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Metamorphic Response in the Damara Belt: Goscombe, Foster, Gray and Wade 2016

ELECTRONIC APPENDIX 2: ZIRCON AND MONAZITE U-Pb GEOCHRONOLOGY

Introduction

There is a paucity of direct metamorphic age determinations from metamorphic parageneses in most parts of the Damara Orogen, particularly in the Barrovian series orogenic margins. This study attempted to address this by undertaking a select number of in situ metamorphic monazite U-Pb age determinations by Ben Wade at Adelaide University (see below). These robust metamorphic age constraints along with literature U-Pb age determinations from metamorphic monazite and zircon in the Central Zone (e.g. Jung et al., 2000, 2001; Jacob et al., 2000) form the basis for characterising the age of peak metamorphism and matrix assemblages across the Damara Orogen (Appendix 1). This robust framework has been expanded further by less accurate indirect metamorphic age constraints. Minimum age constraints for metamorphism have been sourced from new U-Pb magmatic zircon ages undertaken by David Foster at Florida University (see below) and other intrusive ages available in the literature. Maximum limiting age constraints for metamorphism have been sourced from maximum deposition ages indicated by youngest detrital zircons, and minimum deposition ages where they exist. Ar-Ar muscovite and hornblende cooling ages in the literature (Foster et al., 2009; Gray et al., 2006), indicate the minimum age of metamorphism in rocks formed above ~400-500 ºC, and peak metamorphic ages in low-grade phyllites.

A systematic detrital zircon study undertaken by Foster has established that the Damara Sequence consists of two isolated marginal basin sequences of different provenance, deposited on the Congo and Kalahari cratonic margins (Newstead, 2010; Foster et al., 2014). The separation of these two cratonic margins, as well as the location of the suture between them at the Uis Pass Line, has been verified by the available Nd data from meta-sediments (Foster et al., 2014; Goscombe et al., 2003, 2005), which are collated below. The detrital zircon study is the first undertaken in the Damara Orogen and so further refines stratigraphic relationships and the age range of different sedimentary units. Crucially for this metamorphic study, the zircon separates for the detrital study have also been utilized further for metamorphic age constraints in three ways. (1) Metamorphic zircons were returned in higher-grade samples from the Central Zone and Southern Zone. (2) Maximum limiting age of metamorphism is constrained by the youngest detrital zircons in the population. (3) Detrital metamorphic zircon grains have been found in zircon populations from molasse samples. These constrain the age of metamorphic events experienced in the source region within the internal parts of the Damara Orogen. New age determinations generated specifically for this metamorphic study are described below and all other published age determinations from the Damara Orogen are collated in Appendix (1).

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Monazite Geochronology Analytical Procedures

In situ U-Pb monazite geochronology was undertaken via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) following the method of Payne et al (2008). Dr Ben Wade at Adelaide Microscopy in the University of Adelaide undertook analyses. Thin sections of samples SZ44a, BG6-94A, BG9-345A, SZ41A, SMZ1, BG14-599, BG14-368, BG14-475b, BG14-494b, BG14-537 and BG13-214 were imaged on a Philips XL30 SEM using a back-scattered electron detector (BSE) in which the presence, textural location, and compositional zonation of monazite grains were determined. U-Pb analyses were carried out on an UP-213 New Wave Nd-YAG laser attached to an Agilent 7500cs ICP-MS. Ablation was conducted in a helium atmosphere after which argon gas added immediately after the cell to aid transport of material. A spot size of 12-15 micron was chosen depending on size of monazite grains, with a laser frequency of 4 Hz resulting in an average fluence of 6 J/cm2. A single analytical spot consisted of a 50s gas blank followed by 40s of data acquisition with the laser firing. Measured isotopes were 204Pb, 206Pb, 207Pb, and 238U with dwell times of 10, 15, 30, and 15 ms respectively. Mass 204Pb was measured as a monitor of common lead content, and due to the unresolvable isobaric interference of 204Hg on 204Pb common lead corrections were not conducted.

Age calculations were carried out using the data reduction software Glitter developed by Macquarie University, Sydney. Down-hole element fractionation was corrected in the Glitter software via the use of the external monazite standard Madel (thermal ionization mass spectrometry (TIMS) normalization data: 207Pb/206Pb age = 491.7 Ma; 206Pb/238U age = 514.8 Ma; 207Pb/235U age = 510.4 Ma; Payne et al. 2008), with an overestimated absolute uncertainty of 1% assigned to each normalisation age. Accuracy was verified using an in-house monazite of known age (94-222/Bruna-NW, c. 450 Ma; Payne et al. 2008), and the distributed monazite standard 44069 (U-Pb ID-TIMS age 424.9±0.4 Ma). Over the course of the study the average external precision of the Madel standard was ±10 for 207Pb/206Pb, ±3 for 206Pb/238U, and ±3 for 207Pb/235U (2σ; n=31). The weighted average ages for 94-222/Bruna-NW were 460±12 for 207Pb/206Pb, 455±5 for 206Pb/238U, and 454±3 for 207Pb/235U (95% confidence; n=20). The weighted average ages for 44069 were 424±9 for 207Pb/206Pb, 426±2 for 206Pb/238U, and 425±2 for 207Pb/235U (95% confidence; n=51).

Due to the unresolvable 204Hg on 204Pb interference, uncorrected isotope ratios are used for all reported age calculations, with concordia plots generated using Isoplot/Ex 3.71 (Ludwig, 2008). Intercept ages are calculated for samples SZ44a, BGD06-94A, BG9-345A, and SZ41A via linear Tera-Wasserburg regression, with decay-constant errors propagated. Weighted average age calculations (at 95% confidence) have been performed for sample SMZ1 using uncorrected 206Pb/238U ratios.

Monazite Sample Descriptions

Sample BG6-94a

From OPN1 drill core at 170.5 m depth, on Okaputa Farm at longitude 17.06727º, latitude -20.05394º. In fareast profile at -175 km from Okahandja Lineament. Damara Sequence in Otavi Domain in the Northern Zone. Minerals analysed with PT calculation available. Microphotographs available. Garnet-kyanite-biotite metapelite schist. Coarse-grained metapelite schist with pre-kinematic 1 mm garnet porphyroblasts enveloped by the main foliation. Main matrix foliation consists of kyanite, orange biotite, quartz, plagioclase, monazite and pyrite. Kyanite laths envelop garnets. No staurolite confirmed by electron microscope. Garnet contains plagioclase and rare calcite inclusions. Biotite is partially retrogressed to chlorite. Plagioclase is rarely enclosed by kyanite coronas. Monazite found in SEM.

SMG: pl-carb inclusions > qtz-pl-bt-ky-sill?-py-mnz foli > grt porph

Sample BG9-345a

From 31.5 km in central profile and 10,000 m from granite. Swakop Group: Kuiseb Formation in South Okahandja Zone. Minerals analysed with PT calculation available. Microphotographs and bulk composition available. Garnet, staurolite, biotite, muscovite, quartz and plagioclase metapelite

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schist with medium-grained, well-aligned biotite in polygonal granoblastic annealed quartz-plagioclase matrix with no grainshape. Matrix foliation consists of orange brown biotite1, quartz, oligoclase plagioclase and zircon. Biotite1 is zoned with annitic biotite cores and siderophyllitic biotite rims. Matrix is over-printed by siderophyllitic biotite2 blocks, which are over-grown by Fe-staurolite porphyroblasts, which are over-printed by idioblastic Mn-Mg-almandine garnet porphyroblasts that are overgrown by Na-muscovite laths and sieve andalusite. Staurolite has few inclusions and preserves main foliation inclusion trails. Garnet porphyroblasts are small and free of inclusions. Muscovite laths are large and over-grow the main foliation and resorb staurolite margins. Large sieve like andalusite overgrows and slightly resorbs staurolite and overgrows garnet, and biotite1, biotite2 and quartz define inclusion trails. Muscovite and andalusite are in equilibrium as symplectite intergrowths. There is rare chlorite growth after andalusite. Garnet zoning shows atypical growth.

SMG: bt1-qtz-pl-zrn foli > bt2 > st porph > grt porph > ms-and intergrowths > chl retro

Sample SMZ1

From 105 km in east profile. Duruchaus Formation in North Southern Margin Zone. Minerals analysed with PT calculation and garnet profile available. Microphotographs available. Garnet-staurolite metapelite. Early fine-grained muscovite, ilmenite and quartz foliation is over-printed by garnet, Fe-staurolite and green siderophyllitic biotite porphyroblasts. Staurolite is over-grown by large post-kinematic Mg-almandine garnet idioblasts with no inclusions. Biotite is partially retrograded by corundophilite chlorite. Garnet zoning shows atypical growth.

SMG: ms-qtz-ilm-rt(foli) > bt-st-ilm(porph) > grt(big porph) > chl

Sample SZ41a

From 51 km in west profile. Damara Sequence in North Southern Zone. Minerals analysed with PT calculation and garnet profile available. Microphotographs, bulk composition and BSE image available. Metapelite schist with matrix foliation consisting of quartz, siderophyllitic biotite, albite plagioclase1, kyanite, tourmaline and Na-muscovite. Kyanite and biotite are in textural equilibrium. Matrix is over-grown by idioblastic Mn-Mg-almandine garnet porphyroblasts with few inclusions. Fe-staurolite and ilmenite porphyroblasts are latest formed and over-print the matrix and contain inclusions of garnet, albite plagioclase and ilmenite. Ilmenite has rutile exsolution lamellae. Staurolite is retrograded by chlorite and muscovite2 growth on margins and moats. Matrix plagioclase1 is zoned. Plagioclase2 coronas enclose muscovite grains. Latest formed is late ripidolite chlorite clots. Garnet zoning shows typical growth and diffusion rim.

SMG: pl-bt-ky-tur(foli) > grt(porph,incs) > st-ilm(porphs) > ms > rt(exsoln) > pl(coro) > chl

Sample SZ44a

From 49 km in west profile. Damara Sequence in North Southern Zone. Minerals analysed with PT calculation available. Microphotographs available. Metapelite schist with garnet, staurolite and kyanite porphyroblasts. Early fine-grained main foliation consists of muscovite and quartz with biotite, kyanite, oligoclase plagioclase and Mn-ilmenite. Main foliation is crenulated with siderophyllitic biotite growth axial planar to crenulations. Mg-Mn-almandine garnet and Fe-staurolite porphyroblasts are post-kinematic and over-print the main foliations and crenulations. Staurolite may be partially over-printing garnet. There are some late-stage muscovite2 laths with Na-muscovite rims and retrograde ripidolite chlorite. Garnet zoning shows atypical growth and diffusion rim.

SMG: pl-ms(foli) > ky?-bt(cren) > st-grt-kyn?-ilm(porph) > ms > chl(retro)

Sample BG14-368

From contact aureole metapelite on the western margin of West Ugab Granite, at longitude 013.79477º east, latitude -21.10838º south. Medium biotite-muscovite schist with flat 3mm cordierite and andalusite porphyroblasts. Fine-grained aligned polygonal granoblastic schist. Main foliation matrix consists of: quartz, K-feldspar, unverified minor plagioclase, minor muscovite

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(unverified), dominant blocky straw to brown siderophyllite biotite1. Main foliation crenulated orthogonal to main foliation. Biotite2 growth within and parallel to crenulation forming accumulation seam. Crenulations envelop cordierite and andalusite poikiloblasts. Rare fresh cordierite is poikiloblastic, interstitial XMg=0.69-0.70 with minor Mn-cordierite end-member. Rare fibrolite grew across cordierites and main foliation. Rare early andalusite poikiloblasts have not been verified. Rare unknown opaque, calcite? and 20um monazite. Garnet is absent.

SMG: qtz-pl?-kfs-bt-ms?-op S4 main foliation > S4 and?-crd porphs > fib, S7 bt cren

Sample BG14-475B

From contact aureole metapelite in subsurface granite aureole northeast of the West Ugab Granite, at longitude 013.85742º east, latitude -21.09100º south. Very fine foliated S2 matrix with thermal overprint of blocky siderophyllitic biotite laths and large cordierite (XMg=0.63-0.65 with some Mn-crd) 5-8mm in outcrop and S7 biotite crenulation seams. Cordierite predates andalusite in outcrop? Fine S2 foliation is parallel to bedding: muscovite, quartz, rare plagioclase (not confirmed), ilmenite (with 3% hematite, 8% Mn-ilm) and minor brown siderophyllitic biotite1. Stubby biotite2 laths are straw to orange-brown and mostly orthogonal to bedding and also random. Late ripidolitic chlorite laths grew across the biotite2 laths. Cordierite and andalusite are large poikiloblastic porphyroblast blobs and also replace pelite beds. Cordierite and andalusite overgrows the S2 foliation and is overgrown by the biotite2 blocks. S7 is spaced late discrete crenulation planes. Biotite3 plates grow in the S7 crenulation plane and are parallel to it, forming a biotite accumulation S7 seam. S7 crenulates S2 and biotite2 laths appear to post-date S7 but not conclusive. Chlorite laths are post-S7. Small 10um monazite. All muscovite in main foliation, no late muscovite.

SMG: qtz-pl-ilm-bt1-sericite S2 main foliation > early S4 crd porphs >? S4 and porphs > S4 bt2 laths > S7 bt3 cren (or laths pre-S7?) > chl laths

Sample BG14-494B

From probable contact aureole or regional metamorphic parageneses, near Strathmore Granite, sampled from Dead Sea mine pit at longitude 014.20247º east, latitude -21.78435º south. Coarse-grained well aligned real polygonal granoblastic metapelite schist. Matrix consists of well aligned straw to orange siderophyllitic biotite, equant polygonal granoblastic quartz and andesine plagioclase with lower Ca in rims. Muscovite is large late plates across foliation. Metamorphic monazite up to 20um in size. Detrital zircons present. Garnet occurs as small equant idioblastic porphyroblasts that grew across the biotite foliation and muscovite laths. Minor round quartz inclusions in garnet. Garnet has weak inverse growth zoning of: alm=49 to 47.7%, py=13% to 9%, grss=2.6 to 2.5%, spss=35 to 40%, indicating late growth during cooling through the peak. Rock devoid of opaques.

SMG: qtz-pl-bt S4 matrix foliation > S4 ms plates > S4 grt porphs

Sample BG14-537

From contact aureole metapelite on eastern margin of Baddocks Bay Granite at longitude 013.88752º east, latitude -21.50850º south. Coarse-grained, static contact metamorphosed metapelite with random polygonal granoblastic matrix. Matrix consists of straw to brown siderophyllitic biotite, detrital zircon, quartz, oligoclase plagioclase with lower Ca in rim, unknown opaque. Matrix also contains polygonal granoblastic poikiloblastic muscovite. Matrix andalusite grains are smaller than muscovite poikiloblasts. Andalusite enclosed by muscovite moats. Muscovite laths resorb andalusite leaving small relict andalusite inclusions. Thus muscovite poikiloblasts post-date andalusite. Some biotite is replaced by retrograde chlorite. Monazite grains are ~20um.

SMG: qtz-pl-bt-op-and S4 matrix > S4 ms porphs > chl retro

Sample BG14-599

From garnet-cordierite metapelite granulite in North Central Zone, sampled from west Omaruru River at longitude 014.59990) east, latitude -21.88720) south. Very coarse-grained polygonal granoblastic with straight margins. All phases in textural equilibrium, weak alignment of grainshape. Matrix consists of straw-brown to red-brown annite biotite, quartz, oligoclase plagioclase with

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higher Ca in rim, K-feldspar / microcline (none verified, but present in outcrop). Garnet is irregular shaped poikiloblasts with round biotite and quartz inclusions. Garnets zoned with inclusions clustered in core and fewer and larger inclusions in rim. Garnets are early formed matrix phase, with resorbed irregular shapes, have partial moats and embayments of plagioclase and cordierite-quartz-biotite symplectite and rarely totally occluded within matrix cordierite. Cordierite (XMg=73%) is a later formed matrix phase, coarse-grained and in equilibrium with matrix phase. Also overgrows some biotite and embayments and moats on garnet. Cordierites are largely devoid of inclusions. Some cordierites have concentrations of sillimanite inclusions in their cores. The sillimanite is fine grained in foliation trails that are crenulated and also in swirls. The sillimanite is occluded prograde sillimanite clusters that the cordierite nucleated around. Retrograde muscovite is rare on cordierite margin. Garnets are almandine with flat grt1 to inner portion of grt2 and resorbed margin: alm=67-68% with 71 to 76% rim, py=28-29% with 24 to 19% rim, grss=1.6-1.7% with 1.5 to 1.7% rim, spss=2.6% with 2.8-3.3% rim. Large monazite present.

SMG: sill incs > qtz-pl-kfs-bt-grt1-PM1 matrix > grt2 porph > crd-pl-qtz-bt moats, crd late matrix > bt foli > PM2-grt-crd-bt paratectic > bt foli

Sample BG13-214

From sub-surface granite contact aureole northeast of the West Ugab Granite, at longitude 013.83663º east, latitude -21.11043º south. Metapelite schist with quartz-psammite bedding bands. Matrix is unaligned polygonal granoblastic thermal metamorphism texture of quartz, common plagioclase, biotite, ilmenite, apatite and fine (<10 um) monazite. Monazite occurs in quartz-biotite bands and is uncommon in plagioclase-biotite bands. Muscovite appears to be absent in thin section, though late-stage muscovite laths and andalusite porphyroblasts occur in outcrop. Quartz grains have matrix biotite moats, which do not occur around plagioclase grains. Bedding is folded giving S5-S7 axial planar crenulations. Biotite-ilmenite accumulates as biotite-rich bands parallel to S5-S7 crenulations. The individual biotite plates are parallel to or at low-angles to the S5-S7 plane. There is also significant post-S5-S7 biotite growth oblique to orthogonal to the crenulations, indicating that the peak of metamorphism was after S5-S7 deformation. Idioblastic garnets (1-2 mm) have undeflected S5-S7 ilmenite inclusion trails that indicate that garnet growth and the peak of metamorphism was after deformation. Late stage chlorite laths grew across the S5-S7 crenulations.

SMG: qtz-pl-bt-ilm-ap S4 main foliation > S5-S7 bt-ilm cren > grt-bt-mnz [crd-and] porphs > chl, [ms] laths

Monazite Geochronology Results

Sample BG6-94a

Back-scattered electron image of representative monazite grains in sample BG6-94a indicate textural equilibrium with the matrix assemblage (Figure A3.1). Isotopic data from n=19 determinations in this sample give a 2 lower intercept Pb207/Pb206 age of 510±4 Ma with MSWD of 0.14 (Figure A3.2).

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Figure A3.1: Back scattered electron images of the textural settling of a selection of matrix monazite grains analysed for age determinations in Northern Zone sample BG6-94a.

Figure A3.2: Lower intercept age from monazite in Northern Zone sample BG6-94a, on Tera-Wasserburg plot. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

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Sample BG9-345a

Back-scattered electron image of representative monazite grains in sample BG9-345a indicate textural equilibrium with the matrix assemblage (Figure A3.3). Isotopic data from n=15 determinations in this sample give a 2 lower intercept Pb207/Pb206 age of 522±6 Ma with MSWD of 0.14 (Figure A3.4).

Figure A3.3: Back scattered electron images of the textural settling of a selection of matrix monazite grains analysed for age determinations in Okahandja Zone sample BG9-345a.

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Figure A3.4: Lower intercept age from monazite in Okahandja Zone sample BG9-345a, on Tera-Wasserburg plot. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

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Sample SMZ1

Back-scattered electron image of representative monazite grains in sample SMZ1 indicate textural equilibrium with the matrix assemblage (Figure A3.5). Isotopic data from n=27 determinations in this sample form a near concordant cluster (Figure A3.6). Isotopic determinations give a 2 weighted mean 206Pb/238U age of 517±4 Ma for 95% confidence from 26 of the 27 determinations, with MSWD of 1.3 and probability of 0.11 (Figure A3.7).

Figure A3.5: Back scattered electron images of the textural settling of a selection of matrix monazite grains analysed for age determinations in Southern Margin Zone sample SMZ1.

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Figure A3.6: Isochron of monazite data from Southern Margin Zone sample SMZ1, on Tera-Wasserburg plot. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

Figure A3.7: Weighted mean Pb207/Pb206 age determination from 26 monazites in Southern Margin Zone sample SMZ1. Isotopic analyses by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

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Sample SZ41a

Back-scattered electron image of representative monazite grains in sample SZ41a indicate textural equilibrium with the matrix assemblage (Figure A3.8). Isotopic data from n=16 determinations in this sample give a 2 lower intercept Pb207/Pb206 age of 529±5 Ma with MSWD of 0.33 (Figure A3.9).

Figure A3.8: Back scattered electron images of the textural settling of a selection of matrix monazite grains analysed for age determinations in Southern Zone sample SZ41a.

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Figure A3.9: Lower intercept age from monazite in Southern Zone sample SZ41a, on Tera-Wasserburg plot. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

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Sample SZ44a

Back-scattered electron image of representative monazite grains in sample SZ44a indicate textural equilibrium with the matrix assemblage (Figure A3.10). Isotopic data from n=16 determinations in this sample give a 2 lower intercept Pb207/Pb206 age of 524±9 Ma with MSWD of 0.047 (Figure A3.11).

Figure A3.10: Back scattered electron images of the textural settling of a selection of matrix monazite grains analysed for age determinations in Southern Zone sample SZ44a.

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Figure A3.11: Lower intercept age from monazite in Southern Zone sample SZ44a, on Tera-Wasserburg plot. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

Sample BG14-368

Isotopic data from n=17 of 19 determinations in this sample give a final corrected 2 lower intercept Pb207/Pb206 age of 529±11 Ma. Preliminary uncorrected age was 520±6 Ma.

Sample BG14-475B


Sample BG14-494B


Sample BG14-537


Sample BG14-599


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Sample BG13-214

Isotopic data from is widely scattered in this sample because monazite grains were too small for clean analysis. Pb206/U238 ages range 510-520 Ma (Figure A3.12).

Figure A3.12: Scatter of ages from monazite in contact aureole sample BG13-214. Isotopic analyses are by ICPMS and age determination undertaken by Ben Wade, Adelaide Microscopy.

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Zircon Geochronology Analytical Procedures

Zircons separated from samples for detrital zircon studies in the Damara Orogen (Foster et al, 2014) have returned [1] maximum deposition ages, [2] a number of metamorphic zircon ages and [3] detrital metamorphic zircon ages, all useful for constraining metamorphic events in the region. Results of detrital zircon geochronology in samples from the Kaoko Belt and Damara Orogen have been published (Newstead, 2010; Foster et al., 2014). Analyzed meta-sediment samples that also returned metamorphic ages are from the Central Zone (DF9-44, CZ53b and CZ35), Southern Zone (SZ40) and basement in the Central Zone (DF9-43). Meta-psammite samples returning no metamorphic data but with maximum deposition ages are; DF9-26, DF9-30, CZ29, CZ40, SZ13, DF9-12a and DF9-4 from the Damara Orogen and DF6-40, DF6-41, DF6-46, DF6-45, DF6-44 and DF6-43 from the Nama Basin. Prof. David Foster (University of Florida) has also undertaken a number of magmatic ages from granite plutons bracketing key deformation relationships in the; Ugab Zone (DF9-37, BG13-98, BG13-99, BG13-239, BG14-569, U305, U255a and U259), Southern Zone (BG9-322) and Central Zone (BG16-5, BG16-10a, BG16-11, BG16-12a and BG16-12b). These granite age determinations have been undertaken as part of ongoing structure-tectonic studies in the Damara Orogenic System (Goscombe et al., submitted).

Methodology modified from Foster et al. (2009, 2014) and described in Newstead (2010). Grain separates were hand-picked, mounted in epoxy along with the zircon standard, and then ground and polished to reveal internal surfaces. U-Pb analyses of zircons were performed by LA-MC-ICP-MS at the University of Florida using a Nu Plasma multi-collector inductively coupled plasma source mass spectrometer (MC29 ICP-MS) equipped with three ion counters and 12 Faraday detectors, U-Pb collector block and a New Wave 213 nm Nd-Yag laser (Kamenov et al., 2004). Data calibration and drift corrections were based on multiple ablations of the reference zircons from the Duluth Gabbro (Paces and Miller, 1993) collected from the Forest Center location (FC-1). Analyses of the standard were made between every three unknown analyses. 206Pb/238U ages were used for grains displaying ages <1000 Ma and 207Pb/206Pb ages were used for grains displaying ages >1000 Ma. The analyses were plotted on conventional concordia diagrams and cumulative density diagrams using ISOPLOT (Ludwig, 1995) to assess discordance due to multistage Pb loss, metamorphism or mixing of growth zones. Discordant grains that plotted along reliable discordia were assumed to be of the upper intercept age and are included in probability plots as such. Discordant analyses that did not intersect the concordia curve or plot along discordia were generally removed from consideration and are not included in age populations plotted on histograms and cumulative probability plots because of the possibility of multiple stages of Pb loss and metamorphism and/or recrystallization.

Zircon Sample Descriptions

Sample DF9-44, Damara Meta-sediment

Sample collected for provenance work from the Etusis Formation in the Nosib Group. A coarse-grained quartz-feldspar meta-psammitic gneiss with biotite and flattened 2x2 cm discs of cordierite. Cordierites have been flattened in the main foliation and retrograded to chlorite. Main foliation is a foliated gneissic fabric that is parallel to compositional layering, with a weak biotite lineation. There is no grain refinement.

Sample CZ53b, Damara Meta-sediment

Sample collected for provenance work from the Tinkas Formation in the Swakop Group. Sample is a meta-psammite layer within lower amphibolite facies metapelite schist. Matrix assemblage in host metapelite schists consists of quartz, oligoclase plagioclase, siderophyllitic biotite, monazite, Mn-ilmenite, Na-muscovite and ripidolite chlorite porphyroblasts.

Sample CZ35, Damara Meta-sediment

Sample collected for provenance work from the Karibib Formation in the Swakop Group. Sample is meta-psammite with biotite.

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Sample SZ40, Damara Meta-sediment

Sample collected for provenance work from the Kuiseb Formation in the Swakop Group in the North Southern Zone. Sample is meta-psammite with biotite from a layer within metapelite schists. The host metapelite schist has matrix assemblage with early Na-muscovite, siderophyllitic biotite, quartz, ilmenite and andesine plagioclase and post-kinematic porphyroblasts of Mn-Mg-almandine garnet, Fe-staurolite and secondary biotite laths

Sample DF9-37 (BG9-296) and BG13-98, West Ugab Granite

Late-kinematic granite sampled for magmatic age determination. Sample is from Ugabmond Domain in the western Ugab Terrane. No obvious fabric within granite or alignment of biotites at the granite margin, indicating late-kinematic crystallization of the granite. Weak alignment of K-feldspar phenocrysts and xenoliths occurs within 1 m of the granite margin. A late, spaced disjunctive cleavage enhanced by weathering, forms in the 30 cm margin parallel to the granite contact. Granite cuts D3 cleavage in host meta-sediments. Granite contact is cut by a 30 cm leuco-granite dykes and parallel quartz veins.

Sample BG13-99, Aplite dyke in West Ugab Granite

Sample is late-kinematic aplite dyke in the late-kinematic granite from the Ugabmond Domain in the western Ugab Terrane. No fabric in the aplite or alignment of micas is evident in these aplite dykes, which are the third magmatic phase recognised in the Ugabmond Granite. In the host schists, these aplite dykes post-date D4 fabrics but are re-rotated and weakly folded by the latest stages of N-S shortening in the Ugab Zone (D5). The aplite dykes are also weakly folded by the latest deformation event recognised in the region, weak E-W shortening (D7).

Sample BG13-239, Pegmatite dyke in West Ugab Granite

Sample is late-kinematic pegmatite dyke on east margin of the West Ugab Granite from the Ugabmond Domain. It apparently post-dates most deformation, but D4, D5 and D7 fabrics are not developed in the area the pegmatite was sampled from. Elsewhere similar late-stage pegmatites are folded by D7 and are formed distant from the West Ugab Granite and associated with the sub-surface granite aureole in the northeast area.

Sample BG14-569, Baddocks Bay Granite

Post-kinematic Baddocks Bay Granite on the Skeleton Coast at longitude 013.88115º east, latitude -21.51105º south. Is a biotite-rich granite with moderate number of rounded resorbed turbidite greywacke xenoliths. Granite cuts main phase chevron folding (D2) and N-S shortening (D4), and pre-dates weak NE-SW shortening (D5) and E-W shortening (D7).

Sample BG9-298 (DF9-39), Neoarchaean basement in Ogden Mylonite Zone

Sheared granitic orthogneiss within the Ogden Mylonite Zone on the Skeleton Coast, at longitude 013.55765º east, latitude -21.08345º south. Dark, hard and glassy annealed biotite, quartz, feldspar mylonitized granitoid. This is the predominant rock type in the Ogden Mylonite Zone and is closely associated with bands of mylonitized granitic orthogneiss with relict K-feldspar porphyroclasts and ribbons. Weak aggregate lineation only evident on margin of quartz vein. Early quartz veins are isoclinally folded. Oblique quartz vein experienced some shortening after mylonitization. No brittle over-print evident. In area also have sheared granitic orthogneiss with K-feldspar ribbons.

Sample BG9-297 (DF9-38), Palaeoproterozoic basement in Ogden Mylonite Zone

Sheared granitic orthogneiss within the Ogden Mylonite Zone on the Skeleton Coast, at longitude 013.56605º east, latitude -21.08345º south. Mylonitized granite orthogneiss with relict K-feldspar porphyroclasts and aggregate ribbons, with mylonite assemblage of quartz-plagioclase-biotite-K-feldspar. This granitic orthogneiss forms pink bands within the dark grey biotite-rich mylonite matrix.

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Sample BG9-322, Damara granite sill in Southern Zone

Post-kinematic granite sampled for magmatic age determination to give minimum age constraint on peak metamorphism age in Southern Zone. Sample is from a 1 m wide biotite granite sill in the north Southern Zone north of the Matchless Belt, in the Harmonie Farm campsite. Granite sill cross-cuts the main foliation in the host schists at a very low angle of discordance (~4º), biotite in the granite is randomly aligned and there is no penetrative foliation within the granite, indicating it post-dates main foliation events (D1-D3). A weak quartz grainshape foliation in the granite is developed indicating minor flattening strains. Consequently, the granite sills probably coincide with the peak of metamorphism, bracketed by main phase foliations and later vertical flattening (D6). A late, spaced disjunctive cleavage forms in the 3 cm margin parallel to the granite contact.

Sample DF9-43, Basement within Central Zone

Basement granitic orthogneiss sampled for magmatic age determination. Sample is from basement inlier within Central Zone of the Damara Orogen. Sample is granitic orthogneiss within basement immediately (20 m) below the unconformity with Etusis Formation at the Khan River. Unconformity and granite is undeformed with no grain refinement fabrics within the 50 m of section.

Sample BG16-11, Partial melt in Central Zone

Peak metamorphic coarse-grained partial melt segregation pool in Kuiseb Schist metapelite granulite with matrix assemblage of garnet-cordierite-biotite-K-feldspar-plagioclase-quartz. Partial melt contains garnet and cordierite paratectic phases. Sampled from west Omaruru River in the North Central Zone at longitude 014.60208º east, latitude -21.88763º south.

Sample BG16-12a, Early aplite in Central Zone

Early pink aplite sill generation, post-dates but is largely concordant to gneissic layering and main foliation. These contain poikiloblastic garnet and probably represent pooling of melt associated with the peak of metamorphism. Early aplite sills are boudinaged by ongoing flattening and SW-directed transport, with melt pooling in neck zones and cut by two later pegmatite generations. Transport during boudinage is the same as earlier main phase deformation, indicating these aplite sills were injected during main phase orogenesis in the Central Zone. Sampled from west Omaruru River in the North Central Zone at longitude 014.60105º east, latitude -21.88712º south.

Sample BG16-12b, Early biotite pegmatite in Central Zone

Earliest generation of discordant pegmatite cross-cuts main deformation phases and early partial melting and aplite sill generations. Pegmatite experienced only weak boudinaged and is probably axial planar to latest-phase upright folding by E-W shortening. Pegmatite assemblage is biotite-plagioclase-K-feldspar-quartz±garnet. These pegmatites have irregular pseudo-boudinage margins indicating syn-magmatic collapse of the dyke producing “cauliflower-like” irregular margins of coarse crystals. Sampled from west Omaruru River in the North Central Zone at longitude 014.60105º east, latitude -21.88712º south.

Sample BG16-10a, Late biotite-alkali feldspar pegmatite in Central Zone

Latest generation of discordant pegmatite are biotite-alkali feldspar pegmatites forming box-work and bi-vergent inclined conjugate dyke sets that trend E-W. Intruded late, after all ductile deformation and magmatic events, and accompanying E-W shortening and N-S extension directions. These dykes make up to 20% of outcrop in the Khan Formation and significantly less in the Kuiseb Schists. Sampled from west Omaruru River in the North Central Zone at longitude 014.60594º east, latitude -21.88775º south.

Sample BG16-5, Early leucogranite sill in Central Zone

Earliest leucogranite sill generation, post-dates stromatic partial melt segregations and peak metamorphic matrix parageneses. Is concordant with peak metamorphic gneissic layering and stromatic melt segregations. Sills are tight to isoclinally folded by the main phase fold event that produces regional large-scale folding and axial planar main foliation. Consequently, these sills post-date peak metamorphism and pre-date main phase folding. Leucogranite sill contains poikiloblastic

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garnet and probably represent pooling of melt associated with high-grade metamorphic conditions. Early pre-peak thin stringer partial melt segregations with garnet only, are also folded by this same main phase folding event. Main foliation associated with the isoclinal to tight folding, wraps, flattens and stretches early prograde garnet within the Kuiseb Schist host. In low strain zones prograde to peak garnet is enclosed by cordierite coronas formed during decompression. Sampled from north of the Khan River in the South Central Zone at longitude 015.17050º east, latitude -22.31783º south.

Detrital zircon samples

Samples of mostly meta-psammites collected for detrital zircon provenance work are listed below. All of these same samples and others collect in a profile across the southern margin of the Damara Orogen into the Central Zone, have also been analysed for whole-rock Nd. Results from detrial zircon cores from the Damara Sequence are published in Foster et al. 2014. The metamorphic rim data from Damara Sequence strata and the Nama Group are in Newstead, 2010. The raw data for these samples is tabluated at the end of this Appendix.

Sample BG6-91 is meta-psammite from the Mulden Group molasse in the Northern Foreland of the Damara Orogen. Sample DF9-26 is meta-psammite from the basal Kuiseb Formation in the Swakop Group, from the Northern Zone. Sample DF9-30 is coarse-grained quartzite with minor feldspar from the middle to upper Kuiseb Formation in the Swakop Group, from the Northern Zone. Sample CZ29 is biotite meta-psammite from the Khan Formation in the Nosib Group, from the Central Zone. Sample CZ40 is meta-psammite from the Rossing Formation in the Swakop Group, from the Central Zone. Sample SZ13 is biotite meta-psammite from the Kuiseb Formation in the Swakop Group, from the Southern Zone.

Sample DF9-12a is quartzite from the Chausib Member in Hakosberg Formation in Kuibis Subgroup of the Nama Group. Located in the Southern Margin Zone in sequences deposited on the Kalahari Craton. Sample DF9-4 is massive sugary meta-sandstone with quartz, feldspar, muscovite and streaky biotite foliation. Sample is from Naos Diamictite formation in Vaalgras Subgroup of the Hakos Group. Located in the Southern Margin Zone in sequences deposited on the Kalahari Craton. Sample DF6-40 is un-metamorphosed psammite from the Dabis Formation in the Kuibis Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton.

Sample DF6-41 is un-metamorphosed psammite from the Schwarzrand Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton. Sample DF6-46 is un-metamorphosed muscovite psammite from the Schwarzrand Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton.

Sample DF6-45 is un-metamorphosed psammite from the Stockdale Formation in the Fish River Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton. Sample DF6-44 is un-metamorphosed psammite from the Breckhorn Formation in the Fish River Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton. Sample DF6-43 is un-metamorphosed psammite from the Nababis Formation in the Fish River Subgroup of the Nama Group. Located in the Southern Foreland in sequences deposited on the Kalahari Craton.

Zircon Geochronology Results

Sample DF9-44, Damara Orogen Meta-sediment

Maximum deposition pooled age for this sample is 861±15 Ma, based on 4 grains with 5.9 to 11.7 % discordance. This sample also contains a single metamorphic zircon with a reliable concordant age of 542±9 Ma showing only -0.30 % discordance. This age gives an indication of the age of metamorphism experienced by this sample.

Sample CZ53b, Damara Orogen Meta-sediment

Maximum deposition age for this sample is 617±22 Ma, based on 1 grain with 2.3 % discordance. An older maximum deposition age for this sample is 645±7 Ma, based on 11 grains with -6.2 to 5.0 % discordance. This sample also contains a single metamorphic zircon with an unreliable age of

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582±25 Ma, with 7.1 % discordance. This age gives a maximum age of metamorphic zircon growth experienced by this sample.

Sample CZ35, Damara Orogen Meta-sediment

Maximum deposition pooled age for this sample is 634±10 Ma, based on 3 grains with 4.5 to 8.3 % discordance. An older maximum deposition age for this sample is 651±10 Ma, based on 3 grains with -0.97 to 10.2 % discordance. This sample also contains a single metamorphic zircon with an unreliable age of 585±12 Ma, with 10 % discordance. This gives a maximum age of metamorphic zircon growth experienced by this sample.

Sample SZ40 (DF6-22), Damara Orogen Meta-sediment

Maximum deposition age for this sample is 636±9 Ma, based on 1 grain with 3.7 % discordance. This sample also contains a single metamorphic zircon with an unreliable age of 517±8 Ma, with 3.3 % discordance. This age gives an indication of the age of a metamorphic event experienced by this sample.

Sample DF9-26 (BG9-277), Damara Orogen Meta-sediment

Maximum deposition pooled age for sample DF9-26 (BG9-277) is a Pb206/U238 weighted mean age of 611±10 Ma, based on 6 grains with 1.81 to 10.1 % discordance. This sample has a metamorphic zircon with an inaccurate Pb206/U238 age of 543±17 Ma, based on 1 grain with 10 % discordance.

Sample DF9-30 (BG9-283), Damara Orogen Meta-sediment

Maximum deposition age for sample DF9-30 (BG9-283) is a Pb206/U238 age of 619±8 Ma, based on 1 grain with 3 % discordance.

Sample DF9-37 (BG9-296) and BG13-98, West Ugab Granite

Many of the zircon grains from the West Ugab granite were metamict and high in common Pb. The grains with no common lead and discordance less than 2% are considered here. LA-MC-ICPMS analysis of a tight cluster of n=10 zircon grains from grey granite sample DF9-37 of main phase West Ugab Granite, give a weighted mean Pb206/U238 magmatic age of 511.9±5.2 Ma. LA-MC-ICPMS analysis of n=5 zircon grains from grey granite sample BG13-98 of main phase West Ugab Granite, give a weighted mean Pb206/U238 magmatic age of 515±7 Ma. Geologically, samples DF9-37 and BG13-98 are the same main grey granite phase within the same contiguous West Ugab Granite pluton. When pooled together, these give a weighted mean Pb206/U238 magmatic age of 514.6±3.4 Ma from n=15 zircon grains, with MSWD=1.8 and probability=0.032. Other biotite porphyritic granite samples from the South Granite pluton immediately to the east, give similar ages of 515±5 Ma and ~517 Ma on the basis of only n=4 and n=2 zircon grains respectively. When all four biotite granite samples from the western Ugab region are pooled (U255a, U259, BG13-98 and DF9-37), n=21 zircon grains give a weighted mean Pb206/U238 magmatic age of 515.7±3.1 Ma, with MSWD=2.2 and probability=0.001 (Figure A3.13). The age similarity suggests both South Granite and West Ugab Granite plutons may be connected at depth. However, pooling of South Granite samples on their own, and with aplite and pegmatite samples, give older 519±11 Ma and 521.7±4.1 Ma ages respectively, alternatively suggesting a slightly older pluton in the east (see below).

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Figure A3.13: Weighted mean Pb206/U238 age determination from western Ugab biotite porphyritic granite samples. Isotopic analyses by MC-ICPMS and age determination undertaken by Prof. David Foster, University of Florida.

Sample BG13-99, Aplite dyke in West Ugab Granite

MC-ICPMS analysis of n=5 out of >30 zircon grains with less than 2.1% discordance from aplite dyke sample BG13-99 associated with the West Ugab Granite, give a weighted mean Pb 206/U238

magmatic age of 519.3±3.3 Ma. The remainding zircons are metamict due to high U concentrations. Like the host grey granite phase of the West Ugab Granite, this aplite dyke pre-dates weak NE-SW shortening folds (D5) and weak E-W shortening folds (D7). The age for this aplite dyke is within error of the main phase grey granite pluton of 515±3 Ma age that it appears to intrude. This aplite dyke is close to the granite margin and field relations are ambiguous whether it is occluded or crosscuts the granite pluton (see below). In an attempt to get a more accurate age, zircons from all aplite (BG13-99) and pegmatite (BG13-239) samples have been pooled. Pooling n=7 zircons give a weighted mean Pb206/U238 magmatic age of 520.9±6.9 Ma, with 1.3% discordance, 95% confidence, MSWD=7.8, probability=0.0 (Figure A3.14). This pooled age confirms the older age of the aplitic to pegmatic dykes northeast of the main grey granite pluton.

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Figure A3.14: Weighted mean Pb206/U238 age determination from aplite and pegmatite samples in the western Ugab region. Isotopic analyses by MC-ICPMS and age determination undertaken by Prof. David Foster, University of Florida.

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Sample BG13-239, Pegmatite dyke in West Ugab Granite

MC-ICPMS analysis of a tight cluster of n=3 out of 7 zircon grains from pegmatite dyke sample BG13-239 northeast of the West Ugab Granite, give an inaccurate weighted mean Pb206/U238

magmatic age of 521±24 Ma. The remainding zircons are metamict due to high U concentrations. This pegmatite is distal from the West Ugab Granite and possibly associated with a sub-surface granite body, and like aplite dykes also pre-dates weak E-W shortening folds (D7).

This pegmatite sample is distal from the West Ugab Granite and possibly associated with a sub-surface granite body mapped by contact aureoles, and thus consistent with this interpretation. Similarly, there are numerous aplite dykes in host sediments that could potentially also pre-date and be unrelated to the West Ugab Granite pluton. However, most aplite dykes appear to root back into the West Ugab Granite body. Aplites in host sediments are strongly folded by D4 and cut by S4 foliations, and consequently a portion may be older than the syn-D4 main grey granite phase.

Magmatic age determinations from samples U259 and U255a in South Granite (below), east of the West Ugab Granite pluton, give ages very similar to the aplite (BG13-99) and pegmatite (BG13-239). On the basis of metamorphic isograd mapping, all four samples are associated with sub-surface to exposed granite to the east of the West Ugab Granite, and collectively may represent a slightly older granite pluton, named South Granite. MC-ICPMS analysis of a pooled population of n=15 zircon grains from samples U259, U255a, BG13-99 and BG13-239 east of the West Ugab Granite, give an accurate weighted mean Pb206/U238 magmatic age of 521.7±4.1 Ma, with MSWD=1.4, probability=0.15 (Figure A3.15). This age is interpreted to characterise a slightly older magmatic body immediately east of the West Ugab Granite. An older age for South Granite is consistent with contact metamorphic mineral growth occurring earlier than in West Ugab Granite aureoles and pre-dating S4 foliations. The scatter in zircon ages suggests that some disturbance of the older zircons may be related to the West Ugab Granite.

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Figure A3.15: Weighted mean Pb206/U238 age determination from 15 zircons pooled from aplite, pegmatite and biotite granite samples associated with exposed and sub-surface South Granite to the east of the West Ugab Granite. Isotopic analyses by MC-ICPMS and age determination undertaken by Prof. David Foster, University of Florida.

Samples U255a and U259, South Granite in West Ugab area

MC-ICPMS analysis of n=4 out of 20 zircon grains from biotite granite sample U255a in South Granite, give a weighted mean Pb206/U238 magmatic age of 515±5 Ma. MC-ICPMS analysis of n=1 out of 20 zircon grains from biotite granite sample U259 in South Granite, give an inaccurate weighted mean Pb206/U238 magmatic age of ~517 Ma. When pooled together, samples U255a and U259 from South Granite, give a weighted mean Pb206/U238 magmatic age of 519±11 Ma from n=5 zircon grains, with 2.2% discordance, 95% confidence, MSWD=3.9 and probability=0.00 (Figure A3.16).

Figure A3.16: Weighted mean Pb206/U238 age determination from 5 zircons pooled from biotite porphyritic granite samples from South Granite pluton. Isotopic analyses by MC-ICPMS and age determination undertaken by Prof. David Foster, University of Florida.

Sample BG14-569, Baddocks Bay Granite

MC-ICPMS analysis of zircons from granite sample BG14-569 give a preliminary weighted mean Pb206/U238 magmatic age of 490±15 Ma, with age constrained to be <507 Ma. Baddocks Bay Granite post-dates N-S shortening crenulations (D4) and pre-dates NE-SW shortening folds (D5), and is thus expected to be younger than the syn-D4 West Ugab Granite of ~516 Ma age.

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Sample U305, Doros Granite

MC-ICPMS analysis of a single zircon grain from Doros Granite sample U305, gives an inaccurate concordant Pb206/U238 magmatic age of 522±14 Ma. This age is within error of published 528±5, 530±5 and 533±6 Ma ages from the Doros Granite (Schmidtt et al., 2011).

Sample BG9-298, Neoarchaean basement in Ogden Mylonite Zone

MC-ICPMS analysis of n=15 zircon grains from sheared granitic orthogneiss sample BG9-298 (DF09-39) within the Ogden Mylonite Zone, give an upper intercept Pb207/Pb206 magmatic age of 2606.3±7.7 Ma and MSWD=1.02. This age is similar to Neoarchaean age determinations from the Andib Terrane in the eastern parts of Central Kaoko Belt, within and adjacent to the Purros Mylonite Zone. These relationships indicate that the Ogden Mylonite Zone must be the lateral extension of the Purros Mylonite Zone containing sheared Central Kaoko Belt transported to the south. As a result, the Ogden Mylonite Zone is not juvenile Coastal Terrane rocks and is not the lateral extension of the Three Palms Mylonite Zone. The isotopic data also give an inaccurate lower intercept Pb206/U238 age of 562±98 Ma, interpreted to be due to resetting by peak (M2) metamorphism in the Kaoko Belt.

Sample BG9-297, Palaeoproterozoic basement in Ogden Mylonite Zone

MC-ICPMS analysis of n=25 zircon grains from sheared granitic orthogneiss sample BG9-297 (DF09-38) within the Ogden Mylonite Zone, give an upper intercept Pb207/Pb206 magmatic age of 1861.8±5.4 Ma and MSWD=1.9. This age is similar to Palaeoproterozoic age determinations from the sheared orthogneiss in the Central Kaoko Belt, within and adjacent to the Purros Mylonite Zone. These relationships indicate that the Ogden Mylonite Zone must be the lateral extension of the Purros Mylonite Zone containing sheared Central Kaoko Belt transported to the south. As a result, the Ogden Mylonite Zone is not juvenile Coastal Terrane rocks and is not the lateral extension of the Three Palms Mylonite Zone. These isotopic results also give an inaccurate lower intercept Pb206/U238

age of 518±89 Ma, interpreted to be due to resetting by (M3) metamorphism in the Kaoko Belt / Damara Belt junction.

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Sample BG9-322, Damara granite sill in Southern Zone

MC-ICPMS analysis of only n=2 zircon grains from granite sill sample BG9-322 within the Southern Zone, give an inaccurate Pb206/U238 magmatic age of ~513±17 Ma, with preliminary uncorrected age of 503±5 Ma. Further sampling and analysis has been undertaken to improve the precision of this age determination. These granite sills are bracketed by main phase foliations and later vertical flattening (D6), and thus interpreted to coincide with or immediately post-date the peak of metamorphism. The ~513 Ma age is consistent with being the lower age limit for the peak of metamorphism in the Southern Zone, otherwise dated between ~530-517 Ma.

Sample DF9-43, Basement within Central Zone

Magmatic age for this granitic orthogneiss sample is 1027.9±2.2 Ma, based on weighted mean of a tight cluster of 38 grains, with MSWD of 1.19 and probability of 0.2 (data published in Foster et al., 2014). This sample contains one metamorphic zircon with an age of 520±25 Ma, with -1.0 % discordance.

Sample BG16-11, Partial melt in Central Zone206Pb/238U age for crystallization of peak metamorphic partial-melt pool is 518.4±1.9 Ma, based on weighted mean of 21 grains, with MSWD of 0.94 and probability of 0.54.

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Sample BG16-12a, Early aplite in Central Zone206Pb/238U age for crystallization of syn-peak, syn-kinematic aplite sill is an inaccurate age of 528.1±6.9 Ma based on weighted mean of 10 grains, with MSWD of 2.9 and probability of 0.002.

Sample BG16-12b, Early biotite pegmatite in Central Zone206Pb/238U age for crystallization of post-peak syn-kinematic biotite pegmatite is 517.4±1.9 Ma, based on weighted mean of 41 grains, with MSWD of 1.6 and probability of 0.012.

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Sample BG16-10a, Late biotite-alkali feldspar pegmatite in Central Zone206Pb/238U age for crystallization of post-kinematic biotite-alkali feldspar pegmatite is 516.3±1.3 Ma, based on weighted mean of 54 grains, with MSWD of 0.88 and probability of 0.72.

Sample BG16-5, Early leucogranite sill in Central Zone206Pb/238U age for crystallization of syn-peak leucogranite sill is 530.0±2.7 Ma, based on weighted mean of 35 grains, with MSWD of 1.3 and probability of 0.094.

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Detrital zircon samples with no metamorphic data

Maximum deposition age for sample BG6-91 is 590±42 Ma, based on 1 grain with 8.8 % discordance.

Maximum deposition pooled age for sample CZ29 is 861±21 Ma, based on 2 grains with 13.1 and 16.9 % discordance.

Maximum deposition age for sample CZ40 is 817±99 Ma, based on 1 grain with 7.24 % discordance.

Maximum deposition age for sample SZ13 is 607±22 Ma, based on 1 grain with 0.24 % discordance. An older pooled maximum deposition age for this sample is 638±18 Ma, based on 3 grains with 0.24 to 3.4 % discordance.

Maximum deposition age for sample DF9-12a is 891±28 Ma, based on 1 grain with 8.9 % discordance.

Maximum deposition pooled age for sample DF9-4 is 1018±16 Ma, based on 3 grains with 1.6 to 4.3 % discordance.

An unreliable maximum deposition age for sample DF6-40 is 982±25 Ma, based on 1 grain with 14.1 % discordance. An older maximum deposition age for this sample is 1029±18 Ma, based on 1 grain with 9.2 % discordance.

Maximum deposition age for sample DF6-41 is 598±21 Ma, based on 1 grain with 9.3 % discordance. Younger ages from this sample give a pooled age of 545±20 Ma, based on 2 grains with 4.4 to 7.5 % discordance. This young age is equivalent to the depositional age of this rock unit and the zircons are interpreted to be reworked syn-depositional volcano-clastic zircon.

Maximum deposition pooled age for sample DF6-46 is 588±20 Ma, based on 3 grains with 3.0 to 11.5 % discordance.

Maximum deposition pooled age for sample DF6-45 is 550±5 Ma, based on 13 grain with 0.11 to 9.8 % discordance. Younger ages from this sample give a pooled age of 534±6 Ma, based on 11 grains with 3.6 to 11.5 % discordance. This young age is equivalent to the depositional age of this rock unit and the zircons are interpreted to be reworked syn-depositional volcano-clastic zircon.

Maximum deposition pooled age for sample DF6-44 is 552±14 Ma, based on 2 grains with 0.37 to 7.73 % discordance. Younger ages from this sample give a pooled age of 531±9 Ma, based on 2 grains with 2.9 to 4.2 % discordance and 519±14 Ma, based on 2 grains with 9.5 to 10.2 %

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discordance. These young ages are equivalent to the depositional age of this rock unit and the zircons are interpreted to be reworked syn-depositional volcano-clastic zircon.

Maximum deposition age for sample DF6-43 is 549±17 Ma, based on 1 grain with 1.9 % discordance.

Ar-Ar Thermochronology Results

Ar-Ar thermochronology on hornblende, muscovite, biotite and K-feldspar, have been undertaken in the Kaoko and Damara Belts by Prof. David Foster (University of Florida), as part of ongoing tectonic research in the Damara Orogenic System. Results have already been published (Foster et al., 2009; Gray et al., 2006; Goscombe et al., 2005), and a small number of unpublished results are collated in Appendix (1).

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Whole-rock Nd Results

Meta-sediments were collected in a profile across the southern margin of the Damara Orogen from the Southern Margin Zone into the Central Zone, as well as Kaoko Belt samples, to characterize different aged and sourced basinal sequences from whole-rock Nd analyses. Summaries of this provenance data are plotted on the time-space diagram for Damara Orogenic System stratigraphy (Figure 3 in paper). Most analyses were undertaken at the University of Florida under the supervision of Prof. David Foster (Newstead, 2010; Foster et al., 2014). Others have been previously published (Goscombe et al., 2003, 2005; Goscombe and Gray, 2007). The results of all these analyses are listed below.

Basinal Sequences Deposited on Coastal Terrane Magmatic Arc [average Nd -2.725]

Sample KK87c from the Coastal Terrane Sequence in the Coastal Terrane has Nd of -6.1.

Sample NK168 from the Coastal Terrane Sequence in the Coastal Terrane has Nd of +1.06.

Sample NK183 from the Coastal Terrane Sequence in the Coastal Terrane has Nd of -4.05.

Sample NK186 from the Coastal Terrane Sequence in the Coastal Terrane has Nd of -1.81.

Basinal Sequences Deposited on Probable Oceanic Crust in Kaoko Belt [average Nd -4.428]

Sample U306c from the Zerrissene Turbidites in the Ugab Zone has Nd of -1.84.

Sample DF6-21 from the Zerrissene Turbidites in the Ugab Zone has Nd of -2.2.

Sample BG9-294 from the Zerrissene Turbidites in the Ugab Zone has Nd of -13.3.

Sample DF6-8 from the Khumib Turbidites in the Kaoko Belt Orogen Core has Nd of -2.1.

Sample KK105f from the Khumib Turbidites in the Kaoko Belt Orogen Core has Nd of -2.7.

Basinal Sequences Deposited on Congo Craton Margin in Kaoko Belt [average Nd -7.914]

Sample NK89b from the Orogen Core in the Kaoko Belt has Nd of -14.57.

Sample NK84a from the Orogen Core in the Kaoko Belt has Nd of -5.88.

Sample NK58 from the Orogen Core in the Kaoko Belt has Nd of -3.17.

Sample NK189b from the Orogen Core in the Kaoko Belt has Nd of -6.87.

Sample K1336b from the Orogen Core in the Kaoko Belt has Nd of -12.5.

Sample K209 from the External Nappes of the Kaoko Belt has Nd of -11.3.

Sample NK199c from the External Nappes of the Kaoko Belt has Nd of -1.11.

Basinal Sequences Deposited on Congo Craton Margin in Damara Orogen [average Nd -10.05]

Sample CZ29 from the Khan Formation in the Central Zone has Nd of -18.8.

Sample CZ40 from the Rossing Formation in the Central Zone has Nd of -14.6.

Sample CZ53b from the Tinkas Formation in the Central Zone has Nd of -2.4.

Sample CZ35 from the Karibib Formation in the Central Zone has Nd of -1.2.

Sample CZ49 from the Damara Sequence in the Central Zone has Nd of -12.1.

Sample CZ38b from the Damara Sequence in the Central Zone has Nd of -11.2.

Basinal Sequences Deposited on Probable Oceanic Crust in Damara Orogen [average Nd -3.52]

Sample SZ40 from the Kuiseb Formation in the Southern Zone has Nd of -3.2.


Sample SZ47b from the Kuiseb Formation in the Southern Zone has Nd of -2.5.

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Sample SZ65a from the Kuiseb Formation in the Southern Zone has Nd of -4.2.

Sample IE4 from the Kuiseb Formation in the Southern Zone has Nd of -2.9.

Sample IE1a from the Kuiseb Formation in the Southern Zone has Nd of -4.0.

Basinal Sequences Deposited on Kalahari Craton Margin [average Nd -8.09]

Sample BG9-246 from the Damara Sequence in the Southern Margin Zone has Nd of -5.0.




Sample SZ99b from the Damara Sequence in the Southern Margin Zone has Nd of -7.4.

Sample SZ87b from the Damara Sequence in the Southern Margin Zone has Nd of -7.2.

Sample DF6-16 from the Damara Sequence in the Southern Margin Zone has Nd of -21.3.

Sample DF6-48 from the Damara Sequence in the Naukluft Nappe has Nd of -6.6.

Sample DF6-49 from the Tsumis Group in the Southern Foreland has Nd of -3.2.

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References

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Foster, D.A., Goscombe, B.D., Newstead, B., Mapani, B., Mueller, P.A., Gregory, L.C. and Muvangua, E. 2014. U-Pb age and Lu-Hf isotopic data of detrital zircons from Neoproterozoic Damara Sequence: Implications for pre-Gondwana proximity of Congo and Kalahari. Gondwana Research (in press).

Goscombe, B.D., Hand, M., Gray, D. and Mawby, J., 2003. The metamorphic architecture of a transpressional orogen: the Kaoko Belt, Namibia. Journal of Petrology 44, 679-711.

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Paces, J.B. and Miller, J.D. 1993. Precise U-Pb ages of Duluth Complex and related mafic intrusions, Northeastern Minnesota: Geochronological insights to physical, petrogenic, palaeomagnetic and tectonomagmatic processes associated with the 1.1 Ga midcontinent rift system. Journal of Geophysical Research 98B, 13997-14013.

Payne, J.L., Hand, M., Barovich, K.M., Wade, B.P., 2008. Temporal constraints on the timing of high-grade metamorphism in the northern Gawler Craton: implications for assembly of the Australian Proterozoic. Australian Journal of Earth Sciences 55, 623-640.

Schmitt, R.S., Trouw, R.A.J., Passchier, C.W., Medeiros, S.R. and Armstrong, R. 2012. 530 Ma syntectonic syenites and granites in NW Namibia – their relation with sollision along the junction of the Damara and Kaoko belts. Gondwana Research 21 362-377.

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