On the edge: U–Pb, Lu–Hf, and Sm–Nd data suggests reworking of the Yilgarn craton margin during formation of the Albany-Fraser Orogen

Precambrian Research 187 (2011) 223–247

Contents lists available at ScienceDirect

Precambrian Research journal homepage: www.elsevier.com/locate/precamres

On the edge: U–Pb, Lu–Hf, and Sm–Nd data suggests reworking of the Yilgarn craton margin during formation of the Albany-Fraser Orogen C.L. Kirkland a,∗ , C.V. Spaggiari a , M.J. Pawley a , M.T.D. Wingate a , R.H. Smithies a , H.M. Howard a , I.M. Tyler a , E.A. Belousova b , M. Poujol c a b c

Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, Australia GEMOC, Macquarie University, Sydney, NSW 2109, Australia Géosciences Rennes UMR CNRS 6118, Université Rennes 1, 35042 Rennes Cedex, France

a r t i c l e

i n f o

Article history: Received 25 July 2010 Received in revised form 23 February 2011 Accepted 2 March 2011 Available online 22 March 2011 Keywords: U–Pb Lu–Hf Sm–Nd Zircon Baddeleyite Albany-Fraser Orogen Biranup Zone Fraser Zone

a b s t r a c t The Albany-Fraser Orogen is considered to be a response to Mesoproterozoic continent–continent collision between the combined North and West Australian Cratons and the combined East Antarctic and South Australian Cratons. However, the tectonic history of the orogen and its components remain enigmatic. Recently, the Kepa Kurl Booya Province has been defined as the crystalline basement of the orogen and divided into the Fraser, Biranup, and Nornalup Zones. New geochronology shows that the Biranup Zone includes 1710–1650 Ma granitic to gabbroic intrusions and is a substantial crustal component extending at least 1200 km along the southern and southeastern margins of the Yilgarn Craton. Previous models interpreted the Biranup Zone as an exotic terrane accreted to the Yilgarn Craton during Mesoproterozoic collision, but new data presented here indicate a strong link to the craton margin during the Paleoproterozoic. Proterozoic magmatism commenced in the Biranup Zone at 1708 ± 15 Ma with metasyenogranite emplacement. This granite has εHf values of −10 to −8 and whole rock εNd of −15, consistent with a reworked Archean Yilgarn source. Volcaniclastic deposition in the Biranup Zone occurred at 1689 ± 6 Ma, and was rapidly followed by granitic intrusion at 1686 ± 8 Ma. Deformation during the Zanthus Event is constrained by 1676 ± 6 Ma folded migmatitic leucosomes and 1679 ± 6 Ma cross-cutting axial planar leucosomes. A younger suite of granitic and gabbroic rocks, which exhibit distinct mingling and hybridization textures, is dated at 1665 ± 4 Ma. Magmatism in the eastern Biranup Zone displays high-K, calc-alkaline chemistry and a trend towards more juvenile compositions from 1710 to 1650 Ma. Based on the rapidly evolving tectonomagmatic history, modification of the original Yilgarn-like source by juvenile material, and the geochemical evolution of the melts, a feasible tectonic scenario for the Biranup Zone is an arc to back-arc setting on the active Yilgarn Craton margin. Such a model is supported by the 2684 ± 11 Ma magmatic crystallization age of an isolated Archean fragment, which has clear Yilgarn affinity, within the Biranup Zone. The region was subsequently compressed and tectonically dismembered during Stages I (1345–1260 Ma) and II (1215–1140 Ma) of the Albany-Fraser Orogeny. Stage I was dominated by voluminous mafic and granitic magmatism, represented by the Fraser Zone intrusions and the Recherche Supersuite. Two granites from the Fraser Zone, dated at 1298 ± 4 Ma, have εHf values overlapping Biranup Zone compositions, indicative of a reworked Biranup source. The Biranup Zone was dominated by granulite facies metamorphism during Stage II. Zircons from the northeastern edge of the Fraser Zone are overgrown by two generations of zircon rims. The earlier rims, at c. 1270 ± 11 Ma, are broken and overgrown by a low-uranium fracture-filling phase at 1193 ± 26 Ma. This indicates uplift and brittle deformation between Stages I and II. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.

1. Introduction

∗ Corresponding author. E-mail addresses: [email protected], [email protected] (C.L. Kirkland).

The recognition, on craton margins, of allochthonous (exotic) terranes (e.g. Thomas and Astini, 1996; Daly et al., 1991) as opposed to autochthonous units (e.g. Tanner and Sutherland, 2007) is fundamental in understanding the geological evolution of a region.

0301-9268/$ – see front matter. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.precamres.2011.03.002

224

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Fig. 1. Crustal elements of easternmost Gondwana (modified from Fitzsimons, 2003; Tyler, 2005; Spaggiari et al., 2009). Paler and darker shades of the same pattern reflect areas with or without outcrop. AG, Terre Adélie–King George V Land; BH, Bunger Hills; CC, Coompana Complex (concealed by the Officer and Eucla Basins); CC, Curnamona Craton; DG, Denman Glacier region; M–F–W, Madura, Forrest, and Waigen Complexes (undivided; concealed by the Gunbarrel, Officer, and Eucla Basins); PB, Prydz Bay; WI, Windmill Islands.

Not only does this distinction have a bearing on the displacement magnitudes that must be invoked to transport lithological units to their current locations, but most importantly reflects the tectonic environment. For example, large compressional or transpressional kinematics, usually in subduction-related accretionary settings, are required to juxtapose exotic fragments, whereas suspect terranes are less likely to be found in extensional settings where margin rifting occurs. Initial models for the Proterozoic evolution of Australia emphasised intracratonic deformation involving a single plate (e.g. ensialic model of Etheridge et al., 1987). However, more recent work favours plate tectonic processes in which Proterozoic Australia is made up of three major, distinct cratons: the West Australian Craton, the North Australian Craton, and the South Australian Craton (Myers et al., 1996; Tyler, 2005; Fig. 1). Proterozoic orogens on the extremities of these cratons have been proposed as subduction-related convergent margins, which added to and eventually amalgamated the three cratons. Examples of regions of Proterozoic convergent margin tectonism include the Halls Creek Orogen (Sheppard et al., 2001), the Rudall Complex (Smithies and

Bagas, 1997), the Capricorn Orogen (Occhipinti et al., 1999), the Arunta Orogen (Collins and Shaw, 1995; Scrimgeour, 2003), parts of the Gawler Craton (Betts and Giles, 2006), the Musgrave Province and the Albany-Fraser Orogen (Myers et al., 1996; Bodorkos and Clark, 2004). In the recent literature, there is growing consensus that Proterozoic Australia involved protracted subduction, accretion, crustal reworking, and episodic continental back-arc basin development in interior regions (e.g. Betts and Giles, 2006; Korsch et al., 2010). However, the specific details of recent models for Proterozoic Australia, such as subduction zone location, polarity, and orientation of juxtaposed blocks, is diverse (Betts and Giles, 2006; Betts et al., 2002; Dawson et al., 2002; Fitzsimons, 2003; Giles et al., 2002, 2004; Myers et al., 1996; Payne et al., 2009; Wade et al., 2008; Howard et al., 2010). One of the lesser known cratonic margins is the southeastern West Australian Craton, which contains the Albany-Fraser Orogen. Understanding the evolution of this orogen will help chart both the development of the West Australian Craton and, in turn, its relationship to the other Proterozoic cratons and their margins. Specifically, using geochronology, isotope ratio measurements, major- and trace-element geochemistry,

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

225

Fig. 2. Simplified interpreted bedrock geology map of the eastern Albany-Fraser Orogen and eastern Yilgarn Craton (adapted from Spaggiari et al., 2009), showing locations of the geochronology samples. The map shows only basement geology and no basin cover. MBG, Mount Barren Group; MRF, Mount Ragged Formation; WF, Woodline Formation. Inset shows the location of Mesoproterozoic tectonic units of Australia; MP, Musgrave Province; PO, Paterson Orogen; N, Northampton Complex; L, Leeuwin Complex; AFO, Albany-Fraser Orogen. Sample ids maybe truncated to the last two digits where multiple samples have similar initial digits.

226

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

and field and geophysical observations, we argue that it is possible to ascribe the development of this margin to autochthonous processes, with tectonic modification due to the Mesoproterozoic continent–continent collision of the combined North and West Australian Cratons with the combined East Antarctic and South Australian Cratons (Myers et al., 1996; Bodorkos and Clark, 2004).

2009). These rocks were deformed during the Mesoproterozoic Albany-Fraser Orogeny, including substantial north- to northwestdirected thrusting of the Stirling Range Formation and Mount Barren Group (Myers, 1990; Dawson et al., 2002; Jones, 2006; Griffin, 1989). 2.2. Biranup Zone

2. Regional geology The Albany-Fraser Orogen is an arcuate orogenic belt adjacent to the southern and southeastern margins of the Archean Yilgarn Craton in Western Australia (Fig. 2). The predominant tectonic and metamorphic features of the belt are generally considered to have developed during the Mesoproterozoic Albany-Fraser Orogeny, which is thought to have occurred in two stages (Clark et al., 2000): continental collision during Stage I (c. 1345–1260 Ma), and intracratonic reactivation during Stage II (c. 1215–1140 Ma). Both stages have been interpreted to involve oblique dextral movement and the northwestward transport of thrust slices (Myers, 1993, 1995; Bodorkos and Clark, 2004). Giles et al. (2004) proposed that the orogeny was a response to Mesoproterozoic rotation of the Mawson Craton onto the West Australian Craton. The dominant lithologies of the Albany-Fraser Orogen are amphibolite to granulite facies paragneiss and orthogneiss, intruded by late-tectonic granite plutons. The nomenclature of the tectonic units of the orogen has evolved from the initial categorization of Myers (1990, 1995) to Spaggiari et al. (2009). The Albany-Fraser Orogen is divided into a series of mostly faultbounded zones, each with distinct lithotectonic character (Myers, 1990, 1995; Spaggiari et al., 2009). These lithotectonic units include the Northern Foreland, the Kepa Kurl Booya Province (a pre-collisonal Stage I basement component), the Recherche and Esperance Supersuites, and various Mesoproterozoic cover rocks. The Kepa Kurl Booya Province is further divided into the Biranup Zone, the Fraser Zone (formerly the Fraser Complex of Myers (1985)), and the Nornalup Zone (Myers, 1990, 1995; Spaggiari et al., 2009). The Kepa Kurl Booya Province is in fault contact with the Archean Yilgarn Craton to the northwest. To the east, the province is obscured by the Eucla Basin, and its relationship with the Madura, Forrest, Waigen, and Coompana Complexes and the western Gawler Craton is unknown (Fig. 1).

The Biranup Zone is a belt of mid-crustal rocks that girdles the southern and southeastern margin of the Yilgarn Craton (Fig. 2; Myers, 1990; Spaggiari et al., 2009). The zone is dominated by intensely deformed orthogneiss, paragneiss, and metagabbro, with ages of c. 1710–1620 Ma. The central Biranup Zone contains reworked 1690–1660 Ma orthogneiss, minor paragneiss, and Mesoproterozoic granitic intrusions (Nelson et al., 1995; Spaggiari et al., 2009). It includes the Dalyup and Coramup Gneisses (Myers, 1995), although both lithological units are chiefly composed of granitic rocks with similar crustal histories and hence the distinction between Dalyup and Coramup Gneisses may not be meaningful (Bodorkos and Clark, 2004). The lack of evidence for a similar Paleoproterozoic magmatic or tectonothermal event in the southern Yilgarn Craton at this time has led to the suggestion that the Biranup Zone was an exotic terrane accreted to the Yilgarn Craton margin during Stage I of the Albany-Fraser Orogeny (Nelson et al., 1995; Clark et al., 2000; Spaggiari et al., 2009). A potential link has been suggested between the Biranup Zone and the Warumpi Province of the southern Arunta Orogen (Spaggiari et al., 2009). 2.3. Nornalup Zone To the south and east of the Biranup Zone, a different group of Proterozoic granitic and sedimentary gneisses, intruded by younger granites, has been defined as the Nornalup Zone (Fig. 2; Myers, 1990). In the Nornalup Zone, pre-orogenic basement rocks are solely represented by the Malcolm Gneiss, which comprises paragneiss intruded by both mafic and felsic rocks, all of which are intruded by granites of the 1330–1280 Ma Recherche Supersuite (Clark et al., 1999, 2000). Detrital zircons from the Malcolm Gneiss have yielded a maximum depositional age of 1560 ± 40 Ma (GSWA 112128; Nelson, 1995g) with other detritus dated at 1807 Ma and minor age components at 2033 to 2734 Ma. The detrital zircon age spectrum of the Malcolm Gneiss indicates age components unrecognised within the Albany-Fraser Orogen (Kositcin, 2007).

2.1. Northern Foreland 2.4. Fraser Zone The Northern Foreland comprises the component of the Archean Yilgarn Craton that was reworked to produce mostly amphibolite to granulite facies rocks during the Albany-Fraser Orogeny (Fig. 2). It consists of 3000–2600 Ma gneisses and granites, faultbounded packages of metasedimentary rocks, and younger dolerite dykes (Spaggiari et al., 2009). The Munglinup Gneiss was originally defined by Myers (1993, 1995) as an allochthonous Archean unit within the Biranup Zone (formerly Biranup Complex). However, recent geochronology from the Munglinup Gneiss indicates that it represents overprinted Archean Yilgarn Craton rocks (c. 2660 Ma) and it is now considered part of the Northern Foreland (GSWA, 2007; Spaggiari et al., 2009). Hf isotopes from the Northern Foreland yield model ages clustering at c. 3.2 Ga, which implies a reworked Archean Hf source similar to many intrusive rocks within the Eastern Goldfields Superterrane (GSWA, unpublished data). Paleoproterozoic sedimentary rocks of the Woodline Formation (Hall and Jones, 2005; Hall et al., 2008), Mount Barren Group (Nelson, 1996; Dawson et al., 2002; Vallini et al., 2005), and Stirling Range Formation (Rasmussen et al., 2002) are part of the Northern Foreland and are interpreted to represent unconformable sequences on the Yilgarn Craton (Hall et al., 2008; Spaggiari et al.,

The northeasterly trending Fraser Zone contains the c. 1300 Ma Fraser Range Metamorphics (Spaggiari et al., 2009), a suite of interleaved thin slivers of granitic gneiss, metasedimentary rocks, and mafic rocks, that are now mostly pyroxene granulites or mafic amphibolites (Fig. 2; Myers, 1985; Clark et al., 1999; De Waele and Pisarevsky, 2008; Spaggiari et al., 2009). Myers (1985) interpreted the mafic rocks in the Fraser Zone as part of a large layered mafic intrusion, whereas Condie and Myers (1999) argued that they represent remnants of multiple magmatic arcs. Doepel (1975) interpreted both the metagranitic and metamafic components of the Fraser Zone as an exhumed block of lower crust. The Fraser Range Metamorphics are dominated by a northeasterly trending, steeply dipping foliation (Myers, 1985; Clark et al., 1999). Boundaries between the rock units were previously interpreted to be major thrust faults that interleaved slivers of older ‘basement’ gneiss and metasedimentary rocks with the mafic rocks (Myers, 1985). However, it is now known that the granitic and metasedimentary rocks previously interpreted as ‘basement’ are similar in age to the mafic rocks (Clark et al., 1999; De Waele and Pisarevsky, 2008; this study). Kinematic indicators and aeromag-

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

netic data indicate a significant dextral shear component along the northwestern edge of the Fraser Zone, defined by the Fraser Fault, which separates the Biranup Zone from Fraser Zone rocks (Fig. 2). Crystallization of gabbro within the Fraser Zone is dated at 1291 ± 8 Ma (De Waele and Pisarevsky, 2008) by U–Pb on zircon and at 1291 ± 21 Ma by a whole-rock Sm–Nd isochron (MSWD = 0.25; (Fletcher et al., 1991). A minimum age constraint on the mafic rocks is provided by an intrusive charnockitic orthogneiss cutting the gabbros at 1301 ± 6 Ma (Clark et al., 1999). Early metamorphism in the Fraser Zone at 1304 ± 7 Ma is recorded by zircon rims developed within a quartz metasandstone interlayered with amphibolite and pyroxene granulite with a maximum depositional age of 1466 ± 17 Ma (Wingate and Bodorkos, 2007b). A biotite–whole-rock Rb–Sr isochron date of 1268 ± 20 Ma is interpreted to reflect the time of cooling below the isotopic closure temperature for biotite in this rock (Fletcher et al., 1991). All isotopic results from the Fraser Zone indicate a short time interval for igneous crystallization at c. 1300 Ma, and essentially coeval granulite-facies metamorphism. Retrogression, cooling, and uplift occurred shortly after metamorphism (Fletcher et al., 1991; Clark et al., 1999; De Waele and Pisarevsky, 2008). 2.5. Mesoproterozoic reworking and the Recherche and Esperance Supersuites The Mesoproterozoic Albany-Fraser Orogeny is the principal event that amalgamated the Biranup, Nornalup, and Fraser Zones, and reworked the margin of the Yilgarn Craton to produce the Northern Foreland. The Biranup and Nornalup Zones were intruded by granitic rocks of the c. 1330–1280 Ma Recherche Supersuite (formerly Recherche Granite of Myers, 1995), which is associated with Stage I tectonism (Nelson, 1995a; Clark et al., 1999, 2000; Bodorkos and Wingate, 2008a). Metagranitic rocks dated at c. 1330–1280 Ma are also found in the Fraser Range Metamorphics (Wingate and Bodorkos, 2007a; De Waele and Pisarevsky, 2008). Following Stage I uplift, erosion of the Nornalup Zone and Recherche Supersuite granitic rocks produced massive quartzites and thin pelitic layers of the Mount Ragged Formation (Fig. 2; Clark et al., 2000). The Mount Ragged Formation contains 1154 ± 15 Ma rutile, indicating burial and metamorphism during Stage II (Clark et al., 2000). Stage II is thought to have taken place in an intracontinental setting (Bodorkos and Clark, 2004). Minor extension occurred during Stage II during intrusion of the margin-parallel Gnowangerup–Fraser Dyke Suite at c. 1210 Ma (Wingate et al., 2000), which was associated with a regionally elevated geothermal gradient (Dawson et al., 2003). There is also evidence of alternating extension and contraction during Stage II at c. 1180 Ma in the central Biranup Zone, which produced several phases of boudinage and folding (Barquero-Molina, 2009; Spaggiari et al., 2009). The c. 1330–1280 Ma Recherche Supersuite (Clark et al., 1999) and the c. 1140 Ma Esperance Supersuite (Myers, 1995; Nelson, 1995c; Nelson et al., 1995) mark two major magmatic events that coincided with Stages I and II of the Albany-Fraser Orogeny, respectively (Clark et al., 2000). 3. Ion microprobe (SHRIMP) U–Th–Pb geochronology We present U–Th–Pb results from fifteen samples, which span the entire eastern portion of the Albany-Fraser Orogen (east Biranup Zone and Fraser Range Metamorphics; Fig. 2). The locations of all samples are shown in Fig. 2, and a summary of the location, petrography, and U–Pb date for each sample is given in Table 1. U–Pb data tables, together with external and internal uncertainties from replicate analyses of standards, are available online as Supplementary material (Table A). Details of the analytical method-

227

ology are given in Appendix A. All geochronology results are shown in a stacked Tera-Wasserburg concordia diagram (Fig. 3). Group letters ascribed to zircon analyses refer to the interpretation of the result and correspond to those listed in the Supplementary material Table. Representative cathodoluminescence images of all zircon samples are provided as online Supplementary material. 3.1. Magmatism at c. 1700 Ma in the eastern Biranup Zone The Bobbie Point Metasyenogranite, of which sample 194737 is representative, is an extensive granitic intrusion that crops out about 30 km northeast of the Tropicana-Havana gold deposit (Fig. 2). The metasyenogranite is seriate-textured to locally porphyritic, with deep pink to red K-feldspar phenocrysts. Locally, the metasyenogranite contains xenoliths or enclaves of gabbroic rocks. The metasyenogranite exhibits a weak, northeasterly trending, solid-state foliation, which is locally mylonitic, with welldeveloped strain gradients. Numerous thin quartz veins are aligned sub-parallel to the foliation (Fig. 4a). 3.1.1. 194737 Zircons recovered from this sample are subhedral to euhedral, yellow to brown, up to 200 ␮m long, and have aspect ratios up to 4:1. Cathodoluminescence (CL) images reveal idiomorphic zoning. Three analyses are >5% discordant and are not considered geologically significant. The remaining 14 analyses define one coherent group (Group I), which yields a weighted mean 207 Pb*/206 Pb* date of 1708 ± 15 Ma (MSWD = 1.8). The analyses have low to moderate U contents (36–164 ppm) and moderate to high Th/U ratios (0.73–1.23). The date of 1708 Ma is interpreted as the age of magmatic crystallization of the metasyenogranite. 3.2. Volcaniclastic sediment deposition at c. 1680 Ma in the eastern Biranup Zone A package of north-northwesterly trending, southwesterly dipping metasedimentary rocks, belonging to the Biranup Zone, are exposed along Ponton Creek, about 15–20 km north of Zanthus and the transcontinental railway. These rocks, of which sample 194731 is representative, are mostly psammitic gneisses with sparse garnet and, locally, thin leucosomes. Fine bedding laminations and cross-bedding are preserved and indicate younging to the westsouthwest (Fig. 4b). The foliation, defined by biotite and quartz, is sub-parallel to bedding, and contains a mineral lineation that plunges shallowly to the southwest. Locally, the psammitic gneiss has been intruded by metagranite and coarse pegmatite (neither of which is present in the sample), and is flanked by migmatitic granite gneiss and foliated metagranodiorite that exhibit the same foliation and lineation. 3.2.1. 194731 Zircons isolated from sample 194731 are subhedral and slightly rounded. They are mainly colourless, up to 400 ␮m long, and have aspect ratios up to 4:1. CL images reveal a range of textures including oscillatory zoning and homogenous domains. Eight analyses are characterized by >10% discordance. The dates obtained from these eight analyses (Group D) are not considered geologically significant. The remaining 32 analyses of 32 zircons (Group Y) yield a weighted mean 207 Pb*/206 Pb* date of 1689 ± 6 Ma (MSWD = 1.5), interpreted as the age of magmatic crystallization of the igneous source of this detritus and also the maximum age of deposition. 3.3. Deformation at c. 1680 Ma; the Zanthus Event Migmatitic, hornblende-biotite-garnet granitic gneiss exposed along Ponton Creek belong to the eastern Biranup Zone. Outcrops of

228 Table 1 Zircon U–Th–Pb ages of samples in the eastern Albany Fraser Orogen. Easting and Northing uses WGS84 datum, MGA Zone 51. Abbreviations of mineral names after Kretz (1983). All uncertainties are at the 95% confidence level. Type refers to material crushed for zircon extraction. Sample

Type

Archean remnant 194709 Whole rock Biranup Zone 194737

Whole rock Whole rock

194730 194729

Leucosome dominant Leucosome only

194720

Whole rock

Lithology (petrology)

Magmatism

Metamorphism

Inheritance

492878 E 6392895 S (MOUNT ANDREW)

Metasyenogranite (Fsp, Qtz, Hbl, Pl, Px, Bt, Zrn, Ttn)

2684 ± 11 Ma

1171 ± 30 Ma

–

662415 E 6792732 S (SCHERK RANGE) 561726 E 6579780 S (YANDALLAH) 562765 E 6582098 S (YANDALLAH) 562765 E 6582098 S (YANDALLAH)

Metasyenogranite (Or, Qtz, Ms, Mag, Ttn, Py, Zrn)

1708 ± 15 Ma

–

–

Psammitic gneiss (Qtz, Kfs,Grt, Py, Bt, Zrn)

1689 ± 6 Ma

–

–

Migmatitic metamonzogranite with folded leucosomes (Qtz, Pl, Kfs, Bt, Hbl, Ttn, Aln, Zrn, Ap) Axial planar leucosome in migmatiticmetamonzogranite (Qtz, Pl, Kfs, Bt, Ttn, Aln, Zrn, Ap) Metadiorite (Pl, Qtz, Mc, Bt, Grt, Hbl, Ep, Ap, Zrn)

1676 ± 6 Ma

–

–

1679 ± 6 Ma

–

–

1665 ± 6 Ma

–

–

Metagabbronorite (Pl, Opx, Cpx, Bt, Ol, Mag, Spl, Hbl)

1664 ± 7 Ma

–

–

Orthogneiss (Pl, Qtz, Bt, Mc, Ms, Ttn, Zrn, Aln)

1686 ± 8 Ma

1203 ± 11 Ma

1749, 1766 and 1809Ma

Orthogneiss (Qtz, Pl, Kfs, Grt, Bt, Mc, Ttn, Zrn, Hbl)

1671 ± 7 Ma

1205 ± 20 Ma

–

Orthogneiss (Qtz, Pl, Kfs, Bt, Grt, Hbl, Ttn, Zrn)

1666 ± 11 Ma

1162 ± 39 Ma

–

Orthogneiss (Or, Qtz, Pl, Bt, Grt, Ap, Zrn)

1675 ± 9 Ma

1193 ± 9

1780Ma, ≥ 2340 Ma

Orthogneiss (Mc, Qtz, Pl, Grt, Ttn, Bt, Zrn)

1683 ± 8 Ma

1201 ± 15 Ma

–

Migmatitic gneiss (Pl, Qtz, Mc, Bt, Ep, Ttn, Ms, Ap, Zrn)

1657 ± 5 Ma

1270 ± 11 Ma and 1193 ± 26 Ma

–

Monzogranite (Qtz, Mc, Pl, Bt, Grt, Hbl, Ap, Zrn)

1297 ± 8 Ma

–

1701–1684Ma

Banded orthogneiss with mafic schlieren (Qtz, Kfs, Afs, Bt, Pl, Zrn, Ttn)

1298 ± 5 Ma

–

1770 Ma

546153 E 6534950 S (COONANA) 194721 Whole rock 546142 E 6535047 S (COONANA) Biranup Zone (retaining evidence of overprinting) 194701 Whole rock 419829 E 6330456 S (BURDETT) 194725 Whole rock 540851 E 6541647 S (COONANA) 194726 Whole rock 540239 E 6549701 S (COONANA) 194734 Whole rock 561862 E 6579939 S (YANDALLAH) 194728 Melanosome only 560358 E 6583678 S (YANDALLAH) Gwynne Creek Gneiss 194735 Whole rock 492904 E 6418535 S (FRASER RANGE) Fraser Zone 194711 Whole rock 492904 E 6418535 S (FRASER RANGE) 194719 Whole rock 503090 E 6475794 S (SYMONS HILL)

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

194731

Location (100 K map)

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

229

Fig. 3. Stacked Tera-Wasserburg concordia diagrams for zircons and baddeleyites analysed by ion microprobe. Error crosses are 2. Data are arranged according to geographic location: southwest at the bottom to northeast at the top. Those data points not lying within the concordia space for that sample are shown with an arrow to their respective sample. The Fraser Zone data is shown on a grey background. Inset lower right shows Th/U versus 207 Pb/206 Pb age for selected samples with metamorphic zircon overgrowths from the Biranup Zone and magmatic zircon from the Fraser Zone. Inset upper left shows concordia diagram for Archean remnant 194709.

230

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Fig. 4. (a) Bobbie Point Metasyenogranite (194737) showing quartz veining. (b) Ponton Creek psammitic gneiss (194731) showing fine laminations and cross bedding. (c) Migmatitic, hornblende-biotite granitic gneiss at Ponton Creek, with early layer-parallel folded leucosomes (194730). (d) Axial planar leucosomes (194729), which themselves are folded. (e) View of platform showing the axial planar parallel lensoid leucosomes that were sampled. Hammer head is to the north. (f and g) Eddy Suite of rapakivitextured metagranodiorite extensively mingled with metagabbronoritic rocks. (h) Coarse-grained strongly foliated monzogranitic gneiss (194711) with sinistral shear bands. (i) Asymmetrically ponded leucosome (host rock is sample 194734). (j) Asymmetric deformed pegmatite (host rock is Gwynne Creek Gneiss sample 194735).

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

the gneiss in this area are characterised by a northwesterly trending gneissosity, consistent with aeromagnetic data, which indicates that this is a widespread regional trend within the eastern Biranup Zone. This fabric is truncated by the northeasterly trending fabric of the Fraser Zone to the southeast (Fig. 2). The gneisses along Ponton Creek contain an early gneissic fabric with centimetre-scale, layerparallel leucosomes, (Fig. 4c), folded into northwesterly trending isoclinal folds with an axial planar foliation. These rocks are represented by sample 194730. A second generation of leucosomes, represented by sample 194729, was intruded parallel to the axial planes of the folds, and was sampled by chiseling out leucosome material from the axial plane (Fig. 4d and e). At several nearby outcrops, the northwesterly trending gneissosity and layer-parallel leucosomes are overprinted by centimetre-scale, north-northeast trending, melt-filled, dextral shears. In one case, the outcrop also contains an east-southeast-trending, melt-filled, sinistral shear zone that is along-strike from a dextral shear, indicating a conjugate pair. Significantly, the second-generation leucosomes in the shear zones are texturally continuous with the first-generation gneissosity-parallel leucosomes, indicating that the two generations formed during a single event. These observations also indicate that leucosome injection occurred during a period of northeastsouthwest directed shortening, the age of which is constrained by the zircon U–Pb results from these samples. 3.3.1. 194728 Sample 194728 is a quartzofeldspathic gneiss of the eastern Biranup Zone and was recovered from an east-west track close to Ponton Creek (Fig. 2). Both melanosome and leucosome contain garnet. Zircons separated from the melanosome are euhedral, up to 300 ␮m long, with generally high aspect ratios up to 6:1, and are colourless to black. CL images display oscillatory zoning, which in places is contorted. Older cores are present within some grains, and thin homogeneous overgrowths mantle many crystals. Twenty analyses are >5% discordant, but appear to have only been affected by recent radiogenic-Pb loss. Twenty-two analyses of zircon rims (Group M), with generally low Th/U ratios of c. 0.05, yield a weighted mean 207 Pb*/206 Pb* date of 1201 ± 15 Ma (MSWD = 1.6), interpreted as the timing of a high-grade metamorphic overprint. Twenty-four analyses of oscillatory zoned zircons (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1683 ± 8 Ma (MSWD = 2.2), interpreted as the crystallization age of the granitic protolith to the gneiss. One analysis (Group P) located on a homogeneous zircon core yields a 207 Pb*/206 Pb* date of 1610 Ma. This crystal is interpreted to have been subject to ancient radiogenic-Pb loss. 3.3.2. 194730 Zircons from sample 194730, a migmatitic metamonzogranite with folded coarse-grained leucosomes, are euhedral, yellow to dark brown, up to 700 ␮m long, and have aspect ratios up to 6:1. CL images reveal ubiquitous oscillatory zoning. Seven analyses are characterized by >5% discordance, and are not considered geologically significant. Sixteen zircons (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1676 ± 6 Ma (MSWD = 2.0), interpreted as the age of the layer-parallel leucosomes formed during migmatization of the monzogranite. The alternative interpretation – that the date reflects the age of initial granitic magmatism – is regarded as unlikely, because the grain morphology and crystal size are consistent with growth in a pegmatite. Furthermore, the date is apparently younger, though within uncertainty, of melanosome material from a less-migmatized quartzofeldspathic gneiss (194728) in the same area, and is also consistent with the result from leucosome-only material (sample 194729) separated from the host rock (see below). Two analyses (Group P) yield 207 Pb*/206 Pb* dates of 1645 and 1596 Ma and are interpreted to reflect ancient radiogenic-Pb loss. A single analysis (10.1; Group

231

M), which yields a 207 Pb*/206 Pb* date of 1247 ± 18 Ma (1) and indicates a low Th/U ratio (0.02; Fig. 3), is interpreted to reflect the timing of high-grade metamorphism that caused either metamorphic zircon growth or near-complete radiogenic-Pb loss from a pre-existing zircon. 3.3.3. 194729 Sample 194729 is from a leucosome injected into the axial planes of the folds in the same outcrop from which sample 194730 was collected. Both the gneissosity and also the early generation of layer-parallel leucosomes (as dated by sample 194730) are folded, whereas these late-generation leucosomes post-date some folding in this outcrop. Other examples of this axial planar set of leucosomes are themselves folded in a similar orientation to those that have affected the gneissic foliation and early leucosomes (Fig. 4d). This implies either that deformation outlasted crystallization of the younger leucosomes or that there was a period of folding subsequent to the initial deformation event. Zircons separated from the granitic leucosome are euhedral, yellow to dark brown, up to 700 ␮m long, and have aspect ratios up to 6:1. CL images reveal ubiquitous oscillatory zoning. The grain morphology is very similar to crystals from sample 194730, and is consistent with both crystallizing from similar fluids. All analyses are <5% discordant and define a single group of 18 analyses (Group I), which yield a weighted mean 207 Pb*/206 Pb* date of 1679 ± 6 Ma (MSWD = 2.0), interpreted as the age of crystallization of the axial planar leucosome. As with 194730, these zircons are unlikely to date inherited material from the enclosing host rock because the large euhedral crystals are more consistent with growth in a pegmatitic leucosome. 3.4. Mingled norite and granodiorite emplacement at c. 1665 in the eastern Biranup Zone: the Eddy Suite The Eddy Suite, which ranges from megacrystic metamonzogranite and equigranular metasyenogranitic gneiss to rapakivitextured metagranodiorite and metagabbronoritic rocks, occurs in the eastern Biranup Zone, and is well exposed west of Harris Lake. The metagranodiorite contains ovoid K-feldspars, up to 3 cm long with a mm-wide mantle of more calcic feldspar, and rounded quartz phenocrysts up to 6 mm in diameter, in a medium-grained groundmass. These textures are typical of magma mingling, and suggest that the metagranodiorite is a hybrid of the megacrystic metamonozogranite and a mafic end-member, likely the metagabbronorite. The metagabbronorite is fine- to medium-grained, and forms irregular enclaves that have lobate, commonly gradational, boundaries with the metagranodiorite, suggesting the two phases are comagmatic. These rocks are heterogeneously deformed, such that mingling textures are preserved in some areas (Fig. 4f and g), although most exposures exhibit a pervasive gneissosity and localised mylonite zones. The magmatic rocks are interpreted to intrude metasedimentary rocks that are probably part of the same succession as the psammitic gneiss in the Ponton Creek area described above (sample 194731). 3.4.1. 194720 Sample 194720 is a metadiorite from the Eddy Suite, sampled about 6 km southeast of Harris Lake. Zircons isolated from this sample are subhedral to euhedral, colourless to brown, up to 300 ␮m long, and have aspect ratios up to 5:1. CL images reveal oscillatory zoning. The analyses are concordant and define one coherent group. Twenty-three analyses (Group I) yield a concordia age of 1665 ± 6 Ma (MSWD = 1.7), interpreted as the age of magmatic crystallization of the diorite.

232

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

3.4.2. 194721 Sample 194721 is a metagabbronorite from the Biranup Zone, collected c. 100 m north of 194720. The rock has an ophitic texture. Baddeleyites isolated from this sample are subhedral to euhedral, brown to black, up to 300 ␮m long, and have aspect ratios up to 3:1. The analyses are concordant to slightly discordant, owing in part to orientation-related bias in 238 U/206 Pb* (Wingate and Compston, 2000). Five analyses affected by instrument instability (Group D) are unreliable, and are not considered geologically significant. Twenty-two analyses of 19 crystals (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1664 ± 7 Ma (MSWD = 0.74), interpreted as the age of magmatic crystallization. Four analyses of three grains (Group P) yield younger 207 Pb*/206 Pb* dates of 1599–1548 Ma and are interpreted to have lost radiogenic Pb. The date of 1664 ± 7 Ma is essentially identical to the age of the metadiorite (194720) that mingled with this rock. 3.5. Rifted fragment of Yilgarn Craton within the Biranup Zone Within the Biranup Zone, a north- to northeast-trending metasyenogranitic body, approximately 12 km long and 4 km wide, is distinct in being garnet-absent, weakly to locally strongly foliated, and has only minor occurrences of leucosome cross-cutting the foliation. The contact with strongly migmatised orthogneiss of the Biranup Zone is not exposed, but dated Biranup Zone orthogneiss lies directly to the northwest (Nelson, 1995h), on the inboard side of the orogen. Outcrop observations and aeromagnetic data indicate that the metasyenogranite, of which sample 194709 is representative, is an isolated fragment surrounded by orthogneisses of the Biranup Zone. 3.5.1. 194709 Sample 194709 is from weakly foliated metasyenogranite near Cave Rock, about 8 km north of Mount Andrew (Fig. 2). This sample yielded colourless to dark brown, subhedral to euhedral zircons. Euhedral growth zoning is common, and many crystals are overgrown by homogeneous rims with low CL response. Eight analyses of zircon rims (Group M) yield a weighted mean 207 Pb*/206 Pb* date of 1163 ± 14 Ma (MSWD = 2.0), interpreted as the age of metamorphism. Eighteen analyses (Group I) define a discordia which intersects concordia at 2684 ± 11 and 1171 ± 30 (MSWD = 1.4). The upper intercept is interpreted as the age of igneous crystallization of the granite, the lower intercept is within uncertainty of the age of the zircon rims and is interpreted as the age of radiogenic-Pb loss during metamorphism. Four analyses (Group P) indicate 207 Pb*/206 Pb* dates of 2585–1587 Ma, and are interpreted to have undergone multiple phases of radiogenic-Pb loss. Groups I and P together define a discordia which intersects concordia at 2669 ± 24 and 1137 ± 45 (MSWD = 3.4). However, the high MSWD is interpreted to reflect the combined effects of ancient and recent radiogenic-Pb loss. 3.5.2. Magmatism at c. 1300 Ma in the Fraser Zone Metagranitic rocks exposed in the Fraser Zone vary from metamonzogranite to metasyenogranite, and occur as sheets interlayered with metagabbros and metasedimentary rocks. Rocks of the Fraser Zone are typically metamorphosed to amphibolite or granulite facies and strongly foliated, although massive rocks can locally be found in the centre of the zone. The zone is bounded by major structures, including the Fraser Fault along the northwestern margin, and a large shear zone (Newman Shear Zone) along its southeastern boundary. The southeastern tip of the Newman Shear Zone contains strongly deformed, coarse-grained, garnet-bearing monzogranitic gneiss, represented by sample 194711. The monzogranitic gneiss varies between an L- and S-tectonite and has a strong, northeasterly trending, subvertical solid-state foliation and

a mineral lineation that plunges shallowly to the northeast. Locally developed C–S planes and extensional shear bands indicate a sinistral sense of shear (Fig. 4h). In the southern part of the Fraser Zone, east of the Fraser Fault (Fig. 2), metasyenogranitic gneisses, represented by sample 194719, are typically compositionally banded, contain mafic schleiren, and are interlayered with metagabbroic rocks. 3.5.3. 194711 Sample 194711 is a coarse-grained, strongly foliated monzogranitic gneiss from the Newman Shear Zone. Zircons from this sample are euhedral, up to 400 ␮m long, with moderate to high aspect ratios, and are pale brown to black. CL images display oscillatory zoning which in places is contorted. Older cores are present within some grains. Ten analyses >5% discordant are not considered further. Sixteen analyses (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1297 ± 8 Ma (MSWD = 1.15), interpreted as the timing of magmatic crystallization of this granite. Four analyses of cores (Group X) yield 207 Pb*/206 Pb* dates of 1701–1684 Ma, interpreted as the ages of inherited material incorporated into this granite. 3.5.4. 194719 Sample 194719 is a foliated, medium- to coarse-grained, seriatetextured, metasyenogranitic gneiss collected from the same locality as sample FR21of De Waele and Pisarevsky (2008), south of Symons Well. The zircon crystals are euhedral, up to 500 ␮m long, with generally high aspect ratios, and are dark brown to black. CL images display faded oscillatory zoning with convoluted textures indicative of dissolution–reprecipitation (Vavra et al., 1996). Seven analyses (Group D) are >5% discordant, are imprecise or unreliable, and are not considered geologically significant. Thirteen analyses (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1298 ± 5 Ma (MSWD = 1.9), interpreted as the age of magmatic crystallization. Uranium content is variable but also generally high (312–2307 ppm). Seven analyses (Group P) which indicate 207 Pb*/206 Pb* dates of 1283–1278 Ma are interpreted to have undergone ancient Pb loss. Uranium content indicated by these analyses is also high (815–1995 ppm). Radiogenic Pb-loss is the preferred interpretation for Group P based on the high degree of crystal damage estimated from the calculated alpha radiation dosage for all zircons in this rock (Murakami et al., 1991). One core analysis (Group X) yields a 207 Pb*/206 Pb* date of 1770 ± 13 Ma (1), interpreted as the age of a xenocrystic component. Some modernday Pb-loss is also evident within these results. De Waele and Pisarevsky (2008) reported an age of 1296 ± 7 Ma (plus one inherited grain at 1665 Ma) for this rock. 3.6. Zircon growth during metamorphism at c. 1200 Ma in the eastern Biranup Zone Many orthogneisses in the eastern Biranup Zone contain zircons that have distinctly younger overgrowths, reflecting mobility of zirconium-bearing fluids after magmatic crystallization. The samples listed in the following section show evidence of metamorphic zircon growth onto pre-existing zircon crystals. 3.6.1. 194734 Sample 194734 is a garnet-biotite gneiss of the Biranup Zone from Ponton Creek, close to sample localities 194731, 194729, and 194730, described above (Fig. 2). The rock contains coarse- to very coarse-grained leucosomes composed of quartz and K-feldspar that are typically aligned parallel to the northwesterly trending gneissosity to form continuous layers or short lenses. Locally, the leucosome material has asymmetrically ponded in the necks of boudinaged layers (Fig. 4i), suggesting that the ‘way-up’ direction

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

was to the southwest during migmatization, and consistent with the dip of overlying units. The zircons are generally euhedral, up to 500 ␮m long, and colourless to brown. CL images display oscillatory zoning with low-CL-response rims developed on some crystals. Six analyses are >5% discordant and one analysis (5.1) is interpreted as a core-rim mixture (Group D). These seven analyses are not considered geologically significant. Sixteen analyses of 16 zircons (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1675 ± 9 Ma (MSWD = 1.7), interpreted as the age of magmatic crystallization of the granitic protolith to the gneiss. Uranium contents indicated by these analyses are low to moderate (781–74 ppm). Two analyses (Group P), which yield 207 Pb*/206 Pb* dates of 1641 and 1613 Ma, are interpreted to have undergone ancient radiogenicPb loss. One core analysis (Group X) yields a 207 Pb*/206 Pb* date of 1780 ± 9 Ma (1␴), which is interpreted as the age of an inherited component. Four analyses of four rims yield a concordia age of 1193 ± 9 (MSWD = 1.4), interpreted as the age of a metamorphic overprint. One discordant analysis (18.1) has a 207 Pb*/206 Pb* date of c. 2340 Ma, which is a minimum age, indicating an inherited component of probable Archean age. 3.6.2. 194701 Sample 194701 is a compositionally banded orthogneiss previously mapped as Munglinup Gneiss (GSWA, 2007), southwest of the Fraser Zone (Fig. 2). However, the U–Pb data indicate that it belongs to the Biranup Zone. The orthogneiss exhibits a welldeveloped gneissosity and layer-parallel leucosomes, and contains parasitic folds to a large-scale southwesterly plunging antiform, which forms part of a northeasterly trending, elongate dome structure. The zircons are euhedral, up to 300 ␮m long, with generally high aspect ratios up to 6:1, and are colourless to pale brown. CL images display oscillatory zoning, which in places is contorted. Older cores are present within some grains, and thin homogeneous overgrowths mantle many crystals. Sixteen analyses (Group D) are greater than 5% discordant, and are not considered geologically significant. Four analyses of zircon rims (Group M), with low Th/U ratios of 0.004–0.12, yield a concordia age of 1203 ± 11 Ma (MSWD = 1.05), interpreted as the timing of a high-grade metamorphic overprint. Twenty-three analyses (Group I) indicate moderate Th/U ratios of 0.21–1.25, and yield a weighted mean 207 Pb*/206 Pb* date of 1686 ± 8 Ma (MSWD = 1.9), interpreted as the crystallization age of the granitic protolith. Some of these analyses are located on grains with disrupted internal textures, which may reflect dissolution and reprecipitation of inherited zircon during a c. 1686 Ma melting event. Three analyses of zircon cores (Group X) yield 207 Pb*/206 Pb* dates of 1749, 1766, and 1809 Ma, interpreted to reflect the ages of inherited material, although these crystals may have undergone some radiogenic-Pb loss during the 1680 Ma melting event. Three analyses (Group P) yield 207 Pb*/206 Pb* dates between 1626 and 1657 Ma and are interpreted to have undergone ancient radiogenic-Pb loss. 3.6.3. 194725 Sample 194725 is a coarse-grained, garnet-rich orthogneiss from approximately 8 km south of Uraryie Rock in the eastern Biranup Zone (Fig. 2). The orthogneiss contains K-feldspar phenocrysts and has a strong, northeasterly trending gneissic foliation and well-developed lineation. On a regional scale, the outcrop occurs in an area of large-scale, easterly trending, refolded folds, adjacent to a major northerly trending shear zone. Zircon grains from this sample are euhedral, up to 400 ␮m long, with high aspect ratios, and are colourless to brown. CL images display cores with oscillatory zoning which are overgrown by high-CL-response rims. Seven analyses >5% discordant are not considered further. Nineteen analyses of zircon rims (Group M), have low U contents (40–108 ppm), and yield a strong negative correlation between

233

common-Pb corrected 207 Pb*/206 Pb* dates and f204, implying a systematic error in the 204 Pb corrected dates. This issue is common in ion microprobe analyses where average 204 Pb counts are close to or below the background levels. A regression through Group M data onto concordia from the assumed common Pb composition (207 Pb/206 Pb = 0.925 at 1200 Ma; Stacey and Kramers, 1975) yields an intercept date of 1205 ± 20 Ma (MSWD = 1.7). This result is interpreted as the time of high-grade metamorphism. Because the common Pb content is low and the analyses are near-concordant, neither the form of the common-Pb correction nor its application has significant effect on the calculated age. Nineteen analyses of zircon cores (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1671 ± 7 Ma (MSWD = 1.8), interpreted as the age of magmatic crystallization of this granite. 3.6.4. 194726 Sample 194726 is a medium to coarse-grained, garnet- and biotite-rich equigranular orthogneiss of the eastern Biranup Zone, from Uraryie Rock (Fig. 2). This sample yielded colourless to yellow zircons, which are euhedral and elongate. The grains exhibit idiomorphic zoning, and have homogeneous high-CL-response rims. One analysis >5% discordant and one analysis indicating high within-analysis variation in isotope ratios are not considered further (Group D). Four analyses (Group P) indicating 207 Pb*/206 Pb* dates of 1553–1386 Ma are interpreted to reflect loss of radiogenic Pb. Nineteen analyses (Group I) yield a weighted mean 207 Pb*/206 Pb* date of 1666 ± 11 Ma (MSWD = 2.1), interpreted as the age of magmatic crystallization of the granitic protolith. Six rim analyses (Group M) yield a weighted mean 238 U/206 Pb* age of 1162 ± 39 Ma (MSWD = 0.84). These analyses indicate very low U contents and consequently have elevated analytical uncertainties. Nevertheless, this date serves as the best estimate of the age of a metamorphic overprint on this rock. 3.6.5. 194735 Sample 194735 is a garnet-biotite, quartzofeldspathic migmatitic gneiss (Gwynne Creek Gneiss), taken from the western side of Gwynne Creek near Plumridge Lakes, east of the Tropicana-Havana deposit (Fig. 2). The Gwynne Creek Gneiss is a Mesoproterozoic cover sequence that outcrops along the far northeastern edge of the Fraser Zone, and is dominated by psammitic and semi-pelitic gneiss. It has a maximum depositional age of 1483 ± 12 Ma and a significant 1675 Ma detrital component (Kirkland et al., 2011). The sampled outcrop consists of layered, finely laminated quartzofeldspathic gneiss with layer-parallel leucosomes, and semi-pelitic schist, all intruded by K-feldspar-rich pegmatite veins, which are locally boudinaged and have dextral asymmetry (Fig. 4j). The zircons are euhedral, up to 400 ␮m long, and colourless to pale brown. CL images display cores with oscillatory zoning which are overgrown by low-CL-response, homogeneous overgrowths (“dark overgrowth”). The dark overgrowths are rimmed by homogeneous, high-CL-response zircon (“bright rims”) which are typically <5 ␮m thick (but in places up to 20 ␮m thick). The “bright rims” are found on all grains and heal brittle fractures that dislocate both oscillatory zoned cores and “dark overgrowths” (Fig. 5). Twelve analyses (Group D) that are >1300 Ma and >5% discordant or core-rim mixtures are not considered further. Eight analyses (Group P) yield 207 Pb*/206 Pb* dates from 1634 to 1605 Ma and are interpreted to have lost minor amounts of radiogenic Pb. Thirty-four analyses of 34 oscillatory zircon cores (Group I) yield a concordia age of 1657 ± 5 Ma (MSWD = 1.3), interpreted as the age of magmatic crystallization of the igneous source of this detritus. The CL-bright rims (Group M2; see below) have very low U and Th concentrations consistent with precipitation from metamorphic solutions (e.g. Pettke et al., 2005).

234

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Fig. 5. SEM cathodoluminescence images of selected zircon grains from sample 194735 (for location see Fig. 2). Ellipses indicate analysed regions labelled with the spot identification.

Two analyses of “dark overgrowths” in two grains (Group M) yield a concordia age of 1270 ± 11 Ma (MSWD = 0.43), interpreted to date zircon growth during metamorphism. Three analyses, in three grains, of “bright rims” (Group M2) that were large enough to analyse, yield a concordia age of 1193 ± 26 Ma (MSWD = 0.43). These analyses indicate very low U contents and consequently have low precision. This date is interpreted to reflect the timing of zircon growth from hydrothermal fluids. The “bright rims” heal brittle fractures that transect entire zircon crystals, including the “dark overgrowths”. Brittle deformation in this rock occurred after formation of “dark overgrowths” and prior to crystallization of “bright rims”, and is therefore constrained between 1270 and 1193 Ma.

Ten whole-rock Sm–Nd samples of Biranup Zone intrusions yield εNdi values ranging from −15.24 to −1.11 (Table 3; Fig. 7), with a distinct temporal trend towards more juvenile values through time (Fig. 8). Most of the Sm/Nd ratios are fractionated and higher than normal crustal values. This implies multiple remelting, or segregation of strongly LREE-enriched mineral phases (either by fractional crystallization or by retention as a residue in the source region after partial melting) to produce a complementary LREEdepleted source. Two-stage model ages from Biranup Zone samples with unfractionated Sm/Nd ratios range from 2.3 to 2.6 Ga. Two samples from the Fraser Zone yield εNdi values of −4.1 and −3.97 and one of these samples, which is unfractionated, yields a twostage model age of 2.1 Ga (Table 3).

4. Lu–Hf and Sm–Nd

5. Geochemistry of eastern Biranup Zone intrusive rocks

Values of εHf in zircon and baddeleyite crystals in the Biranup Zone range between evolved values of −12.2 to weakly depleted values of 2.2, which are just slightly more radiogenic than CHUR (Table 2; Fig. 6). Two-stage model ages range from 2.2 to 3.2 Ga. There is a distinct temporal trend within the Biranup Zone Hf data, with younger intrusions indicating more juvenile values. εHf values from zircon in two Fraser Zone granites plot near CHUR (−2.86 to −0.06), with only one analysis (in 194711) more depleted, with an ␧Hf value of +6. TDM C model ages in these granites average c. 2.2 Ga. The most unradiogenic components of the Fraser Zone could have sourced the most radiogenic components of the Biranup Zone. However, a more likely scenario is a heterogeneous source for the Fraser Zone granites, of Biranup Zone Hf mixed with an additional juvenile component added during Stage I.

The c. 1710 Ma Bobbie Point Metasyenogranite (194737) is peraluminous and plots in the “within-plate” field on tectonic discrimination diagrams (Pearce et al., 1984; Fig. 8a; Table 4). The c. 1680 Ma granites (194728 and 194730) are peraluminous and overlap fields for “within-plate” and “volcanic arc” (Fig. 8a). The felsic members of the c. 1665 Ma mingled mafic-felsic rocks (the Eddy Suite; 194720, 194725, 194726, 194734, and 194735) are peraluminous to metaluminous ranging in composition from granite to granodiorite, and either overlap the “volcanic arc” and “within-plate” fields, or lie within the “volcanic arc” field on various tectonic discrimination diagrams (Fig. 8a; Pearce et al., 1984). A REE plot for the 1710 Ma Bobbie Point Metasyenogranite shows heavy REE enrichment and a very distinctive negative Eu anomaly (Fig. 8b), defining a distinct “wing shape” profile. Similar patterns

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

235

Table 2 Lu–Hf isotopic analysis of zircon and baddeleyite grains from the Fraser and Biranup Zones. Sample no–grain no. spot no Biranup Zone 194720–2.1R 194720–2.1C 194720–4.1C 194720–4.1R 194720–6.1C 194720–6.1R 194720–7.1C 194720–7.1R 194720–9.1C 194720–9.1R 194720–11.1C 194720–11.1R 194720–14.1C 194720–14.1R 194720–17.1C 194720–17.1R 194720–19.1C 194720–19.1R 194731–02.1 194731–03.1 194731–06.1 194731–09.1 194731–13.1 194731–22.1 194731–28.1 194731–30.1 194721–1.1 194721–2.1 194721–3.1 194721–4.1 194721–7.2 194721–8.2 194721–11.2 194721–14.2 194721–15.2 194721–20.2 194701–3.1 194701–14.1 194701–33.1 194701–34.1 194701–36.1 194701–37.1 194701–41.1 194701–43.1 194737–1.1 194737–2.1 194737–10.1 194737–11.1 194737–14.1 Fraser Zone 194719–9.1 194719–11.1 194719–15.1 194719–16.1 194719–20.1 194719–22.1 194719–24.1 194711–4.1 194711–8.1 194711–10.1 194711–11.1 194711–16.1 194711–19.1 194711–21.1 194711–26.1

207

Pb*/206 Pb* age (Ma)

176

Hf/177 Hf

± 1SE

176

Lu/177 Hf

176

Yb/177 Hf

176

Hf/177 Hf(i)a

εHfa

±1SE

TDM (crustal)b

1658 1658 1646 1646 1698 1698 1663 1663 1647 1647 1640 1640 1623 1623 1670 1670 1640 1640 1660 1697 1732 1697 1666 1701 1677 1717 1668 1657 1688 1657 1665 1639 1666 1662 1652 1660 1661 1707 1658 1686 1724 1680 1659 1661 1766 1719 1721 1700 1715

0.281729 0.281729 0.281736 0.281817 0.281754 0.281696 0.281703 0.281682 0.281730 0.281684 0.281669 0.281709 0.281642 0.281682 0.281659 0.281750 0.281663 0.281686 0.281705 0.281676 0.281720 0.281449 0.281639 0.281603 0.281704 0.281679 0.281767 0.281746 0.281775 0.281757 0.281763 0.281764 0.281782 0.281755 0.281798 0.281768 0.281577 0.281585 0.281649 0.281652 0.281623 0.281607 0.281635 0.281640 0.281477 0.281543 0.281494 0.281483 0.281441

0.000010 0.000016 0.000012 0.000016 0.000012 0.000023 0.000008 0.000012 0.000015 0.000014 0.000012 0.000011 0.000011 0.000006 0.000010 0.000035 0.000021 0.000014 0.000015 0.000009 0.000015 0.000028 0.000021 0.000020 0.000029 0.000016 0.000009 0.000009 0.000010 0.000007 0.000011 0.000012 0.000008 0.000015 0.000012 0.000008 0.000005 0.000010 0.000007 0.000011 0.000007 0.000009 0.000010 0.000011 0.000010 0.000011 0.000009 0.000013 0.000012

0.000541 0.001121 0.001254 0.001154 0.001013 0.000676 0.000894 0.000814 0.001514 0.000967 0.000829 0.000605 0.000974 0.000699 0.000966 0.001609 0.000949 0.000637 0.001086 0.001619 0.001003 0.002715 0.002373 0.001605 0.001789 0.001056 0.000123 0.000195 0.000068 0.000096 0.000087 0.000080 0.000089 0.000138 0.000110 0.000054 0.000399 0.000639 0.000662 0.000703 0.001293 0.000738 0.000632 0.001322 0.001359 0.002426 0.001204 0.000997 0.001201

0.026571 0.060132 0.059127 0.061642 0.050982 0.033322 0.043890 0.035869 0.075555 0.041971 0.040970 0.030297 0.046985 0.034641 0.046717 0.057272 0.042558 0.029926 0.055526 0.065196 0.053659 0.097947 0.084676 0.056943 0.079816 0.056658 0.006396 0.009103 0.004378 0.005368 0.004925 0.005014 0.005457 0.005759 0.004932 0.003085 0.020482 0.034387 0.034189 0.039937 0.071678 0.040770 0.033813 0.071950 0.067403 0.135297 0.060559 0.048376 0.061876

0.281712 0.281694 0.281697 0.281781 0.281721 0.281674 0.281675 0.281656 0.281683 0.281654 0.281643 0.281690 0.281612 0.281661 0.281628 0.281699 0.281634 0.281666 0.281671 0.281624 0.281687 0.281362 0.281564 0.281551 0.281647 0.281645 0.281763 0.281740 0.281773 0.281754 0.281760 0.281762 0.281779 0.281751 0.281795 0.281766 0.281564 0.281564 0.281628 0.281630 0.281581 0.281584 0.281615 0.281598 0.281432 0.281464 0.281455 0.281451 0.281402

−0.6 −1.3 −1.4 1.6 0.6 −1.1 −1.8 −2.5 −1.9 −2.9 −3.5 −1.8 −5.0 −3.2 −3.3 −0.8 −3.8 −2.6 −2.0 −2.9 0.2 −12.2 −5.7 −5.3 −2.5 −1.7 1.4 0.3 2.2 0.8 1.2 0.7 1.9 0.9 2.2 1.4 −5.8 −4.7 −3.6 −2.9 −3.8 −4.7 −4.0 −4.6 −8.1 −8.0 −8.3 −8.9 −10.3

0.4 0.6 0.4 0.6 0.4 0.8 0.3 0.4 0.5 0.5 0.4 0.4 0.4 0.2 0.3 1.2 0.7 0.5 0.5 0.3 0.5 1.0 0.7 0.7 1.0 0.6 0.3 0.3 0.4 0.3 0.4 0.4 0.3 0.5 0.4 0.3 0.2 0.3 0.2 0.4 0.2 0.3 0.3 0.4 0.3 0.4 0.3 0.5 0.4

2.42 2.46 2.46 2.27 2.37 2.47 2.50 2.54 2.49 2.55 2.58 2.48 2.66 2.56 2.60 2.44 2.60 2.53 2.51 2.59 2.42 3.18 2.74 2.75 2.55 2.53 2.29 2.35 2.26 2.32 2.30 2.32 2.26 2.33 2.23 2.29 2.75 2.72 2.60 2.58 2.67 2.69 2.63 2.67 2.98 2.93 2.95 2.97 3.07

1303 1307 1285 1302 1299 1295 1313 1306 1279 1318 1300 1283 1317 1261 1321

0.281942 0.281970 0.281992 0.281921 0.281984 0.281910 0.281966 0.282139 0.281960 0.281881 0.281929 0.281963 0.281902 0.281965 0.281882

0.000010 0.000009 0.000010 0.000009 0.000009 0.000006 0.000011 0.000016 0.000009 0.000009 0.000008 0.000007 0.000008 0.000011 0.000010

0.001073 0.000770 0.001156 0.001120 0.001450 0.001015 0.002514 0.000736 0.000671 0.000641 0.000637 0.000815 0.000989 0.000738 0.000546

0.056821 0.039308 0.064973 0.054905 0.095077 0.053009 0.130979 0.040547 0.036225 0.034756 0.034203 0.045173 0.040880 0.040665 0.029657

0.281916 0.281951 0.281964 0.281893 0.281948 0.281885 0.281904 0.282121 0.281944 0.281865 0.281913 0.281943 0.281877 0.281947 0.281868

−1.4 −0.1 −0.1 −2.2 −0.3 −2.7 −1.6 5.9 −1.0 −2.9 −1.5 −0.9 −2.5 −1.2 −2.7

0.3 0.3 0.3 0.3 0.3 0.2 0.4 0.6 0.3 0.3 0.3 0.2 0.3 0.4 0.3

2.19 2.11 2.09 2.24 2.12 2.26 2.21 1.72 2.14 2.29 2.20 2.14 2.27 2.15 2.29

C and R, appended to the spot number refer to grain centre and edge, respectively. a 176 Hf/177 Hfi(i) , εHf(t) and T(DM) are calculated using the 207 Pb/206 Pb age of the grain. b T(DM) crustal is calculated using a two-stage evolution assuming a mean 176 Lu/177 Hf ratio of crust = 0.015.

have been recognised within two-mica granites and leucogranites of the European Hercynides (Webb et al., 1985), and leucogranites in the Central Alps (Schaltegger and Krähenbühl, 1990), and interpreted as magmatic enrichment in a high-silica melt with frac-

tional crystallization dominated by feldspars. Elevated levels of HREE are not consistent with fractionation of a HREE-rich phase such as hornblende or garnet and likely reflect paragenesis at moderate to low pressure. The HREE enrichment trend cannot be

236

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Table 3 Whole rock Nd isotopic data for samples from the Fraser and Biranup Zones. Samples

Unit

Age

Sm

Nd

147

194701 194720 194721 194725 194726 194728 194730 194731 194737 194735 194711 194719

Biranup Biranup Biranup Biranup Biranup Biranup Biranup Biranup Biranup Gwynne Creek Fraser Fraser

1686 1665 1664 1671 1666 1683 1676 1689 1708 1657 1297 1298

2.43 5.29 2.08 6.41 9.46 9.18 9.83 3.00 1.83 5.95 5.85 13.72

12.41 27.68 9.24 28.42 42.00 51.01 46.88 18.87 6.48 35.67 32.31 59.04

0.118122 0.115566 0.136198 0.136285 0.136106 0.108752 0.126786 0.096131 0.170506 0.100817 0.109429 0.140508

a b

Sm/144 Nda

143

Nd/144 Ndb

0.511445 0.511573 0.511918 0.511582 0.511639 0.511436 0.511627 0.511257 0.511567 0.511444 0.511685 0.511955

Error (×10−6 )

143

5 4 5 5 5 4 5 5 5 4 5 5

0.510134 0.510308 0.510429 0.510085 0.510149 0.510233 0.510230 0.510190 0.509651 0.510346 0.510753 0.510758

Nd/144 Ndi

␧Ndi

TDM

TDM ·2stg

−6.36 −3.45 −1.11 −7.67 −6.55 −4.46 −4.70 −5.16 −15.24 −2.92 −4.10 −3.97

2.57 2.31 2.26 2.87 2.76 2.36 2.51 2.34 4.93 2.19 2.03 2.31

2.59 2.34 2.16 2.68 2.59 2.44 2.45 2.50 3.29 2.30 2.11 2.10

1 Sigma uncertainty of 0.5%. Uncertainties are 2 sigma within run precision. Normalized to a La Jolla value of 0.511850. Single and two stage model ages are after Liew and Hofmann (1988).

ascribed to addition during post-magmatic fluid–rock interaction with F-bearing fluids (e.g. Webb et al., 1985), because the mean zircon ␧Hf is decoupled from whole-rock εNd. Zircon εHf is more radiogenic than predicted from whole-rock εNd, indicating that unaltered c. 1710 Ma zircon crystallized through a reservoir with high Lu/Hf decoupled from Sm/Nd. Therefore, elevated HREE is a feature acquired during zircon crystallization. Both 1680 and 1665 Ma magmatic rocks show LREE enrichment and more subdued Eu anomalies (Fig. 8b). Biranup Zone intrusive rocks have increasing Mg# with decreasing age from 1710 to 1665 Ma (Fig. 8c). The rocks also display decreasing Eu/Eu* from 1710 Ma to 1665 Ma (with coefficient of determination for a linear regression of 0.61) consistent with increasing fO2 and/or increasing temperature with time (Drake and Weill, 1975; Fig. 8d). These trends are compatible with a mixing process that had an increasing mantle component (and/or progressively decreasing contribution of evolved crust) in the felsic magmatism through time. A dataset of all eastern Biranup Zone intrusive rocks (this work and GSWA online geochemisty database – http://geochem.doir.wa.gov.au/geochem) indicates a calc-alkaline to predominant high-K calc-alkaline trend, which ranges from metaluminous to weakly peraluminous (Fig. 8e). A Ta/Yb versus Th/Yb plot is useful because these ratios are largely independent of variations caused by the degree of partial melting and crystal fractionation (Fig. 8f). Ta/Yb is a measure of the degree of mantle enrichment or depletion relative to N-MORB. Addition of a subduction component such as hydrous fluid from dewatering of the slab, results in the addition of Th, but not Ta, to the mantle source (producing a vertical trend). Plot 8f indicates that the Biranup Zone gabbros have an active continental margin affinity with the felsic rocks of the zone influenced by subduction zone enrichment or crustal contamination, or both. In MORB-normalized traceelement diagrams, the most primitive plutonic rocks (gabbros with Mg# = 51–60; Ni = 12–176 ppm; Cr = 149–374 ppm) show LILE and LREE enriched patterns with troughs at Nb–Ta and Ti, consistent with subduction-related magmas (GSWA online geochemisty database; samples 183685, 183683, 183681, 183678; http://geochem.doir.wa.gov.au/geochem). Field, petrographic, geochemical, and isotopic evidence (initial εNd values from −3 to −15) support a hybrid nature for the c. 1665 Ma magmas, originating through interaction between mantle-derived magmas and crustal materials. 6. Discussion 6.1. Provenance of the Biranup Zone Previous studies of the Albany-Fraser Orogen have favoured an exotic setting for the Biranup Zone, outboard of the Yilgarn Craton

margin, based on the absence of Archean zircon inheritance and the lack of late Paleoproterozoic magmatism within the Yilgarn Craton (Nelson et al., 1995; Spaggiari et al., 2009). Correlations have been suggested between the Biranup Zone and the western Gawler Craton and the Warumpi Province of the southern Arunta Orogen (Spaggiari et al., 2009). The Warumpi Province initially formed as a magmatic arc between 1690–1670 Ma during the Argilke Igneous Event, associated with high-K calc-alkaline magmatism (Scrimgeour et al., 2005a,b). Further magmatism and accretion of the arc to the Aileron Province (North Australian Craton) occurred during the 1640–1635 Ma Liebig Orogeny (Scrimgeour et al., 2005b). On a continent scale the Biranup Zone may have a connection to the Warumpi Province, for example as part of the same extensive magmatic arc system and plate margin (e.g. Betts et al., 2008), although the Lu–Hf and Sm–Nd data presented here suggest that it was not exotic and evolved in proximity to the Yilgarn Craton, rather than to the Warumpi Province or the Gawler Craton. Furthermore, the existence of an Archean fragment with a typical Yilgarn granite age of 2684 ± 11 Ma (metasyengranite sample 194709), surrounded by Biranup Zone rocks, supports the interpretation that the Biranup Zone was not exotic. The Hf isotopic data from the oldest eastern Biranup Zone intrusive rock (Bobbie Point Metasyenogranite) spans a range of initial Hf isotopic values that encompass Yilgarn Craton-like values to those representative of more juvenile crust. The psammitic gneiss sample (194731) containing a significant c. 1689 Ma detrital zircon age component also displays Hf values that are only slightly more depleted than Yilgarn Craton crust. Younger magmatism in the Biranup Zone becomes increasingly dominated by more depleted values. This pattern suggests melt production from mixed sources: a component with crustal residence ages of > c. 3100 Ma, and an additional juvenile component. This juvenile input progressively, and thoroughly, diluted the isotopic signal from the basement through time and reflects the influence of Paleoproterozoic juvenile input into non-radiogenic Archean sources (Fig. 6). Such a temporal trend can also be seen within individual intrusions. For example, zircon rims in metagranodiorite sample 194720, when outside of analytical uncertainty, always indicate higher εHf values than zircon cores (Fig. 9), implying incorporation of material with a higher Lu/Hf ratio through time. Such a temporal trend towards more juvenile values is also replicated in the whole-rock Nd data, with the most juvenile melts having epsilon values around −1. The most evolved granite in the Biranup Zone, the Bobbie Point Metasyenogranite, has a εNdi value of −15.24, which is within the range of Yilgarn felsic melts at c. 1700 Ma (Champion et al., 2006; Champion and Cassidy, 2007). It is also very similar to the Nd isotopic composition at 1700 Ma of the Munglinup Gneiss, which reflects reworked Yilgarn crust (Spaggiari et al., 2009). The majority of the eastern Biranup Zone and all central

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

237

Table 4 Whole-rock analyses of Fraser and Biranup Zone geochronology samples. Fraser

Age (Ma)

194711 1297

Weight percent SiO2 69.69 Al2 O3 14.12 4.45 Fe2 O3 (t) FeO 3.10 MgO 0.71 CaO 2.36 Na2 O 2.61 K2 O 4.86 TiO2 0.524 P2 O5 0.14 MnO 0.11 LOI 0.24 Parts per million Cs 5.83 Rb 178.0 Ba 967 Sr 141.0 Pb 32.0 Th 14.7 U 2.0 Zr 222 Hf 6.2 Ta 0.7 Y 32.0 Nb 10.7 Sc 12 Cr 11 Ni 6 V 33 Ga 18.0 Zn 59 Cu 9 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

42.50 84.60 10.35 36.80 7.04 1.62 6.07 0.90 5.17 1.01 2.94 0.42 2.70 0.43

Eu/Eu* Mg#

0.755 24.10

La/Nb La/Yb La/Sm Sr/Ba

4.0 15.74 6.04 0.15

Biranup 194719 1298

194728 1683

194730 1676

194737 1708

194720 1665

194725 1671

194726 1666

194734 1675

194735 1657

72.44 12.42 4.25 2.55 0.62 1.46 2.86 4.07 0.48 0.17 0.18 0.92

73.63 12.67 2.17 1.07 0.30 1.46 2.50 5.11 0.33 0.06 0.04 1.54

69.34 13.18 4.71 3.12 0.77 1.88 2.82 4.70 0.56 0.32 0.07 1.44

75.96 11.90 0.91 0.69 0.10 0.03 2.95 5.57 0.109 0.02 0.00 2.37

66.25 14.59 5.89 3.88 1.15 3.38 2.51 4.14 0.792 0.16 0.10 0.82

66.10 14.42 6.32 3.49 1.53 3.90 2.37 3.56 0.82 0.21 0.11 0.46

64.93 14.37 6.87 4.14 1.17 4.03 2.73 3.33 0.86 0.22 0.12 1.12

68.82 13.36 5.66 3.57 1.04 2.36 2.20 4.10 0.73 0.18 0.11 1.26

69.97 14.12 3.25 2.19 0.59 2.10 2.85 4.45 0.33 0.13 0.05 1.98

47.64 15.76 11.21 8.39 13.02 9.04 1.74 0.51 0.80 0.12 0.16 −0.01

7.25 295.7 260 51.9 41.0 15.0 3.7 229 6.9 1.5 107.3 23.4 17 10 5 25 19.8 93 17

5.44 238.4 989 115.4 31.0 21.6 4.3 308 8.2 0.8 54.1 11.0 8 2 2 11 17.1 35 14

7.22 279.6 804 130.2 19.0 32.3 7.7 434 11.5 1.3 71.0 23.3 13 12 7 35 21.7 56 8

0.32 181.2 115 11.2 6.0 13.2 3.2 218 8.1 1.2 64.0 29.2 2

2.17 129.9 1041 164.1 22.2 4.3 1.1 262 6.7 0.7 29.0 12.0 17 24 11 76 20.7 75 18

6.69 163.8 887 222.0 19.2 15.5 1.9 299 7.8 0.9 40.6 14.3 18 44 10 69 19.9 81 14

5.00 130.6 1128 253.7 18.1 8.5 1.8 604 13.5 0.9 51.6 18.2 22 21 10 63 19.5 91 17

8.00 196.1 739 131.6 29.0 18.6 4.0 309 8.1 1.1 42.9 12.6 16 30 12 58 19.3 78 17

1.94 161.5 905 175.9 27.0 11.3 1.0 185 4.8 0.6 30.5 8.8 7 3 2 16 18.1 43 2

0.69 14.2 190 253.3 6.0 1.6 0.3 63 1.7 0.4 17.0 2.9 26 843 572 130 15.8 82 126

59.36 131.20 18.17 66.50 16.08 0.72 16.24 2.72 16.79 3.50 9.86 1.45 9.04 1.42

70.57 132.80 14.85 55.98 10.65 1.58 9.27 1.42 8.48 1.69 4.69

48.96 186.70 13.46 54.80 11.40 1.53 10.62 1.78 11.01 2.31 6.81

7.38 17.40 1.83 6.90 1.90 0.08 3.64 0.97 8.03 1.95 6.42

24.02 95.03 7.25 28.40 6.25 1.15 5.92 1.02 6.92 1.44 4.29

51.53 94.03 9.85 37.80 6.10 1.05 5.32 0.78 4.74 0.97 2.67

7.00 1.06

7.00 1.05

25.53 94.36 7.69 31.97 7.46 1.65 6.97 1.07 6.53 1.33 3.81 0.53 3.44 0.56

31.23 94.40 11.01 52.60 10.90 2.69 10.06 1.46 8.64 1.70 4.74

4.19 0.61

33.45 64.97 8.26 27.59 5.44 1.93 5.84 0.89 4.89 0.97 2.72 0.39 2.35 0.40

4.25 0.63

4.10 0.68

2.38 0.34

8.84 19.16 2.28 10.58 2.45 0.96 2.66 0.43 2.63 0.56 1.56 0.24 1.61 0.24

0.486 21.60

0.423 26.90

0.095 17.80

1.046 27.90

0.697 32.40

0.785 25.20

0.578 26.70

0.561 26.50

2.1 6.99 4.29 0.16

0.3 1.05 3.88 0.10

1.8 7.42 3.42 0.25

1.7 7.35 2.87 0.22

1.9 5.86 3.84 0.18

0.136 22.50 2.5 6.57 3.69 0.20

6.4 16.84 6.63 0.12

3 20.1 13

2.8 14.23 6.15 0.16

5.9 21.65 8.45 0.19

194721 1664

1.147 69.70 3.0 5.49 3.61 1.33

Major elements were determined by wavelength-dispersive XRF on fused disks, precision is better than ±1%. Loss on Ignition (LOI) was determined by gravimetry after combustion. Iron abundances were determined by digestion and electrochemical titration (Shapiro and Brannock, 1962). Trace elements (Ba, Cr, Cu, Ni, Sc, V, Zn, and Zr) were determined by wavelength-dispersive XRF on a pressed pellet (Norrish and Chappell, 1977), Cs, Ga, Nb, Pb, Rb, Sr, Ta, Th, U, Y, and the REEs were analysed by ICP-MS (Eggins et al., 1997; as modified by Pyke, 2000). Precision for trace elements is better than ±10%. Details of standards used for major and trace element analysis are given in Morris and Pirajno (2005).

Biranup Zone samples are more depleted relative to typical Eastern Goldfields Superterrane (Yilgarn Craton) felsic crust. According to the Liew and Hofmann (1988) depleted-mantle model, uncontaminated depleted mantle at 1665 Ma should have a 143 Nd/144 Nd value of 0.506610, whereas the most juvenile sample has a 143 Nd/144 Nd value of 0.510429, and is evidently still affected by crustal material. Assuming an initial Nd isotope composition similar to that of the Bobbie Point Metasyenogranite, about 70% of depleted mantle

input is required to explain the most juvenile melts of the Biranup Zone. Only one eastern Biranup Zone sample (194734) retains an inherited zircon as evidence of an earliest Paleoproterozoic or Archean source component (in the form of a single discordant analysis). Magmatic temperatures at which the intrusive rocks of the eastern Biranup Zone were emplaced can be estimated using the Zr-saturation thermometer (Watson and Harrison, 1983). Calcu-

238

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Fig. 7. εNdi evolution diagram for the Albany-Fraser Orogen, compared to the field (shaded) for Eastern Goldfields Superterrane. The Eastern Goldfields Superterrane field is based on felsic samples with normal crustal ratios from the compilation in the Geological Survey of Western Australia’s online geochemical database (GeoChem Extract; http://geochem.doir.wa.gov.au/geochem/). Central Biranup Zone, Recherche Supersuite, and Munglinup Gneiss samples are from Spaggiari et al. (2009). The depleted mantle (DM) model is from Goldstein et al. (1984).

Fig. 6. (a) Initial 176 Hf/177 Hf evolution diagram for seven samples from the AlbanyFraser Orogen. (b) Event signature plot which shows the general trend of reworking (downwards), mixing (horizontal), or juvenile input (upwards). (c) Stacked histograms for juvenile (>0), intermediate (0 to −5) and evolved εHf (<−5).

lated temperatures fall in the range 797–882 ◦ C, with an average of 828 ◦ C. These are minimum estimates because the general lack of xenocrystic zircons in these rocks suggests that the primary magmas were undersaturated with respect to Zr. It appears likely that pre-existing zircon has been completely reabsorbed during subsequent melting events, hence essentially no record of Archean zircon inheritance has been found. 6.2. The Zanthus Event In the Ponton Creek area of the eastern Biranup Zone, folded leucosomes in a migmatitic monzogranite (194730) yield a U–Pb zircon date of 1676 ± 6 Ma, which is within uncertainty of the crys-

tallization age of cross-cutting axial planar leucosomes (Fig. 4d), dated at 1679 ± 6 Ma (194729). Migmatization must have immediately preceded folding, with subsequent leucosome injection along the axial planes of the folds. Although the younger leucosomes yield an older isotopic age, the two results agree to within uncertainty and imply deformation at 1678 ± 4 Ma. These data, and the outcrop relationships, thus define a previously unrecognised deformation and high-grade metamorphic event, here named the Zanthus Event. The rocks that retain evidence of this event in the Ponton Creek area occur within the centre of a geophysically anomalous zone that is about 85 km long and 25 km wide, and is interpreted as a tectonic slice within the orogen. The slice is characterized by a northwest-trending magnetic fabric, whereas the dominant regional trend of the eastern AlbanyFraser Orogen is to the northeast. This northwesterly fabric matches the northwesterly trend of folds in outcrop. The slice has a distinctive aeromagnetic pattern with open to tight, non-cylindrical folds. This suggests that the Zanthus Event was not a local occurrence, but affected at least the entire tectonic slice. The orientation of the fabric, folds, axial planar leucosomes, and melt-filled dextral shears, implies northeast–southwest directed (present orientation) shortening during the Zanthus Event. The Zanthus Event was followed by intrusion of the Eddy Suite of peraluminous to metaluminous, granitic to gabbroic rocks, with distinct mingling and hybridisation textures. These mingled mafic and felsic rocks crystallized at 1665 ± 4 Ma (weighted mean date for samples 194720 and 194721). 6.3. A tectonic model for the Biranup Zone A tectonic model for the Biranup Zone must account for the following: (1) metaluminous, to weakly peraluminous magmatism showing mineralogical, petrographic and chemical characteristics of high-K calc-alkaline suites, (2) Hf and Nd isotopic signatures that indicate a progressive increase of juvenile material into Archean unradiogenic crust, and (3) chemistry that implies progressive increases in the Fe and Mg content of felsic magmas and a decrease in the Eu/Eu* through time.

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

239

Fig. 8. Geochemical plots for Albany-Fraser rocks. (a) Rb versus Y + Nb tectonic discrimination diagram, syn-COLG = syn-collisional granite; VAG = volcanic arc granite; WPG = within plate granite; ORG = orogenic granite (Pearce et al., 1984). Symbols as in part b. (b) chondrite-normalised trace-element plot for the various magmatic rocks of the Albany-Fraser Orogen (Boynton, 1984). (c and d) geochemical trends with age for felsic rocks within the Biranup Zone. (e) K2 O versus SiO2 plot for all magmatic rocks in the Biranup Zone (GSWA online geochemical database; GeoChem Extract; http://geochem.doir.wa.gov.au/geochem/). Those specimens from this work are indicated with sample numbers. (f) Th/Yb–Ta/Yb discrimination diagram (Pearce, 1982) for all Biranup Zone magmas. Vectors indicate the influence of subduction (S), crustal contamination (C), within plate enrichment (W) and fractional crystallization (F). Dashed lines separate the boundaries of the tholeiitic (TH), calc-alkaline (CA) and shoshonitic (SH) field. Active continental margin and oceanic island arc fields modified after Schulz et al. (2004).

A post-orogenic lithospheric extensional setting influenced by extensive crustal contamination of basaltic magmas derived from mantle source(s) (e.g. Permian magmatism in the European Hercynian belt; Rottura et al., 1998) is consistent with the chemical and isotopic signatures of the magmas. However, an active subduction margin is more favourable because it not only explains the isotopes and chemistry, but also accounts for the regional compres-

sional deformation under granulite facies conditions, and the rapid basin formation, infill, and intrusion by near-contemporaneous felsic magmas. The presence of fragments of Archean crust in the Biranup Zone, and a Yilgarn-like source for these Paleoproterozoic magmas, favours a Yilgarn Craton margin subduction model with a volcanic arc to back-arc system. An active margin model is presented

240

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Fig. 9. εHf values for centre and edge analyses on the same grains from sample 194720.

diagrammatically in Fig. 10. At c. 1710 Ma, westward-dipping subduction (present-day coordinates) produced an early suite of melts, which crystallized in the shallow crust of the Yilgarn Craton margin. Subsequent slab roll-back outboard of the margin led to back-arc spreading and a greater influence of the asthenosphere on the magmas. The associated basin was filled by sediments from c. 1710 Ma arc magmatism and parts of this sedimentary pile underwent progressive dehydration-related melting and deformation due to crustal thickening. Later melts produced within the back-arc region incorporated a greater mantle component, due to increasing extension which allowed greater asthenospheric upwelling. These melts crystallized at c. 1680 Ma and the rocks were rapidly migmatized and deformed during the Zanthus Event at 1678 Ma. The Zanthus Event was associated with northeast–southwest (present orientation) compression that may represent a period of tectonic switching when slab roll-back stalled, possibly driven by seamount arrival. The youngest suite of intrusive rocks (c. 1665 Ma Eddy Suite) show progressively more juvenile influence, through an increase in Mg#, εHf, and εNd, with decreasing age. This implies a return to significant back-arc extension. The effect of back-arc extension and slab roll-back was to rift Archean fragments from their original locations on the Yilgarn margin and isolate them within Paleoproterozoic Biranup Zone rocks. Sample 194709 dates the magmatic crystallization of one of these isolated Archean fragments at 2684 ± 11 Ma. Such ages are widely recognised within the Yilgarn Craton, including the high-Ca granites of the Eastern Goldfields Superterrane (Cassidy and Champion, 2004; Cassidy et al., 2006), the Southern Cross Domain of the Youanmi Terrane (e.g. GSWA 168963; Nelson, 2001), and within the Northern Foreland of the Albany-Fraser Orogen (GSWA 184120; Bodorkos and Wingate, 2008b). The location of this Archean fragment implies that much of the Biranup Zone must have formed within the back-arc region of a Paleoproterozoic subduction zone system. 6.4. Mesoproterozoic overprinting of the Biranup Zone and emplacement of the Fraser Zone The c. 1305–1290 Ma Fraser Zone represents a structurally modified, thick piece of hot mafic crust presently in fault contact with the Biranup Zone. Two granitic samples within the Fraser Range Metamorphics yield a weighted mean date of 1298 ± 4 Ma (MSWD = 0.045), interpreted as the age of magmatic crystallization. This result refines the date of 1293 ± 9 Ma for the crystallization of post-D1 granites (Clark et al., 1999). The foliation within these

two samples most likely formed shortly after their emplacement, consistent with dates from disturbed zircon grains, which suggest a radiogenic-Pb loss event soon after crystallization (Clark et al., 1999; De Waele and Pisarevsky, 2008). Hf isotopic data from these granites imply reworking of an isotopically similar Hf source to the Biranup Zone, but with some indication of additional juvenile material. Within the eastern Albany-Fraser Orogen, 1298 ± 4 Ma oscillatory zoned zircons, indicating Mesoproterozoic magmatism, are restricted to the Fraser Zone and Recherche Supersuite. In the eastern Biranup Zone, the crystallization mechanism and timing of zircon growth was distinctly different, with younger metamorphic rims that mantle inherited zircon cores. No evidence of Recherche Supersuite intrusive rocks or Stage I metamorphism resulting in significant zircon growth has been found within the eastern Biranup Zone. However, Stage II zircon overgrowth is recorded at 1197 ± 8 Ma (weighted mean of six samples; MSWD = 1.2) in the eastern Biranup Zone. These zircon overgrowths show a range of Th/U ratios, from values similar to those in magmatic crystals to lower values of around 0.001 (Fig. 3). The Stage I events responsible for zircon growth within the Fraser Zone and Recherche Supersuite granites do not appear to have produced a significant volume of silicate melt in the eastern Biranup Zone. The central Biranup Zone contains 1690–1660 Ma metagranitic and metasedimentary rocks that yield identical Paleoproterozoic magmatic and depositional ages to the eastern Biranup Zone (Spaggiari et al., 2009). In contrast to the eastern Biranup Zone, Recherche Supersuite granitic rocks that intruded central Biranup Zone rocks include Coramup Hill (1283 ± 13 Ma; Nelson, 1995f), Mount Burdett (1299 ± 18; Nelson, 1995e), and Observatory Point (1322 ± 11 Ma; Bodorkos and Wingate, 2008a; 1288 ± 12 Ma; Nelson, 1995d; Fig. 2). Subsequent high-temperature metamorphism during Stage II, predominantly between 1200 and 1180 Ma, is recorded by metamorphic rims on zircons from orthogneisses, and partial melts and intrusions of felsic and pegmatitic material into orthogneisses (Nelson, 1995b; Spaggiari et al., 2009). A feasible explanation for the apparent lack of Stage I ages in the eastern Biranup Zone is provided by the crustal architecture (Fig. 2), where exhumed fault-bounded slices of eastern Biranup Zone rocks may not have been in the vicinty of Stage I events. The central Biranup Zone rocks that are intruded by Recherche Supersuite granitic rocks are further outboard than the eastern Biranup Zone fault slices (Fig. 2), and hence may have been broadly alongstike from the Fraser Zone intrusions. Zircon overgrowths provide a detailed picture of the Mesoproterozoic evolution of the eastern Albany-Fraser orogen. At 1270 ± 11 Ma, high-U homogenous zircon overgrowths developed on 1657 ± 5 Ma oscillatory zoned detrital zircon cores (sample 194735; Fig. 5) in the Gwynne Creek Gneiss. These crystals were then fractured and mantled by 1193 ± 26 Ma, homogeneous, low-U rims which in-filled the fractures. The oscillatory zoned fragments are not rotated and zoning is continuous although displaced by the fracture-filling zircon. Both the internal structure of the fractured zircons and the very low Th content (below detection) of the in-filling zircon suggest that the fractures were sealed by c. 1193 Ma zircon precipitated from hydrothermal fluids. Very similar fracture-fill features in zircon have been reported from migmatitic rocks elsewhere (Rim´sa et al., 2007). Fractures transecting the zircon crystals are thus bracketed between c. 1270 Ma zircon growth and 1197 Ma zircon rims, implying a period of brittle deformation relating to crustal uplift and cooling between these zircon growth phases. The timing of this uplift is consistent with that in the Fraser Range Metamorphics, which were uplifted to less than ∼400 MPa some time between 1288 and 1260 Ma (Fletcher et al., 1991; Clark et al., 1999). Uplift at this time is also consistent with the presence of Stage I basement-derived detrital zircons within the Mount

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

241

Fig. 10. Schematic diagrams showing the evolution of the Biranup Zone. (a) At c. 1710 Ma subduction under the Yilgarn Craton produced a magmatic arc on its margin. (b) During the period 1700–1690 Ma, continued convergence and slab roll-back with voluminous felsic magmatism produced the accommodation space for a back-arc basin, which was filled with near-coeval volcanic detritus. (c) Tectonic switching during the Zanthus Event, possibly driven by seamount arrival, compressed and deformed the back-arc region. (d) Renewed slab roll-back and continued attenuation of the Yilgarn margin resulted in asthenospheric upwelling, bimodal magmatism, and formation of a mingled norite and granodiorite suite of intrusive rocks. This process resulted in Archean remnants becoming isolated from their ancestral home on the Yilgarn Craton by additions of predominantly juvenile crust.

242

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Ragged Formation, which overlies the eastern Nornalup Zone, and was interpreted to reflect extension and uplift prior to Stage II. This provided key evidence for division of the Albany-Fraser Orogeny into two stages (Clark et al., 2000). These results show that the Gwynne Creek Gneiss, the Fraser Zone, and the Mount Ragged Formation, shared a widespread uplift and cooling event, some time between Stages I and II. This could, therefore, also mark a time of major structural modification of the eastern part of the orogen. There is no evidence of Stage II events within the Fraser Zone, although Stage II ages are prolific across the entire Biranup Zone. Preservation of pre-1250 Ma Rb–Sr cooling ages in the Fraser Range Metamorphics also indicates a lack of Stage II resetting in that area (Fletcher et al., 1991). Nonetheless, an earlier connection between the Fraser and Biranup Zones is implied from inherited zircon ages within intrusive units of the Fraser Range Metamorphics which, although limited, are similar to the ages of intrusions within the Biranup Zone, and inherited Paleoproterozoic material within it. This is compatible with the Fraser Range intrusions being emplaced through rocks of similar age to the Biranup Zone. Furthermore, the Hf isotope signature of the Fraser Range Metamorphics is consistent with the Fraser Zone rocks containing recycled Biranup Zone crust. However, as outlined above, there is no evidence for prolific zircon growth during Stage I thermal events in the eastern Biranup Zone. The earliest growth of zircon rims in the eastern Albany-Fraser Orogen, inboard of the Fraser Zone, is restricted to the Gwynne Creek Gneiss, at c. 1270 Ma, and is at least 10 million years younger than the emplacement of granites in the Fraser Zone and the Recherche Supersuite. These features suggest juxtaposition of the zones, along major structures, some time after Stage I magmatism. The Fraser Fault represents a major structural boundary between the eastern Biranup and Fraser Zones. A tectonic scenario that could explain the absence of Stage I events in the eastern Biranup Zone and lack of Stage II metamorphism in the Fraser Zone is the emplacement of the Fraser Zone by thrusting and extrusion during the uplift event recorded by fractured zircon grains in the Gwynne Creek Gneiss. This event may have placed the Fraser Zone at shallow crustal levels, which was less conducive to zircon growth or regrowth during Stage II. In contrast, the eastern Biranup Zone must have remained in a favourable position for hightemperature metamorphism and zircon growth during Stage II (Table 4). 6.5. Mesoproterozoic tectonic setting and comparison with the Musgrave Province The Mesoproterozoic to Neoproterozoic Musgrave Province lies at the convergence of central Australia’s main Proterozoic structural trends and shares certain chronological similarities with the Albany-Fraser Orogen (Myers et al., 1996; Wade et al., 2008; Fig. 11). The aim of this section is to highlight these similarities. Intrusive rocks with protolith ages between 1345 Ma and 1293 Ma form a significant component within the western Musgrave Province (Howard et al., 2007; Smithies et al., 2009; Fig. 11). The crustal event that produced these melts has been termed the Mount West Orogeny. The age of this event is similar to that of Stage I of the Albany-Fraser Orogeny and specifically overlaps with the emplacement of mafic to felsic components within the Fraser Zone and with emplacement of the Recherche Supersuite. Several studies have suggested that the 1350–1290 Ma events in the Albany-Fraser Orogen involved convergence and suturing of the West Australian Craton and Mawson Craton, with the subducting oceanic slab dipping to the southeast, away from the West Australian Craton (Clark et al., 2000; Bodorkos and Clark, 2004). The tectonic setting of Mount West granites is unclear, although they retain subductionlike geochemistry similar to Andean-style continental arc magmas

(Smithies et al., 2010). Mount West Orogeny granites also have juvenile Nd and Hf isotopic compositions consistent with a continental arc setting (Smithies et al., 2009). Such a correlation leads to wider associations of the Musgrave Province and Albany-Fraser Orogen with other Mesoproterozoic (Grenvillian) orogenic belts. No evidence for a subduction-related suture in the west Musgrave Province exists. This therefore implies a north-dipping slab and an unexposed suture to the south. The Hf isotopic signal from Stage I Fraser Zone granites (1298 ± 4 Ma) is predominantly near CHUR and consistent with reworking of material with 2.0–2.5 Ga crustal residence (Fig. 6a). This is compatible with c. 1300 Ma extensive magmatic reworking of Biranup Zone material, which itself reflects the heavily modified Yilgarn Craton margin. A feasible tectonic setting for Stage I is a subduction zone outboard of the Biranup Zone, which compressed this margin and uplifted a deep lower-crustal segment represented now by the Fraser Zone. If Biranup Zone rocks were the basement for the Fraser Zone there is no necessity for the Fraser Zone to have originated from a position substantially outboard of the craton margin. Clark et al. (2000) and Bodorkos and Clark (2004) favoured southeast-directed Mesoproterozoic subduction during early Stage I, based on pre-1313 Ma magmatism and tectonic activity being restricted to the Nornalup Zone. This included deformation that produced folds with northeast-trending, steeply southeast-dipping axial surfaces, which are bracketed in time by 1330 ± 14 Ma and 1313 ± 16 Ma granitoids (Clark et al., 2000). A significant pressure increase (2–4 kbar) is recognised in the Fraser Zone and central Biranup Zone (Coramup Gneiss) between 1290 and 1280 Ma (Clark et al., 1999; Bodorkos and Clark, 2004), and implies over-thrusting related to west-northwest to northwest convergence of the combined South Australian and Mawson Cratons during Stage I (Myers et al., 1996; Bodorkos and Clark, 2004; Giles et al., 2004). This indicates that the southeastern margin of the West Australian Craton was active in the Mesoproterzoic, which resulted in closure of an ocean basin by the arrival and docking of the combined South Australian and Mawson Cratons (Bodorkos and Clark, 2004; Giles et al., 2004). The Musgrave Orogeny (1220–1150 Ma) is interpreted to reflect a period of intracratonic extension and is synchronous with Stage II tectonothermal activity in the Albany-Fraser Orogen (Fig. 11). Stage II commenced with high-temperature metamorphism of the eastern Nornalup Zone and the Biranup Zone between 1225 and 1215 Ma (Clark et al., 2000; Spaggiari et al., 2009). This was followed by emplacement of the c. 1210 Ma Gnowangerup–Fraser Dyke Suite (Wingate et al., 2000, 2005). Stage II events recorded in the AlbanyFraser Orogen are widespread in the Northern Foreland, Biranup, and Nornalup Zones, and include pluton emplacement (Esperance Supersuite) as well as prolific metamorphic zircon growth (Nelson et al., 1995; Spaggiari et al., 2009; Kirkland et al., 2010). In the central Biranup Zone, granulite facies metamorphism took place at c. 1180 Ma and again between 1170 and 1150 Ma (Spaggiari et al., 2009), or was a prolonged event throughout this period. In the eastern Biranup Zone, metamorphic zircon growth is defined at 1197 ± 6 Ma (Fig. 11). Significant extension during Stage II of the Albany-Fraser Orogeny is evident in central Biranup Zone orthogneisses at Bremer Bay, where leucosomes formed in the necks of boudins at c. 1180 Ma (Barquero-Molina, 2009; Spaggiari et al., 2009). The range of Stage II ages throughout the Biranup Zone appears to reflect metamorphism in a predominantly extensional regime within an intracratonic setting. Protracted extension is consistent with the tectonic scenario proposed for the west Musgrave Province, where repeated or continuous ultrahigh-temperature metamorphism appears to have spanned the interval encompassing both the c. 1200 Ma and c. 1180 Ma events recognized in the Albany-Fraser Orogen. However, the Musgrave Province shows no evidence of the c. 1680 Ma Zanthus tectonomagmatic event imply-

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

243

Fig. 11. Time-space diagram for the Albany-Fraser Orogen and the west Musgrave Province. The diagram includes all ion microprobe (SHRIMP) U–Pb zircon and baddeleyite ages determined by the Geological Survey of Western Australia within the region. Within each major lithostratigraphic domain (Recherche Supersuite, Fraser Zone, eastern and central Biranup Zone) the data are arranged in geographic order from southwest at the bottom to northeast at the top. n = Number of analyses. All data can be downloaded from http://www.dmp.wa.gov.au/geochron. The region names for the Musgrave Province are after Smithies et al. (2010).

244

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

ing that the Paleoproterozoic active Yilgarn margin was not in proximity to this region (Fig. 11).

7. Conclusions The eastern Biranup Zone is composed of 1710–1650 Ma granitic to gabbroic intrusions and metasedimentary rocks, and lies adjacent to the entire southern and southeastern margins of the Yilgarn Craton over a distance of about 1200 km. The 1708 ± 15 Ma Bobbie Point metasyenogranite has a Hf isotopic signature indicating predominately a reworked Archean Yilgarn source. Volcaniclastic deposition in the Biranup Zone is dated at 1689 ± 6 Ma. These volcanogenic sediments were intruded by granitic rocks at 1686 ± 8 Ma, very soon after deposition. The Hf isotopic signature of detrital zircons from the volcaniclastic rocks is consistent with a source incorporating both Yilgarn crust and juvenile material. A suite of granitic and gabbroic rocks, the Eddy Suite, with distinct mingling and hybridisation textures, is dated at 1665 ± 4 Ma. In this suite, younger igneous rocks incorporated a greater juvenile mantle-derived component, as indicated by both the whole-rock chemistry and Hf isotopes. The isotopic features of the Biranup Zone indicate it is not exotic to the margin of the Yilgarn Craton, but instead represents a Paleoproterozoic active margin. On this margin back-arc processes isolated Archean fragments, dated at 2684 ± 11 Ma, in a Paleoproterozoic magmatic arc. In the eastern Biranup Zone, folded leucosomes in a migmatitic monzogranite yield a U–Pb zircon date of 1676 ± 6 Ma, which is identical to that for crystallization of cross-cutting axial planar leucosomes at 1679 ± 6 Ma. This indicates high-temperature metamorphism and deformation, including isoclinal folding, in the eastern Biranup Zone at c. 1680 Ma. This event is here named the Zanthus Event. Based on the rapidly evolving tectonomagmatic history, the original Yilgarn-like Hf isotopic signature modified by juvenile material, and the geochemical evolution of high-K calcalkaline magmas, a feasible tectonic scenario for the Biranup Zone is an evolving arc to back-arc within an active margin on the Yilgarn Craton. This region was subsequently compressed and tectonically dismembered during Stages I and II of the Albany-Fraser Orogeny. Two strongly foliated granite samples within the Fraser Range Metamorphics yield a weighted mean date of 1298 ± 4 Ma, interpreted as the age of magmatic crystallization during Stage I of the Albany-Fraser Orogeny. A major foliation-forming event within the Fraser Zone must have occurred after c. 1300 Ma. These Fraser Zone granites have initial Hf isotopic ratios compatible with juvenile input into a Biranup Zone source, implying a Biranup Zone basement to the Fraser Zone. The eastern Biranup Zone preserves no evidence of Stage I intrusive activity, suggesting it was structurally emplaced to its present position after Stage I. However, evidence of Stage II metamorphic overprinting is indicated by the widespread development of low-uranium zircon overgrowths at 1197 ± 6 Ma. Within the Gwynne Creek Gneiss, high-U zircon overgrowths are fractured and then overgrown by a younger phase of metamorphic zircon. This indicates a period of crustal uplift and cooling between 1270 and 1197 Ma. The timing of this uplift is comparable with that in the Fraser Zone and Mount Ragged Formation. The Mount West Orogeny of the Musgrave Province and Stage I of the Albany-Fraser Orogeny, at c. 1300 Ma, share a similar timing and may reflect development of an arc system and its compression against the craton margin. In the case of the Fraser Zone, it was originally rooted on the outer Biranup Zone, and reflects the upthrusting and juxtaposition of lower crustal rocks. Stage II of the Albany-Fraser Orogeny was contemporaneous with the Musgrave Orogeny and likely reflects predominant intracratonic extension along pre-existing sutured craton edges.

Acknowledgements Zircon and baddeleyite analyses were conducted using the SHRIMP II ion microprobes at the John de Laeter Centre for Mass Spectrometry at Curtin University, in Perth, Australia. Geological Survey of Western Australia’s Carlisle laboratory staff are thanked for their diligent efforts in mineral separation. M. Prause is thanked for assistance in drafting the figures. D. Vilbert is thanked for performing the Nd analyses. C. Forbes is thanked for a constructive review. P. Cawood is thanked for efficient editorial handling. The authors publish with permission of the Executive Director of the Geological Survey of Western Australia. Appendix A. U–Pb Zircon and baddeleyite separation was performed by crushing and elutriation, followed by heavy-liquid and magnetic separation. The resulting hand-picked zircon or baddeleyite crystals were mounted with zircon standards (CZ3, OG1, and BR266 or Temora2) or baddeleyite (PBR2) in epoxy and ground to half grain thickness to expose crystal interiors. Transmitted and reflected-light images of all grains were produced. After applying a 40 nm-thick gold coating, cathodoluminescence (CL) imaging of all zircons was performed. Operating procedures for U, Th, and Pb isotopic measurements using the SHRIMP ion microprobes are detailed in Wingate and Kirkland (2009). The zircon standard CZ3 was used for concentration calibration (551 ppm 238 U; Claoué-Long et al., 1995) and either Temora2 (Black et al., 2004) or BR266 (Stern, 2001) was used as the zircon U–Pb calibration standard whereas PBR2 was used for baddeleyite (Wingate and Kirkland, 2009). All mounts had the accuracy of 207 Pb*/206 Pb* ratios verified by comparison with the Archean OG1 zircon standard (Stern et al., 2009). No correction for 207 Pb*/206 Pb* fractionation is deemed necessary. Lu–Hf Hafnium isotope analyses were conducted on previously dated zircons mounted in epoxy resin using a New Wave/Merchantek LUV213 laser-ablation microprobe, attached to a Nu Plasma multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICPMS). The analyses employed a beam diameter of ∼55 ␮m and a 5 Hz repetition rate which resulted in ablation pits typically 40–60 ␮m deep. The ablated sample material was transported from the laser cell to the ICP-MS torch by a helium carrier gas. Interference of 176 Lu on 176 Hf was corrected by measurement of interference-free 175 Lu, and using the invariant 176 Lu/175 Lu correction factor 1/40.02669 (DeBievre and Taylor, 1993). Interference of 176 Yb on 176 Hf was corrected by measuring the interferencefree 172 Yb isotope, and using the 176 Yb/172 Yb ratio to obtain the interference-free 176 Yb/177 Hf ratio. The appropriate value of 176 Yb/172 Yb was determined through spiking of the JMC475 hafnium standard solution with ytterbium, and finding the value of 176 Yb/172 Yb (0.58669) required to yield the 176 Hf/177 Hf value for the un-spiked solution. The typical 2 precision of the 176 Hf/177 Hf ratios is +0.00002, equivalent to +0.7 εHf unit. Thirty zircons from the Mud Tank carbonatite locality were analysed, together with the samples, as a measure of the accuracy of the results. Most of the data and the mean 176 Hf/177 Hf value (0.282522 ± 0.000015; n = 30) are within 2 standard deviations of the recommended value (0.282522 ± 0.000042 (2); Griffin et al., 2007). Six analyses of the 91500 zircon standard analysed during this study indicated 176 Hf/177 Hf = 0.282320 ± 0.000021 (2), which is well within the range of values reported by Griffin et al. (2006).

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

Calculation of initial 176 Hf/177 Hf is based on the 176 Lu decay constant of Scherer et al. (2001; 1.867 × 10−11 y−1 ) and ␧Hf values employed the present day chondritic measurement of Blichert-Toft and Albarède, (1997; 0.282772). Calculation of model ages (TDM ) is based on a depleted-mantle source with (176 Hf/177 Hf)i = 0.279718 at 4.56 Ga and 176 Lu/177 Hf = 0.0384 (Griffin et al., 2004). TDM (crustal) ages were calculated assuming that the Hf within each zircon resided within a reservoir with 176 Lu/177 Hf ratio of 0.015, corresponding to an average Continental Crust (Griffin et al., 2002, 2004). Sm–Nd Sm–Nd isotopic values where determined on crushed wholerock samples by isotope dilution. All analyses were carried out at the Géosciences Rennes Laboratory at the University of Rennes 1. Samples were spiked with a 150 Nd–149 Sm mixed solution and dissolved in HF-HNO3 . REE elements were separated using BioRad AG 50W × 8 H + 200–400 mesh cationic resin. Sm and Nd were separated and collected by passing the solution through a further set of ion exchange columns loaded with Ln spec Eichrom resin. Sm and Nd were loaded with HNO3 reagent on to double Re filaments and analysed in a Finnigan MAT262 multicollector mass spectrometer in static mode. In each analytical session, the unknowns were analysed together with the Ames nNd-1 Nd standard, which during the course of this study yielded an average of 0.511964 (standard deviation = 7.23 × 10−6 ). All analyses of the unknowns are adjusted to a nominal 143 Nd/144 Nd value of 0.511850 for the La Jolla standard. Mass fractionation was monitored and corrected using the value 146 Nd/144 Nd = 0.7219. Procedural blanks analysed during the period of these analyses were ∼190 pg and are considered to be negligible compared to the total quantity of Nd in the samples. Appendix B. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.precamres.2011.03.002. References Barquero-Molina, M.S., 2009. Kinematics of bidirectional extension and coeval NWdirected contraction in orthogneisses of the Biranup Complex, Albany-Fraser Orogen, southwestern Australia. The University of Texas at Austin, PhD Thesis. Betts, P.G., Giles, D., 2006. The 1800–1100 Ma tectonic evolution of Australia. Precambrian Research 144 (1–2), 92–125. Betts, P.G., Giles, D., Lister, G.S., Frick, L.R., 2002. Evolution of the Australian lithosphere. Australian Journal of Earth Sciences 49 (4), 661–695. Betts, P.G., Giles, D., Schaefer, B.F., 2008. Comparing 1800-1600 Ma accretionary and basin processes in Australia and Laurentia: possible geographic connections in Columbia. Precambrian Research 166, 81–92. Black, L.P., Kamo, S.L., Allen, C.M., Davis, D.W., Aleinikoff, J.N., Valley, J.W., Mundil, R., Campbell, I.H., Korsch, R.J., Williams, I.S., Foudoulis, C., 2004. Improved 206 Pb/238 U microprobe geochronology by the monitoring of a trace element related matrix effect: SHRIMP, ID-TIMS, ELA-ICP-MS, and oxygen isotope documentation for a series of zircon standards. Chemical Geology 205, 115–140. Bodorkos, S., Clark, D.J., 2004. Evolution of a crustal-scale transpressive shear zone in the Albany Fraser Orogen, SW Australia: 2. Tectonic history of the Coramup Gneiss and a kinematic framework for Mesoproterozoic collision of the West Australian and Mawson cratons. Journal of Metamorphic Geology 22, 713–731. Bodorkos, S., Wingate, M.T.D., 2008a. 184125: Orthopyroxene-bearing dioritic gneiss, Observatory Point; Geochronology Record 703. Geological Survey of Western Australia, 4. Bodorkos, S., Wingate, M.T.D., 2008b. 184120: Monzogranitic gneiss, Pallinup River; Geochronology Record 700. Geological Survey of Western Australia, 4. Boynton, W.V., 1984. Cosmochemistry of the rare earth elements: meteorite studies. In: Henderson, P. (Ed.), Rare Earth Element Geochemistry. Elsevier, Amsterdam, pp. 63–114. Cassidy, K.F., Champion, D.C., 2004. Crustal evolution of the Yilgarn Craton from Nd isotopes and granite geochronology: implications for metallogeny. In: SEG 2004, Predictive Mineral Discovery Under Cover J Muhling: Centre for Global Metallogeny, The University of Western Australia, Publication 33, pp. 317–320. Cassidy, K.F., Champion, D.C., Krapeˇz, B., Barley, M.E., Brown, S.J.A., Blewett, R.S., Groenewald, P.B., Tyler, I.M., 2006. A revised geological framework for the Yilgarn Craton. Geological Survey of Western Australia, Record 2006/8.

245

Champion, D.C., Cassidy, K.F., 2007. An overview of the Yilgarn craton and its crustal evolution. In: Proceedings of Geoconferences , (WA) Inc, pp. 8–13. Champion, D.C., Cassidy, K.F., Smithies, R.H., 2006. Sm–Nd isotope characteristics of the Pilbara and Yilgarn Cratons, Western Australia: implications for crustal growth in the Archean. Geochimica et Cosmochimica Acta 70 (18 Suppl. 1), A95. Claoué-Long, J., Compston, W., Roberts, J., Fanning, C., 1995. Two carboniferous ages: a comparison of SHRIMP zircon dating with conventional zircon ages and 40Ar/39Ar analysis. In: Berggren, W., Kent, D., Aubrey, M., Hardenbol, J. (Eds.), Time Scales and Global Stratigraphic Correlation. Society for Sedimentary Geology, pp. 3–21. Clark, D.J., Kinny, P.D., Post, N., Hensen, B., 1999. Relationships between magmatism, metamorphism and deformation in the Fraser Complex, Western Australia: constraints from new SHRIMP U–Pb zircon geochronology. Australian Journal of Earth Sciences 46, 923–932. Clark, D.J., Hensen, B.J., Kinny, P.D., 2000. Geochronological constraints for a twostage history of the Albany-Fraser Orogen, Western Australia. Precambrian Research 102, 155–183. Collins, W.J., Shaw, R.D., 1995. Geochronological constraints on orogenic events in the Arunta Inlier: a review. Precambrian Research 71, 315–346. Condie, K.C., Myers, J.S., 1999. Mesoproterozoic Fraser Complex: geochemical evidence for multiple subduction-related sources of lower crustal rocks in the Albany Fraser Orogen, Western Australia. Australian Journal of Earth Sciences 46, 875–882. Daly, J.S., Aitcheson, S.J., Cliff, R.A., Gayer, R.A., Rice, A.H.N., 1991. Geochronological evidence from discordant plutons for a late Proterozoic orogen in the Caledonides of Finnmark, northern Norway. Journal of the Geological Society 148, 29–40. Dawson, G.C, Krapeˇz, B., Fletcher, I.R., McNaughton, N.J., Rasmussen, B., 2002. Did late Paleoproterozoic assembly of proto-Australia involve collision between the Pilbara, Yilgarn and Gawler Cratons? Geochronological evidence from the Mount Barren Group in the Albany-Fraser Orogen of Western Australia. Precambrian Research 118, 195–220. Dawson, G.C., Krapeˇz, B., Fletcher, I.R., McNaughton, N.J., Rasmussen, B., 2003. 1.2 Ga thermal metamorphism in the Albany-Fraser Orogen of Western Australia: consequence of collision or regional heating by dyke swarms? Journal of the Geological Society, London 160, 29–37. De Waele, B., Pisarevsky, S.A., 2008. Geochronology, paleomagnetism and magnetic fabric of metamorphic rocks in the northeast Fraser Belt, Western Australia. Australian Journal of Earth Sciences 55, 605–621. DeBievre, P., Taylor, P., 1993. Table of the isotopic composition of the elements. International Journal of Mass Spectrometry and Ion Processes 123, 149. Doepel, J.J.G., 1975. Albany-Fraser Province. The Geology of Western Australia: Western Australia Geological Survey. Memoir 2, 94–102. Drake, M.J., Weill, D.F., 1975. Partition of Sr, Ba, Ca, Y, Eu2+, Eu3+, and other REE between plagioclase, feldspar and magmatic liquid: an experimental study. Geochemica et Cosmochemica Acta 39, 689–712. Etheridge, M.A., Rutland, R.W.R., Wyborn, L.A.I., 1987. Orogenesis and tectonic process in the early to middle Proterozoic of northern Australia. In: Kroner, A. (Ed.), Proterozoic Lithosphere Evolution, Geodynamics Series, 17. AGU, Washington, DC, pp. 131–147. Fitzsimons, I.C.W., 2003. Proterozoic basement provinces of southern and southwestern Australia, and their correlation with Antarctica. In: Yoshida, M., Windley, B., Dasgupta, S. (Eds.), Supercontinent Assembly and Breakup. Geological Society, London, Special Publications, pp. 93–130. Fletcher, I.R., Myers, J.S., Ahmat, A.L., 1991. Isotopic evidence on the age and origin of the Fraser complex, Western Australia: a sample of mid-proterozoic lower crust. Chemical Geology 87, 197–216. Giles, D., Betts, P., Lister, G., 2002. Far-field continental backarc setting for the 1.80–1.67 Ga basins of northeastern Australia. Geology 30 (9), 823–826. Giles, D., Betts, P.G., Lister, G.S., 2004. 1.8–1.5-Ga links between the North and South Australian Cratons and the early-middle Proterozoic configuration of Australia. Tectonophysics 380, 27–41. Goldstein, S.L., O’Nions, R.K., Hamilton, P.J., 1984. A Sm–Nd isotopic study of atmospheric dusts and particulates from major river systems. Earth and planetary Science Letters 70, 221–236. Griffin, T.J., 1989. Widgiemooltha, W.A., second ed. Western Australia Geological Survey, 1:250,000 Geological Series Explanatory Notes: 43. Griffin, W.L., Wang, X., Jackson, S., Pearson, N., O’Reilly, S., Xu, X., Zhou, X., 2002. Zircon chemistry and magma genesis, SE China: in situ analysis of Hf isotopes, Pingtan and Tonglu igneous complexes. Lithos 61, 237–269. Griffin, W.L., Belousova, E.A., Shee, S.R., Pearson, N.J., O’Reilly, S.Y., 2004. Archean crustal evolution in the northern Yilgarn Craton: U–Pb and Hf-isotope evidence from detrital zircons. Precambrian Research 127, 19–41. Griffin, W.L., Pearson, N.J., Belousova, E.A., Saeed, A., 2006. Comment: Hf-isotope heterogeneity in standard zircon 91500. Chemical Geology 233, 358–363. Griffin, W.L., Pearson, N., Belousova, E.A., Saeed, A., 2007. Reply to ‘Comment to short-communication: Hf-isotope heterogeneity in zircon 91500’ by WL Griffin, NJ Pearson, EA Belousova, A Saeed (Chemical Geology 233 (2006) pp. 358–363) by F. Corfu. Chemical Geology, 244: 354–356. GSWA, 2007. South Yilgarn Geological Exploration Package. Western Australia Geological Survey Record, 2007/13. Hall, C.E., Jones, S.A., 2005. The Proterozoic Woodline Formation: New Constraints from Geochronology, Sedimentology and Deformation Studies, Record 2005/5. Geological Survey of Western Australia, pp. 14–15. Hall, C.E., Jones, S.A., Bodorkos, S., 2008. Sedimentology, structure and SHRIMP zircon provenance of the Woodline Formation, Western Australia: implications for

246

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247

the tectonic setting of the West Australian Craton during the Paleoproterozoic. Precambrian Research 162, 577–598. Howard, H.M., Smithies, R.H., Pirajno, F., Skwarnecki, M.S., 2007. Bell Rock, W.A. Sheet 4645: Geological Survey of Western Australia, 1:100,000 Geological Series. Howard, K.E, Hand, M., Barovich, K.M., Payne, J.L., Belousova, E.A., 2010. U–Pb, Lu–Hf and Sm–Nd isotopic constraints on provenance and depositional timing of metasedimentary rocks in the western Gawler Craton: Implications for Proterozoic reconstruction models. Precambrian Research 184, 43–62. Jones, S.A., 2006. Mesoproterozoic Albany-Fraser Orogen-related deformation along the southeastern margin of the Yilgarn Craton. Australian Journal of Earth Sciences 53, 213–234. Kirkland, C.L., Spaggiari, C., Wingate, M.T.D., Smithies, R.H., Pawley, M.J., 2010. New geochronology from the Albany-Fraser Orogen: implications for Mesoproterozoic magmatism and reworking: 2008–2009 Annual Review article. Geological Survey of Western Australia 8. Kirkland, C.L., Wingate, M.J., Spaggiari, C.V., 2011. 182432: semi-pelitic gneiss, Gwynne Creek. Geochronology Record 937. Geological Survey of Western Australia, 4. Korsch, R.J., Kositcin, N., Champion, D.C., 2010. Australian island arcs through time: geodynamic implications for the Archean and Proterozoic. Lithos (Corrected proof). Kositcin, N., 2007. Time-space evolution of the Albany-Fraser Orogen. In: Neumann, N., Fraser, G. (Eds.), Geochronological Synthesis and Time-space Plots for Proterozoic Australia. Geoscience Australia Record 2007/6, pp. 182–201. Kretz, R., 1983. Symbols for rock-forming minerals. American Mineralogist 68, 277–279. Liew, T.C., Hofmann, A.W., 1988. Precambrian crustal components, plutonic associations, plate environment of the Hercynian fold belt of central Europe: indications from a Nd and Sr isotopic study. Contributions to Mineralogy and Petrology 98, 129–138. Morris, P.A., Pirajno, F., 2005. Geology, geochemistry, and mineralization potential of Mesoproterozoic sill complexes of the Bangemall Supergroup, Western Australia. Geological Survey of Western Australia, Report 99. Murakami, T., Chakoumakos, B., Ewing, R., Lumpkin, G., Weber, W., 1991. Alphadecay event damage in zircon. American Mineralogist 76, 1510–1532. Myers, J.S., 1985. In: Survey, W.A.G. (Ed.), The Fraser Complex—A Major Layered Intrusion in Western Australia, pp. 57–66. Myers, J.S., 1990. Albany-Fraser Orogen. Geology and mineral resources of Western Australia. Memoir 3. Western Australia Geological Survey, 255–263. Myers, J.S., 1993. Precambrian history of the West Australian Craton and adjacent orogens. Annual Review of Earth and Planetary Sciences 21, 453–485. Myers, J.S., 1995. Geology of the Albany 1:1,000,000 Sheet. Western Australia Geological Survey 1:1,000,000 Geological Series Explanatory Notes: 10. Myers, J.S., Shaw, R.D., Tyler, I.M., 1996. Tectonic evolution of proterozoic Australia. Tectonics 15, 1431–1446. Nelson, D.R., 1995a. 83690: biotite granodiorite gneiss, Bald Rock. Geochronology Record 78. Geological Survey of Western Australia, 4. Nelson, D.R., 1995b. 83649: Granite pegmatite, Lake Gidong headland. Geochronology Record 97. Geological Survey of Western Australia, 4. Nelson, D.R., 1995c. 83657A: Porphyritic biotite monzogranite, Esperance Harbour jetty Geochronology Record 100. Western Australia Geological Survey, 3. Nelson, D.R., 1995d. 83659: Recrystallized leucogranite, Observatory Point. Geochronology Record 102. Geological Survey of Western Australia 4. Nelson, D.R., 1995e. 83697: Biotite monzogranite gneiss Mount Burdett, Geochronology Record 81. Geological Survey of Western Australia, 4. Nelson, D.R., 1995f. 83700A: Hornblende-biotite syenogranite gneiss, Coramup Hill Quarry. Geochronology Record 82. Geological Survey of Western Australia, 4. Nelson, D.R., 1995g. 112128: Muscovite–biotite–sillimanite paragneiss. Point Malcolm; Geochronology Record 499. Geological Survey of Western Australia, 4. Nelson, D.R., 1995h. 83676A: Hornblende syenogranite gneiss, Mount Andrew; Geochronology Record 77. Geological Survey of Western Australia, 4. Nelson, D.R., 1996. 112170: Metasandstone, Barrens Beach. Geochronology Record 492. Geological Survey of Western Australia, 84–86. Nelson, D.R., 2001. 168963: Mylonitized syenogranite, Mountain Well; Geochronology Record 182. Geological Survey of Western Australia, 4. Nelson, D.R., Myers, J.S., Nutman, A., 1995. Chronology and evolution of the middle Proterozoic Albany-Fraser Orogen, Western Australia. Australian Journal of Earth Sciences 42, 481–495. Norrish, K., Chappell, B.W., 1977. X-ray fluorescence spectrometry. In: Zussman, J. (Ed.), Physical Methods in Determinative Mineralogy. , second ed. Academic Press, London, pp. 201–272. Occhipinti, S.A., Sheppard, S., Tyler, I.M., Nelson, D.R., 1999. Deformation and metamorphism during the c. 2000 Ma Glenburgh Orogeny and c. 1800 Ma Capricorn Orogeny. Geological Society of Australia Abstracts 56, 26–29. Payne, J.L., Hand, M., Barovich, K.M., Reid, A., Evans, D.A.D., 2009. Correlations and reconstruction models for the 2500–1500 Ma evolution of the Mawson Continent. In: Reddy, S.M., Mazumder, R., Evans, D.A.D., Collins, A.S. (Eds.), Palaeoproterozoic Supercontinents and Global Evolution. Geological Society, London, Special Publications, pp. 319–355. Pearce, J.A., 1982. Trace element characteristics of lavas from destructive plate boundaries. In: Thorpe, R.S. (Ed.), Andesites. John Wiley and Sons, New York, pp. 526–548. Pearce, J.A., Harris, N.W., Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology 25, 956–983. Pettke, T., Audétat, A., Schaltegger, U., Heinrich, C., 2005. Magmatic-to-hydrothermal crystallization in the W-Sn mineralized Mole Granite (NSW, Australia): Part II:

evolving zircon and thorite trace element chemistry. Chemical Geology 220, 191–213. Pyke, J., 2000. Minerals laboratory staff develops new ICP-MS preparation method. Australian Geological Survey Organisation (AGSO) Newsletter 33, 12–14. Rasmussen, B., Bengston, S., Fletcher, I., McNaughton, N., 2002. Discoidal impressions and trace-like fossils more than 1200 million years old. Science 296, 1112–1115. Rim´sa, A., Whitehouse, M.J., Johansson, L., Piazolo, S., 2007. Brittle fracturing and fracture healing of zircon: an integrated cathodoluminescence, EBSD, U–Th–Pb, and REE study. American Mineralogist 92, 1213–1224. Rottura, A., Bargossi, G.M., Caggianelli, A., Del Moro, A., Visona, D., Tranne, C.A., 1998. Origin and significance of the Permian high-K alkaline magmatism in the centraleastern Southern Alps, Italy. Lithos 45, 329–348. Schaltegger, U., Krähenbühl, U., 1990. Heavy rare-earth element enrichment in granites of the Aar Massif (Central Alps, Switzerland). Chemical Geology 89, 49–63. Scherer, E., Münker, C., Mezger, K., 2001. Calibration of the lutetium–hafnium clock. Science 293, 683–687. Schulz, B., Bombach, K., Pawlig, S., Braetz, H., 2004. Neoproterozoic to early Palaeozoic magmatic evolution in the Gondwana-derived Austroalpine basement to the south of the Tauern Window, Eastern Alps. International Journal of Earth Sciences 93, 824–843. Scrimgeour, I.R., 2003. Developing a revised framework for the Arunta Region. In: Munson, T.J., Scrimgeour, I.R. (Eds.), Proceedings of the Annual Geoscience Exploration Seminar (AGES) 2003. Northern Territory Geological Survey Record 2003-001. Scrimgeour, I.R., Close, D.F., Edgoose, C.J., 2005a. Mount Liebig, Northern Territory, Sheet SF 52-16, 1:250,000 Geological Map Series and Explanatory Notes. NTGS. Scrimgeour, I.R., Kinny, P.D., Close, D.F., Edgoose, C.J., 2005b. High-T granulites and polymetamorphism in the southern Arunta Region, central Australia: evidence for a 1.64 Ga accretional event. Precambrian Research 142, 1–27. Shapiro, L., Brannock, W.W., 1962. Rapid analysis of silicate, carbonate and phosphate rocks. U.S.G.S., Bulletin, 1144–A. Sheppard, S., Occhipinti, S.A., Tyler, I.M., 2001. Links between regional-scale deformation and granite generation: the Yarlarweelor gneiss complex, Western Australia. Geological Society of Australia Abstracts 64, 172–173. Smithies, R.H., Bagas, L., 1997. High pressure amphibolite–granulite facies metamorphism in the Paleoproterozoic Rudall Complex, central Western Australia. Precambrian Research 83, 243–265. Smithies, R.H., Howard, H.M., Evins, P.M., Kirkland, C.L., Bodorkos, S., Wingate, M.T.D., 2009. The west Musgrave Complex—some new geological insights from recent mapping, geochronology, and geochemical studies. Geological Survey of Western Australia Record 2008/19. Smithies, R.H., Howard, H.M., Evins, P.M., Kirkland, C.L., Kelsey, D.E., Hand, H., Wingate, M.T.D., Collins, A.S., Belousova, E., Allchurch, S. 2010. Geochemistry, geochronology and petrogenesis of Mesoproterozoic felsic rocks in the western Musgrave Province of central Australia, and implications for the Mesoproterozoic tectonic evolution of the region. Geological Survey of Western Australia, Report 106, 73pp. Spaggiari, C.V., Bodorkos, S., Barquero-Molina, M., Tyler, I.M., Wingate, M.T.D., 2009. Interpreted bedrock geology of the South Yilgarn and central Albany-Fraser Orogen, Western Australia. Geological Survey of Western Australia, Record 2009/10, 84. Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters 26 (2), 207–221. Stern, R.A., 2001. A new isotopic and trace-element standard for the ion microprobe: preliminary thermal ionization mass spectrometry (TIMS) U–Pb and electron microprobe data: radiogenic and isotopic studies, current research 2001-F1. Geological Survey of Canada, 11. Stern, R.A., Bodorkos, S., Kamo, S.L., Hickman, A.H., Corfu, F., 2009. Measurement of SIMS instrumental mass fractionation of Pb isotopes during zircon dating. Geostandards and Geoanalytical Research 33, 145. Tanner, P.W.G., Sutherland, S., 2007. The highland border complex, Scotland: a paradox resolved. Journal of the Geological Society 164, 111–116. Thomas, W.A., Astini, R.A., 1996. The Argentine Precordillera: a traveler from the Ouachita embayment of North American Laurentia. Science 273, 752–757. Tyler, I.M., 2005. Australia: Proterozoic. In: Selley, R., Cocks, L., Plimer, I. (Eds.), Encyclopedia of Geology. Elsevier, Oxford, pp. 208–221. Vallini, D., Rasmussen, B., Krapeˇz, B., Fletcher, I., McNaughton, N., 2005. Microtextures, geochemistry and geochronology of authigenic xenotime constraining the cementation history of a Paleoproterozoic metasedimentary sequence. Sedimentology 52, 101–122. Vavra, G., Gebauer, D., Schmid, R., Compston, W., 1996. Multiple zircon growth and recrystallization during polyphase Late Carboniferous to Triassic metamorphism in granulites of the Ivrea Zone (Southern Alps): an ion microprobe (SHRIMP) study. Contributions to Mineralogy and Petrology 122 (4), 337–358. Wade, B.P., Kelsey, D.E., Hand, M., Barovich, K.M., 2008. The Musgrave Province: stitching north, west and south Australia. Precambrian Research 166, 370–386. Watson, E.B., Harrison, T.M., 1983. Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types. Earth and Planetary Science Letters 64 (2), 295. Webb, P.C., Tindle, A.G., Barrit, S.D., Brown, G.C., Miller, J.F., 1985. Radiothermal granites of the United Kingdom: comparison of fractionation patterns and variation of heat production for selected granites. In: High Heat Production (HHP) Granites, Hydrothermal Circulation and Ore Genesis. Inst. Min. Metall., London, pp. 409–424. Wingate, M.T.D., Bodorkos, S., 2007a. 177909: Monzogranite gneiss, Yardilla Bore; Geochronology Record 659. Geological Survey of Western Australia, 4.

C.L. Kirkland et al. / Precambrian Research 187 (2011) 223–247 Wingate, M.T.D., Bodorkos, S., 2007b. 177910: Metamorphosed quartz sandstone, Peters Dam, Geochronology Record 660. Geological Survey of Western Australia, 6. Wingate, M.T.D., Compston, W., 2000. Crystal orientation effects during ion microprobe U–Pb analysis of baddeleyite. Chemical Geology 168 (1–2), 75. Wingate, M.T.D., Kirkland, C.L., 2009. Introduction to geochronology information released in 2009. Geological Survey of Western Australia, 5.

247

Wingate, M.T.D., Campbell, I., Harris, L., 2000. SHRIMP baddeleyite age for the Fraser Dyke Swarm, southeast Yilgarn Craton, Western Australia. Australian Journal of Earth Sciences 47, 309–313. Wingate, M.T.D., Morris, P.A., Pirajno, F., Pidgeon, R.T., 2005. Two large igneous provinces in late mesoproterozoic Australia. Supercontinents and earth evolution symposium, Perth. Perth Geological Society of Australia 81, 151 (Abstracts).