First evidence for Cambrian rift-related magmatism in the West African Craton margin: The Derraman Peralkaline Felsic Complex

    First Evidence for Cambrian Rift-related Magmatism in the West African Craton margin: The Derraman Peralkaline Felsic Complex F. Bea, P. Montero, F. Haissen, J.F. Molina, A. Michard, C. Lazaro, A. Mouttaqi, A. Errami, O. Sadki PII: DOI: Reference:

S1342-937X(15)00197-5 doi: 10.1016/j.gr.2015.07.017 GR 1492

To appear in:

Gondwana Research

Received date: Revised date: Accepted date:

9 April 2015 20 July 2015 29 July 2015

Please cite this article as: Bea, F., Montero, P., Haissen, F., Molina, J.F., Michard, A., Lazaro, C., Mouttaqi, A., Errami, A., Sadki, O., First Evidence for Cambrian Riftrelated Magmatism in the West African Craton margin: The Derraman Peralkaline Felsic Complex, Gondwana Research (2015), doi: 10.1016/j.gr.2015.07.017

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First Evidence for Cambrian Rift-related Magmatism in the West African Craton margin: The Derraman Peralkaline Felsic Complex

Department of Mineralogy and Petrology, University of Granada, Campus Fuentenueva, 18002 Granada, Spain 2

LGAGE, Départementde Géologie, Université Hassan II, Casablanca, Morocco 3

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F. Bea*1, P. Montero1, F. Haissen2, J.F. Molina1, A. Michard3, C.Lazaro1, A. Mouttaqi4, A. Errami4, O. Sadki4

Em. Pr. Université Paris-Sud (Orsay), 10 rue des Jeuneurs, 75002 Paris

Office National des Hydrocarbures et des Mines, 5 Avenue Moulay Hassan, Rabat, Morocco

* Corresponding author. Email: [email protected]. Fax: +34958243358. Phone: +34958246176 1

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Abstract West of the the southern, Archean, part of the Reguibat Rise of the West African Craton the

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Oulad Dlim Massif consists of metamorphic nappes stacked during the Mauritanides (Variscan)

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orogeny. In the Derraman region, about 12 km west of the nappes, we have found strongly

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deformed hypersolvus aeginine-riebeckite A1-type granites with SHRIMP zircon U-Pb ages of

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ca. 525 ± 3 Ma, ε(Nd)525Ma (-5.2 to -6.8.) and Nd model ages TCR ≈ 1.85 Ga. These granites

define two km-sized bodies and a few smaller satellites. One body is emplaced within a 3.12 Ga

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leucocratic gneiss. The other body and its satellites are emplaced within an Archean low-grade metasedimentary sequence with detrital zircons that have ages that peak at 2.84 Ga, 2.91 Ga, and

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3.15 Ga. These Archean gneisses and metapelites rocks define a tectonic unit, hereafter called the Derraman-Bulautad-Leglat (DBL) unit, which was formed from the Reguibat basement at the

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very margin of the WAC. The ~525 Ma Derraman granites are the oldest post-Archean rocks in this unit and were generated in an intraplate rifting environment from melting of crustal fenites during the ubiquitous Cambrian rifting event that affected this part of northern Gondwana. At the present level of knowledge, however, we cannot decide whether the “old” Nd isotope signature of Derraman granites resulted from melting of an old (Paleoproterozoic) fenite source or reflects the signature of the mantle-derived metasomatising fluids. The just-discovered Derraman granites are strikingly similar to other rift-related Cambrian-Ordovician hypersolvus aegirine-riebeckite granites widespread in North Gondwana. Understanding the potential connections between them would help to understand the Cambrian-Ordovician breakdown of northern Gondwana. Keywords: Reguibat Rise; peralkaline, hypersolvus, granite; zircon; SHRIMP dating

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ACCEPTED MANUSCRIPT 1. Introduction The western boundary of the West African Craton (WAC) that crops out between N 21º and N

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23º is marked by a narrow SSW-NNE belt of Paleozoic sediments overlying the south-western

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Reguibat Rise (Fig. 1A-D). West of the Paleozoic cover units, the Oulad Dlim (or Adrar

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Souttouf) massif is currently described as a west-to-east accumulation of tectonic nappes

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emplaced during the Mauritanides (Variscan) orogeny (Sougy, 1969; Sougy and Bronner, 1969;

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Villeneuve and Cornée, 1994; Le Goff et al., 2001; Villeneuve et al., 2006, 2010, 2015; Michard et al., 2008, 2010; Rjimati et al., 2011). The limit of the WAC at depth is somewhere beneath the

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Oulad Dlim massif or to the west of it (Ennih and Liégeois, 2008; Villeneuve et al., 2015). The

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geology of the Oulad Dlim massif itself is still poorly known: the only complete geological map

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is the 1985 1:1,000,000 Geological Map of Morocco (Hollard et al., 1985) it is also partly covered by recent geological maps 1:50,000 (Rjimati et al., 2002a-e; Rjimati and Zemmouri, 2011). Petrographic knowledge about the rocks of this region hardly improved since the syntheses by Alia Medina (1960) and Arribas (1968). There is little robust geochronological data, except some LA-ICPMS zircon work by Gärtner et al. (2013, 2014) in the southern part of the region. These authors found Mesoproterozoic and late Pan-African ages. Montero et al. (2014) also determined a couple of Archean SHRIMP zircon ages by Montero et al. (2014) in areas close to the northeast boundaries of the massif. In the Leglat-Derraman region 12 km west of the alignment of Paleozoic remnants (Fig. 1C) we have recently found two km-sized bodies of gneissified riebeckite-aegirine hypersolvus granites remarkably similar to the ones associated with Cambro-Ordovician rifting in other areas

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ACCEPTED MANUSCRIPT of North Gondwana (e.g., Montero et al., 1998; 2009). Given that granites with such characteristics are excellent tectonic markers we have studied them in detail, presenting here the

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most relevant results concerning their field relationships, petrography, geochemistry, Sr and Nd

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isotopes, and SHRIMP zircon U/Pb ages.

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2. Geological setting

The Reguibat Rise (Fig. 1A, insert) is the northern part of the WAC straddling southern

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Morocco, northern Mauritania, and western Algeria. It was first identified by Menchikoff (1949)

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as an area of crystalline rocks separating two large younger basins, Tindouf and Taoudenni. Later studies have recognized that the Reguibat Rise comprises two segments, one Archean in

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the west and the other Paleoproterozoic in the east, the two having collided during the 2.1-2.0 Ga

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Eburnean Orogeny (Schofield et al., 2006; and references therein). East of the study area, the Reguibat Rise comprises tonalite-trondjhemite-granitoids (TTG) gneisses and migmatites of the

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Aghaylas Suite (Rjimati and Zemmouri, 2002) dated at 2.9 Ga - 3.0 Ga (Montero et al., 2014) that host the Awsard 2.46 Ga kalsilite syenites (Bea et al., 2013; 2014) and a dense network of mafic dikes of probable Paleoproterozoic to Mesoproterozoic age (Dosso et al., 1979; Youbi et al., 2013). Along its western border, the Reguibat Rise is unconformably overlain by discontinuous remnants of Paleozoic cover including Upper Ordovician, Silurian and Devonian sediments (Doloo-Esder = Dhlou-Sdar Unit, Alia Medina, 1960; Zamlat Al Foula Group, Rjimati and Zemmouri, 2002; Dhloat Ensour Group, Gärtner et al., 2013). The Silurian-Devonian strata

are strongly folded as they correspond to the décollement sole of the Oulad Dlim nappes (Michard et al., 2010; Rjimati et al., 2011). Further north along strike (Zemmour), the Devonian sequence is defined up to the Frasnian (Sougy, 1969). This Palaeozoic succession, which was

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ACCEPTED MANUSCRIPT first described as a graben isolated in the basement (Alia Medina, 1960; Arribas, 1968) in fact represents the eastern margin of a shallow sedimentary basin along the west border of the WAC

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(Sougy, 1962a, 1969; Michard et al., 2010).

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The Oulad Dlim massif itself comprises a large variety of rocks affected by an intense tangential deformation and interpreted since Sougy (1962a, 1962b) as the northern part of the

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Mauritanides orogen. Sougy et al. (1969) identified a number of nappes have been distinguished

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by as shown on the Geological Map of Morocco 1:1,000,000 (Hollard et al., 1985). Villeneuve et al. (2006) redefined four main nappes, labeled from west to east: the Oued Togba; Sebkha

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Gezmayet; Dayat Lawda; and Sebkha Matallah Units. In the frontal (eastern) part of the latter unit, Rjimati and Zemmouri (2002) individualized the Tiznigaten (sub-)unit made up of

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greenschist-facies quartzites of supposedly Neoproterozoic age. Recent geochronological data, however, have shown that these quartzites are Cambrian-Ordovician because they contain 510

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Ma detrital zircons (Villeneuve et al., 2015). The geochronological dataset of the Oulad Dlim massif includes K-Ar (Villeneuve et al., 2006) and LA-ICPMS zircon ages concentrated in the Oued Togba-Sebkha Gezmayet Units (Gärtner et al., 2013) and in the metabasites and gneisses of the southern Dayat Lawda and

Sebkha Matallah Units (Gärtner et al., 2014; Montero et al., 2014). The 1400-1000 Ma zircon ages obtained from the western units, Oued Togba and Sebkha Gezmayet, suggests their exotic, Avalon-Meguma origin (Gärtner et al., 2013). In contrast, most of the zircon ages obtained by

Gärtner et al. (2014) from the central and eastern units (Dayat Lawda, Sebkha Matallah) cluster at ca. 634 Ma and 605 Ma, suggesting the occurrence of a late Neoproterozoic event there. The

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ACCEPTED MANUSCRIPT nature of this event, however, is not clear. A significant part of the mafic rocks with Pan-African zircons are, in fact, granulitized gabbros and gabbroanorthosites (Entayat metagabbros) that

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contain very few zircons and have Nd model ages ≥ 2.5 Ga (authors’ unpublished data). Most

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zircons with Pan-African ages are rounded with a “granulitic” look (e.g., Fig 7 in Gartner et al., 2014; and unpublished data of the authors) but some others, less abundant, are more igneous in

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appearance and have ages around 2.5 Ga (sample REG70 of Montero et al., 2014). It is not yet clear, therefore, whether the Pan-African zircon ages of the Entayat metagabbros give evidence

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for a magmatic event involving the formation of juvenile Neoproterozoic magmas or represent a Neoproterozoic high-grade metamorphic event affecting Archean rocks.

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In the Oulad Dlim massif only a minor Variscan overprint was recognized yet. However, in the southernmost part of the massif, Le Goff et al. (2001) suggested a Variscan metamorphic

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event at 330 Ma by Sm–Nd dating of garnet-omphacite from an eclogite-facies metabasite emplaced at ca. 595 Ma. The post-Variscan evolution is that of a passive continental margin, which underwent a complex post-rift history with two moderate burial and exhumation phases (Leprêtre et al., 2015).

3. Field relations The area studied here is the rectangle between N 22º40’30” W 14º36’20” and N 22º34’24” W

16º26’17” (Fig. 1C) located west of the Paleozoic remnants of the Reguibat Rise cover and above the Tiznigaten Quartzites that form the lowermost sub-unit of the Oulad Dlim massif (Rjimati and Zemmouri, 2002; Michard et al., 2010; Rjimati et al., 2011). It is therefore considered a part

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Except for the relief at Derraman Highs and Leglat Highs, the area is flat and mostly covered

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by mobile sand so that lithological contacts are seldom observed. The most abundant rocks are leucocratic granitic gneisses that form the basement of the region. These gneisses crop out

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interspersed with high-grade metapelites, quartzites, and marbles forming what Arribas (1968)

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defined as the Bulautad series. The leucocratic granitic gneisses are mapped as “Arag1b” in

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Rjimati et al. (2002a) map, meaning they are considered equivalent to the Archean Aghaylas Suite of the nearby Reguibat Rise. Consistently, the leucocratic gneiss dated by Montero et al.

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(2014) yielded a zircon U/Pb crystallization age of 2.94 Ga and a premagmatic population at

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Montero et al. (2014).

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3.12 Ga, roughly the same ages as the TTG gneisses of the Awsard cratonic area in the east

The Leglat Highs consist of a low-grade metamorphic schistose sequence overlying the Bulautad gneisses (fig. 1C). Arribas (1968) considered these rocks as Palaeozoic and proposed that they weree the core of a synformal structure called the Leglat syncline. Rjimati et al. (2002) ascribed an Archean age to these rocks (labeled “Arlg2”, part of the Oued Aj-Janna Group together with the Arag1b Suite). Michard et al. (2010) described a strong structural imprint of the eastward, Variscan thrust event superimposed on an older syn-metamorphic foliation. The alkali feldspar granites crop out forming: (i) most of the Derraman Highs, (ii) several small bodies with hidden contacts around Derraman Highs, and (iii) a 2.5 x 1.5 km massif about 5 km north of the Derraman Highs, hereafter called the North Derraman body (Fig. 1C). All of

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ACCEPTED MANUSCRIPT the granites are strongly deformed by narrow ductile shear zones parallel to the main foliation of the host rocks.

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The Derraman Highs body is a ca. 200 m thick granite sheet that dips about 15º - 20º to the

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SW and overlies a schistose series that is apparently identical to the Leglat schists (Fig 2A). The

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contact between the schist and the granites is roughly parallel to the main foliation as a result of the strong deformation that affects both materials (Fig. 2B). When observed in detail, however,

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the contact is clearly intrusive: discordant (Fig. 2C) and locally rich in pegmatite veins,

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especially at the southern contact (Fig. 2D). Meter-thick dikes of fine-grained granites crop out parallel to the main contact and appear to be interlayered with the basal schists. The dikes

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contain abundant xenoliths of folded schist (Fig. 2E) thus revealing that these were already

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deformed when the granites intruded. The small bodies around the Derraman Highs are also

of erosion.

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emplaced within the schists and apparently appear detached from the main sheet simply because

The North Derraman body, on the other hand, intrudes the Bulautad (Arag1b) leucocratic gneisses. The body chiefly comprises coarse-grained alkali feldspar granites that are more massive and less deformed than those of the Derraman Highs. South of the North Derraman body, schists identical to the ones underlying the Derraman Highs form small hills that are the core of a N110°E synform located between the two main granite bodies (Fig. 1 C).

4. Samples and methods For this work we have studied 26 samples. Twenty three correspond to the Derraman granites, one is a basement gneiss sampled just at the contact of the North Derraman body, and the other

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ACCEPTED MANUSCRIPT two are Leglat schists, one from the Derraman Highs and the other from the Leglat Highs. Table I contains the geographic coordinates of all samples. All of them were studied under the optical

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microscope and analyzed for major and 40 trace elements. A subset of 10 samples, 8 granites, the

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basement gneiss and the 2 schists were also analyzed for Sr and Nd isotopes. Zircon concentrates were extracted from 6 samples, 4 granites, the basement gneiss, and the schist from Leglat

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Highs. Attempts to extract zircon from one sample collected from the mylonitic schists

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underlying the Derraman Highs body were unsuccessful because of the extremely fine grain size.

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About 5 to 7 kg of each sample were crushed in a jaw crusher until Ø < 2 mm. After homogenization and splitting, about 50 g of the resulting sand was ground in a tungsten carbide

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ring-mill until very fine powder for chemical and isotopic analyses. This procedure caused no

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µm for mineral separation.

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detectable contamination except in Co and W. The rest of the sand was then crushed to Ø < 300

Whole-rock major-element and Zr determinations were performed by X-ray fluorescence after fusion with lithium tetraborate. Typical precision was better than ±1.5% for an analyte concentration of 10 wt.%, and ± 2.5% for 100 ppm Zr. Trace elements were determined by ICPMS after HNO3+HF digestion of 0.1000 g of sample powder in a Teflon-lined vessel at 180 ºC and 200 psi for 30 min, evaporation to dryness, and subsequent dissolution in 100 ml of 4 vol.% HNO3; the precision was better than ±5% for analyte concentrations of 10 ppm. The concentration of Hf was calculated from the ICPMS-determined Zr/Hf and the XRF-determined Zr concentration. Samples for Sr and Nd isotope analysis were digested with HNO3+HF in the 9

ACCEPTED MANUSCRIPT same way as before using ultra-clean reagents and analyzed by thermal ionization mass spectrometry (TIMS) in a Finnigan Mat 262 spectrometer after chromatographic separation with

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ion-exchange resins. Normalization values were 86Sr/88Sr=0.1194 and 146Nd/144Nd=0.7219.

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Blanks were 0.6 and 0.09 ng for Sr and Nd respectively. The external precision (2s), estimated by analyzing 10 replicates of the standard WS-E (Govindaraju et al., 1994) was better than

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±0.003% for 86Sr/88Sr and ±0.0015% for 146Nd/144Nd. 87Sr/86Rb and 143Sm/144Nd were directly

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determined by ICP-MS following the method developed by Montero and Bea (1998), with a

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precision better than ±1.2% and ±0.9% (2s), respectively.

Major-element analyses of minerals were obtained by wavelength-dispersive analyses with a

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CAMECA SX100 electron microprobe using natural and synthetic standards. Accelerating

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voltage was 20 kV and beam current was 20 nA. The precision was close to ±4% for an analyte concentration of 1 wt.%.

Zircon was separated by panning, first in water and then in ethanol. The concentrate was purified by hand picking. About 50 -100 zircons grains of each sample plus several grains of standards were cast on a 3.5 cm diameter epoxy mount (megamount), polished and documented using optical (reflected and transmitted light) and scanning electron microscopy (secondary electrons and cathodoluminescence). After extensive cleaning and drying, mounts were coated with ultra-pure gold (8 - 10 nanometers thick) and inserted into the SHRIMP for analysis. Each selected spot was rastered with the primary beam for 120 s prior to the analysis, and then analyzed 6 scans, following the isotope peak sequence 196Zr2O, 204Pb, 204.1background, 206Pb, 207

Pb, 208Pb, 238U, 248ThO, 254UO. Every mass in every scan is measured sequentially 10 times

with the following total counting times per scan: 2 s for mass 196; 5 s for masses 238, 248, and

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ACCEPTED MANUSCRIPT 254; 15 s for masses 204, 206, and 208; and 20 s for mass 207. The primary beam, composed of

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16O16O+, is set to an intensity of about 5 nA, with a 120 µm Kohler aperture, which generates

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achieving a resolution of about 5000 at 1% peak height.

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17 x 20 micron elliptical spots on the target. The secondary beam exit slit is fixed at 80 µm,

All calibration procedures are performed on the standards included on the same mount. Mass

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calibration is done on the REG zircon (ca. 2.5 Ga, very high U, Th and common lead content). Every analytical session started measuring the SL13 zircon, which is used as a concentration

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standard (238 ppm U). The TEMORA-2 zircon (416.8 ± 1.1 Ma, Black et al., 2003), used as

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isotope ratios standard, was then measured every 4 unknowns. Data reduction and age

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calculations were done with the SHRIMPTOOLS software (available from www.ugr.es/fbea).

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5. Petrography and mineralogy

The most abundant facies of the Derraman granites are medium- to coarse-grained rocks composed of a gray groundmass of quartz and alkali feldspar in which dark clots of mafic minerals define a deformational planar to plano-linear foliation (Fig. 2F). The grain size decreases locally because of grain-size reduction caused by narrow ductile subhorizontal shearzones. This effect is less marked in North Derraman that in Derraman Highs where the granites show decametric thick bands of intensely deformed fine-grained facies alternating with less deformed coarse-grained facies (Fig. 2B). The granites are homogeneous except for the effects of the deformation. Microgranular enclaves are extremely rare, and xenoliths of the host rocks are only seen in the dikes. Centimetric quartz veinlets are found locally, but they appear to be quartz ribbons resulting from the deformation rather than of late-magmatic hydrothermal segregations. 11

ACCEPTED MANUSCRIPT The granites are all hypersolvus with agpaitic textures and are variably mylonitic. The alkali feldspar is mostly mesoperthite with optically homogeneous zones that have an average

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composition close to Ab60Or40. The least deformed granites are composed of large

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porphyroclasts of alkali feldspar and quartz, separated by streaks of fine- to medium-grained aggregates of blue amphibole, greenish clinopyroxene, biotite, ilmenite, and magnetite, often

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accompanied by fibrous stilpnomelane, phengitic muscovite, fluorite, zircon, rare apatite, and a

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plethora of REE-bearing minerals including monazite, fergusonite, aeschynite, samarskite, parisite, etc. The relative abundances of amphibole, clinopyroxene, and biotite are variable. The

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most abundant facies have amphibole > clinopyroxene > biotite, but there are also facies with either clinopyroxene or biotite as the dominant varietal mineral also occur. The biotite-rich facies

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are also the richest in fluorite and often contain phengitic muscovite. The stilpnomelane fibrousradiate aggregates are particularly common in the clinopyroxene-rich facies. Poikilitic calcite

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crystals are also found.

The fine-grained facies are markedly mylonitic. The original agpaitic texture is still recognizable because of the presence of large fragments of mesoperthite scattered among bands of fine-grained aggregates of quartz and feldspar; microscopic quartz ribbons are common. Most of the original clinopyroxene, amphibole and biotite have been transformed to fine-grained aggregates of Fe (Ti) oxides. The blue amphiboles are intermediate between Ca-rich riebeckite and sodian ferrorichterite (NaB ≈ 1.0 -1.62; CaB ≈ 0.25-0.75 a.f.u. per 23 Oxygens, Table 2a), and have moderately high F contents (0.13-0.34 a.f.u). In some cases, they show a more calcic core of ferrorichterite (NaB ≈ 0.7, CaB ≈ 1 a.f.u.). The green clinopyroxene is aegirine-augite with nearly constant composition

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ACCEPTED MANUSCRIPT (Na ≈ 0.50-0.52 a.f.u., Table 2b). The biotite compositions are close to the annite end-member

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(Fe ≈ 3.93-4.78, Mg ≈ 0.69- 1.39 a.f.u. per 22 Oxygens, Table 2c). They have low Ti (<0.30

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a.f.u.) and high F (0.25-0.91 a.f.u.), especially in samples with modal fluorite. Phengitic

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muscovites have Si ≈ 6.70-6.88 a.f.u., Fe ≈ 0.96-1.22 a.f.u., and Mg ≈ 0.37-0.55 a.f.u. per 22 Oxygens, 0.477-0.610 a.f.u. Fluorine contents (0.36-0.52 a.p.u.) are lower than in coexisting

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biotite.

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The Bulautad gneisses are strongly deformed fine-grained muscovite leucogranites locally transformed to mylonites. Their major mineralogy consists of quartz, K-feldspar, oligoclase,

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muscovite, and subordinate biotite with ore minerals, apatite and zircon and accessories. They

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have a cataclastic to mylonitic texture, with quartz ribbons and streaks of fine-grained muscovite

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and biotite.

The Leglat schists are formed of alternating layers of mica-schists, quartzites, leptinites, and calc-silicate rocks. The most abundant are quartz-rich mica-schists formed of large rounded crystals of quartz with undulate extinction within a groundmass composed of quartz, muscovite (either as individual crystals or forming streaks and bands), rare alkali feldspar, and minor calcite. The accessories: zircon, apatite, and magnetite, often form clusters of several grains. At the Derraman Highs the schists are considerably more mylonitic than at the Leglat Highs.

6. Geochemistry The major element composition of Derraman granites shows little variations (Table 1). They are highly silicic (SiO2 mean = 75.5 wt.%, S.D. = 0.98 wt.%), subaluminous (ASI mean = 0.93, S.D. = 0.04) because of low Al2O3 (mean =11.2 wt.%, S.D. = 1.0 wt.%) with moderately high Na2O (mean =3.78 wt.%, S.D. = 0.4 wt.%) and K2O (mean =4.52 wt.%, S.D. = 0.27 wt.%), low 13

ACCEPTED MANUSCRIPT MgO (mean = 0.06 wt.%, S.D. = 0.06 wt.%) and high FeO/[FeO+MgO] (mean = 0.96 wt.%, S.D. = 0.04 wt.%). The agpaitic index (A.I. = mol. [Na2O+K2O]/Al2O3) ranges from 0.94 to 1.12 and

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about 40% of the analyzed samples have A.I. ≥ 1, that is, are peralkaline. In the classification for

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high-silica granites of Bea et al. (2000) all samples plot in the A-type granites field (Fig. 3A).

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The major elements show no significant differences between the samples from North Derraman, the Derraman Highs, or the dikes.

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The trace element composition of the Derraman granites is also consistent with the A-type

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filiation (Figs. 3B and 3C). The granites have low concentration of trace alkaline and alkalineearth elements (Table 1) but moderate to high concentrations of HFSE such as Be (2-17 ppm), Y

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(23-457 ppm), Nb (37-165 ppm), Zr (190-2890 ppm), U (1-7 ppm) and Th (7-40 ppm). All

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samples from North Derraman have similar LREE contents, with LaN ≈ 200 and SmN ≈ 100,

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Eu/Eu* between 0.17-0.40, and variable HREE which, when abundant, either decrease smoothly from Gd to Lu or are slightly concave upwards with a minimum in Er (Fig. 4A). The Derraman Highs granites REE contents and profiles vary from those similar to North Derraman to heavily enriched samples with LaN ≈ 800 and a small positive Ce anomaly (Fig. 4B). The samples from the dikes show no significant differences from the main Derraman Highs body (Fig. 4C). The Th/U ratio is close to 5, just slightly higher than the mantle ratio (Th/U ≈ 4, Rogers and Adams 1969). Similarly Nb/Ta is around 16, close to the mantle ratio (Nb/Ta ≈ 17.5, Green, 1995). By contrast, Y/Nb is highly variable; about 40% of studied samples have Y/Nb < 1.2 so that in the Nb-Y-Ce diagram (Fig. 3D) they plot well in the A1 field, that is to say, A-type granites with element ratios similar to ocean island basalts (Eby, 1990, 1992). Most of the other

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ACCEPTED MANUSCRIPT samples plot along the A1-A2 boundary and only the most peralkaline samples plot well within the A2 field, that is, A-type granites with element ratios between average continental crust and

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island arc basalts (Eby, 1990, 1992; Moreno et al,, 2014).

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The concentrations of REE, Zr, Y and Nb, and the element ratios Ga/Al and Y/Nb increase with increasing peralkalinity (Fig. 5A) but Th, U, Be and the element ratios Th/Ta, Nb/Ta and

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Ce/Pb do not. The K/Rb ratio decreases with peralkalinity but the correlation is very poor (R=-

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0.28). Nevertheless, both K/Rb and Rb show excellent correlations with Be, Th, U and the heaviest REE (Fig. 5B). This suggest the existence of several different processes of HFSE and

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REE enrichment which are most likely related to increased activities of either fluoride and alkalifluoride complexes of HFSE and REE in melts and late-magmatic hydrothermal fluids.

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To describe the chemical composition of the host schists and gneisses in detail (Table 1) is beyond the scope of this work. For our purposes it is only necessary to emphasize that they are

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markedly depleted in REE (Fig. 4) and HFSE.

6. Zircon dating

Sample REG122: coarse-grained aegirine-riebeckite granite from North Derraman, with 534 ppm Zr and mol. [Na2O+K2O]/Al2O3 = 1.01. Crystals are short bipyramids or, less commonly, short bipyramidal prisms , euhedral to subhedral, always opaque, dark brown or yellow, with maximum dimensions ranging from 150 µm to 300 µm. Small inclusions are common. Under the cathodoluminescence microscope they often show a well-defined oscillatory zoning (Fig. 6). Twenty two grains were analyzed with the SHRIMP. They contained moderate concentrations of U (129-665 ppm) and Th (61-486 ppm) with mean Th/U = 0.56 and very little common lead (f206<0.2%) (Table 1e). All of them were concordant (discordance < 2%) (Fig. 7). The weighted 15

ACCEPTED MANUSCRIPT means (errors reported at 2 s) of the 204-corrected 206Pb/238U and 207Pb/235U ages are virtually

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that North Derraman has a crystallization age of 527 ± 3 Ma.

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identical, 527 ± 3 Ma (MSWD = 0.33) and 528 ± 3 Ma (MSWD = 0.32). Therefore, we assume

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Sample REG81: coarse-grained aegirine-riebeckite granite from the Derraman Highs, with 734 ppm Zr and mol. [Na2O+K2O]/Al2O3 = 1.03.

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Zircons form anhedral to subhedral bipyramids or short prismatic crystals, brown to yellow

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and usually opaque, with sizes 100 to 200 µm. They have many small inclusions, especially in the crystal cores, and under cathodoluminescence show a strong oscillatory zoning with dark

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cores and lighter rims (Fig. 6).

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Thirty four grains were analyzed with the SHRIMP. Their composition is more variable than

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in REG122, with U between 52 and 817 ppm, Th between 23 and 1118 ppm and higher Th/U averaging around 0.91 (Table 1e). As in the North Derraman granite common lead is also very low, with f206<0.16%. They are slightly more discordant than those of the North Derraman, up to 3% discordance (Fig. 7). Accordingly, the weighted mean (errors reported at 2 s) of the 204corrected 206Pb/238U age, 525 ± 3 Ma (MSWD = 0.57), is slightly higher than the 207Pb/235U age, 520 ± 3 Ma (MSWD = 0.63). We thus assumed that the best estimate of the crystallization age is 525 ± 3 Ma, slightly lower than in North Derraman but still within error.

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ACCEPTED MANUSCRIPT Sample REG127: fined-grained biotite-riebeckite granite from a dike just at the base of the main Derraman Highs body.

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This sample contains 638 ppm Zr and is not peralkaline (mol. [Na2O+K2O]/Al2O3 = 0.97). Zircons are mostly euhedral short prisms or bipyramids, colorless or slightly yellow, with

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maximum dimensions from 100 µm to 200 µm. They are usually clean, transparent and contain

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few inclusions. CL images show gray crystals with a faint oscillatory zoning

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The twenty one grains analyzed with the SHRIMP contained very little common lead (f206<0.3%), variable U (163-966 ppm) and Th (96-1168 ppm), and Th/U clustering around 0.80

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(Table 1e). The weighted averages of common-lead uncorrected 206Pb/238U and 207Pb/235U ages

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are identical, 525 ± 3 Ma (MSWD= 0.86) and 524 ±3 Ma (MSWD = 0.43) respectively, but 204-

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based common-lead correction causes a small discordance (Fig. 7) so that whereas the 206Pb/238U

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age is 524 ± 3 Ma (MSWD = 0.88), the 207Pb/235U age decreases to 518 ± 3 Ma (MSWD = 0.47). We thus assume that the best estimate of the crystallization age is 524 ± 3 Ma, identical within error to the Derraman Highs body.

Sample REG129: fine-grained biotite granite from a dike in the northern part of the Derraman Highs far from the main body. This sample is the least HFSE-enriched of the studied granites, with just 190 ppm Zr, and is not peralkaline (mol. [Na2O+K2O]/Al2O3 = 0.98). Zircons are bipyramidal or short prismatic, usually poorly shaped and strongly colored from milky gray to dark brown; they are translucent to opaque but never transparent. Sizes are variable, from 50 µm to 300 µm. They contain a

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ACCEPTED MANUSCRIPT plethora of small inclusions and cracks. Under CL (Fig. 6) they appear dark gray and structureless, or with a rough oscillatory, in places convolute, zoning.

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Twenty grains analyzed with the SHRIMP showed very little common lead (f206<0.17), variable U (37-850 ppm) and Th (17-873 ppm), and Th/U clustering around 0.55 (Table 1e). As

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in the other granite samples, the weighted averages of common-lead uncorrected 206Pb/238U and Pb/235U ages are identical, 517 ± 4 Ma (MSWD= 0.96) and 518 ± 4 Ma (MSWD = 0.45)

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207

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respectively. The 204-based common-lead correction causes a small discordance (Fig. 7) that

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leaves the 206Pb/238U unchanged at 517 ± 4 Ma (MSWD = 0.95), but decreases the 207Pb/235U

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ages to 513 ± 3 Ma (MSWD = 0.28). We thus assume that the best estimate of the crystallization

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age is 517 ± 4 Ma, significantly younger than the other three granite samples.

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Sample REG123: fine-grained and strongly deformed Bulautad leucocratic gneiss that hosts the North Derraman body.

This sample is a muscovite-biotite peraluminous leucogranite of TTG affinity, with 156 ppm of Zr. Zircons are medium to long prismatic crystals with small rounded pyramidal terminations, they are always opaque brown or milky, never colorless. Sizes vary from 80 µm to 250-300 µm. CL images are gray and show a well-defined oscillatory zoning often alternating with metamictic zones (Fig. 6). Thirty three grains analyzed with the SHRIMP contained negligible common lead (Table 1e) but were variably discordant (Fig. 8). All of them fit extremely well in a single discordia line with upper intercept at 3123 ± 5 Ma (MSWD = 0.5) identical to the 207Pb/206Pb age mean of the

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ACCEPTED MANUSCRIPT 10 most concordant (discordance < 5%) analyses 3123 ± 5 Ma (MSWD = 4.89). We therefore

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assume that the age of crystallization is 3.12 Ga, the oldest so far recorded in the West Reguibat.

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The lower intercept is 527 ± 44 Ma, identical to the age of the North Derraman body hosted by

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the gneiss. It is worth mentioning that another sample of these gneisses dated by Montero et al. (2014) had two zircon populations, one at 2.94 Ga and another at 3.11 Ga thus revealing that the

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Bulautad gneisses, like the Aghaylas gneisses in the neighbouring Reguibat Rise, were reworked

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from ca 3.11 Ga down to 2.94 Ga.

Sample REG30: metapelitic schist from the Leglat Highs.

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It is a fine-grained quartz-sericite schist which contains abundant detrital zircon with different

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morphologies. Crystals are either short, medium, or long partially rounded prisms or, in some

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cases, can be completely rounded. Sizes range from very small < 50 µm to 200-300 µm. In most cases they are opaque dark brown, sometimes milky. Under CL most of the zircons are dark gray, have a well-defined oscillatory zoning that is less commonly convolute or patchy and, in some cases, they show recrystallized white irregular areas or thin rims (Fig. 6). We analyzed 71 zircons, enough to appraise the existing populations (e.g. Fedo et al. 2003). The fraction of common lead was very low in all cases (Table 1e). Considering the 56 analyses with discordance < 2%, the distribution of 207Pb/206Pb ages shows maxima at 2.84 Ga, 2.91 Ga, and 3.15 Ga (Fig. 8). Given that the Nd model ages of the two studied schists (Table 3) range from TCR = 2.91 Ga to 2.89 Ga, we assume that the Leglat schist age is close to the youngest peak, 2.84 Ga.

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ACCEPTED MANUSCRIPT 7. Isotope geology The Sr and Nd isotope composition of the granites and host rocks is shown in Table 3. In

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Derraman, as often happens in hypersolvus granitoids (e.g. Montero et al. 2009), post-magmatic recrystallization has almost totally reset the Rb-Sr isotopic system. In a 87Sr/86Sr vs. 87Rb/86Rb

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well-defined zircon crystallization age at around 525 Ma.

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plot (Fig. 9A), the eight analysed samples scatter around the 220 Ma reference line despite the

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The Sm-Nd system, in contrast, does not seem to have been affected by post-magmatic events. All analyzed samples scatter around the 525 Ma reference line (Fig. 9B), the scatter being caused

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by the REE residence in accessory minerals that are heterogeneously distributed throughout the rock volume.

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The eight studied granites have similar Nd isotope composition. ε(Nd)525Ma is markedly

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negative ranging between -5.2 and -6.8. The Nd model ages (calculated according to Goldstein et al., 1984) average at TCR = 1.83 Ga and so are notably older than the zircon crystallization ages although nowhere near as old as the host rocks which always have TCR ≥ 2.9 Ga (Table 3).

8. Discussion

This work is the first description of the Derraman granites. Accordingly, the following discussion will focus mostly on their origin and their regional significance. Questions related to they HFSE- and REE-saturated mineralogy and the concentration mechanisms of these elements will be left for future, more specific, papers.

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ACCEPTED MANUSCRIPT 8.1 Origin and geodynamic environment

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The two largest Derraman bodies were emplaced at 525 ± 3 Ma and 527 ± 3 Ma, the same age within error. One of the two studied dikes matches this age, but the other is slightly younger, 517

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± 4 Ma. This suggests that the main magmatic pulse occurred at ca. 525 Ma and was followed by some minor sequels that lasted about 8 m.y. The other rocks in the same tectonic unit, the

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Bulautad gneisses hosting North Derraman and the Leglat schists hosting the Derraman Highs, are Archean.

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All facies of Derraman granites are hypersolvus, with sodic pyriboles or annitic biotite, accessory fluorite, and elevated HFSE and REE; so indisputably A type (see Bonin, 2007). More

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problematic is to classify them as either A1 or A2 subtypes (Eby, 1990; 1992), because most samples have Y/Nb around 1.2, the value considered by this author as the best between-group

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discriminant. Some samples plot well within the A1 field, but an equal number of samples also plot well within the A2 field (Fig. 3D). Remarkably, whereas the former are those with mol. [Na2O+K2O]/Al2O3 < 1 and the lowest HFSE and REE contents, the later are just those with mol. [Na2O+K2O]/Al2O3 > 1, Fe/Fe+Mg close to 1, and the largest HFSE and REE accumulations, that is to say, the most fractionated (Fig. 5A). Accordingly, we suggest that values of Y/Nb > 1.2 were acquired during extreme fractionation due to the effect of accessories with very different Y/Nb (samarskite, aeschynite), and that all Derraman magmas originally had chemistry similar to Eby’s A1-type granites. The genetic models for A-type granites can be summarized as follows: (i) partial melting of the residue remaining from generation of an I-type granite (Collins et al., 1982; Clemens et al., 1986), (ii) partial melting of crustal igneous rocks of tonalitic to granodioritic composition

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ACCEPTED MANUSCRIPT (Creaser et al., 1991), (iii) fractionation from mafic magmas variably contaminated with crust materials (Eby, 1990; Turner et al., 1992) (iv) partial or total melting of lower crust fenites

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metasomatised by mantle-derived melts and fluids (Martin, 2006).

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In the present case the first two hypotheses can be excluded because they produce metaluminous post-orogenic A2 granites rather than anorogenic peralkaline A1 granites. We may

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also rule out that Derraman granites might represent extreme differentiates of mantle-derived

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magmas, firstly, because of the lack of coeval mafic rocks, secondly, because the granites have

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ε(Nd)525Ma around -5 to -6 and TCR ≈ 1.83 Ga, which is not consistent with of 525 Ma juvenile

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mantle magmas. The negative ε(Nd)525Ma and the Nd model ages much older than the

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crystallization ages can apparently only be explained in three ways. Either the granites were

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derived from 525 Ma juvenile magmas mixed with Archean crustal components, are 525 Ma melts derived from a ca. 1.8-1.9 Ga crustal source, or are 525 Ma melts derived from materials metasomatised by an “anomalous” mantle component. Numerical modeling shows that the first alternative is unlikely because perceptibly changing the Nd isotope composition of REE-rich Cambrian magmas by assimilation of REE-poor Archean materials, mostly TTG gneisses, requires unrealistically high degrees of assimilation (≥80%) the resulting hybrid magma would, necessarily. be REE-HFSE-poor and calc-alkaline,

thus quite different from the Derraman REE-HFSE—rich aegirine-riebeckite hypersolvus granites (Fig. ). Accordingly, the second alternative, that is to say, melts derived from an old crustal source, seems preferable.

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ACCEPTED MANUSCRIPT Martin (2006) proposed that granites such as Derraman are related to mantle-derived melts and fluids in a zone undergoing extension. This causes the refertilization of the lower and middle

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crust directly above the newly metasomatised upper mantle. The subsequent fusion of the so-

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formed crustal fenites then produces the A-type granite magmas. If the metasomatising fluids have a Nd isotope composition similar to a normal lithospheric mantle and the fenites melt

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shortly after their formation, the resulting A-type granite magmas would have ε(Nd)T around

zero or slightly positive and TCR close to the zircon crystallization age. If, on the other hand, the

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fenites melt long after their formation, or the metasomatic fluids that generated them derived

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from an old lithospheric metasome, the resulting magmas would have markedly negative ε(Nd)T

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and TCR >> zircon U-Pb age such is the case of Derraman.

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Accordingly, we suggest that Derraman magmas derived from melting of crustal fenites during the ubiquitous Cambrian rifting event that affected this part of northern Gondwana (e.g. Montero et al., 2009; Alvaro et al., 2014). At present, however, we cannot decide whether the “old” Nd isotope signature of Derraman granites resulted from melting of an old (Paleoproterozoic) fenite source or reflects the signature of the mantle-derived metasomatising fluids. In any case, however, it indicates the action of an alkaline metasomatism in the lithospheric mantle underlying the Derraman-Bulautad-Leglat unit during the Paleoproterozoic. Ongoing studies on neighboring mafic alkaline and carbonatite massifs of would help to solve this question.

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ACCEPTED MANUSCRIPT 8.2 Regional implications The WAC east of the studied Derraman-Bulautad-Leglat (DBL) unit was essentially stable

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from the Archean to the Cambrian, as shown by the thin veil of Meso- to Neoproterozoic and

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concordant Cambrian deposits preserved south and north of the Reguibat Rise beneath the unconformable Upper Ordovician periglacial sandstones (Ghienne, 2003; Deynoux et al., 2006;

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Rooney et al., 2010). In contrast, the studied DBL unit of the eastern Oulad Dlim massif includes

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the Derraman aegirine-riebeckite A1-type granites dated at 525-517 Ma, which record a Cambrian rifting environment. Therefore, the Bulautad gneisses and Leglat metapelites they

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intrude, dated at ca. 3.12 Ma and 2.84 Ma respectively, apparently originate from an external part of the Archean nucleus, far away from the stable part of the craton. This is consistent with the

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occurrence of a basal thrust unit (Tiznigaten Quartzites, probably Cambrian-Ordovician; Villeneuve et al., 2015) between the DBL unit and the folded, autochthonous, Paleozoic cover of

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the Reguibate Rise. Eastward transport of the DBL unit may be estimated at 20 km at least, comparable with the displacement proposed by Caby and Kiénast (2009) for the westernmost External Units of the Central Mauritanides. The location of the west boundary of the Archean nucleus within the Ouled Dlim nappe stack cannot be established yet. Gärtner et al. (2013) obtained 1400-1000 Ma zircon ages in the westernmost part of the massif (Oued Togba and Sebkha Gezmayet Units) and argued that they represent an exotic terrane from Avalonia-Meguma origin. In the axis of the massif (Adrar Suttuf, Dayat Lawda Unit), Gärtner et al. (2014) dated the dominantly mafic magmatic rocks at ca. 635 and 605 Ma, and assumed they represent a Cryogenian-Ediacaran island arc, i.e. an element of the Pan-African belt, as previously suggested by Villeneuve et al. (2006) and

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ACCEPTED MANUSCRIPT reaffirmed by Villeneuve et al. (2015). However, tthese rocks are strongly metamorphosed in the granulite facies, and besides granulitic-looking Pan-African zircons they also contain 2.43 Ga

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magmatic-looking zircons (Montero et al., 2014). Thiscast doubt on whether this belt consists of

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reworked Archean terranes with some input of juvenile material “à la” Sahara Metacraton

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(Abdelsalam et al., 2002; Liégeois et al., 2012), or is a totally juvenile Neoproterozoic crust.

9. Conclusions

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We obtained robust SHRIMP ages for the rocks forming the Derraman-Bulautad-Leglat (DBL) unit near the bottom of the Ouled Dlim nappes thrust over the Reguibat Rise of the WAC.

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The ca. 525 Ma peralkaline hypersolvus A1-type Derraman leucogranites form two km-sized

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independent bodies, North Derraman and Derraman Highs, and a few small satellites around the latter. The North Derraman body is emplaced in the ca. 3.12 Ga Bulautad gneisses. The

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Derraman Highs body forms a 200 m sheet-like body emplaced within the ca. 2.8 Ga Leglat schist that overlie the Bulautad gneisses. The Derraman granites are enriched in REE and HFSE and have negative ε(Nd)525Ma around -

5 to -6 and TCR ≈ 1.83 Ga, much higher than their zircon U-Pb crystallization age. Derraman magmas were generated in a Cambrian intraplate rifting environme. Their magmatic source consisted of lower crustal fenites. Their the “old” Nd isotope signature may reflect either that the crustal fenite source existed as such since the Paeloproterozoic, or that the mantle-derived metasomatic fluids that caused the fenitization derived from an old lithospheric metasome.

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ACCEPTED MANUSCRIPT The new SHRIMP data for the Archean rocks hosting Derraman has permitted us to separate the Derraman-Bulautad-Leglat (DBL) unit, thrust over the Tiznigaten unit.

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The Derraman-Bulautad-Leglat unit must have been brought closer to the stable Reguibat Rise

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by a few tens of kilometers at least, consistent with the occurrence of the intermediate Tiznigaten

and the folded Paleozoic cover of the Reguibat Rise.

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Quartzites low grade metamorphic unit (Cambrian-Ordovician?) pinched between the DBL unit

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The Derraman granites are strikingly similar to the rift-related Cambrian-Ordovician granites of Iberia (Montero et al., 1998; 2009), also emplaced at the NW border of Gondwana.

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Understanding whether they are connected and, if so, the link between them would help to understand the Cambrian-Ordovician breakdown of northern Gondwana that generated many

Acknowledgments

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terranes that were later amalgamated in the West European Variscides.

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We are indebted to J.H. Scarrow for her help with the English, and to E. Rjimati and A. El Archi for their help during the initial stages of field work. The support from the Moroccan military during field work is also gratefully acknowledged. We are grateful for the fruitful comments of the reviewers, Jean-Paul Liégeois and Jacobo Abati, that helped to greatly improve the manuscript. This paper has been financed by the Spanish grants CGL2013-40785-P and CGL2008-02864, and the Andalusian grant RNM2163. This is IBERSIMS publication nº XX.

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strength elements in peralkaline granitic rocks: The Galineiro orthogneissic complex, northwestern Spain. Canadian Mineralogist 36: 683-700.

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Montero, P.; Haissen, F.; El Archi, A.; Rjimati, E.; and Bea, F. 2014. Timing of Archean crust formation and cratonization in the Awsard-Tichla zone of the NW Reguibat Rise, West

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Precambrian Research 242: 112-137.

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African Craton. A SHRIMP, Nd-Sr isotopes, and geochemical reconnaissance study.

Montero, P.; Talavera, C.; Bea, F.; González-Lodeiro, F.; and Whitehouse, M. J. 2009b. Zircon geochronology and the age of the Cambro-Ordovician rifting in Iberia. Journal of Geology

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117: 174-191.

Moreno, J. A.; Molina Palma, J. F.; Montero, P.; Abu Anbar, M.; Scarrow, J.; Cambeses, A. et

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al. 2014. Unraveling sources of A-type magmas in juvenile continental crust: Constraints from compositionally diverse Ediacaran post-collisional granitoids in the Katerina Ring Complex, southern Sinai, Egypt. Lithos 192-195: 56-85. Rjimati, E.C., Zemmouri, A., 2002. Mémoire explicatif de la carte géologique du Maroc, feuille d’Awsard. Notes et Mémoires du Service géologique du Maroc, 439 bis. Rjimati, E., Zemmouri, A., Benlakhdim, A., Mustaphi, H., Haimouk, M., Hamidi, F., Amzarhrou, M., Esselmani, B., 2002a. Carte Géologique du Maroc, 1:50000, sheet Awsard. Notes et Mémoires du Service Géologique du Maroc, 439. Rjimati, E., Zemmouri, A., Benlakhdim, A., Sahara, M.I.D., Amzaghro, M., 2002b. Carte Géologique du Maroc, 1:50000, sheet Sdar. Notes et Mémoires du Service Géologique du Maroc, 364.

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ACCEPTED MANUSCRIPT Rjimati, E., Zemmouri, A., Benlakhdim, A., Sahara, M.I.D., Amzaghro, M., 2002c. Carte Géologique du Maroc, 1:50000, sheet Agalmin Twarta. Notes et Mémoires du Service

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Géologique du Maroc, 483.

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Rjimati, E., Zemmouri, A., Benlakhdim, A., Sahara, M.I.D., Amzaghro, M., 2002d. Carte

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Gjimogique du Maroc, 1:50000, sheet Sabkhat Lahmayda. Notes et Mémoires du Service Géologique du Maroc, 488.

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Rjimati, E., Zemmouri, A., Benlakhdim, A., Sahara, M.I.D., Amzaghro, M., 2002e. Carte

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Géologique du Maroc, 1:50000, sheet Agroun Fras. Notes et Mémoires du Service Géologique du Maroc, 490.

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Rjimati, E., Zemmouri, A., 2011. Carte Géologique du Maroc au 1/50 000 Feuille Oum Tlayha, Notice Explicative. Notes et Mémoires du Service Géologique du Maroc, 510 bis, 94 pp.

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Rjimati E.C., Michard A., Saddiqi O., 2011. Anti-Atlas occidental et Provinces sahariennes, in Michard et al. (Eds), Nouveaux Guides géologiques et miniers du Maroc, vol.6. Notes et Mémoires du Service géologique du Maroc 561: 9-95. Rogers, J. J. W.; and Adams, J. A. S. (1969). Uranium. In K. H. Wedepohl (Ed.), Handbook of Geochemistry(II-5). Heildelberg: Springer-Verlag. Rooney, A.D. , Selby, D., Houzay, J.P., Renne, P.R. 2010. Re–Os geochronology of a Mesoproterozoic sedimentary succession, Taoudeni basin, Mauritania: Implications for basin-wide correlations and Re–Os organic-rich sediments systematics. Earth and Planetary Science Letters 289: 486–496

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ACCEPTED MANUSCRIPT Schofield, D. I.; Horstwood, M. S. A.; Pitfield, P. E. J.; Crowley, Q. G.; Wilkinson, A. F.; and Sidaty, H. C. O. 2006. Timing and kinematics of Eburnean tectonics in the central Reguibat Shield, Mauritania. Journal of Geological Society 163: 549-560.

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Sougy, J. 1962a. Contribution à l’étude géologique des guelb Bou Leriah (Region d’Aoucert,

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Sahara Espagnol). Bulletin de la Société Géologique de France 7: 436-455.

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Sougy, J. 1962b. West African Fold Belt. Geological Society America Bulletin 73: 871.

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Sougy, J. 1969. Grandes lignes structurales de la chaîne des Mauritanides et de son avant-pays

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(socle précambrien et sa coberture infracambrienne et paléozoïque), Afrique de l’Ouest. Bulletin de la Socié Geologique de France 11: 133-149.

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Sougy, J.; and Bronner, G. 1969. Nappes hercyniennes au Sahara espagnol méridional (tronçon

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nord des Mauritanides). V Coll. Géol. afric. Clermont-Ferrand, 9-12 avril. Ann. Fac. Sc.

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Univ. Clermont 41 (Geol. et Miner. fasc. 19): 75-76. Turner, S. P.; Foden, J. D.; and Morrison, R. S. 1992. Derivation of some A-type magmas by fractionation of basaltic magma: an example from the Padthaway Ridge, South Australia. Lithos 28: 151-179.

Villeneuve, M.; and Cornée, J. J. 1994. Structure, evolution and palaeogeography of the West African craton and bordering belts during the Neoproterozoic. Precambrian Research 69: 307-326. Villeneuve, M.; Bellon, H.; El, A., Abdelkrim; Sahabi, M.; Rehault, J.-P.; Olivet, J.-L. et al. 2006. Événements panafricains dans l’Adrar Souttouf (Sahara marocain). Comptes Rendus Geoscience 338: 359-367. Villeneuve, M., El Archi, A., Nzamba, J., 2010. Les chaînes de la marge occidentale du Craton Ouest-Africain, modèles géodynamiques. Comptes Rendus Geoscience 342 : 1–10.

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ACCEPTED MANUSCRIPT Villeneuve, M., Gärtner, A., Youbi, N., Archi, A.E., Vernhet, E., Rjimati, E., Linnemann, U., Bellon, H., Gerdes, A., Guillou, O., Corsini, M., Paquette, J-L., 2015. The Southern and

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doi: http://dx.doi.org/10.1016/j.jafrearsci. 2015.04.016

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Central parts of the“Souttoufide” belt, Northwest Africa. Journal of African Earth Sciences,

Whalen, J. B.; Currie, K. L.; and Chappell, B. W. 1987. A-type granites: geochemical

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characteristics, discrimination and petrogenesis. Contributions Mineralogy Petrology 95: 407-419.

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Youbi, N.; Kouyate, D.; Soderlund, U.; Ernst, R.E.; Soulaimani, A.; Hafid, A.; Ikenne, M.; El Bahat, A.; Bertrand, H.; Rkha Chaham, K.; Ben Abbou, M.; Mortaji, A.; El Ghorfi, M.;

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Zouhair, M.; El Janati, M., 2013. The 1750 Ma magmatic event of the West African Craton

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(Anti-Atlas, Morocco). Precambrian Research 236, 106-123.

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Figure Captions Figure 1: A, B: Location of the study area in the eastern unit of the Oulad Dlim Massif

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(Moroccan Mauritanides) thrust onto the WAC western margin (modified from Hollard et al., 1985 and Michard et al., 2010). C: Schematic geological map of the Derraman-Leglat

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area based on authors’ observations with data from Arribas (1968) and Rjimati and

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Zemmouri (2002). D: Idealized cross-section (modified after Michard et al., 2010) roughly following the red dashed line in B.

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Figure 2: A). Derraman Highs view from the North Derraman body. Note the granites on top overlying the Leglat schists. B) Alternating bands of fine-grained and coarse-grained

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granites are a result of narrow ductile shear zones and intense mylonitization. C) Intrusive contact of Derraman Highs body with the Leglat schists near the south contact of Derraman Highs. D) Detail of C showing a pegmatoid vein. E) Dikes of peralkaline granite within the

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schists at the base of Derraman Highs. Note the folded xenolith marked with a white arrow.

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minerals.

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F) Mesoscopic aspect of the Derraman granites; note the foliation marked by the dark

Figure 3: A) Major element discriminant diagram for granites with SiO2 > 70 wt.% (Bea et al., 2000). B) and C) Trace element discriminant diagrams for A-type granites of Whalen et al., (1987). Note how the Derraman granites plot in the A-type field. D) A-type granite discriminant plot of Eby (1992). Only the most agpaitic samples plot within the A-2 field. It seems that the Y/Nb > 1.2 resulted from extreme fractionation and is not a primary feature of the magmas, which are of A1-type. Figure 4: Chondrite-normalized plots for Derraman granites. The most enriched samples are found in Derraman Highs and related dikes. The host gneisses and schist contain notably lower concentrations of REE thus it is unreasonable to attribute the higher-thancrystallization Nd model ages of granites to contamination with their Archean hosts. Figure 5: Selected geochemical relationships in Derraman granites. A) Variations with the agpaitic index. Note how Ga/Al, Y/Nb, Zr, Nb, Y and the LREE increase with increasing peralkalinity. B) Variations with K/Rb. Note also the good correlation between K/Rb, which decreases with increasing differentiation, and Be, U, Th, and the HREE. 35

ACCEPTED MANUSCRIPT Figure 6. Cathodoluminiscence images of selected zircon grains from the studied samples. Note the morphology of the Derraman zircons typical of peralkaline rocks. Figure 7: Wetheril concordia plot for Derraman granites. The main magmatic pulse occurred at

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ca. 525 Ma and was followed by some minor events for at least 8 m.y.

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Figure 8: Wetheril concordia plot for the Bulautad gneisses, host of North Derraman, and the Leglat schists, host of Derraman Highs. The detrital zircons of the Leglat schists show

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three age groups that peak at 2.84 Ga, 2.91 Ga, and 3.15 Ga. The last two groups include the two zircon populations found in the Bulautad gneisses (Montero et al., 2014) so

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indicating that they were probably a component of the sedimentary source. The component that supplied the 2.84 Ga has not yet been identified.

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Figure 9: 87Sr/86Sr vs. 87Rb/86Rb and 143Nd/144Nd vs. 147Sm/144Nd plots for the Derraman granites. They scatter around the 220 Ma rather than the 525 Ma reference lines, indicating that the

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Rb-Sr system was reset long after crystallization, perhaps during tangential deformation.

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The Sm-Nd system, on the other hand, does not seem disturbed; the scatter around the 525 Ma reference line is most likely caused by the REE residence in accessory minerals with

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very different Sm/Nd.

Figure 10: Mixing lines for a rock with a composition identical to the average of this area Archean rocks and three different juvenile 525 Ma Nd-Sm-rich magmas with Nd model age of TCR = 620 Ma, slightly older than the zircon crystallization age. These juvenile magmas are assumed to have similar Sm/Nd to Derraman and absolute concentrations x1 (black, short dashes), x3 (blue, long dashes) and x5 (red, solid). The numbers along the lines indicate the fraction of crustal contaminant. Note that in no case is a composition similar to the Derraman granites produced.

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Table 1

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Derraman Highs Granites REG81 REG82 REG83 -14.5445 -14.5543 -14.5677 22.6076 22.6051 22.6152 74.56 75.23 76.33 0.41 0.26 0.19 10.59 11.34 11.58 3.77 3.01 2.09 0.23 0.05 0.09 0.08 0.06 0.05 1.06 0.46 0.43 3.87 3.84 3.79 4.24 4.91 4.75 0.05 0.03 0.03 0.69 0.28 0.87 99.55 99.47 100.20 10.7 8.5 29.3 60.5 65.1 107 0.6 0.16 1.22 1.81 3.48 13.1 42.9 24.7 20 265 266 160 4.58 3.83 2.24 18.5 4.0 4.51 5.62 3.92 3.19 2.56 2.25 1.81 5.01 5.05 3.75 51.7 99.5 105 35.0 40.3 29.8 64.6 65.3 78.7 60.9 66.9 83.5 3.16 3.51 6.03 734 675 616 15.4 18.5 22.3

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REG130 -14.5487 22.6169 75.13 0.19 12.46 2.2 0.02 0.06 0.38 4.10 4.64 0.06 0.26 99.50 12.8 63.6 0.33 5.56 9.44 301 3.81 4.5 2.5 1.03 3.47 112 29.4 130 88.5 5.21 903 31.5

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REG124 -14.5308 22.6694 76.09 0.21 11.67 2.14 0.04 0.07 0.39 4.07 4.45 0.03 0.16 99.32 5.71 43.4 0.3 2.58 4.82 313 2.97 3.7 2.66 0.98 3.32 102 29.7 37.3 40.1 2.21 554 17.6

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REG122 -14.5301 22.6708 76.12 0.19 11.69 1.93 0.06 0.06 0.43 4.15 4.63 0.04 0.17 99.47 7.99 57.1 0.23 2.89 6.17 370 3.57 3.97 2.58 1.01 3.13 109 32.1 57.0 48.9 2.63 535 17.6

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North Derraman Granites REG121 REG125 lon -14.5185 -14.5424 lat 22.6597 22.6664 SiO2 75.33 74.7 TiO2 0.20 0.25 Al2O3 11.94 11.61 FeOtot. 2.22 2.27 MgO 0.07 0.13 MnO 0.06 0.06 CaO 0.64 1.18 Na2O 4.13 4.39 K 2O 4.43 4.06 P2O5 0.03 0.04 LOI 0.37 0.74 total 99.42 99.43 Li 3.3 9.27 Rb 48.9 68.8 Cs 0.44 0.42 Be 3.13 4.8 Sr 8.7 28.7 Ba 344 271 Sc 2.09 4.47 V 2.2 6.52 Cr 2.7 2.92 Ni 1.05 1.65 Cu 2.98 3.49 Zn 121 124 Ga 33.9 30.9 Y 57.5 76.5 Nb 45.8 55.1 Ta 2.53 3.55 Zr 462 577 Hf 10.4 13.4

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Geographic Coordinates (dd.dddd) and Chemical Composition of Derraman Granites and Host Rocks. Major Elements are expressed in weight percent. Traces in ppm.

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REG84 -14.5806 22.629 74.17 0.33 11.12 3.99 0.01 0.09 0.70 3.51 4.51 0.04 0.19 98.66 0.91 87.4 0.25 7.99 7.3 311 3.05 7.04 2.67 1.83 3.47 186 32.8 42.8 82.4 5.05 1232 26.6

REG131 -14.5528 22.6171 73.33 0.27 12.46 2.34 0.16 0.08 0.83 4.13 4.89 0.05 0.46 99.00 5.15 76.8 0.83 6.47 21 376 2.82 7.93 4.21 2.36 6.02 74.1 28.6 68 53.6 3.91 504 15.6

REG132 -14.5466 22.6708 75.11 0.24 11.84 2.44 0.10 0.05 0.29 4.03 4.81 0.06 0.25 99.22 15.0 68.9 0.47 4.02 5.6 291 2.52 5.52 2.74 1.42 3.41 122 30.4 22.8 54.8 2.75 718 15.6

REG133 -14.5919 22.6304 74.85 0.26 10.85 3.32 0.02 0.08 0.77 3.59 4.37 0.02 0.85 98.98 0.43 67.4 0.17 4.85 6.6 90 3.24 1.79 2.12 0.91 4.13 151 33.2 33.3 62.8 3.85 827 12.4

REG135 -14.5787 22.632 75.89 0.20 8.65 6.79 0.02 0.11 0.05 3.57 3.96 0.02 0.17 99.43 1.15 89.2 0.18 17.7 8.2 182 3.56 2.51 2.6 1.15 4.55 340 46.4 458 165 9.48 2861 43

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2.05 9.82 0.37 15.3 3.24 12.5 46.5 116 10.4 36.1 8.0 0.99 7.64 1.35 9.2 2.07 5.91 1.00 6.27 0.91

REG140 -14.554

REG134 -14.5788

REG141 -14.5708

lat

22.6317

22.6317

22.6341

22.63

22.63

22.6236

22.6219

22.6217

22.6322

22.6177

SiO2 TiO2 Al2O3 FeOtot. MgO MnO CaO Na2O K2O P2O5 LOI total

75.42 0.33 10.04 4.13 0.03 0.08 0.18 3.95 4.40 0.02 0.33 98.91

76.5 0.25 10.07 3.72 0.02 0.1 0.26 3.24 4.46 0.03 0.23 98.88

77.09 0.13 10.62 2.7 0.01 0.05 0.17 3.80 4.44 0.01 0.21 99.23

76.48 0.19 11.38 1.96 0.04 0.04 0.3 3.83 4.56 0.04 0.28 99.10

75.85 0.36 10.01 4.79 0.01 0.1 0.18 1.39 5.64 0.03 0.51 98.87

75.75 0.26 11.61 2.04 0.01 0.06 0.54 3.91 4.57 0.03 0.66 99.44

74.01 0.25 12.33 2.03 0.13 0.05 0.65 3.97 4.88 0.05 0.61 98.96

76.71 0.14 11.87 1.21 0.07 0.04 0.5 3.84 4.76 0.02 0.41 99.57

75.11 0.15 9.16 5.33 0.02 0.11 0.32 3.86 4.11 0.02 0.60 98.79

76.52 0.2 11.34 2.00 0.06 0.07 0.42 3.90 4.61 0.03 0.17 99.32

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REG139 -14.554

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0.32 8.53 0.65 21.6 4.22 11.9 59.6 128 14.9 55.8 11.8 1.57 9.71 1.34 7.39 1.6 4.83 0.8 6.55 1.28

REG127 -14.5502

4.09 0.7 4.44 10.1 0.25 0.56 7.32 25.9 2.06 3.83 15.3 21.7 97.9 61.2 191 136 20.5 14.1 73.1 51.2 13.1 11.7 1.77 1.29 10.9 12.9 1.61 2.29 9.66 16.5 2.01 3.81 5.35 11.2 0.89 1.79 5.93 12.3 1.11 2.19 Derraman Dikes REG128 REG129 -14.5511 -14.5509

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4.42 5.72 0.3 3.32 2.21 12.3 101 217 22.7 81.9 15.5 1.87 13 1.99 12.2 2.53 6.93 0.99 7.09 1.34

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0.98 9.23 0.35 22.9 4.67 20.5 70.1 159 17.7 64.4 15.9 0.85 15 2.66 17.9 3.87 10.6 1.69 10.2 1.44

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0.68 3.13 0.25 8.1 1.44 7.32 63.7 135 14.2 50.5 9.9 1.14 8.1 1.24 7.03 1.42 3.64 0.58 3.75 0.59

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0.52 0.99 0.28 3.39 5.13 2.72 0.29 0.35 0.29 14.4 14.4 8.4 1.88 3.54 1.92 9.85 13.9 12.7 74.7 70.1 59.5 167 150 125 16.9 15.7 13.4 60.5 55.4 48.4 12.4 12.2 10.4 1.47 1.31 1.30 10.5 10.8 9.2 1.63 1.77 1.51 9.63 11.1 9.29 1.97 2.37 1.95 5.15 6.44 5.13 0.80 1.05 0.8 4.98 6.57 4.89 0.77 1.01 0.73 Derraman Highs Granites REG137 REG136 REG138 -14.574 -14.574 -14.5638

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0.81 5.77 0.4 13.9 3.44 6.9 35.8 97 8.1 28.2 5.7 0.56 4.67 0.78 4.69 1.00 2.72 0.46 3.07 0.48 Schists REG30 14.4718 9 22.6113 1 86.33 0.09 7.92 0.74 0.40 0.03 0.66 0.01 2.26 0.03 1.65 100.12

0.34 6.59 0.39 21.2 3.25 17.3 94.4 203 21.7 80.2 15.6 1.62 11.8 1.54 6.52 1.15 3.01 0.53 3.75 0.62 REG126 -14.5578

0.42 25.4 0.51 45.3 7.25 37.0 191 558 48.8 186 42.4 5.75 40.2 6.8 44.5 9.54 25.7 4.13 24.8 3.62 Gneiss REG123 -14.5301

22.6533

22.6708

84.71 0.12 8.32 0.81 0.47 0.03 0.71 0.01 2.54 0.05 2.11 99.88

72.31 0.29 14.17 2.02 0.67 0.06 2.26 3.63 2.48 0.09 2.21 100.19

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4.46 82.1 0.7 9.87 26.2 465 3.9 5.39 2.67 1.05 6.56 50.9 24.5 104 87.1 4.71 190 5.29 1.64 6.74 0.39 20.8 3.71 22.7 40.1 80 8.5 28.4 7.3 0.46 7.86 1.52 11.3 2.66 7.86 1.36 8.54 1.20

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8.78 79.7 0.63 6.38 15.5 326 3.11 7.21 3.15 1.2 3.52 75.2 28.6 70.1 54.3 3.89 471 21.0 2.64 8.88 0.51 19.8 2.65 13.1 52.3 110 11.4 39.5 8.7 0.97 8.26 1.47 9.77 2.17 6.17 1.03 6.39 0.91

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2.09 56.6 0.23 5.27 6.0 165 3.83 3.72 2.69 0.99 3.55 82.1 28 44.2 45.9 2.87 638 21.3 3.5 2.04 0.38 14.8 1.97 9.91 64.7 141 15.3 54.7 11.2 0.67 9.15 1.41 8.06 1.59 4.13 0.70 4.18 0.61

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4.36 92.7 0.52 5.0 18.8 228 1.43 2.2 2.27 0.72 4.59 153 41.9 126 101 5.21 1588 22.2 1.74 8.22 0.74 38.5 3.02 24.0 146 425 34.8 130 27.3 2.57 22.2 3.32 18.9 3.93 10.9 1.87 12.0 1.87

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21.2 115 0.83 11.4 7.9 166 3.83 4.3 2.58 1.24 4.01 106 31.6 111 86.4 6.23 609 22.5 2.71 14.12 0.54 29.7 4.16 22.4 52.8 117 12.3 43.5 10 1.03 10.1 1.84 12.8 2.93 8.6 1.52 9.63 1.40

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0.43 120 0.27 16.6 11.0 468 2.61 0.56 2.36 0.97 2.17 186 35 260 145 8.78 1201 36.7 1.15 14.2 0.69 26.6 7.03 40.3 75 145 20.1 75.7 21.5 2.38 22.7 4.14 28.5 6.23 16.9 2.69 15.5 2.00

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6.09 76.3 0.26 5.34 7.6 136 2.84 2.39 2.53 4.34 5.3 203 37.8 110 79.7 5.53 1236 25.5 11.06 2.38 0.54 68.3 3.39 16.0 112 236 26.7 98.9 20.4 2.65 17.7 2.76 16.6 3.37 8.93 1.39 8.35 1.17

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14.7 68.8 0.17 4.37 7.6 188 4.56 3.58 2.64 0.85 4.07 236 39.9 144 98.1 4.84 1350 26.7 8.24 13.4 0.4 41.9 2.7 22.8 177 444 42.2 162 35.6 4.54 29.7 4.22 23.3 4.59 11.3 1.71 9.82 1.28

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Li Rb Cs Be Sr Ba Sc V Cr Ni Cu Zn Ga Y Nb Ta Zr Hf Mo Sn Tl Pb U Th La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

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0.47 90.4 0.15 9.1 7.7 114 2.19 1.0 2.58 0.67 4.03 279.9 43.2 221 111 6.2 1873 28.2 0.46 12.5 0.54 18.9 5.44 23.0 114 389 29.7 115 26.3 3.56 24.9 4.12 26.5 5.57 14.9 2.42 14.9 2.20

23.4 89.9 0.82 13.9 14.9 159 1.34 3.8 2.59 1.21 4.39 87.3 29.0 94.1 64.8 5.47 530 18.2 0.67 16.0 0.51 25.4 3.06 16.3 63.1 140 14.3 49.7 10.6 1.11 10.2 1.78 11.9 2.66 7.52 1.27 7.78 1.14

5.12 25.1 0.88 0.43 31.8 1202 1.48 9.18 14.7 10.4 2.09 13.4 7.75 4.93 1.95 0.18 94.3 2.7 0.12 0.78 0.25 8.65 0.41 5.94 16.7 27.6 2.88 10.5 1.54 0.54 1.24 0.18 0.81 0.17 0.42 0.06 0.42 0.06

6.23 29.3 1.02 0.25 44.7 1335 2.06 10.4 9.23 4.76 1.04 21.6 8.14 5.32 1.77 0.21 79.6 2.5 0.22 2.14 0.21 9.97 0.77 6.96 17.6 29.2 2.99 11.3 1.59 0.61 1.32 0.19 0.99 0.19 0.46 0.07 0.43 0.07

17.2 51.4 0.44 0.99 262 1108 4.03 20.2 7.64 7.67 6.79 41.4 17.5 6.12 5.92 0.45 155 4.2 0.16 0.77 0.30 10.4 1.72 12.67 18.9 43.4 4.35 15.2 2.83 0.58 1.97 0.27 1.21 0.22 0.51 0.07 0.43 0.07

ACCEPTED MANUSCRIPT Table 2a Chemical Composition and Structural Formulae (23 O) of Selected Amphibole Grains 3

4

5

6

7

50.62 0.13 2.07 34.83 1.51 0.68 2.68 5.31 0.93 0.32 0.00 7.995 0.005 0.380 0.015 0.000 4.598 0.354 0.091 0.453 1.108 1.562

51.16 0.12 1.62 34.83 1.53 0.64 2.30 5.54 0.81 0.27 0.00 8.000 0.000 0.299 0.014 0.447 4.106 0.355 0.085 0.386 1.308 1.694

50.39 0.16 2.07 34.46 1.72 0.67 2.91 5.31 1.11 0.36 0.01 7.961 0.039 0.346 0.018 0.000 4.551 0.405 0.090 0.492 1.097 1.589

49.72 1.15 1.70 33.76 1.68 0.83 4.15 4.54 1.24 0.39 0.05 7.873 0.127 0.191 0.137 0.000 4.469 0.397 0.111 0.703 0.991 1.694

50.54 0.14 1.86 34.64 1.62 0.67 2.95 5.24 1.03 0.35 0.00 7.994 0.006 0.341 0.017 0.000 4.580 0.381 0.089 0.500 1.092 1.592

50.69 0.15 1.93 34.62 1.62 0.63 2.71 5.31 1.02 0.33 0.01 8.000 0.000 0.358 0.018 0.042 4.526 0.380 0.084 0.458 1.133 1.591

51.71 0.06 1.38 34.92 1.65 0.64 2.11 5.86 0.57 0.36 0.01 8.000 0.000 0.251 0.007 0.690 3.826 0.380 0.084 0.350 1.412 1.763

0.402 0.250 0.652 0.193 0.014 0.918

0.515 0.208 0.723 0.174 0.000 0.923

0.345 0.113 0.458 0.177 0.002 0.910

0.517 0.187 0.704 0.161 0.000 0.928

0.372 0.162 0.534 0.133 0.000 0.920

50

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D

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0.530 0.223 0.753 0.180 0.003 0.918

8

0.492 0.205 0.697 0.165 0.001 0.922

9 rim

9 core

52.08 0.01 1.26 34.66 1.73 0.59 2.51 5.66 0.32 0.26 0.01 8.000 0.000 0.227 0.001 0.896 3.554 0.396 0.076 0.413 1.436 1.849

52.01 0.04 1.57 34.58 1.62 0.52 2.07 5.93 0.33 0.26 0.00 8.000 0.000 0.285 0.004 0.841 3.606 0.372 0.068 0.342 1.484 1.825

48.64 1.26 2.55 32.54 2.12 0.92 6.34 3.83 0.98 0.68 0.12 7.665 0.335 0.139 0.149 0.000 4.286 0.497 0.123 1.070 0.735 1.805

0.249 0.062 0.311 0.129 0.002 0.900

0.286 0.065 0.350 0.130 0.000 0.907

0.435 0.198 0.633 0.336 0.033 0.896

PT

2

AC CE P

SiO2 TiO2 Al2O3 FeO MgO MnO CaO Na2O K 2O F Cl Si IV Al VI Al Ti 3+ Fe Fe2+ Mg Mn Ca Na (B) Ca + Na (B) Na (A) K (A) sum (A) F Cl Fe/(Fe+ Mg)

1

ACCEPTED MANUSCRIPT Table 2b Chemical Composition and Structural Formulae (6 O) of Selected Clinopyroxene Grains

3

4

5

6

7

51.97 0.09 0.72 28.17 0.81 0.70 10.89 7.08 0.00 1.980 0.032 0.002 0.525 0.424 0.046 0.022 0.444 0.523 0.000 0.902

51.73 0.08 0.62 28.10 0.88 0.79 11.36 6.76 0.00 1.978 0.028 0.002 0.512 0.437 0.050 0.026 0.465 0.501 0.000 0.897

51.88 0.07 0.81 28.36 0.82 0.62 10.10 7.56 0.00 1.971 0.036 0.002 0.575 0.383 0.046 0.020 0.411 0.556 0.000 0.892

51.84 0.08 0.75 28.21 0.86 0.65 10.60 7.29 0.00 1.972 0.034 0.002 0.555 0.397 0.049 0.021 0.432 0.538 0.000 0.890

51.82 0.07 0.72 28.12 0.92 0.73 11.12 7.00 0.00 1.972 0.032 0.002 0.536 0.413 0.052 0.023 0.453 0.517 0.000 0.888

51.69 0.07 0.80 28.05 0.82 0.67 10.51 7.38 0.00 1.970 0.036 0.002 0.566 0.384 0.046 0.022 0.429 0.545 0.000 0.892

52.01 0.04 0.85 27.91 0.83 0.72 10.87 7.13 0.01 1.980 0.038 0.001 0.526 0.415 0.047 0.023 0.443 0.526 0.000 0.898

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8

PT

2

AC CE P

SiO2 TiO2 Al2O3 FeO MgO MnO CaO Na2O K 2O Si Al Ti Fe3+ Fe2+ Mg Mn Ca Na K Fe/Fe+ Mg

1

51.87 0.03 0.85 27.78 0.87 0.68 11.04 6.96 0.01 1.982 0.038 0.001 0.512 0.427 0.050 0.022 0.452 0.516 0.001 0.896

9

10

51.71 0.05 0.68 27.95 0.95 0.78 11.17 6.96 0.01 1.973 0.031 0.001 0.536 0.409 0.054 0.025 0.456 0.515 0.000 0.883

52.40 0.07 0.81 27.84 1.00 0.68 10.54 7.47 0.00 1.978 0.036 0.002 0.551 0.383 0.056 0.022 0.426 0.546 0.000 0.872

ACCEPTED MANUSCRIPT Table 2c Chemical Composition and Structural Formulae (22 O) of Selected Biotite Grains

3

4

5

6

7

36.09 1.85 10.88 35.23 2.93 0.52 0.19 0.02 8.59 0.06 0.57 0.05 5.918 2.082 0.020 0.228 4.829 0.715 0.073 0.034 0.007 1.795 0.005 0.296 0.015 0.871

36.56 1.75 10.78 34.77 3.00 0.50 0.03 0.03 9.02 0.08 0.56 0.02 5.975 2.025 0.051 0.215 4.750 0.729 0.070 0.006 0.009 1.879 0.006 0.288 0.007 0.867

36.38 2.27 10.56 34.44 2.98 0.43 0.03 0.03 9.10 0.21 0.62 0.02 5.956 2.044 0.000 0.279 4.714 0.726 0.060 0.004 0.009 1.900 0.015 0.319 0.006 0.867

36.42 2.00 10.69 34.56 3.08 0.38 0.05 0.03 9.15 0.26 0.60 0.02 5.955 2.045 0.014 0.245 4.724 0.749 0.053 0.009 0.009 1.907 0.018 0.312 0.005 0.863

35.95 1.99 10.45 34.66 3.28 0.43 0.06 0.04 8.56 0.28 0.59 0.03 5.935 2.065 0.000 0.248 4.783 0.805 0.059 0.010 0.012 1.801 0.020 0.308 0.009 0.856

36.38 2.20 10.57 34.64 2.98 0.39 0.01 0.03 9.09 0.28 0.60 0.01 5.953 2.047 0.000 0.270 4.738 0.728 0.055 0.002 0.009 1.896 0.020 0.310 0.004 0.867

36.41 1.99 10.57 34.36 3.00 0.41 0.00 0.02 9.13 0.23 0.51 0.03 5.979 2.021 0.024 0.246 4.716 0.733 0.057 0.000 0.007 1.912 0.017 0.266 0.008 0.865

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8

PT

2

AC CE P

SiO2 TiO2 Al2O3 FeO MgO MnO CaO Na2O K 2O Ba F Cl Si IV Al VI Al Ti Fe2+ Mg Mn Ca Na K Ba F Cl Fe/Fe+ Mg

1

36.27 2.08 10.60 34.69 3.00 0.40 0.03 0.02 9.10 0.22 0.53 0.03 5.949 2.051 0.000 0.256 4.756 0.733 0.056 0.005 0.006 1.902 0.016 0.277 0.009 0.867

9

10

36.75 2.18 10.54 33.91 2.82 0.38 0.00 0.06 9.20 0.16 0.59 0.02 6.022 1.978 0.056 0.268 4.644 0.689 0.053 0.000 0.020 1.921 0.011 0.303 0.006 0.871

35.91 2.16 10.87 33.39 3.70 0.39 0.24 0.06 8.04 0.15 0.51 0.02 5.916 2.084 0.026 0.268 4.598 0.908 0.055 0.043 0.018 1.688 0.011 0.267 0.005 0.835

ACCEPTED MANUSCRIPT

Table 3

REG84

schist REG30

schist REG126

gneiss REG123

23.987 0.782090 0.137

31.89 0.822367 0.123

2.852 0.822367 0.089

1.908 0.771143 0.085

0.588 0.725540 0.110

0.512023

0.512128

0.51209

0.510734

0.510696

0.519510

0.511652

0.511657

0.511665

0.509066

0.509096

0.508698

-6.55 1.07

-6.05 1.06

-5.94 1.30

-5.78 1.14

2.52 2.67

3.11 2.64

1.74 2.95

1.61 1.46

1.63 1.46

2.03 1.80

1.79 1.60

2.93 2.81

2.89 2.78

3.21 3.09

REG134

granites REG135

REG81

REG82

18.018 0.768689 0.122

27.748 0.811415 0.134

30.798 0.81114 0.135

26.013 0.796372 0.131

3.988 0.727273 0.103

7.503 0.751099 0.108

0.512032

0.512143

0.512160

0.512116

0.511981

0.511613

0.511682

0.511696

0.511667

0.511626

-6.81 1.23

-5.46 1.20

-5.19 1.18

-5.76 1.20

1.86 1.67

1.93 1.71

1.92 1.70

1.90 1.70

PT ED

MA

NU

SC

RI

REG122

CE

Rb/86Sr Sr/86Sr 147 Sm/144N d 143 Nd/144N d 143 Nd/144N dt ε(Nd)t TCHUR (Ga) TCR (Ga) TDM (Ga) 87

REG83

REG121

AC

87

PT

Sr and Nd Isotope Composition of Derraman Granites and Host Rocks.

53

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PT

ACCEPTED MANUSCRIPT

AC CE P

TE

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Graphical abstract

54

ACCEPTED MANUSCRIPT Highlights  Derraman granites were emplaced at ca. 525 Ma in Mesoarchean materials

TE

D

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They were generated from lower crustal fenites during the Cambrian rifting

AC CE P



PT

 They are hypersolvus aegirine-riebeckite high-SiO granites 2

55