pb/206Pb
2σ
%
22 21 22 21 13 22 15 19
1226 1252 1251 1278 1128 1237 1240 1245
44 42 43 47 43 46 43 43
90 84 89 82 57 90 59 77
214 76
0 0
4000 4000
-180900 -84000
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value); Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the e
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
M AN U
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
TE D
d
EP
207
AC C
a
A_041 Dark rim A_042 Bright rim A_043 Dark core A_045 Bright core A_046 Dark core A_047 Dark core A_048 Bright core A_049 Bright rim
207
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MK MK MK MK MK MK MK MK Not used
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas
SC
Sample
207
weighted mean 1110.77
uncertainty variance 6.68
22.57
MSWD 1.999
ACCEPTED MANUSCRIPT
Table A8 LA-ICP-MS U-Pb geochronological data for zircons from the Louisvale Granite, eastern Namaqua Sector MI3 RATIOS 207
Pb/235Ub 2.036 2.058 1.920 1.965 2.019 2.045 2.076 2.056 2.047 0.991 2.016 2.024 2.039 1.904
2 σd 0.068 0.070 0.088 0.061 0.065 0.087 0.081 0.067 0.076 0.031 0.072 0.072 0.085 0.140
Dates [Ma]
Pb/238Ub 0.193 0.192 0.176 0.184 0.190 0.192 0.195 0.192 0.192 0.092 0.188 0.190 0.190 0.175
2 σd 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.002 0.004 0.004 0.004 0.004
rhoc 0.67 0.65 0.48 0.70 0.68 0.51 0.56 0.67 0.60 0.70 0.61 0.62 0.53 0.30
-0.012 -0.031 -0.005
0.053 0.032 0.168
#VALUE! #VALUE! #VALUE!
2 σd
rhoc
0.65 0.65 0.65 0.65 0.65 0.47 0.65 0.65 0.64 0.64
0.0756 0.0757 0.0751 0.0775 0.0754 0.0746 0.0754 0.0744 0.0754 0.0751
0.68 0.68 0.68 0.67 0.67 0.66 0.67 0.67
0.0531 0.0538 0.0529 0.0537 0.0534 0.0529 0.0534 0.0532
206
207
Pb/206Pbe 0.0766 0.0779 0.0792 0.0776 0.0771 0.0774 0.0774 0.0779 0.0775 0.0782 0.0777 0.0773 0.0777 0.0787
2 σd 0.0019 0.0020 0.0032 0.0017 0.0018 0.0028 0.0025 0.0019 0.0023 0.0017 0.0022 0.0021 0.0027 0.0055
Not used A_0067-6 fractionation A_007 irregular signal A_0277-6 fractionation
0 0 0
0 0 0
0.00 #DIV/0! #DIV/0!
0.00 0.00 0.00
#VALUE! #VALUE! #VALUE!
0.0000 0.0000 0.0000
Reference materials
RATIOS Pb/235Ub
206
Pb/238U 1136 1131 1044 1087 1122 1130 1146 1130 1130 567 1112 1121 1124 1042
2σ 23 23 21 22 23 23 23 23 23 12 22 23 23 21
206
Pb/238Ub
A_016 A_017 A_018 A_021 A_022 A_023 A_034 A_035 A_051 A_052
78 78 78 79 78 80 77 78 77 77
14 14 14 14 14 14 14 14 14 14
0.29 0.29 0.29 0.30 0.29 0.29 0.29 0.29 0.31 0.31
1.856 1.866 1.868 1.910 1.885 1.852 1.888 1.840 1.871 1.873
0.063 0.063 0.064 0.065 0.064 0.097 0.064 0.063 0.065 0.065
0.1782 0.1788 0.1805 0.1788 0.1813 0.1801 0.1817 0.1794 0.1800 0.1809
0.0039 0.0040 0.0040 0.0040 0.0040 0.0044 0.0040 0.0040 0.0040 0.0040
PL PL PL PL PL PL PL PL
A_008 A_009 A_010 A_031 A_032 A_038 A_039 A_040
625 637 622 612 598 621 628 650
34 34 34 33 33 34 34 35
0.08 0.09 0.08 0.08 0.08 0.08 0.08 0.08
0.395 0.399 0.393 0.401 0.401 0.396 0.398 0.395
0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013
0.0539 0.0537 0.0539 0.0541 0.0545 0.0543 0.0542 0.0538
0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012
207
EP
91500 91500 91500 91500 91500 91500 91500 91500 91500 91500
0 0 0
#VALUE! #VALUE! #VALUE!
-79 -203 -30
344 214 1086
Pb/206Pbe
d
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
Pb/206Pb 1112 1143 1177 1137 1123 1133 1130 1143 1134 1151 1139 1128 1139 1165 0 0 0
2σ 49 51 79 44 46 72 64 48 59 43 55 55 69 135
% 102 99 89 96 100 100 101 99 100 49 98 99 99 89
4000 4000 4000
-78500 -203400 -29700
Conc.
Pb/235U
2σ
0.0019 0.0019 0.0020 0.0020 0.0019 0.0034 0.0020 0.0019 0.0020 0.0020
1066 1069 1070 1084 1076 1064 1077 1060 1071 1072
0.0013 0.0013 0.0012 0.0013 0.0013 0.0013 0.0013 0.0013
338 341 336 342 343 339 341 338
2 σd
207
Pb/238U
2σ
36 36 37 37 37 56 37 36 37 37
1057 1061 1070 1061 1074 1068 1076 1064 1067 1072
22 22 22 22 22 24 22 22 22 22
11 11 11 11 11 11 11 11
339 337 338 340 342 341 340 338
7 7 7 7 7 7 7 7
206
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
207
Dates [Ma]
2 σd
Analysis
TE D
207
Sample
AC C
a
U [ppm]a Pb [ppm]a Th/U meas
#VALUE! #VALUE! #VALUE!
Pb/235U 1127 1135 1088 1104 1122 1131 1141 1134 1131 699 1121 1123 1129 1082
M AN U
MI MI MI
Conc. 2σ 37 39 50 34 36 48 45 37 42 22 40 40 47 79
207
RI PT
MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas A_004 Dark rim 83 16 1.03 A_005 Bright core 91 17 1.08 A_011 Dark core 553 97 0.53 574 105 0.51 A_012 Bright core A_013 Bright core 134 26 1.04 A_014 Dark core 290 56 0.73 A_015 Bright rim 225 44 1.17 A_024 Bright core 148 28 0.91 A_025 Dark core 105 20 0.98 A_026 Dark core 1590 146 0.10 A_028 Bright core 176 33 1.29 A_029 Bright rim 90 17 0.80 A_030 Dark core 88 17 1.15 A_033 Bright core 86 15 0.29
SC
Sample
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
207
2σ
%
1083 1087 1070 1133 1079 1057 1078 1053 1079 1072
51 51 52 50 51 92 52 52 53 53
98 98 100 94 100 101 100 101 99 100
334 363 323 360 347 324 345 339
53 53 53 54 54 55 55 55
101 93 105 95 99 105 99 100
Pb/206Pb
weighted uncertainty variance mean 1124.5 15.79 176.25
MSWD
weighted uncertainty variance mean 1066.87 14.83 36.32
MSWD
339.33
7.6
2.31
1.084
1.111
1.143
ACCEPTED MANUSCRIPT
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Highlights • Voluminous syn- and late- to post-tectonic granitic magmatism in eastern Namaqua Sector • Older syn-tectonic granite gneisses, emplaced 1175-1146 Ma, are fractionated metaluminous to peraluminous leucogranites • Redefined Keimoes Suite comprises weakly foliated 1110-1078 Ma late- to post-tectonic megacrystic, ferroan metaluminous granodiorites and monzogranites • Model ages of both granitic groups reflect mixing of Meso- and Paleoproterozoic sources and reworking of Paleoproterozoic arc crust • Timing of emplacement of granites constrains peak D2 Namaquan deformation in region to ∼1.13-1.11 Ga
S1464-343X(17)30303-5
DOI:
10.1016/j.jafrearsci.2017.07.017
Reference:
AES 2969
To appear in:
Journal of African Earth Sciences
Received Date: 14 February 2017 Revised Date:
2 June 2017
Accepted Date: 17 July 2017
Please cite this article as: Bailie, R., Macey, P.H., Nethenzheni, S., Frei, D., le Roux, P., The Keimoes Suite redefined: The geochronological and geochemical characteristics of the ferroan granites of the eastern Namaqua Sector, Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa, Journal of African Earth Sciences (2017), doi: 10.1016/j.jafrearsci.2017.07.017. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
The Keimoes Suite redefined: The geochronological and geochemical
2
characteristics of the ferroan granites of the eastern Namaqua Sector,
3
Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa
4 Russell Bailie a, *, Paul Hugh Macey b, Sedzani Nethenzheni a, Dirk Frei a, c, Petrus le Roux d
6
a
Department of Earth Sciences, University of the Western Cape, South Africa
7
b
Council for Geoscience, Western Cape Regional Office, South Africa
8
c
Central Analytical Facility, Stellenbosch University, South Africa
9
d
Department of Geological Sciences, University of Cape Town, South Africa
*Corresponding author
11
E-mail address: [email protected]
SC
10
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5
12 ABSTRACT
14
Voluminous granite gneisses and granites straddle the boundary between the Kakamas and Areachap
15
Terranes in the eastern Namaqua Sector (NS) of the Mesoproterozoic Namaqua-Natal Metamorphic
16
Province (NNMP). These rocks have been previously poorly defined and loosely grouped into the
17
Keimoes Suite, but a recent U-Pb age study has suggested the suite be subdivided into syn-tectonic
18
and post-tectonic groups relative to the main phase of the Namaqua Orogeny. This study adds new
19
whole rock geochemical, isotopic and age data for these granites that confirms the subdivision is
20
appropriate. The older group of syn-tectonic granite gneisses, dated between 1175 and 1146 Ma, have
21
penetrative foliations and are largely derived from fractionated, leucogranitic metaluminous to
22
peraluminous magmas with low maficity, low Ti, Mn and Ca. They were derived from mildly
23
depleted sources (εNd(t): -1.47 to 1.78), with Meso- to Paleoproterozoic Nd model ages (1.57-1.91 Ga),
24
and high initial Sr ratios (0.71970-0.75567) suggesting mixing between younger depleted and older,
25
arc-like sources imparting an arc-like signature to the magmas. High initial Sr ratios appear to be an
26
intrinsic character of these granites reflecting those of granites in the region and the highly radiogenic
27
nature of the NS.
28
The weakly to unfoliated late- to post-tectonic megacrystic granodiorites and monzogranites,
29
including charnockites, intruded between 1110 and 1078 Ma and constitute the Keimoes Suite proper.
30
They have I-type characteristics, being strongly metaluminous and locally hornblende- and
31
orthopyroxene-bearing with moderate SiO2 and with arc-type affinities (LILE enrichment relative to
32
the HFSE, Ta-Nb, Ti and P anomalies). However, the granitoids also have high Fe/Mg ratios, along
33
with high HFSE, LILE and REE contents more indicative of A-type granites. They show an
34
increasing maficity, metaluminous character, and general decreasing degree of fractionation with
35
decreasing age. They are similar to the syn-tectonic granites in having εNd(t) values close to zero (-2.95
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1
ACCEPTED MANUSCRIPT to 2.83) and Meso- to Paleoproterozoic model ages (TDM: 1.38-1.99 Ga) but lower initial Sr ratios
37
(<0.723 in general) suggesting derivation from relatively depleted sources with a variable enriched
38
and/or crustal component.
39
The timing of emplacement of the syn-tectonic granites places peak D2 deformation in the eastern NS
40
predominantly at ∼1.16-1.15, varying from ∼1.18-1.13 Ga. There was more voluminous granitic
41
magmatism in the Areachap Terrane to the east during the late- to post-tectonic magmatic episode,
42
whereas the earlier, ∼1.18-1.14 Ga syn-tectonic magmatic episode is more concentrated to the west in
43
the Kakamas Terrane. The broad, protracted period of magmatism in the eastern NS attests to a long-
44
lived duration of high-heat flow in this portion of the southern African crust at this time. Nd model
45
ages of Meso- to Paleoproterozoic age reflect those in other granites throughout the NS suggesting
46
extensive reworking of Paleoproterozoic crust during the 1.2-1.0 Ga Namaquan Orogeny.
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36
47 Keywords:
49
Eastern Namaqua Sector; post-tectonic felsic magmatism; ferroan, metaluminous megacrystic
50
granitoids; variably enriched sources; mixed model ages
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48
51 52
1. Introduction
The Namaqua-Natal Metamorphic Province (NNMP) developed as a Mesoproterozoic mobile belt
54
along the southern and western margin of the Archean-Paleoproterozoic Kaapvaal Craton during the
55
Rodinian supercontinent assembly (Hartnady et al., 1985; Cornell et al., 2006; Li et al., 2008, Fig. 1).
56
The Namaqua Sector (NS), forming the western portion of the NNMP, is dominated by granitic
57
gneisses and granites aged between ~1.3 and 1.0 Ga (e.g. Eglington, 2006 and references therein;
58
Bailie et al., 2011a; Cornell et al., 2012; Bial et al., 2015a; Colliston et al., 2015; Macey et al., 2015).
59
The granitic melts intruded almost continuously over this period but the most significant and
60
voluminous magmatic events occurred during several pulses linked to specific tectono-metamorphic
61
episodes and associated with major developing structures. The timing and location of these major
62
intrusive events varies across the NS and reflect the shift in the tectonic and thermal axis during the
63
long duration, high-T, low-P Namaqua Orogeny (Eglington, 2006; Miller, 2012). Clearly an
64
understanding of the characteristics, age and source of the various granite suites and the tectonics
65
controlling their emplacement is critical to unravelling the complex evolution of the NS and its heat
66
source.
67
The granites, granodiorites and charnockites of the Keimoes Suite intruded the eastern parts of the NS
68
of the NNMP (Fig. 1). A suite is defined as an assemblage of temporally and spatially related
69
magmatic rocks having chemical, mineralogical and textural features or characteristics that together
70
exhibit a continuous variation from one extremity to the other (Bates and Jackson, 1987). The original
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2
ACCEPTED MANUSCRIPT definition of the Keimoes Suite (SACS, 1980) was done before systematic regional mapping and, as
72
acknowledged by the authors, was loosely defined as a collection of intrusive rocks in the Keimoes-
73
Kakamas area, possibly not belonging to a single intrusive rock series and therefore subject to
74
redefinition and reclassification. It was differentiated from the older basement granites of the
75
Kaapvaal Craton to the east and an augen gneiss-dominated domain to the west based on the apparent
76
lack or weakness of the penetrative gneissic foliation (disregarding the localised shear zones). Several
77
refinements of the original definition have been proposed following geological surveys (e.g. Moen,
78
1988, 2007; Slabbert, 1998; Slabbert et al., 1999) and geochemical studies (Geringer et al. 1988) of
79
which the subdivision of Moen (2007) is most widely accepted. More recently, Cornell et al. (2012)
80
proposed subdividing the Keimoes Suite (sensu Moen, 2007) on the basis of new U-Pb ages
81
(Pettersson, 2008; Bailie et al., 2011a; Cornell et al., 2012) and intensity of gneissic fabric into an
82
older syn-tectonic group of foliated rocks (1203 to 1146 Ga), which they term the Augrabies Suite,
83
and a post-tectonic group of granites and charnockites (1113 to 1078 Ga) which remain in the
84
Keimoes Suite.
85
In light of the issues associated with this poorly defined suite, this study contributes new age, whole
86
rock major, trace, rare earth element (REE) geochemical and isotope data combined with a review of
87
the existing map information (intensity of regional gneissic foliation, texture, mineralogy and
88
distribution of granitoids) which can be used to further characterise these granites, their age of
89
emplacement relative to the main tectonothermal events of the eastern Namaqua Sector, as well as the
90
source characteristics. The main objective is to test whether the subdivision of these granitoids into
91
two suites relative to the main Namaquan deformation event, as proposed by Cornell et al. (2012), is
92
valid. The age of emplacement, whole rock geochemical and isotopic characteristics can also
93
contribute to a greater understanding of the role of voluminous granitic magmatism in not only the
94
eastern Namaqua Sector but also throughout the NNMP during the 1.2-1.0 Ga Namaquan Orogeny.
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2. Geological Setting
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97
The granites of the Keimoes Suite intrude the Kakamas and Areachap Terranes in the eastern parts of
98
the NS of the NNMP. The NS covers an area of over 100 000 km2 in the lower Orange River region
99
of the Northern Cape Province of South Africa and the Karas Region of southern Namibia (Hartnady
100
et al., 1985; Cornell et al., 2006; Fig. 1) and consists of Paleoproterozoic (~2.05-1.83 Ga) and
101
Mesoproterozoic (~1.3-1.0 Ga) igneous and metamorphic rocks that were deformed during various
102
phases of the low-P - high T ∼1.2-1.0 Ga Namaquan Orogeny (e.g. Cornell et al., 2006; Eglington,
103
2006; Bial et al., 2015a, b; Thomas et al., 2016; Macey et al., 2017). The NS is subdivided into five
104
terranes/domains defined by differences in lithostratigraphy, radiometric ages, structural trends and
105
intensities and metamorphic histories (e.g. Hartnady et al., 1985; Joubert, 1986; Cornell et al., 2006;
3
ACCEPTED MANUSCRIPT Eglington, 2006; Miller, 2008, 2012; Thomas et al., 2016; Macey et al., 2017; Fig. 1). The tectonic
107
domains are separated by major structural discontinuities and were juxtaposed during several regional
108
thrusting events.
109
The Richtersveld Subprovince forms the westernmost tectonic domain and consists of belts of calc-
110
alkaline, arc-derived volcanic rocks intruded by coeval granodiorite-dominated plutonites at ca. 2.02
111
Ga and ca. 1.88 Ga, respectively. The eastern parts of the subprovince were strongly deformed under
112
amphibolite-facies conditions during the Mesoproterozoic Namaquan Orogeny associated with minor
113
~1.2 Ga granite, leucogranite and gabbroic intrusions (Reid, 1997; Thomas et al., 2016; Macey et al.,
114
2017). The Bushmanland Subprovince is more complex with ∼1.85 Ga granitic gneisses and
115
migmatites dominating the northern parts, whereas in the south belts of high-grade supracrustal
116
gneisses of various ages (∼1.60-1.15 Ga) occur as rafts within voluminous intrusions of pre- to syn-
117
tectonic ~1.20-1.12 Ga granitic augen gneisses and quartzo-feldspathic gneisses and 1.10-1.035 Ga
118
late- to post-tectonic granites (e.g. Robb et al., 1999; Clifford et al., 2004; Eglington, 2006; McClung,
119
2006; Bailie et al., 2007). The Kaaien Terrane is the easternmost tectonic domain of the NS
120
representing a tectonic transition zone between the Kaapvaal Craton and Kheis Province and the NS
121
and is composed of ∼1.77 Ga metaquartzites, ∼1.37 and 1.17-1.10 Ga bimodal volcano-sedimentary
122
rocks and 1.10 Ga granitic intrusions (Van Niekerk, 2006; Bailie et al., 2011a, 2012).
123
The Kakamas Terrane (Fig. 1) is dominated by late Mesoproterozoic granulite-facies meta-
124
sedimentary rocks (~1220-1150 Ma) intruded by various 1.21-1.08 Ga granites, anatectic
125
leucogranites and minor gabbroic rocks (Pettersson et al., 2009; Bial et al., 2015a, b, 2016; Macey et
126
al., 2017). The Kakamas Terrane is regarded as a low-angle imbricate mega-nappe stack separated
127
from the Bushmanland and Richtersveld Subprovinces by major thrust structures (Onseepkans,
128
Hartebeest, Lower Fish River, Kerelbad thrusts; e.g. Praekelt, 1984; Colliston et al., 2015; Macey et
129
al., 2017).
130
The Areachap Terrane, to the east thereof (Fig. 1), is marked by numerous younger Nd model ages, of
131
Mesoproterozoic age (Pettersson et al., 2009) suggesting a juvenile component compared to the
132
dominant Paleoproterozoic model ages in the Bushmanland Subprovince to the west (Yuhara et al.
133
2002, Reid, 1997; Macey et al., 2017). The NW-trending Areachap Terrane is dominated by 1.30-1.22
134
Ga volcaniclastic, volcanic and sedimentary rocks (Areachap Group) representing a metamorphosed
135
juvenile Mesoproterozoic volcanic arc succession (Geringer et al., 1986, 1994; Cornell et al., 1990;
136
Pettersson et al., 2007; Cornell and Pettersson, 2007; Bailie et al., 2010) that was intruded by younger
137
∼1.20 to ∼1.10 Ga granitoids (Pettersson et al., 2007; Bailie et al., 2011a; Cornell et al., 2012). The
138
eastern boundary of the terrane is marked by the Trooilapspan shear zone (TLSZ) and the Brakbosch
139
fault (Fig. 1), whereas the boundary with the Kakamas Terrane is considered to be the Boven Rugzeer
140
Shear Zone (BRSZ) (Fig. 1). The Areachap Group was subjected to upper amphibolite facies
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142
of the Areachap Terrane, in particular, is characterised by a greater dominance of Paleoproterozoic
143
model ages (Geringer et al., 1986; Pettersson et al., 2007; Cornell and Pettersson, 2007) suggesting
144
that an older crustal component was present in the magmatic arc(s) which gave rise to the Areachap
145
Group (Pettersson et al., 2009).
146
The eastern Namaqua Sector was subjected to extensive polyphase low pressure, high temperature
147
metamorphism and deformation during the ∼1.2-1.0 Ga Namaquan Orogeny with four main high
148
grade deformation events recognized in the Kakamas and Areachap Terranes (Cornell et al., 1992,
149
2006; Pettersson et al., 2007; Bailie et al., 2011a; Bachmann et al., 2015). Intense fold and thrust
150
tectonics during the D2 deformation gave rise to large scale tight to isoclinal sub-vertical NW-trending
151
F2 folds and the regional penetrative foliation (e.g. Praekelt, 1984; Macey et al., 2015). Peak
152
metamorphic grade varies from lower granulite facies in the Kakamas Terrane to upper amphibolite
153
facies in the Areachap Terrane diminishing eastward to greenschist facies into the Kaaien Terrane
154
(Stowe, 1983; Cornell et al., 1992, 2006; Bial et al., 2015b, 2016). The main deformation and
155
metamorphism appears to have occurred over a protracted period dated between ~1.20 and 1.15 Ga
156
(Pettersson et al., 2007; Miller, 2012; Bachmann et al., 2015; Bial et al., 2015b). Subsequent D3
157
deformation, associated with M3 metamorphism gave rise to open east-west trending F3 folds at
158
amphibolite facies conditions (∼640oC and 4.8 kbar; Cornell et al., 1992) and was associated with
159
magmatism at around 1.10 Ga (Pettersson et al., 2007; Bailie et al., 2011a). D4 deformation involved
160
later reactivation and dextral strike-slip faulting along major regional shear zones and faults, including
161
the BRSZ, TLSZ, and Brakbosch shear zones (Geringer et al., 1994).Whilst many of the shear zones
162
are likely to have formed during D2 fold and thrust tectonics, they show evidence for extensive
163
reactivation, retrograde M4 metamorphism and vertical and lateral movement (e.g. van Bever Donker,
164
1980, 1991), with many showing a dextral shear sense, e.g. the BRSZ (van Bever Donker, 1991;
165
Miller, 2012), TLSZ and Brakbosch shear zones (Moen, 1999).
166
Regional lithological mapping by the geological survey of South Africa (Moen, 2007; Slabbert, 1998;
167
Slabbert et al., 1999) identified 29 biotite, biotite-hornblende and orthopyroxene-bearing granitoid
168
units in the Upington-Kakamas-Kenhardt region considered to constitute the Keimoes Suite. The
169
subdivision included two subsuites (further subdivided into 7 lithodemes) and was based on the
170
distribution, composition, texture and structural fabric of individual granite bodies (Geringer et al.,
171
1988; Stowe, 1983). Moen (2007) excluded the gabbroic members previously included in the
172
Keimoes Suite and limited it to the granitic units distributed between the Brakbosch fault and
173
Neusspruit-Wolf Kop shear zone (Fig. 1). Moen (2007) suggested a subdivision into syn-tectonic and
174
late-tectonic granites but cautioned that strain intensity is not only dependent on age relative to
175
deformation but the size and mineral composition of the granite.
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177
range from ~1264 to 1020 Ma with some granites giving widely different ages and thus early
178
geochronology (e.g. Geringer and Botha, 1977; Linstrom, 1977; Smit, 1977; Barton and Burger, 1983;
179
Jankowitz, 1987; summarised in Geringer et al. (1988) and Moen (2007)) did not really help to
180
subdivide or determine relative timing of emplacement and the role of the Keimoes Suite in the
181
tectonothermal evolution of the eastern NS. Recent U-Pb zircon dating yielded a range of ages for the
182
Keimoes Suite (as defined by Moen, 2007) between 1.2 and 1.08 Ga (Pettersson, 2008; Bailie et al.,
183
2011a; Cornell et al., 2012).
184
Based on these new ages, Cornell et al. (2012) suggest the Keimoes Suite be subdivided into an older
185
1.2-1.15 Ga syn-tectonic group, and a younger 1.11-1.08 Ga late- to post-tectonic suite, named the
186
Augrabies and Keimoes Suite, respectively. Cornell et al. (2012) proposed grouping the syn-tectonic
187
Vaalputs Granite (1146 ± 14 Ma), formerly included in the Keimoes Suite of Moen (2007), with the
188
similarly-aged Riemvasmaak augen gneiss dated at 1156 ± 8 Ma and 1151 ± 14 Ma (Pettersson,
189
2008). The Augrabies Gneiss, which occurs in close association with the Riemvasmaak Gneiss, has
190
been dated at 1168 ± 6 Ma (Colliston et al., 2015) and presumably would also fall into the Augrabies
191
Suite of Cornell et al. (2012).
192 193
3. Methodology
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Fourteen plutons were sampled during the course of this study. Typically five geochemical samples
195
per pluton were collected depending on the size and accessibility of the outcrops and exposed pluton.
196
Petrographic thin section and geochemical sample preparation were undertaken at the Department of
197
Earth Sciences, University of the Western Cape (UWC), Bellville, South Africa and at the Council for
198
Geoscience (CGS), Pretoria, South Africa. Fifty-four samples were analysed for trace elements,
199
including the rare earth elements (REE), by Inductively Coupled Plasma - Mass Spectrometry (ICP-
200
MS) analysis at the Central Analytical Facility (CAF), Stellenbosch University, with major element
201
contents determined by X-ray fluorescent (XRF) spectrometry at the CGS. Rb-Sr and Sm-Nd isotope
202
analysis was undertaken at the Department of Geological Sciences, University of Cape Town. U-Pb
203
age data were obtained at CAF, Stellenbosch University by laser ablation - single collector - magnetic
204
sector field - inductively coupled plasma - mass spectrometry (LA-SF-ICP-MS). Details of the
205
analytical techniques are given in the Appendix.
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4. Lithological Description
208
The medium- to coarse-grained porphyritic monzogranites, granodiorites and charnockites of the
209
Keimoes Suite (sensu Moen, 2007) intrude the Kakamas and Areachap terranes in the eastern NS of
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211
Rugzeer Shear Zone (BRSZ) which separates the terranes, diminishing in volume and aerial extent
212
both eastward and westward (Fig. 1). The two most voluminous members of the suite, the Vaalputs
213
Granite and Friersdale Charnockite are concentrated along the BRSZ.
214
Moen (1988; 2007), Slabbert (1998), Slabbert et al. (1999); Geringer et al. (1988); Bailie et al.
215
(2011a) and Cornell et al. (2012) provide detailed descriptions of the various members of the Keimoes
216
Suite and these, along with the observations of the 14 plutons studied during this study, are
217
summarized in Table 1.
218
The outcrop extents of the granites vary from small, isolated outcrops, to large, voluminous plutons.
219
Various granites, such as the Colston Granite, comprise two or more members which differ in terms
220
of mineral abundances, colour and texture. The Cnydas Subsuite is a genetically coherent group of
221
syn-tectonic, epizonal granitoids (Fig. 1; Jankowitz, 1987; Moen, 2007; Bailie et al., 2011a). The
222
Kleinbegin Subsuite refers to numerous outcrops of granite that intrude to the west of the Brakbosch
223
fault and is not a genetic grouping as such (Moen, 2007).
224
The Keimoes Suite (sensu Moen, 2007) is characterised by medium- to coarse-grained porphyritic
225
biotite granites varying from monzogranites to granodiorites. K-feldspar (Kfs) is typically more
226
abundant than plagioclase, with biotite being the dominant mafic mineral in most cases (10-15%
227
typically), which helps define a foliation, where developed. Rounded phenocrysts of Kfs are present
228
in some granites, but elsewhere, and more typically, randomly oriented euhedral-subhedral Kfs
229
phenocrysts are present. These vary in abundance from abundant to sparsely distributed. Some
230
younger granites, as defined by poorly developed to unfoliated characteristics, are non-porphyritic.
231
Hornblende is present in some cases (e.g. the Straussburg Granite). Muscovite is present in minor
232
amounts (6% and less) and is more prevalent in those granites which are cross-cut by, or have been
233
subjected to shearing, particularly the Vaalputs and Louisvale granites. Some granites contain
234
pyroxene in variable amounts thus forming charnockites. The most notable are the voluminous,
235
unfoliated Friersdale Charnockite and the Gous Charnockite, a member of the Cyndas Subsuite,
236
exposed in the far northern extent of the eastern NS granites. Both orthopyroxene and clinopyroxene,
237
in the form of augite, are present in these rocks. Garnet is sporadically present in some granites.
238
The granites exhibit variable degrees of foliation development. Foliation can also intensify toward the
239
margins of the pluton or exhibit a magmatic flow structure. As such, some of the foliation, particularly
240
along the margins, may be of magmatic origin rather than tectonic. Where developed the foliation is
241
defined by the mafic minerals, notably biotite, along with muscovite, which envelope or wrap around
242
glomeroporphyritic clusters of the felsic minerals, notably the feldspars (variable amounts of
243
plagioclase, microcline, perthite and orthoclase) as well as quartz, which also occurs in the
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proximity to major crosscutting transcurrent shear zones.
246
Most of the granites contain numerous inclusions, with xenoliths largely reflecting the composition of
247
the intruded country rock. Inclusions also tend to be largely both mafic and leucocratic, with the
248
former typically biotite-rich to amphibolitic. Some granites, however, also contain inclusions of
249
tonalitic composition which are likely magmatic enclaves compositionally related to the host granite
250
representing relics of an earlier magma (e.g. Geringer et al., 1987). Crosscutting granitic and
251
pegmatitic veins are common features. Certain granites, such as the Friersdale Charnockite, crosscut
252
other granites as dykes.
253
Moen (2007) included the Josling Granite within the Keimoes Suite, although, based on an age of
254
1275 ± 7 Ma by Pettersson (2008), acknowledged that it likely does not form part of the Keimoes
255
Suite. The Josling Granite is characterised by a well-developed gneissic fabric, which contrasts with
256
the largely weakly foliated to unfoliated nature of many of the Keimoes Suite granitoids.
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5. Geochronology
The results of the eight granite samples dated during the course of this study are described
260
alphabetically and are summarised in Table 2. Age data from previous studies (Pettersson, 2008;
261
Bailie et al., 2011a; Cornell et al., 2012) are summarized separately below the new age data. The
262
tabulated analytical data may be found in Appendix Tables A1-A8. The uncertainties are expressed as
263
s (sample standard deviation) as opposed to σ, following the recommendations of Horstwood et al.
264
(2016), since only a representative sample of the entire population was taken. Given that the
265
206
266
ratios are used. Weighted mean ages are calculated, with 2% added to the uncertainty in quadrature to
267
account for systematic uncertainty following the recommendations of Hortwood et al. (2016) and
268
Spencer et al. (2016). All data with greater than 10% discordance is not considered in determining the
269
weighted mean age of the sample following a general recommendation by Gehrels et al. (2008).
270
Analyses which show a clear inherited component, as determined from CL imaging and their age, e.g.
271
spots Me1-12 and 13 of the Elsie se Gorra Granite (sample Me1 – Table A3) are also not included in
272
the weighted mean age.
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273 274
5.1. Cnydas Subsuite – Smalvisch Granite
275
Most of the euhedral to subhedral zircons (100 - 250 µm; Fig. 2a) exhibit oscillatory zoning with
276
relatively bright cores. All 24 zircons analysed provided concordant data (99-102%; Table A1) with
277
overlapping core and rim ages and no evidence for older inheritance. These data provide a weighted
8
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mean U-Pb age of 1159 ± 28 Ma which is considered to be the crystallisation age of this granite (Fig.
279
3a).
280 281
5.2. Colston Granite The zircons from the Colston Granite are mostly elongate, ranging in size from 100 to 250 µm (Fig.
283
2b). Most of the larger (>150 µm) euhedral grains have bright cores and show oscillatory zoning, with
284
the smaller zircons (<100 µm) having mostly dark cores. Twenty five spots were analysed (Table A2).
285
The upper intercept age of 1161 ± 16 Ma obtained from all 25 spots is within error of the weighted
286
mean U-Pb age of 1151 ± 28 Ma (Fig. 3b). The latter is taken as the timing of intrusion of the granite.
287
Core and rim ages cannot be distinguished and no zircon inheritance or metamorphic overprinting
288
ages are evident in the data.
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The zircon grains in the Elsie se Gorra Granite range in size from 100 µm to 200 µm (Fig. 2c). Of the
292
21 spots analysed only twelve were less than 10% discordant (Table A3). Of these, a dark, weakly
293
zoned core yielded 206Pb/238U inheritance ages of 1335 ± 35 and 1344 ± 35 Ma (Fig. 2c). The
294
remainder provide a weighted mean U-Pb age of 1175 ± 18 Ma which is considered to be the
295
crystallisation age (Fig. 3c; Table 2). Some cores are discordant having ages of > 1075 Ma possibly
296
reflecting metamorphism.
297 5.4. Josling Granite
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The zircons examined during this study are mostly prismatic (50 - 150 µm). Mostly bright oscillatory
300
zoned cores yield mostly concordant ages, whereas dark weakly zoned to unzoned rims are generally
301
characterised by high U contents (411 - 582 ppm) yielding mostly discordant ages (Fig. 2d). Of the 23
302
spots analysed only 12 yielded concordant data with the rest highly discordant (<61% concordant;
303
Table A4). The remaining concordant data from 12 zircons have a weighted mean U-Pb granite
304
crystallization age of 1217 ± 20 Ma (Fig. 3d), within error of the upper intercept age of 1222 ± 16 Ma.
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5.5. Kanoneiland Granite
307
The zircons of the Kanoneiland Granite are dark, mostly unzoned and form subhedral to anhedral
308
grains 100 - 200 µm in size with moderately to well zoned cores (Fig. 2e). Twenty-two concordant
309
(98-101%; Table A5) analyses provide a weighted mean U-Pb age of 1098 ± 26 Ma which is regarded
310
as the crystallisation age (Fig. 3e). No inherited or metamorphic zircons were found. 9
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5.6. Keboes Granite The zircons of this granite exhibit oscillatory zoning with bright cores and dark rims and range in size
314
from 80 - 250 µm in size (Fig. 2f). Twenty-five spots were analysed, of which only one spot (spot 16
315
– Table A6) is strongly discordant. One concordant analysis (spot 3 – Table A6) of a dark, strongly
316
oscillatory zoned inherited zircon core provides a 206Pb/238U age of 1346 ± 35 Ma. The remaining 23
317
spots provide a weighted mean U-Pb age of 1105 ± 27 Ma (Fig. 3f) within error of the upper intercept
318
age of 1111 ± 10 Ma. The former is taken as the crystallisation age of the Keboes Granite. No
319
metamorphic ages were obtained from the zircons.
321
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5.7. Klipkraal Granite
The zircons from the Klipkraal Granite are mostly subhedral, elongated sector zoned grains (80 µm to
323
150 µm, Fig. 2g). Only 8 spots were analyzed which yield only discordant data (≤90% concordant;
324
Table A7) from which an upper intercept age of 1270 ± 26 Ma (Fig. 3g) was determined. Since the
325
Klipkraal Granite is only weakly deformed and is unlikely to be older than 1.2 Ga this age is regarded
326
as representing inheritance from the Jannelsepan Formation (Areachap Group) country rocks into
327
which the Klipkraal Granite intrudes (Fig. 2) and which has an extrusion age of 1275 ± 7 Ma (Cornell
328
and Pettersson, 2007; Table 2). A weighted mean U-Pb age from two grains with 90% concordance
329
yields an age of ∼1111 Ma. The Klipkraal Granite is considered to be post-tectonic given its weakly
330
deformed nature and likely to have an age of ∼1110 Ma. This granite requires dating again in order to
331
determine its age of emplacement.
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Zircons of this granite range in size from 100 µm to 200 µm, with most having bright, well zoned
335
cores. The rest have dark, moderately to poorly zoned cores (Fig. 2h). Fourteen spots were analysed
336
(Table A8), of which one (spot 26) was badly discordant, and two (spots 11 and 33) each have 89%
337
concordance. The remaining 11 spots provide a weighted mean U-Pb age of 1125 ± 16 Ma which is
338
taken to be the crystallisation age of this granite (Fig. 3h). This is within error of the upper intercept
339
age of 1134 ± 16 Ma of a line fitted through all of the data. There are no inherited ages for this
340
granite.
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5. Geochemistry 5.1. Whole rock major, trace element (TE) and rare earth element (REE) geochemistry 10
ACCEPTED MANUSCRIPT The geochemistry of 54 samples analysed during this project are presented in Tables 3 and 4 as well
345
as Figures 5 to 8 along with fields, in Fig. 5, representing the datasets of Jankowitz (1987) (Cyndas
346
Subsuite – Figs. 4a, b, 5) and Geringer et al. (1988) (Keimoes Suite - Fig. 4a) along with the
347
geochemistry of the Riemvasmaak Gneiss (Geringer, 1973; Saad, 1987) (Figs. 4a, b, 5). In the
348
following section, the data are described for the Keimoes Suite (sensu Moen, 2007) as a whole and as
349
comparisons between the syn-tectonic and post-tectonic granitoid groups (sensu Cornell et al., 2012).
350
The Josling Granite, clearly older than the Keimoes Suite, is included for completeness.
351
The Keimoes Suite granitoids classify mostly as monzogranite and, to a lesser degree, granodiorite on
352
the normative modal Q-A-P Streckeisen (1976) diagram (Fig. 4a). The granites are predominantly
353
ferroan (Fig. 4d), potassic and metaluminous (Fig. 4f). Most of the granites combine to define
354
coherent major element trends on the Harker plots with negative correlations between SiO2 and TiO2,
355
FeO(t), MgO, CaO, MnO and P2O5 (Fig. 5; the last not shown), and weakly positive correlations for
356
Na2O and K2O; Al2O3 does not show a definitive trend (Fig. 5). There are also broadly negative
357
correlations of SiO2 with V, Sc, Co, Zr and Hf.
358
Plots of maficity (defined as moles of Fe and Mg per 100 g of rock or magma – Clemens et al., 2011)
359
against other major and trace elemental concentrations (after Clemens et al., 2011; Clemens and
360
Stevens, 2012) do not define any significant differences in terms of both the major or trace elements
361
between the older ∼1.18-1.15 Ga syn-tectonic granites and the younger ∼1.11-1.08 Ga late- to post-
362
tectonic granites (Fig. 6). Maficity is used rather than traditional indices such as wt.% SiO2 as it is far
363
easier to relate mineralogical and chemical influences on magma composition, and hence potential
364
source differences (Clemens et al., 2011). It relates to the concentration of mafic minerals in the
365
granitic magma, with higher maficities implying a greater mafic mineral content. Such plots (Fig. 6)
366
indicate strong positive correlations between maficity and Ti, Fe, Mg, Mn, Zr and Hf, and less well
367
defined positive trends for Ca, P, and Eu. Na and K define fairly flat, to slightly negative trends
368
against maficity, with Al displaying a flat trend. The large ion lithophile (LIL) elements (Rb and Sr)
369
show flat trends, with Ba showing a very poorly define weakly positive slope.
370
With few exceptions, the trace elements show consistent saw-tooth trace element patterns on primitive
371
mantle-normalised (McDonough et al., 1992) spider diagrams (Fig. 7) with enrichment of Th, U and
372
Pb, and the large ion lithophile elements (LILE) over the high field strength elements (HFSE), and
373
depletions in Cs, Ba, Sr, P, Eu and Ti. All the granites show a prominent negative Nb-Ta ‘trough’
374
usually taken to indicate a subduction-related or crustal signature. The chondrite-normalised
375
(McDonough and Sun, 1995) REE plots are also mostly consistent, with moderate to strong light REE
376
enrichment (Fig. 7; (La/Lu)N: 3.6-20.9). The pattern is concave up with moderate fractionation in the
377
LREE [(La/Sm)N = 2.17-6.28] and moderately flat HREE traces [(Gd/Lu)N = 0.92-2.45]. For almost
378
all the granites Eu shows relatively moderate to strongly negative anomalies [(Eu/Eu*)N = 0.19-0.76]
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380
4-7) having anomalous concentrations in most of the major and trace elements (Figs. 5 to 7), distinctly
381
low concentration REE patterns and positive Eu anomalies and probably should be excluded from the
382
suite. The samples from the Kleinbegin Subsuite have low K2O and higher CaO (Figs. 5, 6) than the
383
remainder of the suite whereas the Elsie se Gorra leucogranite and Keboes Granite show distinctive
384
low maficities (Fig. 6), TE and REE patterns on the trace element spider and REE plots (Fig. 7). The
385
high MgO values for the Cyndas Subsuite in the Jankowitz dataset (Fig. 5) is likely due to analytical
386
error.
387
When comparing the geochemistry of the syn- and post-tectonic granites (sensu Cornell et al., 2012),
388
there is significant overlap in major and trace element compositions with general consistencies in
389
elemental trends, enrichments and depletions. The main distinguishing factors are that the syn-
390
tectonic intrusive rocks are generally more felsic (SiO2 mostly between ~69 and 78 wt.%; Colston
391
Granite is the main exception) and are mildly metaluminous to peraluminous as opposed to the post-
392
tectonic group being strongly metaluminous and having SiO2 values between 60 and ∼70 wt.%. The
393
post-tectonic group has a higher overall, and a narrower range of REE and trace element
394
concentrations relative to the syn-tectonic group (Fig. 7; Tables 3, 4).
395
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5.2. Radiogenic isotope geochemistry
397
The Sr-Nd isotopic data for the granites is given in Table 5 and shown in Fig. 8. Sm/Nd ratios vary
398
between 0.14 and 0.22, but are mostly between 0.18 and 0.21. Initial 143Nd/144Nd ratios vary between
399
0.51107 and 0.51136. Excluding the pre-tectonic ∼1.22 Ga Josling Granite, the εNd(t) values of the
400
granites are close to 0, varying from -2.95 to +2.83 (with a much lower value of -7.51 for the
401
Kleinbegin Granite) (Table 5). Sm-Nd model ages (TDM) vary from Meso- to Paleoproterozoic (TDM =
402
1.38 – 1.99 Ga), apart from older, >2.3 Ga model ages for the Kleinbegin Granite (Fig. 8c; Table 5).
403
Rb/Sr ratios are highly variable, ranging from 0.18 to 5.26, but mostly range between 0.59 and 1.63.
404
Initial Sr ratios [(87Sr/86Sr)I] range between 0.70630 and 0.77130 (Fig. 8a).
405
When comparing the isotopic geochemistry of the syn- and post-tectonic granites (sensu Cornell et al.,
406
2012) both have similar initial Nd ratios, with the syn-tectonic granites having a slightly narrower
407
range (0.51107-0.51128) compared to those of the post-tectonic group (0.51083-0.51136). The model
408
ages of both age groups are essentially the same (Table 5). The syn-tectonic group shows a wider
409
variability in terms of Rb/Sr ratio (0.18 to 5.26) compared to the post-tectonic group (Rb/Sr = 0.24-
410
1.63). Apart from the Keboes Granite, the syn-tectonic granites have higher initial Sr ratios, in general
411
(>0.720), compared to the post-tectonic group (Fig. 8a; Table 5).
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ACCEPTED MANUSCRIPT 6. Discussion
414
6.1. Recommendations for a new stratigraphy for the granitoids of the eastern Namaqua Sector
415
The Keimoes Suite (sensu Moen, 1988, 2007) yielded a wide range of modern U-Pb ages
416
between1275 Ma and 1078 Ma (Pettersson, 2008; Bailie et al., 2011a; Cornell et al., 2012; this study).
417
Based on new age and geochemical data we recommend excluding the much older Josling Granite
418
from the Keimoes Suite. The intrusive rocks can be subdivided on the basis of the intensity of the
419
gneissic fabric (as described by Moen, 2007). The granitoids having moderate to strong penetrative
420
gneissic fabrics (syn-tectonic) have ages between ~1175 and 1125 Ma, whereas the weakly deformed
421
granites and charnockites (late- to post-tectonic) intruded between ~1110 and 1078 Ma. On the basis
422
of age and strain intensity alone, the new age data presented in this paper are in agreement with the
423
subdivision proposed by Cornell et al. (2012). Foliation intensity is, however, not a reliable guide to
424
time of emplacement as various factors may influence this, such as size of the pluton, method of
425
emplacement, extent of magma flow, and the presence or absence of a persisting or waning regional
426
stress field amongst other factors (e.g. Paterson and Tobisch, 1988).
427
Based on its age and geochemistry we recommend excluding the more tonalitic Louisvale Granite
428
from the Keimoes Suite and renaming it the Louisvale Tonalite or Louisvale Gneiss. In agreement
429
with Cornell et al. (2012), we also recommend excluding the pre- to syn-tectonic granites previously
430
included in the Keimoes Suite, restricting it to the post-tectonic granites and charnockites. The newly
431
defined Keimoes Suite is therefore limited to unfoliated ferroan, metaluminous, largely feldspar
432
porphyritic, biotite ± hornblende ± orthopyroxene granites and charnockites with a restricted age of
433
between 1110 and 1078 Ma (Fig. 9) and confined spatially to between the Neusspruit shear zone and
434
Brakbosch fault (Moen, 2007; Fig. 1; Table 6). In this definition, most of the Keimoes Suite granites
435
are situated within the Areachap Terrane, and only the Friersdale Charnockite within the Kakamas
436
Terrane. Slabbert et al. (1999) recognised a number of small, isolated plutons to the south of
437
Kleinbegin that are thought to be associated with or part of the Keimoes Suite. These were not
438
examined as part of this study and require further work in the form of whole rock major, minor, trace
439
element and isotope geochemistry as well as single zircon U-Pb dating in order to clarify their age and
440
association in the eastern NS.
441
Cornell et al. (2012) also proposed grouping the foliated granites (pre- to syn-tectonic Elsie se Gorra,
442
Vaalputs and Colston Granites) with the augen gneisses (Riemvasmaak and Augrabies gneisses) in the
443
“Augrabies Suite”. Based on our new data, we confirm that the grouping of granitic and leucogranitic
444
gneisses aged between 1175 and 1146 Ma may be valid but the term “Augrabies” is already used for
445
the Augrabies Gneiss (Moen, 1988, 2007) and cannot be used for the suite name. Whilst we support
446
the possibility of grouping the pre- and syn-tectonic granite orthogneisses, the paucity of modern
447
geochemical data for these rocks makes it difficult to demonstrate they are co-genetic and therefore
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449
additional work has been completed. We also suggest renaming the Elsie se Gorra and Vaalputs
450
Granites as “gneisses”.
451
The spatially restricted Cyndas Subsuite represent a series of granitoid types (monzogranites to
452
granodiorites) and a range of ages and composition from syn- to post-tectonic times (Jankowitz,
453
1987). As such it constitutes its own separate suite and should possibly be upgraded from a subsuite
454
of the Keimoes Suite, as previously defined (Moen, 2007), to its own separate suite. This study only
455
sampled the Smalvisch Granite of this subsuite and so cannot draw any interpretations or conclusions
456
based on the very limited data. The subsuite requires more extensive research, whole rock
457
geochemical analysis of all the different granites, and more intensive modern U-Pb zircon
458
geochronology than currently available from the work of Jankowitz (1987).
459
The generally unfoliated Colston Granite has an age of 1151 ± 28 Ma (this study) and thus is grouped
460
with the syn-tectonic granites. A similar thermal ionization mass spectrometer (TIMS) zircon age of
461
1156 ± 20 Ma was reported in the summary of Bailie et al. (2011a). Its unfoliated nature may be due
462
to its composition or mode of emplacement. Foliation intensity increases near the pluton margins
463
(Moen, 2007), a feature which does correlate with a syn-tectonic timing of emplacement (Paterson
464
and Tobisch, 1988).
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6.2. General textural, mineralogical and geochemical characteristics of the syn-tectonic granitic
467
gneisses
468
The well-foliated syn-tectonic Elsie se Gorra and Vaalputs granitoids are mostly medium-grained and
469
equigranular, locally with scattered rounded feldspar megacrysts. These grey coloured leucogneisses
470
are dominated by feldspar and quartz with only minor biotite and rare muscovite (Moen, 1988; 2007;
471
Slabbert, 1998). Hornblende is largely absent.
472
The syn-tectonic granites are ferroan monzogranites and granodiorites (Fig. 4; Table 6). Whilst the
473
geochemical characteristics of the syn- and post-tectonic groups show significant overlap, the
474
majority of the syn-tectonic group is more felsic than the post-tectonic granites. The generally high
475
SiO2 content (mostly between ~69 and 78 wt.%,), alkali-rich nature, low maficity, and low Ti, Mg, Fe,
476
Ca and Mn contents (Figs. 6, 7) of these syn-tectonic granite gneisses (the Colston Granite is the
477
exception in all cases) supports possible correlation with the near coeval, similarly acidic, but more
478
strongly deformed Riemvasmaak leucogranite augen gneiss and Augrabies granite gneiss (Fig. 4a, b),
479
although this would need to be tested more rigorously. In the past, these leucogranitic gneisses were
480
distinguished from the large bodies of syn-tectonic Riemvasmaak and Augrabies granite gneisses
481
dominating the western Kakamas Terrane on the basis that the latter are commonly augen-textured
482
(SACS, 1980), despite having similar compositions (Figs. 4, 5) and mineralogies (low biotite contents
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and minor primary muscovite (Moen, 2007)). As such the syn-tectonic granites show similarities to
484
the augen gneisses apart from a well-developed augen texture.
485 6.3. Textural, mineralogical and geochemical characteristics of the late- to post-tectonic Keimoes
487
Suite
488
Mineralogically, many of the post-tectonic granites are typically feldspar porphyritic and have
489
significant amounts of biotite together with, or without, hornblende and/or orthopyroxene (Table 6).
490
Primary muscovite is not identified. In addition, the post-tectonic intrusions become more
491
granodioritic with decreasing age concomitant with an increase in mafic minerals and decreasing K-
492
feldspar content.
493
In terms of whole rock geochemistry, most of the Keimoes Suite granites, excluding the Louisvale
494
Tonalite, show consistent major element trends and classify as ferroan, mostly metaluminous
495
monzogranites (including charnockite) and granodiorites (Fig. 4). The post-tectonic granites show a
496
trend towards more intermediate, aluminous and less alkali compositions with decreasing age (Figs. 5,
497
6), a trend not observed in the syn-tectonic group. They have higher maficities and are less
498
fractionated than the syn-tectonic granites (Figs. 5, 6).
499
The Louisvale Granite differs in being dominantly tonalitic (Fig. 5), and has a major and trace
500
element geochemistry (Figs. 6-8) inconsistent with the other granites and granite gneisses. The
501
Louisvale Granite also has a higher initial 143Nd/144Nd ratio (0.51128), εNd(t) value (1.89) and a
502
younger model age (TDM = 1.49 Ga) than most of the other granites (Fig. 8), and, with a low initial Sr
503
ratio of 0.70630 (Fig. 8a), appears to have been derived from a relatively depleted mantle source with
504
minor crustal contribution. This compositional difference, along with the gneissic nature and age of
505
this granitoid, forms the basis for the exclusion of the Louisvale Granite from the Keimoes Suite.
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6.4. Origins of the granites in the eastern Namaqua Sector
508
6.4.1. Origins of the post-tectonic Keimoes Suite
509
The post-tectonic Keimoes Suite, as defined in this study, has geochemical compositions reflecting
510
mixed or hybrid sources. On one hand, the granites have characteristics suggestive of I-type granites,
511
having more granodioritic compositions, with arc-like affinities (Ta-Nb, Ti and P anomalies – Fig. 7).
512
However, the high Fe/Mg ratios [0.82-3.84, avg. 1.66], and high HFSE, LILE and REE contents, are
513
more suggestive of A-type granites, particularly fractionated A2-type granites (Eby, 1992; Fig. 4e,
514
Loiselle and Wones, 1979).
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516
orthopyroxene as the predominant mafic minerals in these post-tectonic granites and charnockites,
517
argues for the melting of igneous sources with little to no sedimentary source material present giving
518
rise to dry parental magmas. Significant enrichments in Pb, Th, U, LREE relative to the HREE, and
519
the LILE relative to the HFSE, with depletions in Ba, Nb, Ta, Sr, Eu, Ti, Al2O3, V and Sc (Fig. 7)
520
indicate significant crustal contributions to the source magmas. A general geochemical trend to more
521
intermediate compositions with time and decreasing age of emplacement suggests that the initial
522
crustal component was initially greater and was reduced over time giving rise to a greater mantle
523
contribution (e.g. Fig. 8a, c, d).
524
εNd(t) values varying around, and close to zero (Fig. 8) suggest a variably depleted component, being
525
potentially mantle and/or juvenile lower crust. The Nd model ages range from relatively juvenile (as
526
young as 1.38 Ga (Fig. 8c; Table 5)) to Paleoproterozoic (TDM to 1.99 Ga) with potentially Archean
527
crustal contributions (the Kleinbegin Granite - εNd(t): -7.51; TDM: 2.34 Ga). These, combined with arc
528
signatures (Fig. 7), suggest the involvement of both juvenile, Mesoproterozoic crust as well as older,
529
∼1.85-2.0 Ga Paleoproterozoic crust (e.g. the Sperrgebiet and Richtersveld arcs; Reid, 1997; Thomas
530
et al., 2016; Macey et al., 2017). The ∼1.3-1.24 Ga Areachap arc (Pettersson et al., 2007) potentially
531
contributed juvenile Mesoproterozoic material. Mixing between juvenile material, of likely mantle
532
origin, and older Paleoproterozoic material, occurred. The Paleoproterozoic material was reworked at
533
this time. Initial Sr ratios [(87Sr/86Sr)I]] for the eastern NS granitoids, in general, are both high and
534
highly variable (0.70628-0.77130, and generally >0.707 – Table 5]. Such high SrI ratios are typical of
535
the NNMP (e.g. Fig. 12 of Eglington, 2006). Eglington (2006) interpreted these patterns as suggesting
536
reworking of material not older than 2.2 Ga. This is seen in the (87Sr/86Sr)I vs. age plot (Fig. 8d) where
537
the (87Sr/86Sr)I ratios vary along a general mixing trend between the depleted mantle (DM) curve and
538
Paleoproterozoic crust of ∼2.0 Ga age. The Keimoes Suite granites are characterized by high
539
maficities and low SrI ratios, which, in combination with low εNd(t) values, suggest that the older,
540
Paleoproterozoic material may not have been highly radiogenic and the mantle contribution was
541
significantly large.
542
Varying contributions of Meso- to Paleoproterozoic-ages sources to the parental magmas to the
543
Keimoes Suite granites is recorded by the presence of inherited zircons in these granites, e.g. Bailie et
544
al. (2011a). The intercept age determined for the Klipkraal Granite (1270 ± 26 Ma; this study) clearly
545
reflects inheritance and the age of the Areachap arc (Pettersson et al., 2007). Inherited zircons of older
546
Mesoproterozoic age (1346 Ma) are found in the Keboes Granite (this study; Table A1). These
547
inherited zircons thus likely reflect the influence of juvenile material of Mesoproterozoic age in the
548
source area to these granites. Cornell et al. (2012) reported xenocrysts with older ages of 1725 ± 25
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550
clear but may reflect mixing.
551
The tectonic setting of the Keimoes Suite granites, using the Pearce et al. (1984) plots, is dominantly
552
of within-plate granites (WPG) (Fig. 9). The WPG field corresponds to a continental intra-plate to
553
continental back-arc as well as rifting settings and/or post-collision magmatism (Förster et al., 1997).
554
Such settings highlight a period of transcurrent shearing and extension at ∼1100 Ma (Jacobs et al.,
555
1993; Gutzmer et al., 2000; Pettersson et al., 2007; Bailie et al., 2012). It also correlates with the A-
556
type signature and mantle component of these granites related to crustal thinning and resultant mantle
557
upwelling at this time.
558
Cornell et al. (2012) proposed that the Keimoes Suite represents a mixed/hybrid melt generated during
559
late-Namaqua tectonics related to the ~1100 Ma subcontinental scale Umkondo plume (Hanson et al.,
560
2004). Further geochemical and isotopic studies are required in order to test this proposed hypothesis.
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6.4.2. Origins of the syn-tectonic granites and granitic gneisses
563
The pre- to syn-tectonic granites are characterized by fractionated leucogranitic melts that intruded
564
during peak metamorphism and the main deformation in the Kakamas and Areachap terranes
565
(Pettersson et al., 2007; Fig. 10). The syn-tectonic granites are more dominantly leucogranitic, being
566
mafic mineral-poor, and have a more S-type character compared to the late- to post-tectonic Keimoes
567
Suite granites. They exhibit similar enrichments and depletions as the post-tectonic Keimoes Suite
568
granites, particularly with regard to LILE enrichment (Fig. 7). The syn-tectonic granites have εNd(t)
569
values close to 0 (-1.47 to 1.78) (Fig. 9; Table 5) suggesting a mantle component to these melts. A
570
crustal signature is suggested by their leucogranitic compositions, enrichment in Rb, K, Th and U
571
(Fig. 7), and metaluminous to peraluminous characteristics (Fig. 4f). Nd model ages (TDM = 1.57-1.91
572
Ga) (Table 5) suggest variable degrees of mixing between sources of Meso- and Paleoproterozoic age
573
of likely arc derivation as denoted by arc-like signatures (LILE enrichment relative to the HFSE,
574
depletions in Nb, Ta and Ti). As for the Keimoes Suite, inherited zircons of Mesoproterozoic age
575
(1335-1344 Ma) are found in the Elsie se Gorra Granite (this study; Table A9). The syn-tectonic
576
granites are, however, characterized by lower maficities than the post-tectonic granites (Fig. 6)
577
suggesting a lower mafic mineral content and a more fractionated nature (correlating with high SiO2
578
content in general). They are also characterized by higher initial Sr ratios (Fig. 8c) and so likely
579
represent a greater degree of crustal melting, and incorporation of older, ∼2.0 Ga, radiogenic crust
580
relative to the post-tectonic Keimoes Suite. Mixing of radiogenic crust characterized by low εNd(t)
581
values, e.g. those of the Richtersveld Magmatic Arc (RMA) with low εNd(t) values of near 0 (0.53 to -
582
3.19 for the RMA - Macey et al., 2017), may explain the low εNd(t) values of the eastern NS granites.
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585
The period of arc magmatism associated with development of the 1.30-1.24 Ga Areachap arc
586
(Pettersson et al., 2007) due to eastward-directed subduction (Pettersson et al., 2007) was dominated
587
by extensive juvenile magmatism with dominantly Mesoproterozoic Nd model ages (Bailie et al.,
588
2010). A period of peak magmatism between ∼1.23 and 1.18 Ga is seen in the western Kakamas
589
Terrane (Fig. 10; Bial et al., 2015a), corresponding to extensive magmatism within the Bushmanland
590
Subprovince further west (Bailie et al., 2007; Cornell et al., 2009). This is taken to be amalgamation
591
of the Bushmanland Subprovince and Kakamas Terrane at this time. Extensive magmatism is not seen
592
during this period in the Areachap Terrane. Extensive magmatism, however, occurred between ∼1.18
593
Ga and 1.13 Ga in both the Kakamas and Areachap terranes (Fig. 10) associated with closure of the
594
Areachap ocean (Pettersson et al., 2007) leading to reworking of Paleoproterozoic material, and,
595
potentially, of the Areachap arc as well. Mixing of crustal melts with mantle material affected or
596
enriched by subduction processes is likely. Ocean basin closure resulted in peak metamorphic
597
conditions at ∼1.15 Ga. Accretion processes are likely given the low-P, high-T nature of the NS more
598
akin to a continental back-arc scenario compared to a continental collision scenario (Bial et al., 2015a,
599
b). Current interpretations, such as Cornell et al. (2011), interpret the Kakamas Terrane as a separate
600
crustal block that collided, or was juxtaposed with the Areachap Terrane prior to ∼1.12 Ga although
601
current age data do not support a collisional or amalgamation event between the two prior to ∼1.18 Ga
602
(Fig. 10).
603
Late- to post-tectonic magmatism is more voluminous, particularly in the Areachap Terrane (Fig. 10)
604
and is characterized by a substantial juvenile component. Potential slab breakoff, mantle upwelling or
605
collapse, and potential transcurrent shearing (Gutzmer et al., 2000; Bailie et al., 2012), likely resulted
606
in the late- to post-orogenic magmatism at ∼1.12-1.07 Ga characterized by variable mixing between
607
juvenile and older (reworked?) Paleoproterozoic sources. The overall proportion of the older,
608
radiogenic crust is less given the generally lower SrI ratios of the Keimoes Suite granites relative to
609
the more radiogenic, older syn-tectonic granites (Fig. 8), implying a greater non-radiogenic
610
component to the melts.
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6.6. Implications for timing of tectonics in the eastern Namaqua Sector of the NNMP
613
Pettersson et al. (2007) reported an age of 1165 Ma for migmatization and deformation in the
614
Areachap Group which corresponds well with the dating of intrusion of the syn-tectonic granite
615
gneisses between 1175 and 1146 Ma. The emplacement of the syn-tectonic Vaalputs Granite Gneiss
18
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617
Kakamas terranes (Fig. 10) indicates that they were juxtaposed prior to ~1.16 Ga (Table 2).
618
The Louisvale Tonalite that intruded at ∼1125 Ma, is also strongly foliated and provides the
619
maximum age for the peak D2 Namaquan deformation. The minimum age for the D2/Namaquan
620
deformation in the eastern NS is constrained by the post-tectonic Keimoes Suite (sensu Cornell et al.,
621
2012; this study) for which the oldest reliably dated member, the weakly foliated Keboes Granite, has
622
been dated at 1105 Ma. The weak magmatic fabric observed in the margins of some of the post-
623
tectonic granites is considered the result of intrusion into a waning regional stress field (van Zyl,
624
1981).
625
Subsequent open E-W-trending F3 folds, associated with weaker D3 deformation, developed at ∼1.10
626
Ga (Pettersson et al., 2007). The post-tectonic Keimoes Suite is synchronous with this deformation
627
event although these granites are largely weakly foliated to unfoliated. The syn-tectonic Vaalputs
628
Granite and the weakly to unfoliated late- to post-tectonic Keimoes Suite granites are concentrated
629
along the BRSZ (Fig. 1), the boundary between the Kakamas and Areachap terranes, suggesting that
630
this major crustal feature played an important, long-lived role in the emplacement of the granites of
631
the eastern NS.
632
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6.7. Origins and age of Namaquan crust
634
Paleoproterozoic TDM ages are typical for most of the western Namaqua Sector (Reid, 1997; Clifford
635
et al., 1981, 1995, 2004; Yuhara et al., 2001; Bailie et al., 2007; Pettersson et al., 2009; Macey et al.,
636
2017) suggesting that large portions of the NS were derived from the magmatic reworking of
637
Paleoproterozoic crust (e.g. Clifford et al., 2004; Eglington, 2006; Pettersson et al., 2009; Bial et al.
638
2015a, b; Macey et al., 2017) carrying a subduction related arc signature based on geochemical
639
characteristics. εNd(t) values of rocks in the Bushmanland Subprovince to the west show a similar
640
pattern of being all near zero, whereas the SrI values give a large range of highly radiogenic values
641
(Clifford et al., 1981, 1995; Yuhara et al., 2001, 2002) which appears to be another characteristic
642
feature of the NS in general (Eglington, 2006). The subcontinental lithospheric mantle (SCLM) of
643
southern Africa is highly enriched in general having 87Sr/86Sr ratios varying between 0.7114 and
644
0.7550 (concentrates from kimberlite pipes – Richardson et al., 1984). Small variations in εNd(t) values
645
which vary around 0 have been used to suggest derivation from a mantle wedge metasomatised by
646
slab-derived melts (e.g. Wang et al., 2013). In the case of the NS it likely represents reworking of
647
Proterozoic arc-related crust and variable degrees of mixing with juvenile Mesoproterozoic material
648
(Eglington, 2006). Given the limited amount of isotopic data for the eastern NS in general (e.g.
649
Eglington, 2006; Pettersson et al., 2009) more extensive isotopic determinations are required in order
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to more fully assess the origin of the highly radiogenic initial Sr isotopic signatures coupled to low
651
εNd(t) values of the NS.
652 6.8. The pre- to early syn-tectonic Josling Granite
654
The Josling Granite, with a well-developed, gneissic fabric is pre-tectonic with regards to the peak D2
655
deformation (Fig. 10). Pettersson (2008) determined an age of 1275 ± 7 Ma for this granite, whereas
656
the present study determined a younger age of 1217 ± 20 Ma. Based on its age it should be removed
657
from the Keimoes Suite. The Josling Granite may be related to an older cluster of pre-D2 intrusions
658
(1371 to 1220 Ma; Cornell et al., 2012) related to the development of the Areachap arc.
659
The Josling Granite is a feldspathic leucogranite characterized by low maficity (Fig. 6) and a
660
relatively high SiO2 content (Fig. 5) and is relatively fractionated. With a high initial 143Nd/144Nd ratio
661
(0.511158-0.511260), mildly positive εNd(t) values (1.79-3.77), and low initial Sr ratios (0.70674-
662
0.70821; Fig. 8; Table 5) it was derived from a relatively depleted source with a minor crustal
663
component. With model ages varying between 1.45 and 1.63 Ga it also shows mixing of Meso- and
664
Paleoproterozoic aged sources, with the former more dominant. Given its depleted source signature
665
and low initial Sr ratio it likely is related to juvenile magmatism related to development of the
666
Areachap arc, but, with a spread of model ages toward Paleoproterozoic ages, also reflects a generally
667
older Paleoproterozoic aged crustal source component to the magmas in the northern Areachap
668
Terrane (Pettersson et al., 2009; Bailie et al., 2010).
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669 7. Conclusions
671
New U-Pb zircon age data and whole rock geochemistry presented in this study support the new
672
definition of the Keimoes Suite as proposed by Cornell et al. (2012) in which the 1175-1146 Ma syn-
673
tectonic leucogranite and granite gneisses are removed from the suite. The Keimoes Suite (sensu
674
Cornell et al., 2012; this study) is now defined as a group of foliated to unfoliated late- to post-
675
tectonic, largely megacrystic granites and charnockites emplaced during a relatively narrow period
676
between 1110 and 1078 Ma.
677
The 1.11-1.08 Ga post-tectonic Keimoes Suite granites have geochemical compositions reflecting
678
mixed or hybrid sources with both fractionated I-type characteristics (metaluminous, hornblende- and
679
orthopyroxene-bearing and arc-like affinities) as well as fractionated A-type characteristics (high
680
Fe/Mg ratios, high HFSE, LILE and LREE contents). They exhibit an overall trend of increasing
681
maficity (elemental Fe + Mg), Ti, Ca and Mn, and decreasing Si, Na and K with decreasing age
682
becoming increasingly less fractionated and more metaluminous. Isotopic systematics suggest
683
derivation from a mildly depleted source with variable degrees of an enriched and/or crustal
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685
Variable mixing between juvenile Mesoproterozoic and older Paleoproterozoic arc material, the latter
686
likely represented by the Richtersveld arc, contributed to the parental melts and an arc-like signature
687
(LILE enrichment relative to the HFSE, negative Ta-Nb, P and Ti anomalies, enrichment in Pb, K, Th
688
and U). The Keimoes Suite granites were emplaced mostly within the Areachap Terrane of the eastern
689
NS, but the youngest member, the Friersdale Charnockite, intruded both the Kakamas and Areachap
690
Terranes and the tectonic boundary between them. The granites were emplaced during a period of
691
transcurrent shearing and extension at ∼1.11 Ga which was associated with crustal thinning and
692
mantle upwelling, as denoted by their A-type characteristics. The suite is concentrated along the
693
BRSZ suggesting this structure may have played a role in the migration of magmas into the upper
694
crust.
695
By contrast the ∼1.18-1.15 Ga syn-tectonic granites are fractionated metaluminous to peraluminous
696
moderately to strongly foliated leucogranites and gneisses with low maficity, Ti, Ca and Mn, and high
697
Si, Na and K contents suggesting largely pure melts. Isotopic ratios (εNd(t) values close to 0 (-1.47 to
698
1.78)) support a juvenile lower crustal source, but with a likely greater radiogenic crustal component
699
relative to the Keimoes Suite, as denoted by highly variable and high initial Sr isotope ratios likely
700
suggesting reworking of initially radiogenic crust. Nd model ages also suggest mixing between Meso-
701
and Paleoproterozoic aged sources. These granitic gneisses are also more voluminous toward the west
702
compared to the late- to post-tectonic Keimoes Suite granites possibly indicating a potential shift in
703
magmatism with time. The main penetrative fabric forming event in the eastern Namaqua Sector is
704
constrained to between ∼1125 and ∼1110 Ma, the ages of the youngest granite gneiss and the oldest
705
weakly foliated granite, respectively. The juxtapositioning of the Areachap and Kakamas terranes
706
occurred prior to 1.15 Ga.
707
The variable Nd model ages varying to Paleoproterozoic age confirm a dominant Paleoproterozoic arc
708
source in the Namaqua Sector, as also found by previous workers. This Paleoproterozoic aged arc was
709
extensively reworked during the Namaquan Orogeny. Granites in the eastern Namaqua Sector also
710
carry signatures of a more juvenile Mesoproterozoic source, as denoted by Nd model ages and
711
inherited zircons.
712
Further detailed geochemical and structural studies of the eastern Namaqua Sector granites are
713
required. The former is required to determine the more detailed petrogenesis of the syn-tectonic
714
granitic gneisses as well as the Keimoes Suite, with the latter to investigate their means of
715
emplacement. In addition, the relationship between the syn-tectonic granites straddling the boundary
716
between the Kakamas and Areachap terranes and the voluminous granitic gneisses of the central to
717
western Kakamas Terrane is of future research interest.
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ACCEPTED MANUSCRIPT Acknowledgements
720
This project was done in conjunction with the Council for Geoscience (CGS) who funded some of the
721
analyses. The project was also funded by an NRF Y-rated researcher incentive funding grant awarded
722
to RB as well as a CGS bursary to SN. Whole rock geochemical analyses were undertaken by H.
723
Cloete and Melissa Crowley of the CGS (major elements) and Riana Rossouw of the Central
724
Analytical Facility, Stellenbosch University (trace elements). Many thanks to Dr. Luc Chevallier and
725
Dr. Hendrik Minnaar (CGS) for their logistical assistance during the field work phase of the study.
726
Peter Meyer and Janine Becorney of the Department of Earth Sciences, UWC are thanked for
727
technical support. Stefan Büttner and David Cornell are thanked for providing helpful and insightful
728
reviews of an earlier version of this manuscript. Jodie Miller and an anonymous reviewer are thanked
729
for helpful comments that substantially improve this version of the manuscript.
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730 Appendix - Analytical techniques
732
Whole rock geochemistry
733
Major element contents for all representative samples were determined by X-ray fluorescent (XRF)
734
spectrometry at the CGS, Pretoria, on glass beads prepared from a 0.2 g sample following a lithium
735
metaborate/tetraborate fusion and dilute nitric acid digestion. Loss on ignition (LOI) was calculated
736
by the weight difference after ignition to 1000oC. Powdered whole-rock samples were mixed with
737
flux for a sample-to-flux (lithium tetraborate) ratio of 1:10. Thirty-two USGS and GSJ standard
738
reference samples were used for calibration of the instrument.
739
The trace and rare earth element (REE) abundances were determined using inductively coupled
740
plasma mass spectrometry (ICP-MS) at CAF following the same procedure as for the whole rock
741
analyses but with a separate 0.5 g split digested in Aqua Regia and analysed by ICP-MS. Fusion disks
742
prepared for XRF analysis by an automatic Claisse M4 Gas Fusion instrument and ultrapure Claisse
743
Flux, using a ratio of 1:10 sample : flux, were coarsely crushed and a chip of sample mounted along
744
with up to 12 other samples in a 2.4cm round resin disk. The mount was mapped, and then polished
745
for analysis.
746
A Resonetics 193nm Excimer laser connected to an Agilent 7500ce ICP-MS is used in the analysis of
747
trace elements in bulk rock samples at CAF, Stellenbosch University. Ablation is performed in He gas
748
at a flow rate of 0.35l/min, then mixed with argon (0.9l/min) and Nitrogen (0.004l/min) just before
749
introduction into the ICP plasma. For traces in fusions, 2 spots of 173µm are ablated on each sample
750
using a frequency of 10Hz and 100mJ energy.
751
Trace elements are quantified using NIST 612 for calibration and the % SiO2 from XRF measurement
752
as internal standard, using standard – sample bracketing. Two replicate measurements are made on
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ACCEPTED MANUSCRIPT each sample. The calibration standard was run every 12 samples. A quality control standard is run in
754
the beginning of the sequence as well as with the calibration standards throughout. BCR-2 or BHVO
755
2G, both basaltic glass certified reference standards produced by the USGS (Dr Steve Wilson,
756
Denver, CO 80225), is used for this purpose. A fusion control standard from certified basaltic
757
reference material (BCR-2, also from the USGS) is also analysed in the beginning of a sequence to
758
verify the effective ablation of fused material. The precision and accuracy of the results are 2–5%
759
(1σ) for most elements. Detection limits of most trace elements are 0.1 ppm, except for Th and Co
760
(0.2 ppm), Sr (0.5 ppm), Sc and Zn (1 ppm), and V (8 ppm). Most REE have detection limits less than
761
or equal to 0.05 ppm, the exceptions being La and Ce (0.1 ppm), and Nd (0.3 ppm).
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762 Whole rock Rb-Sr and Sm-Nd isotope analysis
764
Rb-Sr and Sm-Nd isotope analysis, for the same eight samples that were analysed for geochronology,
765
was done at the Department of Geological Sciences, University of Cape Town (UCT). Following
766
concentration analysis, separation of Sr and Nd fractions in the same sample dissolutions were
767
undertaken by chromatographic techniques as described by Miková and Denková (2007), after that
768
described by Pin and Zaldegui (1997) and Pin et al. (1994). The Sr fractions were separated using
769
Eichrome Sr resin beds, and the aqueous solution was diluted in 2 ml 0.2% HNO3, ready for Sr
770
isotope ratio determination. The remaining portions were converted to salts, dried down and further
771
dissolved to extract the REEs using AG50W cation resin columns. The REE portions were converted
772
to nitrate, dried down and then diluted in 0.05M HNO3 to collect Nd using Eichrome Ln resin
773
columns. These portions were dried down and diluted in 1.5 ml 2% HNO3 for Nd isotope ratios
774
determination.
775
The determination of Rb, Sr, Sm and Nd concentrations in each sample was performed on a Thermo
776
XSeries II ICP-MS at UCT following dissolution with concentrated HF and HNO3, and dilution with
777
5% HNO3 containing an internal standard. Concentrations were determined in duplicate for each
778
sample. The international standard BHVO-2 was analysed with every batch of samples as a measure
779
to assess accuracy and precision.
780
Sr is analysed as a 200ppb 0.2% HNO3 solution. All Sr isotope analyses of unknowns are referenced
781
to bracketing analyses of the NIST SRM987 reference standard, using a reference value for 87Sr/86Sr
782
of 0.710255. The international reference material BHVO-2 gave a value of 0.703490 ± 15 relative to a
783
value of 0.703479 ± 20 reported by Weis et al. (2006). The long-term UCT average is 0.703479 ± 22
784
(n = 47). All Sr isotope data are corrected for Rb interference using the measured signal for 85Rb and
785
the natural 85Rb/87Rb ratio. Instrumental mass fractionation is corrected using the exponential law and
786
a 86Sr/88Sr value of 0.1194.
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ACCEPTED MANUSCRIPT Nd isotopes are analysed as 50 ppb 2% HNO3 solutions using a Nu Instruments DSN-100 desolvating
788
nebuliser. JNdi-1 is used as a reference standard, with a 143Nd/144Nd reference value of 0.512115,
789
corresponding to the La Jolla standard (Tanaka et al., 2000). The BHVO-2 reference material gave
790
values of 0.512981 ± 10, relative to a value of 0.512984 ± 11 reported by Weis et al. (2006). All Nd
791
isotope data are corrected for Sm and Ce interference using the measured signals for 147Sm and 140Ce,
792
and the natural Sm and Ce isotope abundances. Instrumental mass fractionation is corrected using the
793
exponential law and a 146Nd/144Nd value of 0.7219. The initial 87Sr/86Sr and 143Nd/144Nd ratios were
794
calculated using decay constants of 1.42 x 10-11 y-1 (Steiger and Jäger, 1977) and 6.54 x 10-12 y-1
795
(Begemann et al., 2001), respectively.
796
Measurements of standards BHVO-2 (Weis et al., 2006) and JNdi-1 (Tanaka et al., 2000) for samples
797
S188, 367 and 815 of the Friersdale Charnockite yielded 143Nd/144Nd values of 0.512987 ± 9 and
798
0.512115 ± 7 respectively. The long-term UCT average for BHVO-2 (n = 44) is 0.512985 ± 15
799
relative to the value of 0.512984 ± 11 (Weis et al., 2006). Sr isotope measurements of BHVO-2 and
800
reference material NIST987 for the same samples yielded 87Sr/86Sr values of 0.704375 ± 13 and
801
0.710255, respectively. Measurements of standards BHVO-2 and JNdi-1 for samples Me1, Mcol3,
802
Mkn4, Ml5, Mkb6, Mc8, Mkl3 and Mka6 yielded 143Nd/144Nd values of 0.512981 ± 10 and 0.512115
803
± 7 respectively. Sr isotope measurements of BHVO-2 and reference material NIST987 for the same
804
samples yielded 87Sr/86Sr values of 0.704390 ± 15 and 0.710255, respectively.
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805 U-Pb zircon LA-SF-ICP-MS age dating
807
Zircon crystals were extracted from samples by traditional methods of crushing and grinding,
808
followed by separation with a Wilfley table, heavy liquids, and a Frantz magnetic separator. Samples
809
are processed such that all zircons are retained in the final heavy mineral fraction. A split of these
810
grains (generally 50-100 grains) are selected from the grains available and incorporated into a 1 inch
811
resin mount together with fragments of Plešovice (Sláma et al., 2008) and 91500 (Wiedenbeck et al.,
812
1995) reference materials. The mounts are sanded down to a depth of ~20 µm, polished, imaged, and
813
cleaned prior to isotopic analysis.
814
All U-Pb age data of zircons was conducted by laser ablation - single collector – magnetic sector field
815
- inductively coupled plasma - mass spectrometry (LA-SF-ICP-MS) employing a Thermo Finnigan
816
Element2 mass spectrometer coupled to a Resonetics Resolution HR-S155 excimer laser ablation
817
system at the Central Analytical Facility (CAF), Stellenbosch University. The analyses involve
818
ablation of zircon using a spot diameter of 30 µm and a crater depth of approximately 10-15 µm. A
819
sampling pattern of 30 µm single spot analyses was used. The use of the LA-ICP-MS dating
820
technique does not allow spots of <30 µm to be analysed so that metamorphic rims on zircons could,
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ACCEPTED MANUSCRIPT unfortunately, not be analysed. The methods employed for analysis and data processing are those
822
described by Frei and Gerdes (2009) with the modifications described in Cornell et al. (2016).
823
For quality control, the 91500 (Wiedenbeck et al., 1995), Plešovice (Sláma et al., 2008) and M127
824
(Nasdala et al., 2008; Mattinson, 2010) zircon reference materials were analysed, and the results were
825
consistently in excellent agreement with published ID-TIMS ages. 91500 has a concordia age of 1067
826
± 6 Ma (2s, MSWD = 0.34), M127 a concordia age of 527 ± 3 Ma (2s, MSWD = 0.29) and Plešovice
827
a concordia age of 339 ± 2 Ma (2s, MSWD = 0.47).
828
An in-house spreadsheet using the intercept method for laser induced elemental fractionation (LIEF)
829
correction is used for data processing. Mass discrimination is undertaken by standard-sample
830
bracketing with 207Pb/206Pb and 206Pb/238U normalized to reference material GJ-1 (Jackson et al.,
831
2004). Common Pb correction is accomplished by using the Hg-corrected 204Pb and assuming an
832
initial Pb composition from Stacey and Kramers (1975) at the projected age of the mineral with a 5%
833
uncertainty assigned. Ages are quoted at 2 sigma absolute, with propagation by quadratic addition.
834
Reproducibility and age uncertainty of reference material and common-Pb composition are
835
propagated. Uncertainties of 1.5 for 206Pb/204Pb and 0.3 for 206Pb/207Pb are applied to these
836
compositional values based on the variation in Pb isotopic composition in modern crystalline rocks.
837
For each analysis, the errors in determining 206Pb/238U and 206Pb/204Pb result in a measurement error of
838
~1-2% (at 2-sigma level) in the 206Pb/238U age. The errors in measurement of 206Pb/207Pb and
839
206
840
are substantially larger for younger grains due to low intensity of the 207Pb signal. For most analyses,
841
the cross-over in precision of 206Pb/238U and 206Pb/207Pb ages occurs at ~1.20 Ga (Gehrels et al., 2008),
842
although compilations of LA-ICP-MS and scanning ion mass spectrometer (SIMS) data suggests an
843
older crossover at ∼1.5 Ga (Spencer et al., 2016).
844
Inter-element fractionation of Pb/U is generally ~5%, whereas apparent fractionation of Pb isotopes is
845
generally <0.2%. In-run analysis of fragments of GJ-1 (generally every fifth measurement) with
846
known age of 608.5 ± 0.4 Ma (2-sigma error) (Jackson et al., 2004) is used to correct for this
847
fractionation. The uncertainty resulting from the calibration correction is generally 1-2% (2-sigma) for
848
both 206Pb/207Pb and 206Pb/238U ages. Concentrations of U and Pb and Th/U ratios are calculated
849
relative to the GJ-1 reference zircon.
850
Full analytical and data reduction details for the LA-SF-ICP-MS U-Pb dating undertaken at CAF,
851
Stellenbosch University, including operating procedures, sample preparation, instrument set up, as
852
advocated by Horstwood et al. (2016), are given in electronic supplementary material Table A11, with
853
the results for all quality control materials analysed reported in Table A12 in the electronic
854
supplementary material. Measurements of standards and reference materials are reported in Appendix
855
Tables A1 to A8. Uncertainties shown in these tables are at the 2-sigma level, and include only
M AN U
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Pb/204Pb also result in ~1-2% (at 2-sigma level) uncertainty in age for grains that are >1.0 Ga, but
25
ACCEPTED MANUSCRIPT measurement errors. Analyses that are >10% discordant (by comparison of 206Pb/238U and 206Pb/207Pb
857
ages) or >5% reverse discordant (both in italics in Tables A1 - A8) are not considered when
858
determining weighted mean U-Pb ages (Gehrels et al., 2008 recommended >20%). Inherited cores are
859
highlighted in bold in the data tables.
860
The resulting interpreted ages are shown on Pb*/U concordia diagrams and weighted mean diagrams
861
using the plots generated by Isoplot/Ex 3.0 (Ludwig, 2003). The weighted mean diagrams show the
862
weighted mean (weighting according to the square of the internal uncertainties), the final uncertainty
863
of the age (determined by quadratic addition of the weighted mean and external uncertainties), and the
864
MSWD of the data set. Ages are reported on the basis of 206Pb/238U following the recommendations of
865
Gehrels et al. (2008) as the zircons analysed are all less than ∼1.2 Ga. Spencer et al. (2016), based on
866
previous compilations of LA-ICP-MS zircon analyses, and SIMS zircon analyses, noted that an ∼1.5
867
Ga cross over point from 207Pb/206Pb ages to 206Pb/238U is preferable. The analytical data analysis, data
868
validation and reporting methodologies, as advocated by Horstwood et al. (2016), and the
869
international network of practitioners (LA-ICP-MS U-(Th-)Pb Network, given at the website:
870
http://www.PlasmAge.org/recommendations), have been followed as far as possible.
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871 References
873
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874
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875
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876
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877
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878
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879
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880
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905
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907
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908
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909
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910
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911
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912
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913
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914
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916
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918
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919
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920
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921
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926
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927
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928
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929
Clifford, T.N., Barton, E.S., Stern, R.A., Duchesne, J.-C., 2004. U-Pb zircon calendar for Namaquan
930
(Grenville) crustal events in the granulite-facies terrane of the O’Okiep Copper District of South
931
Africa. J. Petrol. 45, 669-691.
932
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933
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934
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935
Cornell, D.H., Pettersson, Å., 2007. Ion probe zircon dating of metasediments from the Areachap and
936
Kakamas Terranes, Namaqua-Natal Province and the stratigraphic integrity of the Areachap Group. S.
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938
Cornell, D.H., Kröner, A., Humphreys, H.C., Griffin, G., 1990. Age of origin of the
939
polymetamorphosed Copperton Formation, Namaqua-Natal Province, determined by single grain
940
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941
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942
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943
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944
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945
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946
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947
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948
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949
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950
Cornell, D.H., van Schijndel, V., Ingolfsson, O., Scherstén, A., Karlsson, L., Wojtyla, J., Karlsson, K.,
951
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952
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ACCEPTED MANUSCRIPT Cornell, D.H., Pettersson, Å., Simonsen, S.L., 2012. Zircon U-Pb emplacement and Nd-Hf crustal
954
residence ages of the Straussburg granite and Friersdale charnockite in the Namaqua-Natal Province,
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South Africa. S. Afr. J. Geol 115, 465-484.
956
Cornell, D.H., Zack, T., Andersen, T., Corfu, F., Frei, D., Van Schijndel, V., 2016. Th-U-Pb zircon
957
geochronology of the Palaeoproterozoic Hartley Formation porphyry by six methods, with age
958
uncertainty approaching 1 Ma. S. Afr. J. Geol. 119, 473-494.
959
Eby, N., 1992. Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications.
960
Geology 20, 641-644.
961
Eglington, B.M., 2006. Evolution of the Namaqua-Natal Belt, southern Africa – a geochronological
962
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963
Fransson, M., 2008. U-Pb zircon dating of metasedimentary rocks in the Areachap, Kakamas and
964
Bushmanland Terranes in Namaqua Province, South Africa. Masters thesis, Earth Sciences Centre,
965
University of Gothenburg, B series, 49 pp., ISSN 1400-3821.
966
Förster, H.-J., Tischendorf, G., Trumbull, R.B., 1997. An evaluation of the Rb vs. (Y + Nb)
967
discrimination diagram to infer tectonic setting of silicic igneous rocks. Lithos 40, 261-293.
968
Frei, D., Gerdes, A., 2009. Precise and accurate in situ U–Pb dating of zircon with high sample
969
throughput by automated LA-SF-ICP-MS. Chem. Geol. 261, 261–270.
970
Frost, B.R., Barnes, C.G., Collins, W.J., Arculus, R.J., Ellis, D.J., Frost, C.D., 2001. A geochemical
971
classification for granitic rocks. J. Petrol. 42, 2033-2048.
972
Gehrels, G.E., Valencia, V.A., Ruiz, J., 2008. Enhanced precision, accuracy, efficiency, and spatial
973
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974
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1140
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Geochronological, geochemical and Nd–Hf–Os isotopic fingerprinting of an early Neoproterozoic
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1153
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1156
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Zindler, A., Hart, S.R., 1986. Chemical geodynamics. Ann. Rev. Earth Planet. Sci. 14, 493-571.
1162
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List of figures
1164
Fig. 1. Distribution of granites and geochronological sample localities, eastern Namaqua Sector (NS).
1165
Compiled from the 1:250 000 scale map data of Moen (1988) and Slabbert (1998). Inset of the NNMP
1166
in southern Africa (after Cornell et al., 2006).
1167
Fig. 2. Zircon CL images for the dated eastern NS granites. Ages reported next to representations of
1168
analysed spots are 206Pb/238U ages. a. Smalvis Granite, Cyndas Subsuite, b. Colston Granite, c.
1169
Kanoneiland Granite, d. Keboes Granite, e. Louisvale Granite, f. Klipkraal Granite, g. Josling Granite,
1170
h. Elsie se Gorra Granite.
1171
Fig. 3. U-Pb isochron diagrams for the dated eastern NS granites. Plots are generated by Isoplot 3.0
1172
(Ludwig, 2003) but weighted mean ages are given rather than concordia ages. a. Smalvis Granite,
1173
Cyndas Subsuite, b. Colston Granite, c. Elsie se Gorra Granite, d. Josling Granite, e. Kanoneiland
1174
Granite, f. Keboes Granite, g. Klipkraal Granite, h. Louisvale Granite.
1175
Fig. 4. General geochemical characteristics and classification of the eastern NS granites. (a) QAP
1176
classification for granitoids, after Le Maitre et al. (2005), (b) The An-Ab-Or ternary plot to determine
1177
the composition of granite (after O’Connor, 1965), (c) The Na2O + K2O - CaO vs. SiO2 plot (after
1178
Frost et al., 2001), (d) Fe*/Fe*+ MgO vs. SiO2 plot used to determine if the rocks are ferroan or
1179
magnesian (after Frost et al., 2001), (e) The K2O+Na2O/CaO vs. Zr + Nb + Ce + Y plot indicating the
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ACCEPTED MANUSCRIPT predominant A-type nature of the granites (after Whalen et al., 1987), (f) The molar Na2O+K2O/Al2O3
1181
vs. molar Al2O3/Na2O+K2O+CaO plot to differentiate between peralkaline, metaluminous and
1182
peraluminous granites (after Maniar and Piccoli, 1989). The fields for the compositions of the Cyndas
1183
Subsuite (after Jankowitz, 1987) and the Riemvasmaak Gneiss (after Geringer, 1973; Saad, 1987) are
1184
shown for (a) and (b).
1185
Fig. 5. Binary Harker diagrams for major and minor elements for the eastern NS granites. The fields
1186
for the Cyndas Subsuite (after Jankowitz, 1987) and the Riemvaasmaak Gneiss (after Geringer, 1973;
1187
Saad, 1987) are shown for reference.
1188
Fig. 6. Select major and minor element maficity (Mg + Fe) plots for the eastern NS granites.
1189
Fig. 6. (cont.) Select trace element maficity (Mg + Fe) plots for the eastern NS granites.
1190
Fig. 7. Spider diagrams and rare earth element (REE) plots for the syn-tectonic and late- to post-
1191
tectonic granites of the eastern NS granites. The colours and symbols are as for Figs. 5 and 6.
1192
Fig. 8. Isotopic diagrams for the eastern NS granites. a. εNd(t) vs. initial Sr showing major crustal and
1193
mantle sources, b. εNd(t) vs. 147Sm/144Nd, c. εNd(t) vs. age (in Ma), d. Initial Sr [SrI = (87Sr/86Sr)t], where t
1194
is the time of emplacement, vs. age, e. εNd(t) vs. maficity (elemental Fe + Mg), f. Initial Sr [SrI =
1195
(87Sr/86Sr)t] vs. maficity. The upper crust curve (Harris et al., 1986) and a theoretical lower crustal
1196
curve (Ben Othman et al., 1984) are indicated for reference in (a). The positions of the main oceanic
1197
mantle reservoirs identified by Zindler and Hart (1986) shown in (a) are: DM = depleted mantle, BSE
1198
= bulk silicate earth, EMI and EMII = enriched mantle I and II, HIMU = high mantle U/Pb ratio,
1199
PREMA = frequently observed prevalent mantle composition. The mantle source of MORB and the
1200
mantle end-members DMM, PREMA, HIMU, BSE, EMI and EMII are from Zindler and Hart (1986).
1201
The evolution curves for Paleoproterozoic crust of ∼2.4 Ga (c) and ∼2.0 Ga crust (d) is after Eglington
1202
(2006). The data used to plot d) and e) can be found in Appendix Table A10.
1203
Fig. 9. Tectonic setting discrimination diagrams for the late- to post-tectonic Keimoes Suite. a. The
1204
Rb vs. Y + Nb plot of Pearce et al. (1984). b. The Nb vs. Y plot of Pearce et al. (1984) is used because
1205
of the potential mobility of Rb during metamorphism.
1206
Fig. 10. Compilation of magmatic and metamorphic data for the Kakamas, Areachap and Kaaien
1207
terranes of the eastern NS (adapted after Spencer et al., 2015).
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potassic monzogranite
fine-grained, porphyritic
euhedral – subhedral K-fsp phenocrysts (up to 12 mm), qtz, K-fsp, plag, bt, msc
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Table 1 Features of the eastern Namaqua Sector granites (sensu Moen, 2007) (after Stowe, 1983; Geringer et al., 1987, 1988; Moen, 2007; Bailie et al., 2011a; Cornell et al., 2012) Granite Composition Grain Mineralogy Presence Host rocks Contacts Inclusions Age or relative Size of foliation age (in Ma) + ref. Josling leucogranite fine-grained qtz, K-fsp > plag, gneissic, well- Areachap Grp gradational 1275 ± 7b bt-poor, msc developed not part of Keimoese Elsie se Gorra leucogranite coarse-grained qtz, K-fsp, plag, bt moderate to no contacts, msc well-developed isolated outcrops Colston potassic, medium qtz, mcl, plag, bt, minor weakly Korannaland foliation numerous, 1156 ± 20 Ma peraluminous, equigranular, msc developed Group stronger toward mafic (can TIMS – zircon granodiorite porphyritic in central part contacts, no be up to 1 m) Geringer and Botha metam. effects (1977) Cyndas monzogranites variable, qtz, K-fsp, plag, bt ± hbl variable, mostly Korannaland mafic (cognate variable 1155Subsuite medium-coarse, ± msc, pyx (locally) unfoliated Group xenoliths) and 1061 Maa medium-fine metased xenoliths Vaalputs monzogranite, medium rounded phenocrysts of well-developed Korannaland sharp, generally numerous 1146 ± 14 b unevolved equigranular K-feldspar (up to 15 mm), Group concordant, qtz, feldspars, biotite, cross-cutting plag phenocrysts locally Louisvale heterogeneous, medium mafic – variable amts of strong / gneissic Bethesda Fm, concordant, during peak mesocratic to fsp phenocrysts, disharmonic Areachap Grp lit-par-lit, very metamorphism; leucocratic, opalescent blue qtz, flow pattern foliated; deep crustal tonalite to cordierite; leucocratic – gradational with monzogranite elongate mcl phenocrysts Klipkraal and Vaalputs Granites Gouskop medium qtz, K-fsp, plag, no bt moderate semi-pelites poor, subvertical lineation
Bethesda Fm, Areachap Grp, Louisvale Grn
sharp with Areachap Grp, Friersdale Charnockite
very few mafic lenticles
approx. same age as Kanoneiland Granite
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Table 1 (cont.) Features of the eastern Namaqua Sector granites (sensu Moen, 2007) (after Stowe, 1983; Geringer et al., 1987, 1988; Moen, 2007; Bailie et al., 2011a; Cornell et al., 2012) Granite Composition Grain Mineralogy Presence Host rocks Contacts Inclusions Age or relative Size of foliation age (in Ma) + ref. Kanoneiland biotite-rich medium to qtz, K-fsp, plag, bt poor gradational with sharp, crossnumerous late-tectonic monzogranite coarse, nonKeboes, sharp cutting; metam. mafic and porphyritic with Vaalputs aureole present felsic inclusions and Louisvale Gemsbokbult monzogranite medium to qtz, K-fsp, plag, bt, weak Klip Koppies concordant and 1104 ± 11c coarse, staur Granite sheared, foliated equigranular Kleinbegin leucocratic medium to qtz, K-fsp, plag, bt, poor to Dagbreek Fm, clots of mafic 1101 ± 10c Subsuite granodiorite coarse, nonhbl, mgt, hmt unfoliated Jannelsepan Fm, mineral porphyritic Areachap Grp aggregates Klip Koppies monzogranites fine to K-fsp phenocrysts (5poor not exposed, small mafic 1096 ± 10c medium 30 mm), qtz, K-fsp, foliated nearing inclusions intrudes porphyritic plag, bt, msc contacts Gemsbokbult Straussburg bt-rich, medium-coarse, blue opaline qtz, K-fsp moderate to feldspathic sharp, metam. numerous 1089 ± 9d monzogranitic porphyritic (as large phenocrysts), poor quartzite, aureole lensoid granodioritic to locally plag (An20-35), bt, Dagbreek Fm developed mafic granitic minor hbl inclusions Klipkraal variable, commonly non-porph: plag, K-fsp, unfoliated Jannelsepan intrusive into young granodioriticporphyritic, hbl, hyp; porph: qtz, fsps Fm, Areachap Louisvale Granite monzogranite medium-coarse plag phenocrysts, bt, hbl Grp Gif Berg fine to medium, fsp phenocrysts (10 mm), unfoliated sharp, fineyoung porphyritic, qtz, K-fsp, plag, bt, gnt grained, chilled granophyric margin Neilers Drift biotite-rich coarse, nonbt-rich unfoliated intruded by none post-tectonic porphyritic Friersdale Friersdale monzogranite- fine- to opalescent blue qtz, unfoliated Korannaland concordant ellipsoidal 1080 ± 13b Charnockite granodiorite medium-grained, K-fsp, minor plag, Grp, Vaalputs to sharply (3-15 cm) of 1078 ± 12d porphyritic bt – groundmass; and Keboes discordant; mafic + bt, qtz, hyp, aug, Granites contact aureoles quartzitic plag – phenocrysts developed composition Abbreviations: mineralogy: aug – augite, bt – biotite, gnt – garnet, hbl – hornblende, hmt – hematite, hyp – hypersthene, K-fsp – K-feldspar, mgt – magnetite, msc- muscovite, plag – plagioclase, pyx – pyroxene, qtz – quartz; porph – porphyritic; References: a Jankowitz (1987), b Pettersson (2008), c Bailie et al. (2011a), d Cornell et al. (2012), e Moen (2007)
ACCEPTED MANUSCRIPT Table 2 Summary of geochronological data obtained in this study (top) and that from previous studies for the magmatic rocks of the eastern Namaqua Sector (in chronological order)
AC C
Reference this study this study this study this study this study this study this study this study Pettersson et al. (2007) Moen & Armstrong (2008) Moen & Armstrong (2008) Bailie et al. (2011b) Pettersson (2008) Cornell & Pettersson (2007) Bailie (2008) Pettersson et al. (2007) Fransson (2008) Bial et al. (2015a) Bial et al. (2015a) Pettersson (2008) Pettersson (2008) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Bial et al. (2015a) Pettersson (2008) Gutzmer et al. (2000) Colliston et al. (2015) Pettersson (2008) Jankowitz (1987) Pettersson (2008) Pettersson (2008) Jankowitz (1987) Colliston et al. (2015) Bailie et al. (2011a) Pettersson et al. (2007) Bailie et al. (2012) Bailie et al. (2011a) Bial et al. (2015a) Jankowitz (1987) Bailie et al. (2012) Bailie et al. (2012) Bailie et al. (2011a) Pettersson et al. (2007) Jankowitz (1987) Pettersson et al. (2007) Pettersson et al. (2007) Pettersson et al. (2007) Cornell et al. (2012) Jankowitz (1987) Pettersson (2008) Cornell et al. (2012)
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Age of metamorphism
1142 ± 11 Ma 1165 ± 10 Ma
M AN U
Age of emplacement 1217 ± 20 Ma 1175 ± 18 Ma 1151 ± 28 Ma 1159 ± 28 Ma 1125 ± 16 Ma 1105 ± 27 Ma ∼1110 Ma1 1098 ± 26 Ma 1371 ± 9 Ma 1293 ± 9 Ma 1290 ± 8 Ma 1289 ± 9 Ma 1275 ± 7 Ma 1275 ± 7 Ma 1261 ± 18 Ma 1241 ± 12 Ma 1190 ± 27 Ma 1229 ± 16 Ma (lc) 1222 ± 13 Ma (lc) 1220 ± 10 Ma 1203 ± 11 Ma 1201 ± 10 Ma (mg) 1198 ± 46 Ma (mg) 1197 ± 10 Ma (mg) 1197 ± 11 Ma (lc) 1195 ± 16 Ma (mg) 1191 ± 7 Ma (mg) 1189 ± 18 Ma (lc) 1189 ± 6 Ma (mg) 1173 ± 12 Ma 1171 ± 7 Ma 1168 ± 6 Ma (ip) 1156 ± 8 Ma 1155 ± 62 Ma 1151 ± 14 Ma 1146 ± 14 Ma 1120 ± 22 Ma 1107 ± 11 Ma (la) 1104 ± 11 Ma 1104 ± 8 Ma 1101 ± 2 Ma 1101 ± 10 Ma 1101 ± 6 Ma 1100 ± 14 Ma 1100 ± 8 Ma 1098 ± 10 Ma 1096 ± 10 Ma 1095 ± 10 Ma 1094± 11 Ma 1093 ± 11 Ma 1093 ± 10 Ma 1092 ± 9 Ma 1089 ± 9 Ma 1087 ± 17 Ma 1080 ± 13 Ma 1078 ± 12 Ma
TE D
Terrane Areachap Kakamas Areachap Areachap Areachap Areachap Areachap Areachap Kaaien Kaaien Kaaien Kaaien Areachap Areachap Areachap Areachap Areachap Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kakamas Kaaien Kaaien Kakamas Areachap Areachap Kakamas Kakamas Areachap Kakamas Areachap Kaaien Kaaien Areachap Kakamas Areachap Kaaien Kaaien Areachap Kaaien Areachap Kaaien Kaaien Kaaien Areachap Areachap Kakamas Areachap
EP
Granite Josling Granite Elsie se Gorra Granite Colston Granite Smalvisch Granite, CS Louisvale Granite Keboes Granite Klipkraal Granite Kanoneiland Granite Swanartz Gneiss Kalkwerf Gneiss Wilgenhoutsdrif Group Wilgenhoutsdrif Group Josling Granite Areachap Group Areachap Group Areachap Group Areachap Group ZA-93-1 ZA-81-2 Dyasons Klip Gneiss Polisiehoek Granite ZA-68-1 ZA-70-1 ZA-82-2 ZA-80-1 ZA-49-2 ZA-62-1 ZA-103-1 ZA-61-2 Lower Koras Group Lower Koras Group Augrabies Granite Riemvasmaak Gneiss Cyndas E Granodiorite, CS Riemvasmaak Gneiss Vaalputs Granite Smalvisch Granite, CS Karama’am augen gneiss Gemsbokbult Granite Upper Koras Group Upper Koras Group Kleinbegin Granite Naros Granite (957/967) Gous Charnockite, CS Upper Koras Group Upper Koras Group Klip Koppies Granite Upper Koras Group Cyndas E Granodiorite, CS Rooiputs Granophyre Bloubos Granite Upper Koras Grp Straussburg Granite Enna Granite, CS Friersdale Charnockite Friersdale Charnockite
1156 ± 14 Ma
1108 ± 9 Ma 1108 ± 12 Ma (metam.?) 1098 ± 10 Ma 1091 ± 8 Ma 1125 ± 5 Ma 1088 ± 10 Ma
1090 ± 16 Ma
1062 ± 27 Ma 1014 ± 36 Ma
Abbreviations: CS – Cyndas Subsuite; la – LAICPMS, ip – ion probe; lc – leucogranite, mg – mesocratic granite; 1 assumed age based on field relationships and lack of foliation, inherited age of 1270 ± 26 Ma determined
ACCEPTED MANUSCRIPT
Table 3 Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Metamorphic Province granites
AC C
EP
TE D
M AN U
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RI PT
Sample Mkl2 Mkl4 Mkl5 Mkl6 Mkl3 Ml1 Ml2 Ml4 Ml5 Mka1 Mka3 Mka6 Mka7 Mkb1 Mkb2 Mkb4 Mkb6 Mv2 SiO2 66.09 66.74 65.49 65.67 65.52 65.00 66.34 65.48 71.15 69.96 69.31 68.23 69.10 70.24 70.00 73.62 69.70 73.62 TiO2 0.90 0.94 1.11 1.14 0.95 0.58 0.89 0.58 0.29 0.75 0.70 0.73 0.76 0.48 0.50 0.18 0.49 0.32 Al2O3 13.11 12.97 13.85 13.71 13.11 17.18 13.19 16.77 15.23 12.68 13.12 13.73 13.06 13.64 14.07 14.30 14.27 13.26 8.87 8.73 7.24 7.47 8.92 4.82 8.24 4.95 2.23 5.40 5.10 5.45 5.37 3.77 3.71 1.64 3.70 2.69 Fe2O3 MnO 0.20 0.18 0.15 0.15 0.18 0.08 0.17 0.08 0.05 0.12 0.11 0.11 0.11 0.08 0.08 0.03 0.08 0.05 MgO 0.47 0.48 0.97 1.00 0.49 0.99 0.46 1.00 0.61 0.66 0.61 0.72 0.65 0.68 0.69 0.25 0.69 0.28 CaO 2.54 2.48 3.19 3.20 2.55 3.63 2.61 3.51 2.02 2.21 2.32 2.50 2.35 2.10 2.23 0.79 2.27 1.00 Na2O 1.51 2.19 2.26 2.20 2.42 4.90 2.38 4.81 4.88 2.46 2.70 2.80 2.66 2.93 2.98 2.97 3.06 2.69 K2O 5.09 4.33 4.74 4.44 4.52 1.93 4.61 1.95 2.63 4.72 4.75 4.68 4.73 4.82 4.82 5.14 4.81 5.48 P2O5 0.48 0.47 0.45 0.47 0.48 0.35 0.45 0.34 0.10 0.25 0.24 0.26 0.26 0.18 0.18 0.22 0.18 0.18 Cr2O3 0.001 0.001 0.001 0.001 0.003 0.001 0.001 0.003 0.002 0.001 0.005 0.002 0.002 0.005 0.005 0.003 0.002 0.005 L.O.I. 0.13 0.12 0.15 0.13 0.08 0.13 0.16 0.10 0.12 0.14 0.10 0.13 0.08 0.13 0.09 0.09 0.09 0.10 Total 99.39 99.63 99.59 99.58 99.23 99.58 99.50 99.58 99.31 99.34 99.05 99.34 99.14 99.06 99.35 99.24 99.33 99.32 Sc 23.3 25.3 20.9 21.5 26.7 11.5 22.9 11.8 7.5 17.5 16.3 20.1 14.3 12.3 12.1 6.9 11.8 10.0 Ti 5421 5620 6637 6845 5701 3457 5364 3474 1755 4509 4175 4368 4545 2880 2981 1093 2938 1941 V 30.0 26.2 72.9 80.0 35.1 78.2 30.5 51.4 47.6 61.1 52.6 60.3 58.2 50.4 47.4 21.8 79.1 38.9 101.8 72.3 50.7 84.1 149.6 124.4 92.4 134.8 184.4 154.6 66.5 81.9 116.0 131.2 79.4 74.4 102.1 208.9 Cra Co 7.8 7.9 11.7 11.4 9.1 7.7 7.8 5.7 4.4 7.5 7.0 8.0 7.1 5.9 6.0 3.0 8.2 4.0 Ni 7.1 7.4 11.1 11.5 11.7 10.7 8.8 12.2 12.0 9.8 12.4 9.7 10.1 11.5 11.7 8.6 10.3 11.3 Cu 20.2 18.5 25.1 26.7 27.6 47.3 14.9 14.5 33.9 11.7 21.5 14.6 12.2 14.0 20.6 17.8 43.2 29.2 Zn 122.6 124.8 113.9 107.1 146.1 112.0 115.2 71.2 57.8 97.3 93.2 98.7 90.7 71.7 77.8 113.1 129.5 52.9 Rb 174.2 204.1 199.6 186.2 220.2 172.8 189.8 233.6 89.0 245.9 234.5 233.2 227.8 255.7 242.9 335.9 185.6 404.5 Sr 151.1 146.7 165.3 171.2 165.1 292.6 151.9 124.7 501.6 159.6 148.3 142.9 155.3 131.0 130.7 43.1 294.3 63.1 Y 92.5 92.6 69.2 69.0 99.7 19.0 84.5 36.6 5.1 56.2 73.1 69.6 46.7 41.0 40.9 6.2 21.1 60.0 Zr 482.8 419.4 515.3 524.4 534.8 298.9 444.3 225.0 135.5 349.8 298.3 331.9 337.4 229.1 234.6 51.6 307.5 192.6 Nb 24.4 23.6 27.3 28.5 29.6 15.5 24.2 16.0 3.1 22.4 22.7 21.2 21.2 17.3 16.4 12.2 16.4 23.0 Cs 2.5 4.6 2.5 2.1 7.2 11.4 3.8 10.0 1.6 14.3 12.6 11.6 11.3 11.0 10.7 6.1 12.3 13.4 Ba 1443 1467 1198 1186 1588 253 1351 681 1364 874 882 824 870 715 714 174 255 451 Hf 13.7 12.2 14.4 14.2 14.6 7.0 12.3 6.3 3.3 10.0 8.4 9.5 9.5 6.6 6.8 2.0 7.3 6.4 Ta 2.5 2.9 1.5 3.1 3.8 1.6 1.6 3.2 1.0 2.1 2.6 1.9 1.6 3.0 1.5 1.3 1.7 2.8 Pb 41.3 40.9 41.7 39.3 38.6 17.6 36.1 30.3 33.7 32.6 32.0 34.8 31.0 32.5 30.9 37.0 18.0 35.2 Th 36.0 41.8 54.6 51.1 38.3 16.1 38.4 31.9 7.5 22.4 21.5 34.7 22.6 34.4 34.5 6.4 14.5 44.2 U 3.6 3.5 4.5 4.4 4.1 3.9 3.6 3.8 1.7 3.8 2.5 4.0 4.5 7.2 7.6 3.6 3.5 9.8 Note: Mkl – Klipkraal Granite, Ml – Louisvale Granite, Mka – Kanoneiland Granite, Mkb – Keboes Granite, Mv – Vaalputs Granite. All REE normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
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Table 3 (cont.) Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Sector granites
AC C
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Sample Mv3 Mv5 Mv9 Ms1 Ms2 Ms6 Ms7 Mf1 Mf4 Mf6 Mf7 Mc2 Mc6 Mc8 Mc9 Mcol1 Mcol2 Mcol3 SiO2 72.81 69.75 72.71 67.66 68.18 68.29 67.87 66.46 65.40 65.36 65.91 64.18 70.42 71.25 65.78 66.80 65.19 65.51 TiO2 0.29 0.83 0.30 0.96 0.95 0.91 0.99 1.24 1.27 1.30 1.28 1.34 0.66 0.50 1.19 0.86 1.07 1.15 Al2O3 13.35 11.89 13.32 13.37 13.00 13.14 12.92 12.85 13.00 13.15 12.77 13.75 13.42 13.25 13.53 14.04 13.90 13.51 2.74 5.52 2.73 5.52 5.40 5.43 5.45 7.09 7.28 7.37 7.41 7.45 3.99 3.16 6.97 6.06 7.13 7.36 Fe2O3 MnO 0.05 0.12 0.05 0.12 0.11 0.11 0.12 0.15 0.16 0.16 0.16 0.15 0.10 0.06 0.14 0.11 0.13 0.141 MgO 0.26 0.91 0.28 0.95 0.92 0.97 0.93 1.36 1.45 1.35 1.40 1.54 0.62 0.55 1.33 0.96 1.25 1.29 CaO 1.38 2.43 1.43 3.03 2.96 3.01 2.89 3.86 4.16 4.06 3.96 3.71 1.98 1.52 3.43 2.32 2.84 2.91 Na2O 3.03 2.48 3.03 2.77 2.59 2.73 2.61 2.50 2.59 2.62 2.53 2.64 2.93 3.13 2.64 2.27 2.10 2.22 K2O 5.30 4.21 5.34 4.53 4.81 4.39 4.84 3.90 3.81 3.75 3.91 3.87 5.08 5.38 4.11 5.01 4.52 4.39 P2O5 0.11 0.32 0.11 0.30 0.28 0.29 0.27 0.48 0.50 0.51 0.48 0.41 0.21 0.15 0.35 0.31 0.30 0.34 Cr2O3 n.d. 0.004 0.001 0.005 0.004 0.005 0.004 0.002 0.001 0.002 0.003 0.004 0001 0.005 0.02 0.002 0.002 0.001 L.O.I. 0.05 0.12 0.11 0.12 0.13 0.22 0.08 0.11 0.07 0.07 0.06 0.10 0.09 0.10 0.08 0.11 0.11 0.10 Total 99.38 98.59 99.43 99.33 99.34 99.50 98.96 99.99 99.68 99.69 99.87 99.15 99.49 99.05 99.58 98.84 98.56 98.92 Sc 10.7 16.3 10.6 16.6 16.1 19.0 11.9 22.8 21.9 21.3 20.9 10.5 10.7 23.1 15.2 19.0 19.2 15.3 Ti 1766 4991 1787 5736 5689 5453 5928 7422 7588 7774 7683 8012 3959 3013 7123 5130 6416 6892 V 25.6 72.8 22.6 87.5 90.5 91.6 66.8 115.3 115.0 125.9 117.0 50.4 40.2 116.2 68.7 90.8 96.4 89.4 76.3 164.3 60.2 142.6 162.7 68.9 182.2 52.6 79.9 162.4 74.1 107.4 56.5 69.9 104.5 63.8 109.5 142.0 Cra Co 3.3 7.6 3.1 9.4 9.2 10.9 6.8 13.6 12.8 13.3 15.6 5.9 5.2 16.6 10.6 13.3 13.2 9.0 Ni 9.4 14.5 7.5 12.9 14.8 18.1 13.9 16.1 15.1 18.8 18.6 11.0 8.8 20.7 17.4 17.4 15.3 14.4 Cu 29.5 11.9 25.4 14.5 26.3 31.4 13.4 67.7 16.0 100.3 28.9 23.8 17.2 35.8 36.6 29.5 19.2 25.4 Zn 36.5 85.8 39.1 75.6 77.9 90.2 76.7 110.5 99.7 104.8 108.8 112.3 60.8 130.4 83.5 97.4 86.7 70.5 Rb 510.9 196.3 489.6 195.9 224.5 199.2 278.6 156.6 161.4 159.4 167.8 226.7 265.1 193.1 246.5 218.1 217.6 196.3 Sr 67.0 182.2 65.3 188.0 171.5 197.3 126.6 279.4 277.3 264.3 240.0 159.3 162.6 220.1 110.0 118.9 149.1 180.3 Y 116.3 53.4 129.5 48.2 50.3 53.2 50.9 63.1 59.7 59.1 59.9 43.3 49.7 62.8 46.4 56.2 54.2 46.7 Zr 219.5 309.5 266.3 413.2 432.1 410.6 334.3 395.0 422.0 387.0 504.4 351.5 333.0 570.6 351.0 415.6 396.6 420.9 Nb 38.2 21.4 49.5 20.6 22.3 22.9 19.0 22.2 24.9 24.4 27.6 17.1 19.2 26.8 19.8 21.3 22.2 21.3 Cs 26.7 6.1 26.0 6.3 5.6 5.3 13.2 5.3 5.3 5.9 6.8 9.3 3.6 9.6 6.1 7.2 8.3 5.0 Ba 333 883 332 1104 1076 1193 884 1134 1130 1070 1105 753 756 1136 739 856 833 1069 Hf 7.6 8.5 8.8 11.2 12.0 11.0 9.8 10.3 11.1 10.3 13.5 10.0 9.7 15.0 10.3 11.8 10.9 11.1 Ta 4.2 1.7 4.8 1.5 2.7 1.6 2.0 1.5 1.8 2.4 2.6 1.6 1.4 1.8 2.8 1.3 1.5 2.6 Pb 34.0 26.8 33.4 30.8 32.4 37.1 40.6 29.3 27.3 28.8 28.0 22.7 31.7 32.2 34.7 31.8 29.6 32.2 Th 88.4 20.8 89.5 25.0 34.1 57.8 53.8 17.1 17.1 20.1 17.5 24.4 49.2 26.1 32.4 32.1 28.7 19.2 U 23.7 3.9 31.1 4.0 4.4 4.9 6.6 3.7 3.2 4.3 5.9 4.1 6.4 5.5 4.9 4.6 3.9 5.8 Note: Mv – Vaalputs Granite, Ms – Straussburg Granite, Mf – Friersdale Charnockite, Mc – Cyndas Subsuite, Mcol – Colston Granite. All REE are normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
ACCEPTED MANUSCRIPT
Table 3 (cont.) Whole rock major, minor element and trace element geochemistry of the eastern Namaqua Metamorphic Province granites
AC C
EP
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SC
RI PT
Sample Mcol4 Mcol6 Mge1 Mge2 Mge3 Mge5 Mkle1 Mkle2 Mkle3 Me1 Me2 Mks1 Mks2 Mks3 Mks4 Mkn2 Mkn4 Mkn7 SiO2 66.88 65.90 69.64 68.92 68.96 65.70 70.87 70.22 70.52 76.02 75.12 69.14 69.19 68.92 69.00 72.49 71.38 71.31 TiO2 0.97 1.02 0.71 0.82 0.76 1.02 0.47 0.55 0.53 0.28 0.29 0.75 0.74 0.80 0.79 0.30 0.34 0.34 Al2O3 13.79 13.76 13.41 13.05 12.95 12.81 13.66 13.64 13.68 12.07 12.36 12.95 12.97 13.11 13.02 13.84 13.96 14.14 6.19 6.45 4.52 6.07 5.99 8.54 3.49 3.97 3.80 1.77 1.92 5.91 5.73 5.89 5.65 3.09 3.17 3.34 Fe2O3 MnO 0.13 0.14 0.09 0.13 0.12 0.19 0.08 0.08 0.08 0.03 0.03 0.12 0.12 0.12 0.12 0.07 0.08 0.08 MgO 1.61 1.70 0.65 0.60 0.64 0.60 0.80 0.95 0.93 0.22 0.21 0.58 0.56 0.60 0.56 0.34 0.51 0.41 CaO 2.49 2.58 1.84 2.14 2.20 3.16 3.08 3.41 3.26 0.97 0.98 2.11 2.11 2.24 2.20 2.36 2.35 2.62 Na2O 2.26 2.23 2.48 2.26 2.27 2.11 3.47 3.38 3.50 2.72 2.66 2.25 2.32 2.36 2.46 3.54 3.36 3.66 K2O 3.95 4.18 5.51 5.07 5.02 4.97 3.30 2.93 2.87 5.25 5.65 5.21 5.16 4.95 4.97 3.09 3.80 3.12 P2O5 0.27 0.27 0.29 0.32 0.31 0.42 0.11 0.13 0.12 0.05 0.06 0.30 0.30 0.32 0.30 0.09 0.09 0.11 Cr2O3 0.004 0.006 n.d. 0.003 0.001 0.003 0.009 0.009 0.012 0.010 0.006 0.001 0.003 0.005 0.001 0.002 0.009 0.005 L.O.I. 0.16 0.12 0.16 0.09 0.09 0.10 0.08 0.09 0.10 0.09 0.09 0.08 0.05 0.11 0.09 0.08 0.10 0.07 Total 98.71 98.38 99.29 99.48 99.31 99.62 99.40 99.37 99.40 99.47 99.39 99.41 99.25 99.42 99.16 99.29 99.15 99.20 Sc 18.4 19.3 12.2 19.2 19.7 24.5 10.0 12.6 10.8 7.8 7.4 17.8 18.1 18.1 18.1 8.5 8.6 8.9 Ti 5822 6144 4252 4910 4576 6116 2839 3308 3191 1661 1747 4520 4429 4814 4762 1773 2017 2019 V 110.4 110.0 71.8 47.4 53.0 37.6 61.1 77.4 73.6 29.9 38.4 46.1 42.4 49.6 45.8 33.9 39.0 45.9 169.1 67.4 242.6 91.2 161.0 133.2 98.9 167.2 184.0 83.8 225.7 113.3 72.5 147.4 93.2 104.8 96.9 171.3 Cra Co 13.8 14.7 6.9 6.7 7.1 8.2 8.1 9.6 9.0 3.8 3.3 6.5 6.7 6.8 6.5 4.0 4.5 4.6 Ni 21.8 18.9 14.4 10.5 12.0 11.4 15.8 22.9 21.2 11.5 13.3 11.4 22.9 12.2 9.0 11.9 11.3 10.7 Cu 45.5 62.0 21.4 14.3 17.2 32.6 37.6 76.5 43.2 24.5 32.8 17.7 38.8 17.9 13.5 27.1 12.4 13.4 Zn 82.6 85.9 74.8 102.4 103.5 139.0 45.8 53.3 47.5 52.3 31.0 97.6 101.5 96.1 100.8 60.8 65.5 69.4 Rb 188.8 194.0 292.2 209.7 193.1 189.1 107.0 99.1 106.5 276.0 296.1 197.2 206.1 200.3 197.5 98.1 103.0 95.5 Sr 118.4 110.1 133.2 165.5 151.1 167.4 153.5 156.7 156.2 60.0 50.5 142.1 142.9 148.2 145.0 221.4 240.0 249.5 Y 57.8 60.6 54.1 52.7 50.3 77.3 59.6 56.7 44.0 10.4 8.6 49.7 52.3 51.3 50.4 25.2 21.7 22.3 Zr 364.6 387.8 341.5 369.5 351.4 510.2 275.3 307.3 307.7 224.2 171.2 323.9 325.6 340.1 344.0 263.9 205.9 227.3 Nb 18.3 18.6 20.1 20.9 21.6 28.8 11.4 13.3 10.9 9.4 9.7 20.4 19.9 21.3 21.2 12.5 11.5 12.2 Cs 6.8 6.9 13.9 3.5 3.4 2.4 1.8 2.0 2.6 1.7 1.6 5.7 6.5 6.0 6.0 3.0 2.6 2.5 Ba 770 805 931 1115 1102 1369 1135 982 959 523 520 1043 1084 1050 1061 1257 1534 1205 Hf 10.4 11.1 10.1 10.3 9.9 14.1 7.9 8.0 8.4 6.8 5.1 9.2 9.3 9.5 9.6 6.6 5.5 5.9 Ta 1.9 1.3 2.0 1.4 2.9 3.5 0.8 3.0 3.0 0.4 1.6 1.9 1.3 2.2 1.3 1.7 0.7 2.0 Pb 38.6 41.0 39.3 36.9 35.3 39.4 18.9 17.7 16.2 43.2 22.6 34.2 37.5 35.0 34.4 18.0 18.4 17.0 Th 56.4 83.3 55.5 29.0 28.9 37.5 16.9 13.1 5.9 68.7 3.8 27.3 29.1 28.9 28.1 15.7 11.5 12.2 U 6.0 7.6 6.6 3.0 2.3 3.6 2.0 1.6 1.5 3.6 0.8 3.2 3.2 3.2 2.7 2.1 1.9 1.6 Note: Mcol – Colston Granite, Mge – Gemsbokbult Granite, Mkle – Kleinbegin Granite, Me – Elsie se Gorra Granite, Mks – Klip Koppies Granite, Mkn – Josling Granite. All REE are normalized relative to Boynton (1984). All major and minor elements measured in weight percent (wt.%). The trace elements are measured in parts per million (ppm). a Cr concentrations are unreliable due to milling in a Cr-steel mill.
ACCEPTED MANUSCRIPT
Table 4 Whole rock rare earth element (REE) geochemistry of the eastern Namaqua Metamorphic Province granites Ml2 103.52 222.03 26.35 103.69 19.48 2.87 17.13 2.59 15.70 3.15 9.10 1.25 8.80 1.21 0.48 3.33 7.98 1.76 8.93 Ms7 85.65 189.44 20.80 76.07 13.74 1.60 10.54 1.55 8.91 1.75 5.24 0.77 5.56 0.79 0.41 3.91 10.45 1.66 11.35
Ml4 53.35 117.58 13.78 52.96 10.30 1.23 7.93 1.12 7.03 1.31 3.83 0.55 3.89 0.52 0.42 3.25 9.31 1.89 10.71 Mf1 85.38 180.22 21.25 82.44 15.58 3.11 13.73 2.02 12.16 2.40 6.59 0.95 6.60 0.96 0.65 3.44 8.77 1.77 9.25
Ml5 19.56 35.34 3.66 12.65 1.92 0.64 1.49 0.18 0.92 0.16 0.58 0.08 0.50 0.10 1.16 6.40 26.28 1.91 21.09 Mf4 82.24 174.74 20.65 81.01 15.48 3.05 12.62 1.86 11.09 2.36 6.67 0.88 6.02 0.88 0.67 3.33 9.27 1.77 9.70
Mka1 65.37 139.13 16.45 62.91 12.69 2.04 10.83 1.69 10.54 2.06 6.09 0.83 6.09 0.85 0.53 3.23 7.28 1.58 8.00 Mf6 81.60 174.21 20.38 79.82 14.47 2.86 12.22 1.86 11.15 2.25 6.51 0.94 6.21 0.87 0.66 3.54 8.92 1.74 9.74
Mka3 62.96 131.12 15.54 57.83 12.40 2.12 10.88 1.92 12.89 2.67 7.99 1.27 8.62 1.15 0.56 3.19 4.95 1.17 5.71 Mf7 75.10 160.26 19.41 74.52 14.81 2.81 12.45 1.82 11.23 2.31 6.19 0.95 6.24 0.86 0.63 3.18 8.16 1.79 9.07
Mka6 98.31 215.51 25.19 95.24 18.05 2.05 14.47 2.23 13.61 2.63 7.59 1.09 7.29 1.02 0.39 3.42 9.15 1.75 10.00 Mc2 49.27 106.61 12.93 51.03 10.56 1.58 9.12 1.39 8.15 1.58 4.35 0.60 4.39 0.61 0.49 2.93 7.61 1.85 8.42
Mka7 67.66 142.45 16.53 63.29 12.04 2.02 9.46 1.44 8.76 1.72 4.89 0.73 4.91 0.65 0.58 3.52 9.34 1.81 10.87 Mc6 90.58 199.36 23.06 85.25 15.66 1.47 11.75 1.69 9.51 1.89 5.16 0.74 5.05 0.77 0.33 3.63 12.16 1.89 12.25
RI PT
Ml1 35.74 62.61 6.34 23.07 4.48 0.84 3.66 0.51 3.16 0.65 1.86 0.26 1.94 0.27 0.64 5.00 12.52 1.65 13.55 Ms6 120.02 249.90 27.59 96.30 15.76 2.35 11.92 1.72 10.23 1.95 5.43 0.92 5.57 0.86 0.52 4.78 14.61 1.72 14.54
SC
Mkl3 113.05 241.53 29.09 115.35 21.73 3.49 19.64 3.06 18.93 3.72 10.81 1.66 10.57 1.55 0.52 3.26 7.25 1.57 7.60 Ms2 67.71 144.36 17.08 64.72 12.09 2.05 9.56 1.54 9.58 1.92 5.56 0.77 5.46 0.80 0.58 3.51 8.41 1.49 8.87
M AN U
Mkl6 115.41 260.89 31.96 128.49 22.72 2.71 16.34 2.26 13.25 2.67 7.39 0.95 6.82 0.98 0.43 3.19 11.48 2.07 12.27 Ms1 73.18 148.55 16.90 61.83 11.34 2.04 9.14 1.42 8.87 1.80 5.12 0.79 5.10 0.75 0.61 4.05 9.73 1.52 10.21
TE D
Mkl5 119.13 270.33 33.12 129.45 23.56 2.79 16.88 2.24 13.41 2.66 7.24 1.06 6.83 0.85 0.43 3.17 11.82 2.46 14.61 Mv9 112.63 238.91 25.60 89.71 17.65 1.11 16.03 2.99 20.33 4.34 14.11 2.14 14.72 2.14 0.20 4.00 5.19 0.93 5.48
EP
Mkl4 120.82 255.03 30.50 118.87 23.20 3.37 19.40 2.91 17.69 3.61 9.94 1.46 9.32 1.32 0.49 3.27 8.79 1.82 9.54 Mv5 66.64 142.83 16.81 64.49 12.55 2.11 11.01 1.67 10.24 2.08 5.73 0.78 5.69 0.79 0.55 3.33 7.95 1.73 8.79
AC C
Sample Mkl2 La 103.83 Ce 223.32 Pr 26.61 Nd 104.60 Sm 20.62 Eu 3.07 Gd 17.96 Tb 2.74 Dy 16.71 Ho 3.49 Er 10.26 Tm 1.40 Yb 9.85 Lu 1.40 Eu/Eu* 0.49 (La/Sm)N 3.16 (La/Yb)N 7.15 (Gd/Lu)N 1.59 (La/Lu)N 7.70 Sample Mv3 La 118.57 Ce 250.73 Pr 27.17 Nd 93.04 Sm 18.88 Eu 1.08 Gd 16.65 Tb 3.05 Dy 18.48 Ho 4.08 Er 11.86 Tm 1.94 Yb 13.03 Lu 1.96 Eu/Eu* 0.19 (La/Yb)N 3.94 (La/Sm)N6.17 (Gd/Lu)N1.05 (La/Lu)N 6.30
Mkb1 57.27 124.67 14.96 56.94 10.99 1.40 8.43 1.30 7.63 1.56 4.22 0.62 4.25 0.63 0.44 3.27 9.14 1.67 9.53 Mc8 89.12 186.30 21.56 82.17 15.08 2.59 12.87 1.85 11.71 2.30 6.77 0.96 6.53 0.98 0.57 3.71 9.25 1.63 9.49
Mkb2 56.39 122.74 14.40 56.07 10.90 1.28 8.36 1.25 7.46 1.48 4.52 0.60 4.31 0.59 0.41 3.25 8.87 1.77 10.03 Mc9 69.85 157.29 18.94 75.11 15.22 1.68 11.96 1.68 9.58 1.74 4.68 0.67 4.41 0.62 0.38 2.88 10.75 2.40 11.80
Mkb4 14.42 31.79 3.66 14.74 3.78 0.51 3.00 0.35 1.52 0.18 0.50 0.08 0.47 0.08 0.46 2.39 20.67 4.61 18.65 Mcol1 79.73 178.27 21.39 85.87 17.20 1.88 13.84 1.96 11.34 2.06 5.84 0.84 5.28 0.79 0.37 2.91 10.25 2.17 10.51
Mkb6 32.64 57.10 5.93 21.09 4.33 0.88 3.41 0.57 3.35 0.71 2.25 0.34 2.11 0.25 0.70 4.73 10.51 1.68 13.51 Mcol2 77.56 170.32 20.31 80.20 15.95 2.09 12.67 1.78 10.75 2.07 5.58 0.74 5.38 0.75 0.45 3.05 9.77 2.10 10.82
Mv2 65.69 148.41 17.34 66.56 13.65 0.94 10.85 1.68 10.58 2.19 6.30 0.97 6.35 0.98 0.24 3.02 7.02 1.37 6.95 Mcol3 37.60 91.58 12.07 50.80 10.22 2.00 8.81 1.34 8.39 1.68 5.21 0.70 4.92 0.73 0.65 2.31 5.18 1.49 5.35
ACCEPTED MANUSCRIPT
Table 4 (cont.) Whole rock rare earth element (REE) geochemistry of the eastern Namaqua Metamorphic Province granites
AC C
EP
TE D
M AN U
SC
RI PT
Sample Mcol4 Mcol6 Mge1 Mge2 Mge3 Mge5 Mkle1 Mkle2 Mkle3 Me1 Me2 Mks1 Mks2 Mks3 Mks4 Mkn2 Mkn4 Mkn7 La 92.78 113.28 90.99 78.42 77.15 99.25 40.73 43.85 24.68 65.99 27.59 73.65 73.85 76.40 73.30 55.38 41.62 43.64 Ce 205.12 258.90 198.85 168.21 165.08 221.45 96.18 98.12 56.56 147.24 53.75 157.39 154.36 162.46 156.94 103.80 76.42 82.31 Pr 24.49 30.53 21.91 19.78 19.41 26.62 11.97 12.10 7.39 16.03 5.38 18.72 18.55 19.20 18.37 11.23 8.39 8.75 Nd 93.73 113.78 80.82 77.13 75.62 107.31 46.45 46.17 31.63 57.14 19.16 71.41 73.00 75.16 71.77 40.20 29.83 32.26 Sm 17.46 19.78 14.42 14.98 14.71 20.26 9.78 9.05 6.99 8.96 3.33 14.17 14.49 14.95 14.12 7.59 5.37 5.66 Eu 1.74 1.97 1.79 2.40 2.23 3.08 1.33 1.48 1.24 1.17 1.07 2.11 2.20 2.25 2.22 1.49 1.27 1.40 Gd 12.91 15.17 10.82 12.44 11.49 16.51 9.28 8.70 6.68 6.11 2.99 11.54 11.89 11.89 11.97 6.40 4.60 4.72 Tb 1.89 2.08 1.62 1.77 1.64 2.44 1.60 1.47 1.16 0.65 0.36 1.71 1.65 1.68 1.65 0.90 0.70 0.72 Dy 11.10 11.84 9.54 10.05 9.68 14.73 10.35 9.20 7.31 2.78 1.94 9.32 9.96 9.57 9.79 5.11 4.00 4.24 Ho 2.18 2.29 1.98 1.93 1.94 2.96 2.22 1.94 1.57 0.46 0.36 1.87 1.97 1.87 1.90 0.91 0.80 0.84 Er 6.12 6.20 5.56 5.61 5.27 8.53 6.18 5.77 4.59 1.08 0.76 5.17 5.49 5.43 5.54 2.61 2.22 2.20 Tm 0.86 0.90 0.80 0.77 0.77 1.18 0.85 0.90 0.66 0.12 0.12 0.73 0.75 0.73 0.78 0.37 0.33 0.32 Yb 5.69 5.93 5.72 5.42 5.18 8.05 5.59 5.86 4.61 0.78 0.71 4.99 5.13 4.87 5.12 2.40 1.99 2.07 Lu 0.80 0.83 0.88 0.77 0.74 1.16 0.76 0.88 0.71 0.13 0.11 0.70 0.72 0.70 0.75 0.35 0.29 0.29 Eu/Eu* 0.35 0.35 0.44 0.54 0.52 0.52 0.43 0.51 0.55 0.49 1.04 0.50 0.51 0.52 0.52 0.65 0.78 0.83 (La/Yb)N 3.33 3.59 3.96 3.28 3.29 3.07 2.61 3.04 2.22 4.62 5.20 3.26 3.20 3.20 3.26 4.58 4.86 4.84 (La/Sm)N11.06 12.95 10.78 9.82 10.11 8.36 4.94 5.08 3.63 57.14 26.36 10.01 9.76 10.65 9.72 15.64 14.21 14.33 (Gd/Lu)N1.99 2.26 1.52 1.99 1.94 1.76 1.51 1.23 1.17 5.71 3.23 2.06 2.06 2.10 1.97 2.23 2.00 2.00 14.19 10.74 10.55 10.92 8.88 5.56 5.22 3.62 51.84 25.08 11.03 10.73 11.35 10.13 16.26 15.20 15.56 (La/Lu)N 12.02 Note: Mv – Vaalputs Granite, Ms – Straussburg Granite, Mf – Friersdale Charnockite, Mc – Cyndas Subsuite, Mcol – Colston Granite, Mkl – Klipkraal Granite, Ml – Louisvale Granite, Mka – Kanoneiland Granite, Mkb – Keboes Granite, Mv – Vaalputs Granite Mcol – Colston Granite, Mge – Gemsbokbult Granite, Mkle – Kleinbegin Granite, Me – Elsie se Gorra Granite, Mks – Klip Koppies Granite, Mkn – Josling Granite. All REE are normalized relative to Boynton (1984). The REE are measured in parts per million (ppm).
ACCEPTED MANUSCRIPT
Table 5 Isotopic data for the granites of the eastern Namaqua Sector for this study, and those from literature data, arranged from oldest to youngest according to emplacement age
AC C
EP
TE D
M AN U
SC
RI PT
143 87 Granite Sm Nd Sm/ Nd/ 2σ σ 147Sm/ (143Nd/ Age εNd(t) εNd(o) TCHUR TDM Rb Sr Rb/ (87Sr/ Rb/ SrI Ref.a 144 144 144 86 86 (ppm) (ppm) Nd Nd Nd Nd)o (Ma) (Ma) (Ma) Sr Sr)o Sr Josling 5.4 29.8 0.18 0.51203 9 0.1089 0.51116 1217 1.79 -11.90 1059 1630 103.0 240.0 0.43 0.72662 1.1406 0.70674 1 Josling 4.2 27.3 0.15 0.51200 6 0.0928 0.51126 1217 3.77 -12.41 934 1447 114.4 207.6 0.55 0.73373 1.4638 0.70821 1 Elsie se 9.0 57.1 0.16 0.51192 10 0.0949 0.51119 1175 1.40 -13.93 1068 1571 276.0 60.0 4.60 0.95515 12.227 0.74944 1 Cyndas 15.1 82.2 0.18 0.51205 10 0.1110 0.51120 1159 1.17 -11.55 1053 1637 193.1 220.1 0.88 0.79434 2.3304 0.75567 1 Cyndas 11.8 65.0 0.18 0.51205 7 0.1094 0.51122 1159 1.56 -11.38 1019 1600 221.8 174.1 1.27 0.77653 3.3840 0.72038 1 Colston 10.2 50.8 0.20 0.51200 8 0.1217 0.51107 1151 -1.47 -12.52 1303 1908 196.3 180.0 1.09 0.78169 2.8965 0.73396 1 Colston 10.3 47.8 0.22 0.51215 7 0.1307 0.51116 1151 0.24 -9.48 1121 1829 221.3 42.1 5.26 0.95662 13.963 0.72653 1 Vaalputs 11.0 55.7 0.20 0.51215 7 0.1196 0.51125 1146 1.78 -9.53 966 1619 187.2 180.5 1.04 0.76491 2.7556 0.71970 1 Louis 1.9 12.7 0.15 0.51196 12 0.0918 0.51128 1125 1.89 -13.23 985 1487 89.0 501.6 0.18 0.71389 0.4715 0.70630 1 Klipkr 108.6 576.8 0.19 0.51197 10 0.1139 0.51114 1110b -1.25 -13.01 1227 1798 1101 825.7 1.33 0.77235 3.5419 0.71608 1 -2.50 -13.94 1349 1910 175.2 161.2 1.09 0.76482 2.8869 0.71896 1 Klipkr 20.8 108.6 0.19 0.51192 8 0.1160 0.51108 1110b Keboes 4.3 21.1 0.21 0.51198 14 0.1242 0.51107 1105 -2.64 -12.89 1388 1993 185.6 294.3 0.63 0.79779 1.6753 0.77130 1 Kleinbe 7.4 37.4 0.20 0.51170 7 0.1196 0.51083 1101 -7.51 -18.34 1853 2344 221 179 1.23 0.76380 3.2795 0.71212 1 Kanon 18.1 95.2 0.19 0.51208 10 0.1146 0.51125 1098 0.57 -10.96 1044 1651 233.2 142.9 1.63 0.79110 4.3332 0.72300 1 Kanon 1.7 12.1 0.14 0.51197 5 0.0835 0.51136 1098 2.83 -13.08 903 1383 129.6 533.1 0.24 0.71753 0.6458 0.70738 1 Klip Ko 9.7 53.1 0.18 0.51195 7 0.1105 0.51115 1096 -1.44 -13.52 1224 1777 209 149 1.40 0.72387 3.7259 1 Strauss 15.4 98.1 0.16 0.51176 10 0.0949 0.51108 1089 -2.95 -17.12 1313 1780 157.9 228.0 0.69 0.74612 1.8398 0.71744 1 Friers 14.2 79.4 0.18 0.51203 8 0.1082 0.51127 1078 0.41 -11.81 1042 1612 164.8 262.2 0.63 0.73666 1.6695 0.71090 1 Friers 14.4 78.8 0.18 0.51201 9 0.1105 0.51123 1078 -0.35 -12.24 1110 1682 164.9 277.1 0.60 0.73434 1.5807 0.70995 1 Friers 14.3 76.6 0.19 0.51201 10 0.1129 0.51121 1078 -0.67 -12.23 1140 1720 160.1 271.0 0.59 0.73407 1.5692 0.70987 1 Josling 6.9 30.8 0.22 0.51227 20 0.1359 0.51119 1217 2.36 -7.12 915 1716 2 Vaalputs 10.5 53.9 0.19 0.51202 20 0.1174 0.51113 1146 -0.50 -12.13 1195 1792 2 Gemsbok 14.0 77.9 0.18 0.51198 12 0.0930 0.51131 1104 1.91 -12.76 961 1471 3 Kleinbe 13.7 88.7 0.15 0.51164 8 0.1187 0.51079 1101 -8.44 -19.41 1938 2409 3 Klip Ko 14.6 74.6 0.20 0.51202 10 0.1257 0.51112 1096 -2.06 -12.02 1321 1950 3 Strauss 11.6 58.0 0.20 0.51197 10 0.1206 0.51111 1089 -2.49 -13.09 1342 1933 2 Friers 14.9 78.7 0.19 0.51200 20 0.1143 0.51119 1078 -1.08 -12.45 1179 1761 2 Friers 14.7 77.4 0.19 0.51198 20 0.1144 0.51117 1078 -1.42 -12.78 1212 1788 2 a References: 1 – this study, 2 – Pettersson et al. (2009), 3 – Bailie et al. (2011a) b Presumed as no U-Pb zircon emplacement age determined; age estimated based on field relationships Abbreviations: Elsie se – Elsie se Gorra, Friers – Friersdale Charnockite, Gemsbok – Gemsbokbult, Kanon – Kanoneiland, Kleinbe – Kleinbegin, Klip Ko – Klip Koppies, Klipkra – Klipkraal, Louis – Louisvale, Strauss - Straussburg
Sample No. Mkn4 Mkn Me1 Mc8 Cyn1 Mcol3 Col1 Vaal Ml5 Mkl3 Klp Mkb6 Kle1 Mka6 Kan1 Klip Str1 S188 S815 S367
ACCEPTED MANUSCRIPT
Late- to post-tectonic granites (Keimoes Suite) c Monzogranite to variable, Granodiorite; mostlybt-rich for mediumsome, ferroan, grained, metaluminous most porphyritic/ megacrystic
εNd(t) range
Host rocks + contacts
SrI range
TDM model ages (Ma)
gneissic, welldeveloped
Areachap Grp, gradational
moderate to well-developed
Korannaland -1.47 to 0.71970- 1571-1908 Grp, foliation 1.78 0.74944 stronger toward contacts, concordant
RI PT
Presence of foliation
1217
1175-1146
M AN U
SC
1.79 to 0.70674- 1447-1716 3.77 0.70821
Emplacement age (in Ma)
strong / gneissic Bethesda Fm, 1.89 disharmonic Areachap Grp, flow pattern concordant, lit-par-lit, foliated, gradational with syn-tectonic granites
0.70630
1487
1125
TE D
Table 6 Summary of proposed subdivision of the eastern Namaqua Sector granites Granite Composition Grain Mineralogy Size Early syn-tectonic granite Josling leucogranite fine-grained qtz, K-fsp > plag, metaluminous bt-poor, msc Syn-tectonic granites a, b leucogranite coarse- to qtz, K-fsp, plag, bt, to granodiorite, mediumminor msc ferroan, grained, metaluminous typically to peraluminous medium, equigranular Louisvale heterogeneous, medium mafic – variable amts of mesocratic to fsp phenocrysts, leucocratic, opalescent blue qtz, tonalite to cordierite; leucocratic – monzogranite, elongate mcl phenocrysts ferroan, metaluminous
Areachap Grp, -2.95 to 0.70738- 1383-1993 d 1110-1078 older granites; 2.83 c 0.77130 country rocks Dagbreek Fm, Korannaland Grp; sharp, cross-cutting; metam. aureole a The Cyndas Subsuite is excluded from this table due to showing a range of different granite varieties within the subsuite. Generalizations with regard to element contents and petrogenesis cannot not, therefore, be made. b The summary is generalized for the overall age grouping. c Generalized summary for the Keimoes Suite as each granite can show variable and differing aspects relative to the other Keimoes Suite granites. c excluding the Kleinbegin Granite (εnd(t) = -7.51 to -8.44), d Excluding the Kleinbegin Granite (TDM = 2344-2409 Ma)
AC C
EP
qtz, K-fsp, plag, bt ± hbl weak/poor to ± opx (in some); K-fsp unfoliated phenocrysts
Abbreviations: mineralogy: bt – biotite, fsp – feldspar, hbl – hornblende, K-fsp – K-feldspar, mcl – microcline, msc- muscovite, opx – orthopyroxene, plag – plagioclase, pyx – pyroxene, qtz – quartz; porph – porphyritic; Fm – Formation, Grp – Group, metam. – metamorphic, amts - amounts
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Mc8-01 Mc8-02 Mc8-03 Mc8-04 Mc8-05 Mc8-06 Mc8-07 Mc8-08 Mc8-09 Mc8-10 Mc8-11 Mc8-12 Mc8-13 Mc8-14 Mc8-15 Mc8-16 Mc8-17 Mc8-18 Mc8-19 Mc8-20 Mc8-22 Mc8-23 Mc8-24 Mc8-25
Dark core Dark core Dark core Dark core Bright core Dark core Bright core Dark core Bright core Dark rim Dark core Bright core Bright core Bright core Dark core Bright core Bright core Bright core Dark core Bright core Bright core Bright core Dark core Dark rim
Mc8
Mc8-21 irregular signal
Pb/235Ub
2 σd
206
Pb/238Ub
2 σd
rhoc
2σ
43 47 50 43 58 48 49 44 52 47 49 48 46 48 57 45 50 59 49 51 44 45 43 49 avg.
0.080 0.085 0.092 0.080 0.107 0.087 0.091 0.081 0.095 0.087 0.090 0.088 0.084 0.087 0.106 0.083 0.093 0.108 0.090 0.095 0.080 0.081 0.079 0.089
0.1957 0.1961 0.1973 0.1953 0.1988 0.1966 0.1998 0.1976 0.1979 0.1987 0.1952 0.1963 0.1969 0.1966 0.1990 0.1948 0.1985 0.1967 0.1990 0.2003 0.1942 0.1937 0.1956 0.1956
0.0056 0.0057 0.0058 0.0056 0.0058 0.0057 0.0058 0.0057 0.0059 0.0057 0.0057 0.0057 0.0057 0.0057 0.0059 0.0056 0.0058 0.0058 0.0058 0.0059 0.0056 0.0056 0.0056 0.0056
0.76 0.72 0.68 0.76 0.59 0.70 0.69 0.76 0.67 0.72 0.68 0.71 0.74 0.71 0.60 0.72 0.67 0.57 0.69 0.67 0.75 0.74 0.76 0.68
0.0786 0.0780 0.0786 0.0783 0.0791 0.0777 0.0786 0.0781 0.0781 0.0787 0.0781 0.0785 0.0791 0.0783 0.0786 0.0771 0.0781 0.0775 0.0780 0.0789 0.0778 0.0779 0.0774 0.0786
0.0019 0.0022 0.0025 0.0019 0.0032 0.0023 0.0024 0.0019 0.0026 0.0022 0.0024 0.0023 0.0021 0.0023 0.0031 0.0021 0.0025 0.0033 0.0024 0.0026 0.0020 0.0021 0.0019 0.0024
1156 1152 1161 1152 1170 1151 1170 1158 1158 1167 1149 1156 1164 1156 1167 1139 1161 1150 1162 1174 1143 1142 1144 1155
0
0
#DIV/0!
0.00
#VALUE!
-0.002
0.018
#VALUE!
0.0000
#VALUE!
0
U [ppm]a Pb [ppm]a Th/U meas
716 547 71 70 70
39 30 13 13 13
0.10 0.08 0.33 0.34 0.34
207
Pb/235Ub
0.40 0.40 1.84 1.87 1.88
2 σd
206
Pb/238Ub
0.02 0.02 0.08 0.08 0.08
0.054 0.054 0.179 0.181 0.181
2 σd
0.002 0.002 0.005 0.005 0.005
rhoc
0.71 0.72 0.70 0.70 0.70
Conc.
Pb/235U
207
2.121 2.109 2.138 2.108 2.167 2.106 2.165 2.129 2.129 2.156 2.102 2.123 2.147 2.123 2.156 2.070 2.137 2.102 2.139 2.179 2.082 2.079 2.086 2.120
207
Pb/206Pbe
EP
PL-06 PL-07 91500-06 91500-07 91500-08
Dates [Ma]
1.14 2.56 1.95 1.13 1.69 1.83 1.75 1.25 1.51 1.40 2.07 1.78 1.46 1.66 2.57 2.25 1.99 2.07 1.57 1.83 0.78 0.68 2.12 1.13
Pb/238U
2σ
1152 1155 1161 1150 1169 1157 1174 1163 1164 1168 1150 1155 1159 1157 1170 1147 1167 1158 1170 1177 1144 1141 1152 1152 1159
30 31 31 30 31 31 31 31 32 31 31 31 31 31 32 30 31 31 31 31 30 30 30 30
-10
115
206
0.0534 0.0532 0.0746 0.0751 0.0751
2 σd
0.0015 0.0015 0.0023 0.0023 0.0023
2σ
%
1162 1146 1161 1155 1173 1139 1161 1151 1149 1165 1149 1159 1175 1155 1161 1123 1149 1134 1147 1169 1141 1143 1130 1162
48 56 62 48 78 58 59 49 65 55 62 58 52 57 77 54 63 83 60 64 51 52 49 60
99 101 100 100 100 102 101 101 101 100 100 100 99 100 101 102 102 102 102 101 100 100 102 99
0
4000
-10200
207
Pb/206Pb
#VALUE!
Dates [Ma]
Conc.
Pb/235U
2σ
340 339 1061 1071 1072
14 14 45 45 45
207
Pb/238U
2σ
339 339 1063 1071 1073
10 10 29 29 29
206
207
Pb/206Pb
344 338 1057 1071 1071
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207 d
Pb/235U calculated using (207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the 206Pb/238U and the 207Pb/235U ratio.
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).e Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
a
PL PL 91500 91500 91500
2 σd
31 12 9 29 8 11 9 28 6 13 12 11 19 11 15 19 10 10 9 9 28 22 43 23
RATIOS Analysis
Pb/206Pbe
160 61 45 148 40 57 46 144 33 66 61 54 95 57 76 97 53 53 48 44 142 113 220 116
Reference Materials Sample
207
M AN U
Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8 Mc8
207
RI PT
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas
TE D
Sample
SC
Table A1 LA-ICP-MS U-Pb geochronological data for zircons from the Smalvisch Granite, Cyndas Subsuite, eastern Namaqua Sector Mc8 RATIOS
2σ
%
64 62 61 60 60
98 100 101 100 100
weighted Uncertainty mean age variance
1159.0
27
88.85
weighted uncertainty variance mean 339.1 4.36 1069.15
9.31
17
MSWD 1.000
MSWD
1.535
ACCEPTED MANUSCRIPT
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mcol-01 Dark core 66 13 0.82 Mcol-02 Dark rim 62 12 0.57 Mcol-03 Bright rim 66 13 0.60 Mcol-04 Dark core 194 38 0.72 Mcol-05 Bright core 55 11 0.88 Mcol-06 Bright core 113 21 0.83 Mcol-07 Bright core 99 18 0.42 Mcol-08 Bright core 35 7 0.73 Mcol-09 Bright core 100 20 0.57 Mcol-10 Dark core 59 12 0.79 Mcol-11 Dark rim 96 19 0.40 Mcol-12 Dark core 121 24 0.46 Mcol-13 Dark core 61 12 0.87 Mcol-14 Dark core 112 22 0.56 Mcol-15 Bright core 89 18 0.99 Mcol-16 Dark core 187 36 0.37 Mcol-17 Bright core 46 9 0.68 Mcol-18 Dark core 134 26 0.64 Mcol-19 Dark core 181 36 0.98 Mcol-20 Bright rim 104 20 0.41 Mcol-21 Dark core 149 29 0.83 Mcol-22 Bright core 42 8 0.70 Mcol-23 Dark rim 125 25 0.33 Mcol-24 Bright core 95 18 0.99 Mcol-25 Bright core 65 13 0.71
207
Pb/235Ub 2.152 2.104 2.150 2.117 2.141 2.046 2.012 2.150 2.098 2.120 2.079 2.138 2.127 2.137 2.144 2.098 2.129 2.123 2.128 2.124 2.119 2.135 2.168 2.025 2.128
2σ 0.086 0.093 0.086 0.078 0.094 0.109 0.083 0.104 0.096 0.088 0.086 0.088 0.117 0.129 0.084 0.101 0.093 0.091 0.081 0.088 0.088 0.109 0.100 0.087 0.103 d
206
Pb/238Ub 0.1981 0.1964 0.1972 0.1950 0.1971 0.1887 0.1866 0.1983 0.1955 0.1963 0.1938 0.1966 0.1981 0.1967 0.1974 0.1936 0.1975 0.1961 0.1967 0.1950 0.1971 0.1978 0.1977 0.1879 0.1969
Dates [Ma] 2 σd 0.0057 0.0056 0.0057 0.0055 0.0057 0.0054 0.0053 0.0058 0.0056 0.0057 0.0056 0.0056 0.0057 0.0056 0.0057 0.0055 0.0058 0.0056 0.0056 0.0056 0.0056 0.0058 0.0057 0.0054 0.0058
rhoc 0.72 0.65 0.72 0.77 0.66 0.53 0.70 0.60 0.63 0.69 0.70 0.69 0.53 0.48 0.73 0.59 0.67 0.67 0.75 0.69 0.69 0.57 0.62 0.67 0.60
207
Pb/206Pbe 0.0788 0.0777 0.0791 0.0787 0.0788 0.0786 0.0782 0.0786 0.0778 0.0784 0.0778 0.0789 0.0779 0.0788 0.0788 0.0786 0.0782 0.0786 0.0785 0.0790 0.0780 0.0783 0.0795 0.0782 0.0784
2 σd 0.0022 0.0026 0.0022 0.0019 0.0026 0.0035 0.0023 0.0030 0.0028 0.0023 0.0023 0.0024 0.0036 0.0042 0.0021 0.0031 0.0026 0.0025 0.0020 0.0024 0.0023 0.0033 0.0029 0.0025 0.0030
Conc. 2σ 47 51 46 43 51 60 46 56 53 48 47 48 64 70 46 55 51 49 44 48 48 59 54 49 56
207
Pb/235U 1166 1150 1165 1154 1162 1131 1120 1165 1148 1155 1142 1161 1158 1161 1163 1148 1158 1156 1158 1156 1155 1160 1171 1124 1158
Reference Materials
RATIOS Sample
Analysis
PL PL 91500 91500 91500
PL-04 PL-05 91500-03 91500-04 91500-05
U [ppm]a Pb [ppm]a Th [ppm] Th/U meas Th/U calc
547 579 82 81 79
30 31 15 15 14
43 46 27 27 26
0.08 0.08 0.33 0.33 0.33
0.03 0.03 0.09 0.09 0.09
207
Pb/235Ub
0.40 0.40 1.93 1.87 1.87
2 σd
1s%
0.02 0.02 0.10 0.08 0.08
2.07 2.45 2.50 2.14 2.08
206
Pb/238Ub
0.054 0.054 0.180 0.181 0.180
1 σd
2 σd
1s%
rhoc
0.001 0.001 0.003 0.003 0.003
0.002 0.002 0.005 0.005 0.005
1.44 1.44 1.46 1.46 1.45
0.69 0.59 0.58 0.68 0.70
207
Pb/206Pbe
0.0536 0.0538 0.0778 0.0749 0.0752
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
2σ 31 30 31 30 31 29 29 31 30 31 30 30 31 30 31 30 31 30 30 30 30 31 31 29 31
2σ 55 66 54 46 65 88 58 76 70 59 58 59 92 104 52 76 64 62 49 59 59 82 70 63 76
207
Pb/206Pb 1167 1140 1174 1165 1167 1163 1152 1163 1143 1156 1142 1169 1144 1167 1167 1162 1152 1161 1158 1172 1146 1154 1185 1152 1157
Pb/235 U calculated using ( 207 Pb/206 Pb)/(238 U/206 Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the 206 Pb/238 U and the 207 Pb/235 U ratio.
1 σd
2 σd
1s%
0.0008 0.0011 0.0016 0.0012 0.0011
0.0016 0.0021 0.0032 0.0023 0.0022
1.4925 1.9892 2.0306 1.5629 1.4902
EP
TE D
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD). e Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
d
Pb/238U 1165 1156 1160 1149 1160 1114 1103 1166 1151 1155 1142 1157 1165 1158 1161 1141 1162 1154 1158 1149 1160 1163 1163 1110 1159
weighted uncertainty mean variance
% 100 101 99 99 99 96 96 100 101 100 100 99 102 99 100 98 101 99 100 98 101 101 98 96 100
1151.4
27.54
285.31
MSWD 1.042
Dates [Ma]
1 σd
0.01 0.01 0.05 0.04 0.04
a
207
206
SC
Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3 Mcol3
M AN U
Sample
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Table A2 LA-ICP-MS U-Pb geochronological data for zircons from the Colston Granite, eastern Namaqua Sector Mcol3 RATIOS
Pb/235U
2σ
342 344 1091 1071 1069
14 17 55 46 45
207
Conc. Pb/238U
2σ
340 341 1066 1073 1068
9 10 29 29 29
206
Pb/206Pb
2σ
%
354 362 1142 1065 1073
67 88 80 62 59
96 94 93 101 100
207
Age Display analysis 207Pb/206Pb 2.8 2.8 2.7 2.7 2.7
PL PL 91500 91500 91500
340 341 1142 1065 1073
weighted 1σ
2σ
conc %
5 5 40 31 30
9 10 80 62 59
96 94 93 101 100
mean
340.45 1068.95
uncertainty variance 4.36 0.305 9.28
10.41
MSWD 1.984 1.499
ACCEPTED MANUSCRIPT
Table A3 LA-ICP-MS U-Pb geochronological data for zircons from the Elsie se Gorra Granite, eastern Namaqua Sector Me1 RATIOS Pb/235Ub 1.40 1.14 2.01 2.23 2.22 2.23 2.73 2.75 0.96 1.04 0.93 1.60 2.26 2.22 2.01 2.21 1.85 2.20 2.21 1.89 2.21
2 σd 0.05 0.04 0.10 0.10 0.08 0.09 0.10 0.10 0.03 0.04 0.03 0.06 0.08 0.08 0.09 0.08 0.07 0.08 0.08 0.12 0.09
Pb/238Ub 0.134 0.109 0.183 0.203 0.203 0.202 0.230 0.232 0.087 0.096 0.088 0.147 0.198 0.202 0.181 0.202 0.169 0.201 0.201 0.170 0.201
2 σd 0.004 0.003 0.005 0.006 0.006 0.006 0.007 0.007 0.003 0.003 0.003 0.004 0.006 0.006 0.005 0.006 0.005 0.006 0.006 0.005 0.006
rhoc 0.81 0.80 0.59 0.67 0.76 0.74 0.77 0.78 0.80 0.74 0.80 0.79 0.78 0.77 0.67 0.78 0.78 0.77 0.78 0.47 0.74
0.012 -0.006 -0.010 -0.017 0.039 0.009 0.025 -0.114 -0.008
0.023 0.005 0.037 0.057 0.071 0.023 0.014 0.473 0.013
#VALUE! -0.48 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
206
Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1
Me1-07 metamict - irregular signal 0 Me1-08 metamict - irregular signal 0 Me1-09 metamict - irregular signal 0 Me1-10 metamict - irregular signal 0 Me1-11 metamict - irregular signal 0 Me1-17 metamict - irregular signal 1 Me1-20 metamict - irregular signal 0 Me1-25 metamict - irregular signal 0 Me1-29 metamict - irregular signal 0
0 0 0 0 0 0 0 0 0
0.00 #DIV/0! #DIV/0! #DIV/0! #DIV/0! 0.02 #DIV/0! 0.37 #DIV/0!
0.00 0.26 0.00 0.00 0.00 0.00 0.00 0.00 0.00
#VALUE! 0.46 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
a
Pb/206Pbe 0.0758 0.0763 0.0795 0.0797 0.0794 0.0800 0.0860 0.0862 0.0798 0.0789 0.0770 0.0793 0.0827 0.0795 0.0805 0.0793 0.0796 0.0795 0.0794 0.0806 0.0795
0.0000 -0.3152 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
#VALUE! 0.4827 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
TE D
Not used
Dates [Ma] 2 σd 0.0016 0.0016 0.0031 0.0026 0.0019 0.0021 0.0020 0.0020 0.0017 0.0020 0.0017 0.0017 0.0019 0.0019 0.0026 0.0018 0.0018 0.0019 0.0018 0.0044 0.0021
207
Conc. 2σ
207
Pb/235U 889 774 1118 1190 1188 1189 1336 1343 684 725 668 972 1200 1187 1118 1186 1065 1181 1183 1079 1183
32 28 54 51 45 46 50 50 25 28 24 35 44 44 48 44 39 44 43 67 46
206
Pb/238U 810 665 1085 1191 1192 1185 1335 1344 540 589 542 882 1167 1187 1071 1189 1007 1180 1183 1014 1183
0 237 0 0 0 0 0 0 0
#VALUE! 415 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
78 -39 -67 -110 249 57 160 -782 -49
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value); Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
EP
d
AC C
207
2σ 22 18 29 31 31 31 35 35 15 16 15 24 31 31 28 31 27 31 31 27 31
RI PT
207
SC
Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1 Me1
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Me1-01 Dark core 2110 283 0.29 Me1-02 Dark core 2214 241 0.26 Me1-03 Bright rim 325 60 0.67 Me1-04 Dark core 519 105 0.14 Me1-05 Bright core 526 107 0.12 Me1-06 Bright core 549 111 0.12 Me1-12 inherited core (dark) 353 81 0.21 Me1-13 inherited core (dark) 330 76 0.20 Me1-14 Bright rim 3748 327 0.05 Me1-15 Bright rim 3470 332 0.06 Me1-16 Bright core 2462 216 0.10 Me1-18 Bright core 1913 281 0.34 Me1-19 Bright core 438 87 0.15 Me1-21 Bright core 270 55 0.21 Me1-22 Dark core 861 156 0.34 Me1-23 Bright rim 515 104 0.24 Me1-24 Bright core 1024 173 0.21 Me1-26 Bright core 338 68 0.15 Me1-27 Dark rim 965 194 0.28 Me1-28 Bright core 353 60 0.22 Me1-30 Bright core 223 45 0.21
M AN U
Sample
148 33 239 375 437 147 91 3440 84
207
Pb/206Pb 1090 1102 1184 1190 1181 1197 1337 1342 1193 1170 1121 1180 1262 1186 1210 1180 1186 1184 1182 1212 1184 0 0 0 0 0 0 0 0 0
weighted uncertainty variance
2σ
%
mean
42 43 77 63 47 50 45 44 42 51 43 43 44 46 63 45 45 46 45 105 52
74 60 92 100 101 99 100 100 45 50 48 75 92 100 89 101 85 100 100 84 100
1174.74
4000 0 4000 4000 4000 4000 4000 4000 4000
78200 -39200 -67100 -110000 248500 56700 159700 -782000 -49300
17.57
931.01
MSWD 1.104
ACCEPTED MANUSCRIPT
Table A4 LA-ICP-MS U-Pb geochronological data for zircons from the Josling Granite, eastern Namaqua Sector Mkn4 RATIOS Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4 Mkn4
Mkn5-01 Mkn5-02 Mkn5-03 Mkn5-04 Mkn5-07 Mkn5-08 Mkn5-09 Mkn5-10 Mkn5-11 Mkn5-12 Mkn5-13 Mkn5-14 Mkn5-15 Mkn5-16 Mkn5-17 Mkn5-18 Mkn5-19 Mkn5-20 Mkn5-21 Mkn5-22 Mkn5-23 Mkn5-24 Mkn5-25
Dark rim Bright core Bright core Dark rim Bright core Dark rim Dark rim CL bright core CL dark rim Bright core Bright core Dark rim Dark rim CL bright core CL dark rim Dark core Dark core CL dark core CL bright rim Bright core Bright core CL bright core CL dark rim
Mkn5-05 Mkn5-06
not zircon not zircon
U [ppm]a Pb [ppm]a Th/U meas 1923 188 0.02 76 16 0.52 54 11 0.47 1283 124 0.08 46 9 0.59 582 121 0.60 411 86 0.62 51 11 0.60 3411 149 0.02 303 22 0.10 42 5 0.64 1858 191 0.02 2572 115 0.01 92 19 0.65 1335 130 0.03 337 70 0.58 113 23 0.87 2632 172 0.07 968 106 0.05 297 61 0.30 182 38 0.52 140 29 0.30 1609 141 0.04
207
Pb/235Ub 1.088 2.350 2.329 1.023 2.309 2.310 2.330 2.345 0.396 0.839 1.445 1.146 0.401 2.325 1.089 2.315 2.298 0.741 1.231 2.288 2.331 2.272 0.970
2 σd 0.040 0.100 0.111 0.038 0.106 0.084 0.085 0.103 0.015 0.044 0.140 0.042 0.015 0.091 0.041 0.086 0.092 0.033 0.049 0.101 0.149 0.088 0.038
206
Pb/238Ub 0.0977 0.2097 0.2082 0.0967 0.2068 0.2082 0.2094 0.2084 0.0438 0.0740 0.1270 0.1030 0.0449 0.2079 0.0977 0.2084 0.2083 0.0652 0.1096 0.2057 0.2073 0.2060 0.0878
Dates [Ma] 2 σd 0.0028 0.0061 0.0063 0.0028 0.0061 0.0060 0.0060 0.0062 0.0013 0.0021 0.0037 0.0030 0.0013 0.0061 0.0028 0.0060 0.0061 0.0019 0.0032 0.0061 0.0062 0.0060 0.0025
rhoc 0.80 0.69 0.64 0.78 0.64 0.79 0.79 0.68 0.77 0.56 0.30 0.79 0.79 0.74 0.78 0.78 0.72 0.66 0.72 0.67 0.47 0.75 0.74
0.005 0.020
#VALUE! #VALUE!
Not used Mkn4 Mkn4
2 1
0 0
0.00 0.00
0.00 0.00
#VALUE! #VALUE!
0.002 0.026
RATIOS Sample
Analysis
PL PL PL PL PL
A_135 A_136 A_137 A_138 A_139
U [ppm]a Pb [ppm]a Th/U meas
500 496 500 494 405
27 27 27 27 22
0.08 0.08 0.08 0.08 0.08
207
Pb/235Ub
0.40 0.40 0.40 0.39 0.40
2 σd
0.02 0.02 0.02 0.02 0.02
206
Pb/238Ub
0.054 0.055 0.054 0.054 0.054
2 σd
rhoc
0.002 0.002 0.002 0.002 0.002
0.73 0.73 0.72 0.72 0.66
2 σd 0.0018 0.0025 0.0030 0.0018 0.0029 0.0018 0.0018 0.0026 0.0016 0.0036 0.0076 0.0018 0.0015 0.0021 0.0019 0.0019 0.0022 0.0027 0.0023 0.0026 0.0046 0.0021 0.0021
0.0000 0.0000
207
Pb/206Pbe
0.0528 0.0533 0.0534 0.0528 0.0531
Conc. 2σ
207
Pb/235U 748 1228 1221 715 1215 1215 1221 1226 339 619 908 775 342 1220 748 1217 1212 563 815 1209 1222 1204 689
27 52 58 27 56 44 45 54 13 32 88 28 13 48 28 45 49 25 33 53 78 47 27
Pb/238U 601 1227 1219 595 1212 1219 1226 1220 276 461 770 632 283 1218 601 1221 1220 407 670 1206 1214 1208 542
2σ
12 164
30 128
Pb/238U
2σ
341 343 340 338 340
10 10 10 10 10
206
#VALUE! #VALUE!
0 0
#VALUE! #VALUE!
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
Pb/206Pb 1217 1228 1225 1113 1222 1208 1214 1236 794 1250 1258 1213 768 1224 1216 1210 1197 1258 1233 1214 1235 1196 1202 0 0
2σ
%
43 60 71 47 69 44 44 62 50 84 176 44 48 51 45 46 54 64 54 63 109 51 52
49 100 100 53 99 101 101 99 35 37 61 52 37 99 49 101 102 32 54 99 98 101 45
4000 4000
11900 163800
0.0014 0.0015 0.0015 0.0015 0.0018
Conc.
Pb/235U
2σ
338 343 340 336 339
13 14 14 13 15
207
206
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
d
17 33 34 16 33 32 32 33 8 13 21 17 8 32 17 32 32 11 18 33 33 32 15
207
Dates [Ma] 2 σd
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
EP
a
Pb/206Pbe 0.0808 0.0813 0.0811 0.0767 0.0810 0.0805 0.0807 0.0816 0.0656 0.0822 0.0825 0.0807 0.0648 0.0811 0.0808 0.0806 0.0800 0.0825 0.0815 0.0807 0.0816 0.0800 0.0802
TE D
Reference Materials
207
RI PT
Comment
SC
Analysis
M AN U
Sample
207
Pb/206Pb
321 342 344 320 335
2σ
%
62 62 62 63 74
106 100 99 105 101
weighted mean uncertainty variance 1217.43 19.78 38.43
MSWD 1.091
weighted mean uncertainty variance 340.15 6.95 2.53
MSWD 1.250
ACCEPTED MANUSCRIPT
Table A5 LA-ICP-MS U-Pb geochronological data for zircons from the Kanoneiland Granite, eastern Namaqua Sector Mka6 RATIOS
Mka6 Mka6 Mka6
Mka6-06 Mka6-07 Mka6-08 Mka6-09 Mka6-10 Mka6-11 Mka6-12 Mka6-13 Mka6-16 Mka6-17 Mka6-18 Mka6-20 Mka6-21 Mka6-22 Mka6-23 Mka6-24 Mka6-25
Bright core Dark core Bright core Dark core Dark core Bright core Dark core Bright core Bright core Bright core Bright core Bright core
Mka6-14 irregular cPb Mka6-15 irregular cPb Mka6-19 metamict
2 σd 0.075 0.075 0.076 0.077 0.095
Dates [Ma]
Pb/238Ub 0.1803 0.1811 0.1791 0.1785 0.1803
2 σd 0.0053 0.0053 0.0053 0.0052 0.0053
rhoc 0.73 0.73 0.72 0.71 0.58
206
Pb/206Pbe 0.0752 0.0752 0.0748 0.0750 0.0752
2 σd 0.0021 0.0021 0.0021 0.0022 0.0031
207
393 219 300 365 267 255 700 339 194 422 156 339 267 219 265 128 229
73 41 56 69 50 48 131 64 36 79 29 64 49 41 50 24 42
0.44 0.40 0.33 0.48 0.40 0.36 0.13 0.42 0.50 0.34 0.43 0.27 0.41 0.36 0.34 0.46 0.48
1.961 1.958 1.965 1.977 1.974 1.959 1.970 1.973 1.944 1.976 1.988 1.981 1.950 1.945 1.993 2.013 1.938
0.072 0.073 0.072 0.073 0.073 0.073 0.072 0.073 0.073 0.073 0.107 0.074 0.075 0.074 0.075 0.084 0.075
0.1854 0.1872 0.1873 0.1879 0.1880 0.1869 0.1867 0.1881 0.1857 0.1875 0.1888 0.1883 0.1850 0.1862 0.1892 0.1901 0.1853
0.0053 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0054 0.0055 0.0054 0.0053 0.0054 0.0055 0.0056 0.0055
0.78 0.77 0.78 0.78 0.78 0.77 0.79 0.78 0.77 0.78 0.54 0.78 0.75 0.76 0.77 0.70 0.76
0.0767 0.0759 0.0761 0.0763 0.0761 0.0760 0.0766 0.0761 0.0760 0.0764 0.0764 0.0763 0.0764 0.0758 0.0764 0.0768 0.0759
0.0018 0.0018 0.0017 0.0017 0.0018 0.0018 0.0017 0.0018 0.0018 0.0017 0.0035 0.0018 0.0019 0.0019 0.0018 0.0023 0.0019
0 2 1
0 0 0
0.00 0.00 0.00
0.00 0.00 0.00
#VALUE! #VALUE! #VALUE!
-0.020 0.007 -0.006
0.041 0.006 0.009
#VALUE! #VALUE! #VALUE!
0.0000 0.0000 0.0000
#VALUE! #VALUE! #VALUE!
RATIOS Sample
Analysis
PL PL PL PL PL
PL-01 PL-02 PL-03 PL-04 PL-05
U [ppm]a Pb [ppm]a Th/U meas
501 493 488 493 521
27 26 26 27 28
207
Pb/235Ub
0.08 0.13 0.08 0.08 0.08
0.39 0.39 0.40 0.40 0.40
2 σd
0.02 0.03 0.02 0.02 0.02
206
Pb/238Ub
0.054 0.053 0.054 0.054 0.054
2 σd
TE D
Reference Materials rhoc
0.002 0.002 0.002 0.002 0.002
Pb/206Pbe
0.72 0.37 0.73 0.65 0.70
0.0528 0.0535 0.0531 0.0533 0.0532
2σ
0.0015 0.0040 0.0015 0.0018 0.0016
2σ
43 43 44 44 54
Pb/238U 1069 1073 1062 1059 1068
1102 1101 1104 1108 1107 1101 1105 1106 1096 1107 1112 1109 1098 1097 1113 1120 1094
41 41 41 41 41 41 40 41 41 41 60 41 42 42 42 47 43
1096 1106 1107 1110 1111 1104 1103 1111 1098 1108 1115 1112 1094 1101 1117 1122 1096
29 29 29 29 29 29 29 29 29 29 30 30 29 29 30 30 30
0 0 0
#VALUE! #VALUE! #VALUE!
-129 46 -40
271 38 57
Pb/238U
2σ
340 335 340 340 340 339.0
10 10 10 10 10
207
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
29 29 29 29 29
2σ
338 337 339 340 339
14 27 14 15 14
206
206
Pb/238U and the 207Pb/235U ratio.
AC C
1110
1100
1090
1080
1070
1060 0
200
400
U [ppm]
600
800
2σ
%
55 55 57 58 81
100 100 100 99 100
1114 1092 1098 1103 1099 1096 1110 1097 1094 1106 1106 1104 1107 1089 1106 1116 1092
46 47 46 45 46 47 44 46 48 45 90 46 50 49 48 59 50
98 101 101 101 101 101 99 101 100 100 101 101 99 101 101 101 100
0 0 0
4000 4000 4000
-129400 46000 -39600
207
Pb/206Pb 1073 1074 1063 1069 1073
Conc.
Pb/235U
207
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975). 1120
Date [Ma]
d
206
Dates [Ma]
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
EP
a
2 σd
207
Conc.
Pb/235U 1070 1073 1062 1062 1070
207
RI PT
Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Mka6 Not used
Pb/235Ub 1.869 1.878 1.847 1.846 1.868
207
SC
Mka6 Mka6 Mka6 Mka6 Mka6
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mka6-01 low U! - bright core 78 14 0.33 Mka6-02 low U! - dark core 77 14 0.33 low U! - bright core 81 14 0.33 Mka6-03 Mka6-04 low U! - bright core 82 15 0.33 Mka6-05 low U! - bright core 80 14 0.33
M AN U
Sample
207
Pb/206Pb
322 348 331 343 336
2σ
%
63 163 62 75 67
106 96 103 99 101
weighted uncertainty variance mean 1097.51 25.37 336.21
MSWD
weighted uncertainty variance mean 339.03 6.93 3.57
MSWD
1.048
1.248
ACCEPTED MANUSCRIPT
Table A6 LA-ICP-MS U-Pb geochronological data for zircons from the Keboes Granite, eastern Namaqua Sector Mkb6 RATIOS Pb/235Ub 1.973 2.002 2.763 1.999 1.842 2.022 1.967 1.977 1.984 2.013 2.033 1.985 1.970 2.046 1.965 1.095 1.939 2.000 1.957 1.928 1.962 1.955 2.009 1.991 1.877
2 σd 0.078 0.077 0.104 0.073 0.067 0.081 0.076 0.075 0.073 0.077 0.080 0.075 0.073 0.076 0.073 0.040 0.073 0.073 0.081 0.074 0.080 0.077 0.078 0.077 0.070
206
2 σd
206
Pb/238Ub 0.1873 0.1878 0.2323 0.1893 0.1737 0.1895 0.1871 0.1872 0.1881 0.1901 0.1901 0.1875 0.1871 0.1923 0.1872 0.1044 0.1854 0.1898 0.1865 0.1839 0.1877 0.1862 0.1896 0.1881 0.1773
Dates [Ma]
2 σd 0.0055 0.0055 0.0067 0.0054 0.0050 0.0055 0.0054 0.0054 0.0054 0.0056 0.0055 0.0054 0.0054 0.0056 0.0054 0.0030 0.0054 0.0055 0.0054 0.0053 0.0054 0.0054 0.0055 0.0055 0.0051
rhoc 0.75 0.75 0.77 0.79 0.79 0.72 0.75 0.77 0.78 0.77 0.73 0.77 0.78 0.78 0.77 0.78 0.76 0.79 0.70 0.75 0.71 0.74 0.75 0.75 0.78
207
2 σd
rhoc
207
0.005 0.005 0.005 0.005 0.005
0.71 0.71 0.71 0.65 0.70
Pb/206Pbe 0.0764 0.0773 0.0863 0.0766 0.0769 0.0774 0.0763 0.0766 0.0765 0.0768 0.0776 0.0768 0.0764 0.0772 0.0761 0.0761 0.0758 0.0764 0.0761 0.0761 0.0758 0.0761 0.0769 0.0767 0.0768
Reference materials
RATIOS Analysis
91500 91500 91500 91500 91500
A_101 A_102 A_103 A_104 A_105
U [ppm]a Pb [ppm]a Th/U meas
80 81 82 84 84
14 15 15 15 15
207
Pb/235Ub
0.34 0.33 0.34 0.34 0.34
1.87 1.88 1.88 1.87 1.83
207
Pb/235U 1106 1116 1346 1115 1061 1123 1104 1108 1110 1120 1127 1111 1105 1131 1103 751 1095 1116 1101 1091 1103 1100 1118 1112 1073
Conc. weighted uncertainty variance 2σ 44 43 50 41 38 45 43 42 41 43 44 42 41 42 41 28 41 41 46 42 45 44 43 43 40
206
Pb/238U 1107 1110 1346 1117 1033 1119 1105 1106 1111 1122 1122 1108 1106 1134 1106 640 1097 1120 1103 1088 1109 1101 1119 1111 1052
0.08 0.08 0.08 0.09 0.08
0.180 0.181 0.181 0.180 0.178
a
Pb/206Pbe
0.0751 0.0756 0.0751 0.0753 0.0746
2 σd
e
0.0022 0.0022 0.0022 0.0026 0.0023
2σ
1069 1074 1074 1069 1058
44 45 44 49 45
Pb/238U
2σ
1069 1070 1075 1065 1058
29 29 29 29 29
206
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
AC C
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
EP
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
d
30 30 35 30 27 30 30 29 29 30 30 29 29 30 29 18 29 30 29 29 30 30 30 30 28
207
Pb/206Pb 1106 1129 1345 1111 1119 1132 1102 1110 1108 1116 1137 1116 1105 1126 1098 1097 1090 1106 1098 1097 1091 1099 1117 1114 1115
2σ
%
52 50 46 44 44 55 51 48 45 48 53 48 46 47 47 45 49 45 58 50 57 53 50 51 47
100 98 100 101 92 99 100 100 100 100 99 99 100 101 101 58 101 101 100 99 102 100 100 100 94
mean 1104.94
27
465
Conc. weighted uncertainty variance
Pb/235U
207
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
2σ
Dates [Ma]
Pb/238Ub
TE D
Sample
2 σd 0.0020 0.0020 0.0021 0.0017 0.0017 0.0022 0.0020 0.0018 0.0017 0.0019 0.0021 0.0019 0.0018 0.0018 0.0018 0.0017 0.0019 0.0017 0.0022 0.0019 0.0022 0.0020 0.0020 0.0020 0.0018
RI PT
207
SC
Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6 Mkb6
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas Mkb6-01 Bright core 107 20 0.55 Mkb6-02 Bright core 157 29 0.52 37 0.40 Mkb6-03Inherited core 161 Mkb6-04 Dark core 401 76 0.35 Mkb6-05 Dark rim 559 97 0.28 Mkb6-06 Bright rim 137 26 0.39 Mkb6-07 Bright core 133 25 0.30 Mkb6-08 Dark core 184 34 0.49 Mkb6-09 Dark rim 328 62 0.40 Mkb6-10 Bright core 153 29 0.30 Mkb6-11 Dark core 167 32 0.46 Mkb6-12 Bright rim 215 40 0.29 Mkb6-13 Bright core 275 51 0.39 Mkb6-14 Bright core 251 48 0.55 Mkb6-15 Bright core 237 44 0.51 Mkb6-16 Dark core 1447 151 0.28 Mkb6-17 Dark core 308 57 0.51 Mkb6-18 Dark rim 1068 203 0.31 Mkb6-19 Bright core 111 21 0.35 Mkb6-20 Bright core 156 29 0.26 Mkb6-21 Bright core 163 31 0.40 Mkb6-22 Bright core 116 22 0.37 Mkb6-23 Bright core 204 39 0.29 Mkb6-24 Bright core 169 32 0.41 Mkb6-25 Dark core 703 125 0.29
M AN U
Sample
207
Pb/206Pb
1070 1084 1071 1078 1057
2σ
%
58 58 58 70 61
100 99 100 99 100
mean 1067.3
12.05
31.37
MSWD 1.045
MSWD 1.250
ACCEPTED MANUSCRIPT
Table A7 LA-ICP-MS U-Pb geochronological data for zircons from the Klipkraal Granite, eastern Namaqua Sector MKl3 RATIOS
MK MK
A_044 cPb inclusions A_050 cPb inclusions
192 460 422 943 1058 139 763 932
36 82 80 166 112 26 92 150
0.84 0.33 1.77 0.11 0.12 0.70 0.20 0.11
0 1
0 0
#DIV/0! 0.00
Pb/235Ub
2 σd
2.10 2.02 2.14 2.03 1.12 2.13 1.36 1.82
0.07 0.06 0.07 0.07 0.03 0.07 0.04 0.06
0.00 0.00
#VALUE! #VALUE!
Dates [Ma]
2 σd
rhoc
0.187 0.178 0.189 0.176 0.105 0.189 0.121 0.161
0.004 0.004 0.004 0.004 0.002 0.004 0.003 0.003
0.69 0.71 0.70 0.67 0.71 0.68 0.70 0.70
0.0812 0.0823 0.0823 0.0834 0.0773 0.0817 0.0818 0.0820
-0.028 -0.013
0.032 0.012
#VALUE! #VALUE!
0.0000 0.0000
206
Pb/238Ub
207
Pb/206Pbe
Conc.
Pb/235U
2σ
0.0018 0.0018 0.0018 0.0020 0.0017 0.0019 0.0018 0.0018
1147 1122 1163 1124 764 1158 873 1051
#VALUE! #VALUE!
0 0
2 σd
b
207
Pb/238U
2σ
36 35 36 36 23 37 27 33
1106 1057 1117 1046 646 1116 735 961
#VALUE! #VALUE!
-181 -84
206
Pb/206Pb
2σ
%
22 21 22 21 13 22 15 19
1226 1252 1251 1278 1128 1237 1240 1245
44 42 43 47 43 46 43 43
90 84 89 82 57 90 59 77
214 76
0 0
4000 4000
-180900 -84000
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value); Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the e
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
M AN U
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
TE D
d
EP
207
AC C
a
A_041 Dark rim A_042 Bright rim A_043 Dark core A_045 Bright core A_046 Dark core A_047 Dark core A_048 Bright core A_049 Bright rim
207
RI PT
MK MK MK MK MK MK MK MK Not used
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas
SC
Sample
207
weighted mean 1110.77
uncertainty variance 6.68
22.57
MSWD 1.999
ACCEPTED MANUSCRIPT
Table A8 LA-ICP-MS U-Pb geochronological data for zircons from the Louisvale Granite, eastern Namaqua Sector MI3 RATIOS 207
Pb/235Ub 2.036 2.058 1.920 1.965 2.019 2.045 2.076 2.056 2.047 0.991 2.016 2.024 2.039 1.904
2 σd 0.068 0.070 0.088 0.061 0.065 0.087 0.081 0.067 0.076 0.031 0.072 0.072 0.085 0.140
Dates [Ma]
Pb/238Ub 0.193 0.192 0.176 0.184 0.190 0.192 0.195 0.192 0.192 0.092 0.188 0.190 0.190 0.175
2 σd 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.002 0.004 0.004 0.004 0.004
rhoc 0.67 0.65 0.48 0.70 0.68 0.51 0.56 0.67 0.60 0.70 0.61 0.62 0.53 0.30
-0.012 -0.031 -0.005
0.053 0.032 0.168
#VALUE! #VALUE! #VALUE!
2 σd
rhoc
0.65 0.65 0.65 0.65 0.65 0.47 0.65 0.65 0.64 0.64
0.0756 0.0757 0.0751 0.0775 0.0754 0.0746 0.0754 0.0744 0.0754 0.0751
0.68 0.68 0.68 0.67 0.67 0.66 0.67 0.67
0.0531 0.0538 0.0529 0.0537 0.0534 0.0529 0.0534 0.0532
206
207
Pb/206Pbe 0.0766 0.0779 0.0792 0.0776 0.0771 0.0774 0.0774 0.0779 0.0775 0.0782 0.0777 0.0773 0.0777 0.0787
2 σd 0.0019 0.0020 0.0032 0.0017 0.0018 0.0028 0.0025 0.0019 0.0023 0.0017 0.0022 0.0021 0.0027 0.0055
Not used A_0067-6 fractionation A_007 irregular signal A_0277-6 fractionation
0 0 0
0 0 0
0.00 #DIV/0! #DIV/0!
0.00 0.00 0.00
#VALUE! #VALUE! #VALUE!
0.0000 0.0000 0.0000
Reference materials
RATIOS Pb/235Ub
206
Pb/238U 1136 1131 1044 1087 1122 1130 1146 1130 1130 567 1112 1121 1124 1042
2σ 23 23 21 22 23 23 23 23 23 12 22 23 23 21
206
Pb/238Ub
A_016 A_017 A_018 A_021 A_022 A_023 A_034 A_035 A_051 A_052
78 78 78 79 78 80 77 78 77 77
14 14 14 14 14 14 14 14 14 14
0.29 0.29 0.29 0.30 0.29 0.29 0.29 0.29 0.31 0.31
1.856 1.866 1.868 1.910 1.885 1.852 1.888 1.840 1.871 1.873
0.063 0.063 0.064 0.065 0.064 0.097 0.064 0.063 0.065 0.065
0.1782 0.1788 0.1805 0.1788 0.1813 0.1801 0.1817 0.1794 0.1800 0.1809
0.0039 0.0040 0.0040 0.0040 0.0040 0.0044 0.0040 0.0040 0.0040 0.0040
PL PL PL PL PL PL PL PL
A_008 A_009 A_010 A_031 A_032 A_038 A_039 A_040
625 637 622 612 598 621 628 650
34 34 34 33 33 34 34 35
0.08 0.09 0.08 0.08 0.08 0.08 0.08 0.08
0.395 0.399 0.393 0.401 0.401 0.396 0.398 0.395
0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013
0.0539 0.0537 0.0539 0.0541 0.0545 0.0543 0.0542 0.0538
0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012
207
EP
91500 91500 91500 91500 91500 91500 91500 91500 91500 91500
0 0 0
#VALUE! #VALUE! #VALUE!
-79 -203 -30
344 214 1086
Pb/206Pbe
d
Pb/235U calculated using ( 207Pb/206Pb)/(238U/206Pb * 1/137.88). c Rho is the error correlation defined as the quotient of the propagated errors of the
Quadratic addition of within-run errors (2 SD) and daily reproducibility of GJ-1 (2 SD).
e
Pb/206Pb 1112 1143 1177 1137 1123 1133 1130 1143 1134 1151 1139 1128 1139 1165 0 0 0
2σ 49 51 79 44 46 72 64 48 59 43 55 55 69 135
% 102 99 89 96 100 100 101 99 100 49 98 99 99 89
4000 4000 4000
-78500 -203400 -29700
Conc.
Pb/235U
2σ
0.0019 0.0019 0.0020 0.0020 0.0019 0.0034 0.0020 0.0019 0.0020 0.0020
1066 1069 1070 1084 1076 1064 1077 1060 1071 1072
0.0013 0.0013 0.0012 0.0013 0.0013 0.0013 0.0013 0.0013
338 341 336 342 343 339 341 338
2 σd
207
Pb/238U
2σ
36 36 37 37 37 56 37 36 37 37
1057 1061 1070 1061 1074 1068 1076 1064 1067 1072
22 22 22 22 22 24 22 22 22 22
11 11 11 11 11 11 11 11
339 337 338 340 342 341 340 338
7 7 7 7 7 7 7 7
206
U and Pb concentrations and Th/U ratios are calculated relative to the GJ-1 reference zircon. b Corrected for background and within-run Pb/U fractionation and normalised to reference zircon GJ-1 (ID-TIMS values/measured value);
207
207
Dates [Ma]
2 σd
Analysis
TE D
207
Sample
AC C
a
U [ppm]a Pb [ppm]a Th/U meas
#VALUE! #VALUE! #VALUE!
Pb/235U 1127 1135 1088 1104 1122 1131 1141 1134 1131 699 1121 1123 1129 1082
M AN U
MI MI MI
Conc. 2σ 37 39 50 34 36 48 45 37 42 22 40 40 47 79
207
RI PT
MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3 MI3
Analysis Comment U [ppm]a Pb [ppm]a Th/U meas A_004 Dark rim 83 16 1.03 A_005 Bright core 91 17 1.08 A_011 Dark core 553 97 0.53 574 105 0.51 A_012 Bright core A_013 Bright core 134 26 1.04 A_014 Dark core 290 56 0.73 A_015 Bright rim 225 44 1.17 A_024 Bright core 148 28 0.91 A_025 Dark core 105 20 0.98 A_026 Dark core 1590 146 0.10 A_028 Bright core 176 33 1.29 A_029 Bright rim 90 17 0.80 A_030 Dark core 88 17 1.15 A_033 Bright core 86 15 0.29
SC
Sample
206
Pb/238U and the 207Pb/235U ratio.
Corrected for mass-bias by normalising to GJ-1 reference zircon (~0.6 per atomic mass unit) and common Pb using the model Pb composition of Stacey & Kramers (1975).
207
2σ
%
1083 1087 1070 1133 1079 1057 1078 1053 1079 1072
51 51 52 50 51 92 52 52 53 53
98 98 100 94 100 101 100 101 99 100
334 363 323 360 347 324 345 339
53 53 53 54 54 55 55 55
101 93 105 95 99 105 99 100
Pb/206Pb
weighted uncertainty variance mean 1124.5 15.79 176.25
MSWD
weighted uncertainty variance mean 1066.87 14.83 36.32
MSWD
339.33
7.6
2.31
1.084
1.111
1.143
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
Highlights • Voluminous syn- and late- to post-tectonic granitic magmatism in eastern Namaqua Sector • Older syn-tectonic granite gneisses, emplaced 1175-1146 Ma, are fractionated metaluminous to peraluminous leucogranites • Redefined Keimoes Suite comprises weakly foliated 1110-1078 Ma late- to post-tectonic megacrystic, ferroan metaluminous granodiorites and monzogranites • Model ages of both granitic groups reflect mixing of Meso- and Paleoproterozoic sources and reworking of Paleoproterozoic arc crust • Timing of emplacement of granites constrains peak D2 Namaquan deformation in region to ∼1.13-1.11 Ga