Precambrian Research 128 (2004) 237–255

Palaeoproterozoic crustal accretion and collision in the southernCapricorn Orogen: the Glenburgh Orogeny

S.A. Occhipintia,∗, S. Sheppardb, C. Passchierc, I.M. Tylerb, D.R. Nelsonba Tectonics Special Research Centre, School of Applied Geology, Curtin University of Technology, P.O. Box U1987, Perth 6845, Australia

b Geological Survey of Western Australia, 100 Plain St., East Perth 6004, WA, Australiac Institut fuer Geowissenschaften, Mainz University, Mainz 55099, Germany

Abstract

The Capricorn Orogen in central Western Australia records the Palaeoproterozoic collision of the Archaean Pilbara and YilgarnCratons. Until recently only one orogenic event was thought to be the cause of this collision, the 1830–1780 Ma CapricornOrogeny. However, recent work has uncovered an older event, the Glenburgh Orogeny that occurred between 2000 and 1960 Ma.The Glenburgh Orogeny reflects the collision of a late Archaean to Palaeoproterozoic microcontinent (the Glenburgh Terrane)with the Archaean Yilgarn Craton and is therefore tectonically distinct as well as significantly older than the widespread1900–1800 Ma tectonothermal events recorded in northern Australia.

The Glenburgh Terrane preserves a different history from either the Yilgarn or Pilbara Cratons. Granitic gneiss protolithsdated at ca. 2550 Ma were intruded by widespread granite magmatism dated at 2005–1970 Ma, accompanied by high-grademetamorphism and deformation throughout the terrane. At ca. 1960 Ma silicic granite of the Bertibubba Supersuite intruded thenorthern margin of the Yilgarn Craton along the Errabiddy Shear Zone, a crustal-scale shear zone that today marks the contact ofthe Glenburgh Terrane and Yilgarn Craton. At ca. 1950 Ma silicic dykes intruded the southernmost part of the Glenburgh Terrane,marking the end of the Glenburgh Orogeny. East of the Glenburgh Terrane the Glenburgh Orogeny resulted in the cessation ofmafic volcanism in the Bryah Basin, and the basin’s eventual closure. Siliciclastic, carbonate and chemical sedimentary rockswere deposited in the Padbury Basin that formed a retro-arc foreland basin on top of the Bryah Basin, and probably records thelater stages of the Glenburgh Orogeny collision.© 2003 Elsevier B.V. All rights reserved.

Keywords: Palaeoproterozoic; Western Australia; Plate tectonics; Orogeny; Deformation; Capricorn Orogen

1. Introduction

The Capricorn Orogen is a zone of deformed andmetamorphosed igneous and sedimentary rocks cutby granite intrusions that lies between the ArchaeanYilgarn and Pilbara Cratons (Fig. 1). The age of theCapricorn Orogeny was previously loosely bracketedas 2200–1600 Ma by Rb–Sr and Sm–Nd age-dating

∗ Corresponding author.E-mail address: occhipis@lithos.curtin.edu.au (S.A. Occhipinti).

(Libby et al., 1986; Fletcher et al., 1983), but morerecently has been constrained to 1830–1780 Maby U–Pb sensitive high resolution ion microprobe(SHRIMP) dating (Occhipinti et al., 1999b). TheCapricorn Orogeny has been interpreted as an in-tracratonic deformation event within a continuousArchaean basement (Gee, 1979; Windh, 1992), or,more recently, as the result of north–south conver-gence and subsequent collision of the Archaean Pil-bara and Yilgarn Cratons (Tyler and Thorne, 1990;Myers, 1993; Myers et al., 1996). Krapez (1999)and

0301-9268/$ – see front matter © 2003 Elsevier B.V. All rights reserved.doi:10.1016/j.precamres.2003.09.002

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EDMUND ANDCOLLIER BASINS

Granite and gneiss(>2610 Ma)Y

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Fig. 1. Simplified regional geology maps of the main tectonic elements of the Western Australian Craton and the southern part of the Capricorn Orogen including theGlenburgh Terrane (Gascoyne Complex and including the Carrandibby Inlier), the Errabiddy Shear Zone, the Yarlarweelor Gneiss Complex, and the Bryah and PadburyBasins. The locations ofFigs. 2–4are outlined.

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Krapez and Martin (1999)suggested that prior tothe Capricorn Orogeny a rift developed within alarger craton at ca. 2045–1995 Ma, leading first tothe development of oceanic crust, and then the on-set of a southeast dipping subduction zone beforeregional-scale sinistral strike–slip movements at ca.1815 or 1770 Ma. However, none of these previousmodels have considered an earlier orogenic event nowrecognised in the region—the Glenburgh Orogeny—which is a deformational, metamorphic and mag-matic event that has been dated at 2005–1960 Maby U–Pb SHRIMP geochronology (Occhipinti et al.,1999a; Sheppard et al., 2001a,b). This orogenic eventprobably reflects northwest–southeast or west–eastaccretion of a late Archaean to Palaeoproterozoic mi-crocontinent to, or collision of the Pilbara–GascoyneCraton (Sheppard et al., 2004) with, the ArchaeanYilgarn Craton, forming the Errabiddy Shear Zone.

The Gascoyne Complex, which is a major tectonicunit within the Capricorn Orogen, is wedged betweenthe Archaean Pilbara and Yilgarn Cratons and largelycomprises variably deformed and metamorphosedgranites, mafic to ultramafic igneous rocks, and sedi-mentary rocks. Until recently, the southern part of theGascoyne Complex, referred to as the Glenburgh Ter-rane bySheppard and Occhipinti (2000), was thoughtto contain a significant amount of deformed and meta-morphosed Archaean rocks of the Narryer Terrane ofthe northwestern Yilgarn Craton (3730–2610 Ma) andsome 1800–1600 Ma granite intrusions (Williams,1986; Myers, 1990). Recent remapping and SHRIMPU–Pb zircon geochronology found that the graniticrocks in the Glenburgh Terrane can be divided intotwo main groups; ca. 2550 basement tonalite, granodi-orite and monzogranites; and 2005–1970 Ma graniticrocks of the Dalgaringa Supersuite (Sheppard et al.,2004). Granites of the Dalgaringa Supersuite do notintrude the northwestern margin of the Yilgarn Cra-ton. No rocks characteristic of those found in eitherthe Archaean Yilgarn or Pilbara Cratons have beendated in the Glenburgh Terrane. This confirms that theErrabiddy Shear Zone forms the boundary betweenthe Glenburgh Terrane and the northwest YilgarnCraton (Fig. 1; Occhipinti et al., 1999b, 2001).

A hiatus in tectonothermal activity in the south-ern Capricorn Orogen occurred between ca. 1950 and1830 Ma, that is between the end of the GlenburghOrogeny and the start of the Capricorn Orogeny. Thus,

far no models for the development of the CapricornOrogen have accounted for the Glenburgh Orogeny,the 1950–1830 Ma hiatus in tectonothermal activity inthe region, and the lack of formation of arc-type mag-matic rocks during and preceding, the 1830–1780 MaCapricorn Orogeny.

Previous structural studies in the southern Capri-corn Orogen (Fig. 1) have mainly focused on theBryah and Padbury Basins (Hynes and Gee, 1986;Windh, 1992; Martin, 1994; Occhipinti et al., 1998b),althoughWilliams (1986)presented an interpretationof the structure and metamorphism of the GascoyneComplex, including its southern part—the GlenburghTerrane. Various broad tectonic interpretations of thesouthern part of the Capricorn Orogen have been pre-sented (Myers, 1993; Myers et al., 1996; Pirajno andOcchipinti, 2000) In this paper we describe the tec-tonic and temporal framework of the 2000–1960 MaGlenburgh Orogeny.

2. Regional geology of the southern CapricornOrogen

The southern part of the Capricorn Orogen (Fig. 1)contains variably exposed early to late Archaeangranite and granitic gneiss, Palaeoproterozoicmetasedimentary and mafic meta-igneous rocks, andPalaeoproterozoic granite and granitic gneiss. Theseunits are locally overlain by Palaeoproterozoic toMesoproterozoic sedimentary rocks. Four differenttectonic units are recognised within the southern partof the Capricorn Orogen—the Glenburgh Terrane,the Errabiddy Shear Zone, the Yarlarweelor GneissComplex and the Bryah–Padbury basins (Figs. 1–4).The sequence of 2000–1950 Ma deformation, meta-morphic and magmatic events within each of theseunits is outlined inFig. 5.

The Yarlarweelor Gneiss Complex (Fig. 4) com-prises 3300–2600 Ma granites, granitic gneiss andsupracrustal rocks of the Narryer Terrane (YilgarnCraton) that were locally deformed and intrudedby biotite monzogranite of the 1965–1945 Ma Bert-ibubba Supersuite (Wooramel suite ofOcchipinti etal., 1999b), and then metamorphosed, and deformedand intruded by voluminous granite at 1820–1780 Ma.The intrusion of ca. 1800 Ma granites was either sub-parallel or highly discordant with respect to gneissic

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Fig. 2. Simplified map of the Glenburgh Terrane, showing the trend of folds and foliations in the region, and the northern domain (NGT) and southern domain (SGT).

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Fig. 3. Simplified geology map of the Errabiddy Shear Zone, showing the main tectonic units and structural trend.

242 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

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Fig. 4. Simplified map of the Yarlarweelor Gneiss Complex and Bryah and Padbury Basins area showing them main structural elements.

layering in Archaean granitic gneiss, and range fromwell foliated to massive and undeformed. The Yarlar-weelor Gneiss Complex is in faulted contact with thelow- to locally medium-grade ca. 2000 Ma sedimen-tary and mafic igneous rocks of the Bryah and PadburyBasins in the south and east. To the west, the ErrabiddyShear Zone cuts the Yarlarweelor Gneiss Complex andseparates it from rocks of the Glenburgh Terrane.

The Glenburgh Terrane of the Gascoyne Complexconsists of metamorphosed granitic rocks, and am-phibolite, mafic granulite, pelitic schist, calc-silicategneiss and dolomitic marble (Fig. 2). At ca. 2000 Matonalites, trondhjemites, monzogranites and gran-odiorites of the Dalgaringa Supersuite intruded intoca. 2550 Ma granodiorites, tonalites and monzo-granites. In parts of the Glenburgh Terrane the ca.2550 and 2000 Ma (Nelson, 2000; Occhipinti et al.,2001) granites were deformed and metamorphosedto form gneisses that are collectively termed theHalfway Gneiss (Occhipinti and Sheppard, 2001;

Occhipinti et al., 2001). Elsewhere, in the GlenburghTerrane the Dalgaringa Supersuite mostly consistsof 2005–1970 Ma granites that have been metamor-phosed and heterogeneously deformed so as to locallyform well-banded granitic gneiss. However, originaligneous relationships between different phases of thesupersuite can be observed in numerous low-strainzones. The older parts of the Dalgaringa Supersuitewere metamorphosed and deformed by ca. 1989 Ma,and intruded by mesocratic and leucocratic tonaliteat ca. 1975 Ma (Occhipinti and Sheppard, 2001).The granites of the Dalgaringa Supersuite have com-positions similar to Phanerozoic subduction-relatedgranites and may have formed in an Andean-typesetting (Sheppard et al., 1999, 2003). Supracrustalrocks including mafic schist and gneiss, pelitic schist,calc-silicate gneiss and dolomitic marble, form dis-tinct bands within the granitic gneiss units and arecalled the Moogie Metamorphics (Occhipinti andSheppard, 2001).

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Error bars for U-Pb SHRIMP dates on zircon. For:

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Quartpot Pelite

MOOGIE METAMORPHICS

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Padbury Group

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Trondhjemite

Deformation &Metamorphism

Igneous crystallisationages

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Detrital grains(maximum age ofsedimentary protolith)

LEGEND

Unconformable and/orfaulted contact

? ???

? ???

? ???

? ???? ???

? ???

? ???

Maximum age for deformationand metamorphismunconstrained

? ???

? ???

? ???

Fig. 5. Summary of 2000–1950 Ma geology in the southern Capricorn Orogen.

244 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

Xenocrystic zircons within rocks of the DalgaringaSupersuite all have Palaeoproterozoic ages (Sheppardet al., 2004). However, in the northern part of theGlenburgh Terrane one sample of a 2550± 7 Mameta-tonalite component of granitic gneiss of theHalfway Gneiss contained early and late Archaeanxenocrystic zircons dated at ca. 2663–3300 Ma(Occhipinti et al., 2001), indicating that the HalfwayGneiss was at least in part derived from older Ar-chaean rocks.

The Errabiddy Shear Zone separates the YilgarnCraton from the Gascoyne Complex, and contains faultslices of both units, as well as the Yarlarweelor GneissComplex (Fig. 3). The shear zone also contains theCamel Hills Metamorphics—calc-silicate gneiss andpelitic schists and gneisses that are not present inother parts of the Capricorn Orogen. U–Pb SHRIMPage-dating of zircon from two samples indicates thepelitic schists were locally migmatised at 1966±5 Maand 1951±13 Ma, and intruded by 1970±15 Ma trond-hjemite indicating that metamorphism of the peliticschists and intrusion of the trondhjemite occurred overonly a few million years (Occhipinti et al., 2001).Detrital zircons from within the pelitic schists aredominated by ca. 2250–2000 Ma ages, whereas withinthe calc-silicate gneisses, detrital zircons are mostly2700–2608 Ma in age (Nelson, 1998). This indicatesthat the latest Archaean to Palaeoproterozoic parts ofthe Glenburgh Terrane were a possible source of sedi-ment for the pelitic schists, whereas the Archaean Yil-garn Craton is a more likely source for the sedimen-tary protolith of the calc-silicate gneisses.

Well-foliated granite and pegmatite banded graniticgneiss of the Warrigal Gneiss are locally included asfault-bounded wedges in the Errabiddy Shear Zone.These granites have been dated at 2700–2600 Ma(Nelson, 2000; Occhipinti et al., 2001), similar toages of late Archaean granites of the Narryer Terraneof theYilgarn Craton.

The Bryah and Padbury Basins consist of thevolcano-sedimentary Bryah and Padbury Groups,which were deposited along the northern marginof the Yilgarn Craton between 2000 and 1800 Ma(Occhipinti et al., 1998b; Pirajno and Occhipinti,2000; Pirajno et al., 1998; Fig. 4). It has been sug-gested the basins may have developed in an intracra-tonic setting (Gee, 1979; Windh, 1992) although,more recently they have been interpreted to have

formed in an inter-cratonic setting, on a continentalmargin, or in a rift-setting (Krapez and Martin, 1999;Occhipinti et al., 1998b; Pirajno et al., 1998).

The Bryah Group contains metamorphosed andpoly-deformed siliciclastic and chemical sedimentaryrocks, together with voluminous mafic to ultramaficvolcanic rocks, and minor intrusive rocks of theNarracoota Formation. The meta-mafic rocks locallycontain pillow structures, sheeted dykes, a layeredmafic-ultramafic igneous complex, sea-floor metaso-matism and trace and rare-earth element geochem-istry that support an oceanic crust model for theirorigin (Pirajno and Occhipinti, 2000; Pirajno et al.,1998). An area of mafic hyaloclastitic rocks in thesouthern part of the Bryah Basin suggests eruption ofmafic lava in shallow waters, locally characterised byexplosive activity, and it has been suggested it proba-bly represents a proto-oceanic rift that separated theMarymia Inlier (a rifted part of the Yilgarn Craton;Fig. 4) from the Yilgarn Craton (Pirajno et al., 2004;Pirajno and Occhipinti, 2000). Pirajno and Occhipinti(2000)suggested that this rift was linked to back-arcopening during south-facing subduction, north of theYilgarn Craton. After the cessation of oceanic vol-canism, cooling resulted in thermal subsidence andbasin development on top of the Narracoota Forma-tion leading to the deposition of turbidites, and thenfinally chemical sedimentary rocks in the relativelyshallow waters of a starved basin.

The Padbury Group consists of polydeformed andmetamorphosed siliciclastic and chemical sedimentaryrocks, which have been interpreted as developing ina retro-arc foreland basin (Padbury Basin) on top ofthe Bryah Group (Martin, 1994). The Padbury Groupmay record the convergence of the Glenburgh Terraneand the Yilgarn Craton.

The Yarlarweelor Gneiss Complex, Errabiddy ShearZone, Glenburgh Terrane and the Bryah and PadburyGroups were variably metamorphosed and deformedduring the 1830–1780 Ma Capricorn Orogeny. Fel-sic granites of the Moorarie Supersuite dated at1830–1790 Ma intruded all four domains, althoughrocks of the Bryah and Padbury Groups were only lo-cally intruded by granite close to their faulted contactwith the Yarlarweelor Gneiss Complex (Martin, 1994;Reddy and Occhipinti, 2004). These granites weremetamorphosed at high-grade within the YarlarweelorGneiss Complex (Occhipinti et al., 1998a), but in the

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greenschist facies elsewhere in the southern Capri-corn Orogen. Locally these granites are well foliated,and in some places sheets or dykes were folded.

3. Deformation and metamorphism

In the following discussion structural and metamor-phic events are annotated according to the orogenicevent during which they were formed, and numberedaccording to their relative age based on field rela-tionships and/or their interpreted or bracketed age.Two main deformation events are recognised dur-ing the Glenburgh Orogeny—D1g and D2g (Figs. 2and 5). Fabrics developed during the GlenburghOrogeny were typically deformed during the Capri-corn Orogeny and, in most domains, metamorphosedin the greenschist facies and locally overprinted dur-ing the 1070–750 Ma Edmundian Orogeny (Martinand Thorne, 2001). Fig. 5 summarizes the key struc-tural and metamorphic elements, and magmatic eventsthat developed between ca. 2000 and 1950 Ma in eachof the tectonic units.

3.1. Glenburgh Orogeny

The Glenburgh Orogeny comprises two main defor-mation events: D1g and D2g (Figs. 2 and 5). The agesof these two events have been constrained in the south-ern part of the Glenburgh Terrane (SGT) by extensiveSHRIMP U–Pb zircon dating on rocks that are eitheroverprinted by, or cut the structural fabrics. The timingof the D2g deformation event is also constrained in theErrabiddy Shear Zone by SHRIMP U–Pb dating. Else-where in the Capricorn Orogen, including the north-ern part of the Glenburgh Terrane (NGT), the ages oftectonic fabrics that developed prior to the CapricornOrogeny have been less accurately determined; thusthese fabrics can only be broadly correlated with thosedated in the SGT.

Deformation during the Capricorn Orogeny wasless intense in the SGT than in the other domains,allowing the older structural and metamorphic historyto be unravelled. However, even in the SGT the olderstructural sequence can be difficult to discern, asthe rocks have been heterogeneously deformed withthe same structural elements not being developedeverywhere.

3.1.1. D1g structures and M1g metamorphismThe earliest known deformation event (D1g) of the

Glenburgh Orogeny has been solely identified in theGlenburgh Terrane, and produced a foliation, S1g. Thisearly deformation fabric is associated with medium-to high-grade metamorphism (amphibolite to granulitefacies; M1g; Occhipinti and Sheppard, 2001), and de-veloped in the ca. 2550 and 2000 Ma granitic rocks,mafic gneisses and pelitic schists. Metamorphism out-lasted deformation and locally granoblastic texturesare strongly developed.

In the SGT an early foliation (S1g) developed insome of the metamorphosed fine- to medium-grainedca. 2000 Ma granodiorites, tonalites and monzogran-ites. The granitoids are generally banded and con-tain an anhedral granoblastic texture. Locally in thesouthern most part of the SGT, meta-monzogranitedykes dated at 1987± 4 Ma (Occhipinti et al., 2001;Nelson, 1999) are sub-parallel to the easterly trend-ing axial surfaces of tight to isoclinal, moderatelyplunging folds (correlated with the D1g deformationevent) in ca. 2000 Ma tonalite gneiss. Elsewhere inthe SGT meta-diorite dykes in ca. 2000 Ma foliatedgranites, dated by SHRIMP U–Pb analyses of zirconat 1989±3 Ma (Nelson, 1999), are sub-parallel to S1gand have not been folded. Therefore, only local fold-ing of S1g occured prior to ca. 1990 Ma and foliationsin both ca.1990 and 2000 Ma meta-granites are com-monly sub-parallel. These structures either developedduring a progressive D1g deformation event (Fig. 5),or are a result of large-scale strain partitioning. Fur-ther work, including direct age-dating of metamorphicfabrics and detailed mapping, is required to solve thisproblem.

In the NGT, a gneissosity (S1g) in the HalfwayGneiss is deformed about sub-horizontal to gentlydipping folds. The axial surfaces of these folds aresub-parallel to flat or gently dipping D2g faults thatform the contact between the Halfway Gneiss andthe Moogie Metamorphics. The development of thegneissic fabric is correlated with the D1g deformationevent in the southern domain and must have developedafter 2006± 6 Ma (Occhipinti et al., 2001), which isthe age of the youngest dated granitic component ofthe Halfway Gneiss, but before ca. 1800 Ma, the ageof granite that cuts the gneiss.

The original trend of S1g structures in the SGT isdifficult to assess largely due to overprinting during

246 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

the Capricorn Orogeny; however, in the CarandibbyInlier, the southwesternmost exposed part of the Glen-burgh Terrane (Fig. 1), the rocks are largely unaf-fected by younger tectonism. Here meta-tonalite andmeta-diorite sheets, which have igneous crystallisa-tion ages of ca. 2002 Ma (Nelson, 2000), are steeply tovertically dipping and northerly trending. In addition,axial surfaces of isoclinal folds in a pegmatite bandedgranitic gneiss, with a precursor granite age of ca.2500 Ma (Occhipinti et al., 2001), are also northerlytrending and steeply dipping.

The presence of mafic granulites, strips ofmigmatitic pelitic granulite within metagranites andgranitic gneisses of the Dalgaringa Supersuite in thecentral part of the SGT, indicates that these rockslocally were metamorphosed at high grade duringD1g (Occhipinti and Sheppard, 2001). However, thesehigh-grade conditions were not recorded everywhere,with amphibolite facies assemblages dominant in theSGT. The amphibolite facies rocks are not the productof retrogression of the granulite facies rocks, as norelict granulite facies minerals or textures indicativeof higher grade are present. Rocks metamorphosedunder both amphibolite facies and granulite faciesconditions were juxtaposed after M1g.

3.1.2. D2g structures and M2g metamorphismThe second regional deformation event, D2g is as-

sociated with a metamorphic event M2g, and is recog-nised in the Glenburgh Terrane, the Errabiddy ShearZone, parts of the Yarlarweelor Gneiss Complex, andpossibly in the Bryah and Padbury Basins.

3.1.2.1. Glenburgh Terrane. In the SGT mesoscopicupright folds (F2g) are widespread. Most of the foldsare tight or isoclinal, but in local zones of low D2gstrain they are open to close. The F2g folds trendwesterly or southwesterly, and plunge moderately tovery steeply to the east and northeast or to the westand southwest. However, these folds probably origi-nally developed as northerly or northeasterly trendingstructures (Occhipinti and Sheppard, 2001), and havebeen re-orientated during the Capricorn Orogeny. Thepossible northerly or northeasterly trend for the D2gfabrics in the Glenburgh Terrane can be seen in theCarrandibbly Inlier in the SGT in which the Capri-corn Orogeny has had little effect. In addition the trend

of ca. 1950 Ma granitic dykes, which cut D1g andD2g deformation fabrics, changes from east or south-easterly trending in the Carrandibby Inlier (Fig. 1) tosouth–southeasterly trending in the south–central partof the SGT, also reflecting this re-orientation.

The first regional foliation in the Moogie Meta-morphics within the NGT, is a sub-horizontal togently dipping foliation, correlated with S2g. Thisfoliation developed sub-parallel to bedding forminga composite S0/S2g fabric and is associated with amedium-grade M2g metamorphic event. The S2g foli-ation is also axial planar to sub-horizontal folds (F2g)of bedding observed in the Moogie Metamorphicswhere they deform quartzite (Fig. 6a), and of locallywell-developed S1g in the Halfway Gneiss, e.g. east of2 mile bore (at MGA 405800E 7229350N;Fig. 6b).

In the NGT some well-developed easterly trendingstretching lineations and S2g foliations are indica-tive of mylonitic development. The stretching lin-eations are generally sub-parallel to the fold axis of awest–northwesterly regional-scale antiform that devel-oped during the Capricorn Orogeny (Occhipinti andSheppard, 2001). The fold axis of the antiform rangesfrom sub-horizontally plunging to steeply plung-ing, probably due to later re-folding (Occhipinti andSheppard, 2001).

In thin-sections oriented parallel to the stretchinglineation and normal to the foliation, the fabric isusually symmetric, including feldspar augen, but lo-cally asymmetric augens and shear bands are present.In the central part of the NGT asymmetric struc-tures observed in the field and in thin section indi-cate top-to-the-west or-northwest movement. In thenorthern part of the NGT within the Halfway Gneissboth rotated feldspar porphyroblasts and some S–Cfabrics indicate possible top-to-the-northwest shearsense or south-over-north movement. Flat D2g faultsrepresented by mylonite zones between the HalfwayGneiss and the Moogie Metamorphics are also presentwithin the region.

In some areas, particularly in the Moogie Metamor-phics north of the Dalgety Fault (Fig. 2) in the NGT,massive quartz veins up to several kilometres longtrend sub-parallel to the S0/S2g fabric in micaceousmetasedimentary rocks, and the contacts between theMoogie Metamorphics and the Halfway Gneiss. Theseunits are commonly well foliated and may be veins,or deformed and metamorphosed quartz sandstone.

S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255 247

Fig. 6. Photographs of the early structures in the Moogie Metamorphics and the Halfway Gneiss. (a) Sub-horizontal to gently inclinedisoclinal fold in quartzite from (MGA 380380E 7233100N). (b) Folds in the Halfway Gneiss. S1g is folded about isoclinal folds and istransposed into S2g which is refolded into upright F1n folds. The F1n fold plunges moderately to the east.

Where they are veins they intruded sub-parallel to D2gstructures and fabrics, for example, the S2g foliationin the Halfway Gneiss and F2g sub-horizontal folds inquartzite of the Moogie Metamorphics, and may rep-resent D2g sub-horizontal detachment surfaces.

As mentioned previously the mylonitic fabric witheasterly-trending stretching lineations and flat faultsas well as the D2g sub-horizontal detachment surfacesin the Moogie Metamorphics, are deformed arounda regional-scale Capricorn-age fold. In addition thestretching lineations are sub-parallel to the hingelines of mesoscale parasistic folds to the large-scaleCapricorn-age antiform. This may be because theshear zone in which the mylonite developed had theshape of an easterly trending (more open?) fold, whichwas subsequently tightened. However, it is unlikelythat the mylonite formed in its present geometricalorientation as folds parallel to the lineation are tootight to be mechanically possible as corrugations in anactive mylonite zone. Therefore, it is more likely thatthe shear zone was affected by N–S shortening afterdevelopment of the shallow mylonitic fabric—that isduring the Capricorn Orogeny.

The Mumba Pelite was probably metamorphosedat medium-grade (amphibolite facies) during M2g;however, the M2g mineral assemblages in the MumbaPelite are typically completely overprinted (generallypseudomorphed) by lower grade mineral assemblages(Occhipinti and Sheppard, 2001). Locally garnet ispartially or completely pseudomorphed by chloritoidand chlorite, and chlorite may have pseudomorphed

biotite. In addition mats of sericite appear to representcompletely pseudomorphed sillimanite or staurolite.

During D2g a penetrative foliation developed inthe ca. 1975 Ma Nardoo Granite, which intruded the2005–1989 Ma components of the Dalgaringa Su-persuite in the SGT. The S2g foliation is defined byelongate biotite or, in places, by lenses and veins ofpegmatite up to a few centimetres wide forming agneissosity. Clots of fine-grained biotite after garnetare typically developed in this gneissosity. The D2gdeformation event occurred prior to ca. 1950 Ma, theage of granitic dykes that cut the S2g foliation in theNardoo Granite (Occhipinti and Sheppard, 2001).

The effects of M2g are commonly difficult todifferentiate from M1g (Occhipinti and Sheppard,2001). Mafic granulites, and amphibolites with M1gassemblages contain little evidence of M2g, prob-ably because of local anhydrous conditions duringM2g. Mineral assemblages formed during M2g in themeta-granites consist of biotite, oligoclase–andesine,and epidote. Locally garnet and hornblende arealso present. The composition of the plagioclase(oligoclase–andesine) together with the presence ofepidote, suggests that the rocks were metamorphosedin the epidote–amphibolite zone (transitional betweenthe amphibolite and greenschist facies) (Miyashiro,1994). High-grade assemblages in calc-silicategneisses and marbles that formed during M1g areoverprinted by lower grade assemblages (Occhipintiand Sheppard, 2001). For example, in the amphibole-and diopside-rich gneisses, pargasite and diopside

248 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

show incipient replacement along rims and fracturesto tremolite, and plagioclase is partially replaced byclinozoisite and a more sodic plagioclase.

During the Capricorn Orogeny in the NGT, apartfrom the Halfway Gneiss and Moogie Metamorphicsbeing folded into a regional-scale antiform, only localdevelopment of a pervasive greenschist facies crenu-lation cleavage (developed sub-parallel to these foldaxial surfaces) and retrogression of higher grade min-eral assemblages occurred (Occhipinti and Sheppard,2001).

3.1.2.2. Errabiddy Shear Zone. The ErrabiddyShear Zone (Figs. 1 and 3) initially developed duringthe 2000–1960 Ma Glenburgh Orogeny (Occhipintiet al., 1999a). Precursor sedimentary and minor maficrocks of the Quartpot Pelite and Petter Calc-silicate ofthe Camel Hills Metamorphics, and granite protolithsto the Warrigal Gneiss, were deformed and meta-morphosed prior to ca. 1960 Ma before being foldedinto upright, tight to isoclinal, easterly trending foldsduring the Capricorn Orogeny. In the Camel HillsMetamorphics and Warrigal Gneiss a metamorphicfoliation, which is locally gneissic or contains a flasertexture, developed during the Glenburgh Orogeny.This foliation, which is now steeply dipping, wasoriginally sub-horizontal or shallowly dipping andprobably northerly or northeasterly trending. The foli-ation is sub-parallel to faulted contacts between someoutcrops of the Warrigal Gneiss and the Camel HillsMetamorphics, which are thought to have developedduring D2g tectonic interleaving within and betweenthese units (Fig. 5).

A sub-horizontal to moderately plunging minerallineation, largely defined by fine-grained biotite, butlocally defined by white mica, is locally well de-veloped on the S2g foliation plane and may havedeveloped during D2g. This mineral lineation gener-ally trends parallel to the fold axes of regional-scaleupright, tight to isoclinal folds. These upright foldsdeveloped post D2g, during the Capricorn Orogeny(Sheppard and Occhipinti, 2000). In the central partof the shear zone, the mineral lineation (defined by bi-otite or white mica) is westerly, to west-southwesterlytrending whereas similar mineral lineations aresouth- or north-trending in the northeastern part ofthe shear zone. Field observations and thin-sectionanalyses of rocks in the central part of the shear

zone, around Erong Homestead (Fig. 3) indicatesthat the sub-horizontally to moderately plunging lin-eations are associated with dextral strike–slip move-ments. These mineral lineations post-date ca. 1960,and could be significantly younger (cf.Reddy andOcchipinti, 2004). In the areas adjacent to, and north-east of Errabiddy Homestead (Fig. 3), sub-horizontallyto moderately plunging mineral lineations are alsoassociated with dextral strike–slip movement; how-ever, it is not clear whether these are related to theGlenburgh Orogeny or subsequent deformation. Tothe east,Reddy and Occhipinti (2004)found thatkinematic indicators that formed along the post-ca.1800 Ma Kerba Fault (a splay off the ErrabiddyShear Zone) consistently illustrated dextral strike–slipmovement, regardless of whether a mineral lineationwas present or not.

The Camel Hills Metamorphics outcrop asfault-bounded blocks throughout the exposed extentof the Errabiddy Shear Zone. Metamorphic mineralassemblages developed in gneissic banding (S2g)within the Camel Hills Metamorphics during D2g,indicate that M2g was a medium- to high-grade event.Locally pelitic and semi-pelitic schist and gneiss ofthe Quartpot Pelite were migmatised during D2g (Fig.7a; Occhipinti and Sheppard, 2001). S2g is a differen-tiated foliation that is largely defined by the alignmentof sillimanite and biotite (although sillimanite is gen-erally pseudomorphed by fine-grained sericite mats)and quartz–plagioclase domains. Garnet does notcontain inclusion trails but is either wrapped by, oroverprints the S2g foliation, thus it most likely crys-tallised synchronously with, or just after D2g. Garnetporphyroblasts are commonly partially or completelypseudomorphed by chloritoid or chlorite, and arealso commonly replaced along rims and fractures byfine-grained biotite, muscovite and quartz.

The southwestern-most outcrops of semi-pelitic orpsammitic rocks of the Quartpot Pelite (Fig. 3) havebeen metamorphosed in the amphibolite facies butdid not attain the metamorphic conditions requiredfor migmatisation. This reflects either a decrease inmetamorphic grade or a loweraH2O, during M2g fromnortheast to southwest along the Errabiddy ShearZone. The resulting metamorphic isograd between themigmatised and unmigmatised rocks was folded intoan upright easterly trending fold during the CapricornOrogeny (D1n).

S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255 249

Fig. 7. Photographs of the Camel Hills Metamorphics. (a) Migmatitic gneiss of the Camel Hills Metamorphics with refractory psammiteand biotite-rich material; (b) calc-silicate gneiss with a boudinage composite S0/S2g fabric.

The Petter Calc-silicate consists of calc-silicateschist and gneiss, para-amphibolite and biotite-richschist, which contain a well-developed S2g foliation.The foliation has parallel to fine, 1 mm to 1 cm thickcompositional layering interpreted as original bed-ding, thus forming a composite S0/S2g fabric, whichis commonly boudinaged (Fig. 7b).

Some Archaean rocks of the northwestern marginof the Yilgarn Craton caught up in the Errabiddy ShearZone during the D2g/M2g event were intruded by gran-ite sheets and plutons of the ca. 1960 Ma BertibubbaSupersuite at the end of the Glenburgh Orogeny.Locally, granites of the Bertibubba Supersuite arefoliated and folded (Sheppard and Swager, 1999;Occhipinti et al., 2001); however, the age of the fab-rics in these granites has not been directly determined,and the granites may have remained undeformed untilthe Capricorn Orogeny.

During the Capricorn Orogeny, tight, upright,shallow to steeply plunging folds deformed thesub-horizontally dipping S2g foliation in the CamelHills Metamorphics. Pervasive retrogression of up-per amphibolite facies assemblages, which formedduring M2g, to greenschist facies assemblages in theCamel Hills Metamorphics also took place (Sheppardand Occhipinti, 2000). In the western and centralparts of the Errabiddy Shear Zone these folds arewesterly trending, whereas in the eastern and north-ern part of the shear zone, they are northeasterly tonortherly trending (Sheppard and Occhipinti, 2000;Occhipinti et al., 2001). These folds were refoldedduring the later stages of the Capricorn Orogeny,

due to east–southeasterly trending dextral strike–slipmovement (Sheppard et al., 2003), and north–southcompression.

3.1.2.3. Yarlarweelor Gneiss Complex. The Yarlar-weelor Gneiss Complex is in faulted contact with theBryah and Padbury Groups (Fig. 4). The gneiss com-plex mainly comprises Archaean granitic gneissesthat were reworked during the Palaeoproterozoic. Al-though it is clear that most of the folds and faultsdeveloped in the gneiss complex formed duringthe Capricorn Orogeny (Occhipinti et al., 1998a;Sheppard and Swager, 1999), it is unclear whetherstructures related to the Glenburgh Orogeny were welldeveloped throughout the complex. However, a foldedfoliation in the ca. 1960 Ma Yamagee Granite (of theBertibubba Supersuite) is older than foliations whichdeveloped in younger Capricorn-age granites in theregion (Sheppard and Swager, 1999) and may havedeveloped soon after the granite formation, during thewaning stages of the Glenburgh Orogeny.

The most dominant structures in the YarlarweelorGneiss Complex are tight, upright shallow to steeplyplunging folds that developed during the CapricornOrogeny. As in the Errabiddy Shear Zone, these foldswere refolded during later stages of the CapricornOrogeny, due to east–southeasterly trending dextralstrike–slip movement (Sheppard et al., 1999; Occhip-inti et al., 1998a), and north–south compression. Inthe Yarlarweelor Gneiss Complex, this appears to haveaccompanied a transition from ductile to brittle con-ditions in the region (Occhipinti and Myers, 1999).

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3.1.2.4. Bryah–Padbury Basins. The earliest defor-mation event in the Bryah Group is present in the PeakHill Antiform area and is correlated with D2g (Fig. 4).It is represented by layer-parallel mylonitic thrustfaults and by folds that were probably sub-horizontalprior to subsequent deformation. In addition, D2gisoclinal folds developed in banded iron-formations(for example, the Robinson Syncline;Fig. 4). Thesefaults and folds were all overprinted during theCapricorn Orogeny by D1n upright east-west strikingregional folds. This contrasts with the interpretationof Occhipinti et al. (1998b)who suggested that D1and D2 structures (now regarded as D2g and D1n, re-spectively) could be interpreted as successive stagesof progressive deformation of the Bryah and PadburyGroups.

During both the Glenburgh and Capricorn Oroge-nies, the Bryah and Padbury Groups were tectonicallyinterleaved with the Yarlarweelor Gneiss Complex(Fig. 4), and during the Capricorn Orogeny theywere intruded by granite (Martin, 1994; Reddy andOcchipinti, 2004) in areas close to the gneiss complex.

The highest grade metamorphic mineral assem-blages in the Bryah and Padbury basins are found inthe contact zones between the Yarlarweelor GneissComplex and the overlying metasedimentary rocks ofthe Padbury Group (Occhipinti et al., 1998; Fig. 4).East of the Yarlarweelor Gneiss Complex, a northerlytrending strip of metamorphosed arkosic sandstone ofthe Padbury Group contains amphibolite facies min-eral assemblages. Metamorphism in the Bryah andPadbury Groups generally does not exceed green-schist facies. The relationships between metamorphicmineral growths and deformation are summarised inPirajno et al. (2000).

4. Tectonic models

Tectono-magmatic events observed across the Glen-burgh Terrane, Errabiddy Shear Zone, YarlarweelorGneiss Complex and Bryah–Padbury basins have beencorrelated temporally, using available U–Pb SHRIMPgeochronological data (Fig. 5). The nature and agesof these elements are used to propose tectonic modelsfor the southern Capricorn Orogen.

The tectonic setting of the Gascoyne Complexis still poorly understood, and previous models do

not take into account the 2000–1970 Ma GlenburghOrogeny (Occhipinti et al., 1999b), and incorrectlysuggested the complex contained reworked crust fromthe Yilgarn Craton (Williams, 1986; Myers, 1990;Muhling, 1990). However, the southern GascoyneComplex consists of Palaeoproterozoic foliated andgneissic granites of the Dalgaringa Supersuite, andlow- to medium-grade metasedimentary rocks of theMoogie Metamorphics (Occhipinti and Sheppard,2001) of the Glenburgh Terrane. Basement to theserocks is probably represented by tectonically inter-leaved latest Archaean (ca. 2550 Ma) gneissic granite,which now makes up much of the Halfway Gneiss.The Archaean granite components of the HalfwayGneiss are younger than any dated Archaean gran-ites from the Pilbara or Yilgarn Cratons, and theirεNd values plot outside of the field of granites of theNarryer Terrane (Yilgarn Craton) (Sheppard et al.,2004). In addition, the Archaean component of theHalfway Gneiss is mostly granodioritic or tonalitic incomposition, which is more mafic than the monzo-granite and syenogranite that dominates the YilgarnCraton. Thus, the Glenburgh Terrane is exotic to theYilgarn Craton, and to the Pilbara Craton which wascratonised prior to ca. 2770 Ma (Fig. 1).

In the southern Capricorn Orogen, magmatism be-tween 2005 and 1970 Ma only took place in the Glen-burgh Terrane, suggesting that the Glenburgh Terraneformed a separate terrane from rocks in the ErrabiddyShear Zone, the Yarlarweelor Gneiss Complex, andthe Bryah and Padbury Basins at this time. This inter-pretation is supported by the restriction of high-grademetamorphism during D1g to the Glenburgh Ter-rane, implying that it was not metamorphosed inits present location. The 2005–1970 Ma DalgaringaSupersuite which is dominated by diorite, tonaliteand granodiorite, contrasts in composition to mostPalaeoproterozoic batholiths of northern Australia,which largely consist of monzogranite and granodi-orite (Wyborn et al., 1992). Major and trace elementcompositions of granites of the Dalgaringa Supersuiteare similar to Phanerozoic subduction-related granitessuggesting that the supersuite may have formed in anAndean-type setting (Sheppard et al., 1999) along themargin of a late Archaean to Palaeoproterozoic con-tinent or microcontinent (Fig. 8). It is likely that theDalgaringa Supersuite developed at about the sametime as the Bryah and Pabury basins, but to the west

S.A.

Occhipinti

etal./P

recambrian

Research

128(2004)

237–255251

SS125A

2000–1970 Ma

MODELS A and B

GlenburghTerrane

GASCOYNECOMPLEX

RiftedArchaean

Craton

YILGARNCRATON

subductionzone Yerrida Basin

Ocean

Ocean

sedimentarybasins

? ?

?

PILBARACRATON

YILGARNCRATON

Ashburton Basin

c. 1800 Mabatholith

GlenburghTerrane

ErrabiddyShearZone

Bryah–PadburyBasins

YARLARWEELORGNEISS

COMPLEX

Limit of Capricorn Orogeny deformation

RiftedArchaean

Craton

YILGARNCRATON

GlenburghTerrane

GlenburghTerrane

ErrabiddyShearZone

Bryah–PadburyBasins

YILGARNCRATON

2000–1970 Ma

proto-NarracootaFormation

Bryah Basin

sedimentationand volcanism

Dalgaringa Supersuite Plutonslatest Archaean crustproto-Halfway Gneiss

sedimentation

mid-ocean rid

geseafloor

W E

W E

15.02.02

proto-YARLARWEELORGNEISS

COMPLEX

Andesitic volcanism

Current erosion level

sedimentation

By ca.1800 Ma

By ca.1960 Ma

Fig. 8. Schematic diagram illustrating the possible tectonic evolution of the southern Capricorn Orogen during the Glenburgh Orogeny. The bottom inset of the CapricornOrogen shows the effects of the ca. 1800 Ma Capricorn Orogeny in the region, which is largely reflected by the current-day geometry of the southern Capricorn Orogen.

252 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

(Fig. 8). However, Dalgaringa Supersuite rocks lo-cally contain an extra structural fabric, which recordsan earlier deformation and metamorphism event thanis observed in the Bryah and Padbury Basins, Yarlar-weelor Gneiss Complex and rocks in the ErrabiddyShear Zone. This could be due to either syn-magmaticdeformation, or regional migration of deformation andmetamorphism from west to east, thus beginning inthe Glenburgh Terrane.

Sedimentary protoliths to the Camel Hills Meta-morphics were sourced from both the Yilgarn Craton,and from now, unexposed, early Palaeoproterozoiccrust. It is possible that these protoliths were depositedin different basin-settings between the convergingGlenburgh Terrane and rifted part of the YilgarnCraton (Fig. 8). In this case the proto-QuartpotPelite may have been deposited as an accretionaryprism, whilst the proto-Petter Calc-silicate may havebeen deposited in a carbonate shelf or platform overand west of a possible rifted part of the YilgarnCraton.

The Bryah and Padbury Basins are poorly dated;however, limited geochronological data on the Bryahand Padbury Groups and cross-cutting relationshipswith younger (ca. 1800 Ma) granite (Martin, 1994)suggest that they were deposited by ca. 2000 Ma.Pirajno and Occhipinti (2000), Myers (1993) andMyers et al. (1996)suggest that the Bryah Basin wasa back-arc basin formed during subduction beneaththe northern margin of the Yilgarn Craton. However,remnants of cordilleran-like magmatic suites have notbeen identified to the north of the Bryah and Pad-bury Basins, although they may be buried beneath theMesoproterozoic Edmund and Collier Basins of theBangemall Supergroup.

Meta-hyaloclastites in the southern part of the BryahBasin appear to have erupted in a shallow-water settingand were emplaced on the Yilgarn crust (Pirajno andOcchipinti, 2000), contrasting with the oceanic set-ting of the metabasites of the Narracoota Formation.Following the cessation of mafic volcanism, thermalsubsidence and rift development led to the deposi-tion of turbidites, followed by chemical sedimentaryrocks in a starved basin (Pirajno and Occhipinti,2000).

The Padbury Group was deposited over the BryahGroup in the Padbury Basin, east of the proto-Errabiddy Shear Zone. The Padbury Group, which

consists of metamorphosed siliciclastic, carbonateand chemical sedimentary rocks, is interpreted asa retro-arc foreland basin, which recorded a colli-sion (Martin, 1994; Fig. 8). The age of the PadburyGroup is poorly constrained; however, in places, itunconformably overlies the Bryah Group (Martin,1994), and deformed rocks of the Padbury Groupare intruded by granite (Martin, 1994) that are corre-lated with ca. 1800 Ma granites in the region. If so,the Padbury Basin would have formed prior to the1830–1780 Ma Capricorn Orogeny, and most likelyduring the 2000–1960 Ma Glenburgh Orogeny. Atthis time, rocks of the Bryah and Padbury Groupswere also deformed into sub-horizontal structures(correlated with regional D2g), and parts of the BryahGroup were thrust over the passive margin of theYilgarn Craton from west to east.

Previous models for the development of theBryah and Padbury Basins, includingPirajno et al.(1998) and Myers (1993), and in partPirajno andOcchipinti (2000)inferred that these basins developednorth of the Yilgarn Craton, during the CapricornOrogeny, and were deformed by it. The Bryah andPadbury Basins, more likely, developed to the westor northwest of the Yilgarn Craton (Fig. 8) during theGlenburgh Orogeny. This would explain the apparentprogression from west to east of rifting throughoutthe basin suggested byPirajno and Occhipinti (2000).In this case the northwestern, or western marginof the Yilgarn Craton would have rifted (prior toca. 2000 Ma) in order to produce the oceanic crust(Pirajno and Occhipinti, 2000), which is the settingof the Narracoota Formation (Fig. 8).

By ca.1960 Ma, the Glenburgh Terrane microcon-tinent had collided with the passive margin of theYilgarn Craton, with both now juxtaposed along theErrabiddy Shear Zone (Fig. 8). Felsic magmatismonly took place in the rifted portion of the YilgarnCraton, which included the proto-Yarlarweelor GneissComplex, and the Camel Hills Metamorphics. TheCamel Hills Metamorphics and any possible riftedfragments of the Yilgarn Craton (possibly some pro-tolith granites to the Warrigal Gneiss?) were meta-morphosed and deformed by this time, and includedin the Errabiddy Shear Zone (Fig. 8). Sheppard et al.(2003)suggested that the Glenburgh Terrane was sub-ducted beneath the Yilgarn Craton during the Glen-burgh Orogeny, because Nd-isotope data show that

S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255 253

the 1965–1945 Ma granite plutons of the BertibubbaSupersuite that intruded the Errabiddy Shear Zoneand the proto-Yarlarweelor Gneiss Complex (Fig. 8),were primarily derived from melting of DalgaringaSupersuite rocks. The intrusion of these ca. 1960 Magranites and similar ca. 1950 Ma granitic dykes intothe southernmost Glenburgh Terrane marks the endof the Glenburgh Orogeny.

In the southern Capricorn Orogen, there is an ab-sence of tectonism and magmatism between the 2000–1960 Ma Glenburgh Orogeny and the 1830–1780 MaCapricorn Orogeny, which probably reflects changesin the tectonic setting of the region during this time.Unlike the Dalgaringa Supersuite, the 1965–1945 MaBertibubba Supersuite and Capricorn-aged granites in-trude across the Glenburgh Terrane, Errabiddy ShearZone, and the Yarlarweelor Gneiss Complex, confirm-ing that the Glenburgh Terrane had accreted onto theYilgarn Craton prior to the Capricorn Orogeny. Capri-corn Orogeny granites consist of monzogranite, withsome syenogranite and granodiorite, whereas the Dal-garinga Supersuite, of the Glenburgh Terrane, containsmore intermediate compositions, more indicative ofarc-type magmatism. However, the regional extent ofthe Glenburgh Terrane is still unknown. It may havecollided and accreted onto the Pilbara Craton (Fig. 1)to form the Ophthalmia fold belt (a northward-vergingfold belt exposed on the southern margin of the Pil-bara Craton) which developed soon after ca. 2450 Ma(Martin et al., 2000), and then collided (together withthe Pilbara Craton) with the Yilgarn Craton during theGlenburgh Orogeny.

5. Conclusions

Extensive regional mapping, and careful samplingfor U–Pb SHRIMP geochronology, and geochemistry(Sheppard et al., 2004) in the southern CapricornOrogen has led to a greater understanding of the re-gion and to the recognition of the existence of the2000–1960 Ma Glenburgh Orogeny. These resultshave allowed the tectonic framework and formationof the Glenburgh Terrane, Errabiddy Shear Zone,Yarlarweelor Gneiss Complex and Bryah–Padburybasins to be pieced together.

Previous models for the evolution of the Capri-corn Orogen have not taken the Glenburgh Orogeny

into account, and only explain the evolution of theorogen in terms of a single Palaeoproterozoic oro-genic event—the Capricorn Orogeny. In the light ofthese new data, these models must be revised. The130 million year hiatus between the end of the Glen-burgh Orogeny and the start of the Capricorn Orogenyin the southern Capricorn Orogen also needs to beexplained.

Tectonic models for the Capricorn Orogeny, whichin recent times has mainly been explained in terms ofcontinent–continent collision (Tyler and Thorne, 1990;Myers et al., 1996; Pirajno et al., 1998) may also re-quire revision. The lack of arc-type granitic rocks agedbetween 1960 and 1830 Ma suggests that the Capri-corn Orogeny may have been the result of intracra-tonic processes (Gee, 1979). The presence of granitesin the Glenburgh Terrane, which may have formed inan Andean-type setting (Sheppard et al., 1999) is con-sistent with the Glenburgh Terrane being accreted tothe northern margin of the Yilgarn Craton during theGlenburgh Orogeny at c. 1960 Ma, possibly as part ofa combined Pilbara–Glenburgh Craton.

Acknowledgements

We gratefully acknowledge Brendan Murphy andDavid Corrigan for their helpful reviews—they greatlyimproved the manuscript. We acknowledge DavidMartin for helpful discussions on the Opthalmiafold belt. We also thank Suzanne Dowsett, DellysSutton and Michael Prause of the Geological Sur-vey of Western Australia for preparation of many ofthe figures. This paper is TSRC publication number207.

References

Fletcher, I.R., Williams, S.J., Gee, R.D., Rossman, K.J.R., 1983.Sm–Nd model ages across the margins of the Archaean YilgarnBlock, Western Australia northwest transect into the ProterozoicGascoyne Province. J. Geol. Soc. Aust. 30, 167–174.

Gee, R.D., 1979. The Geology of the Peak Hill Area. AnnualReport for 1978. Western Australia Geological Survey,pp. 55–62.

Hynes, A., Gee, R.D., 1986. Geological setting and petro-chemistryof the Narracoota Volcanics, Capricorn Orogen, WesternAustralia. Precambrian Res. 31, 107–132.

254 S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255

Krapez, B., 1999. Stratigraphic record of an Atlantic-type globaltectonic cycle in the Palaeoproterozoic Ashburton Province ofWestern Australia. Aust. J. Earth Sci. 46, 71–87.

Krapez, B., Martin, D.M., 1999. Sequence stratigraphy of thePalaeoproterozoic Nabberu Province of Western Australia. Aust.J. Earth Sci. 46, 89–103.

Libby, W.G., de Laeter, J.R., Myers, J.S., 1986. Geochronologyof the Gascoyne Province. Report 50. Western AustraliaGeological Survey, pp. 31.

Martin, D.McB., 1994. Sedimentology, Sequence Stratigraphy, andTectonic Setting of a Palaeoproterozoic Turbidite Complex,Lower Padbury Group, Western Australia. Unpublished Ph.D.Thesis. University of Western Australia.

Martin, D.McB., Powell, C.McA., George, A.D., 2000. Strati-graphic architecture and evolution of the early PalaeoproterozoicMcGrath Trough, Western Australia. Precambrian Res. 99, 33–64.

Martin, D.McB., Thorne, A.M., 2001. New insights into theBangemall Supergroup. GSWA 2001 extended abstracts: Newgeological data for WA explorers. Western Australia GeologicalSurvey, pp. 1–2.

Miyashiro, A., 1994. Metamorphic Petrology. UCL Press Limited,London, 404 pp.

Muhling, J.R., 1990. The Narryer Gneiss Complex of the YilgarnBlock, Western Australia—a segment of Archaean lower crustuplifted during Proterozoic orogeny. J. Metamorph. Geol. 8,47–64.

Myers, J.S., 1990. Precambrian tectonic evolution of part ofGondwana, southwestern Australia. Geology 18, 537–540.

Myers, J.S., 1993. Precambrian history of the West AustralianCraton and adjacent orogens. Ann. Rev. Earth Planet. Sci. 21,453–485.

Myers, J.S., Shaw, R.D., Tyler, I.M., 1996. Tectonic evolution ofProterozoic Australia. Tectonics 15, 1431–1446.

Nelson, D.R., 1998. Compilation of SHRIMP U–Pb zircongeochronology data, 1997, Record 1998/2. Western AustraliaGeological Survey, 242 pp.

Nelson, D.R., 1999. Compilation of geochronology data, 1998,Record 1999/2. Western Australia Geological Survey, 222 pp.

Nelson, D.R., 2000. Compilation of geochronology data, 1999,Record 2000/2. Western Australia Geological Survey, 251 pp.

Occhipinti, S.A., Myers, J.S., 1999. Geology of the Moorarie1:100,000 sheet, Geological Series Explanatory Notes. WesternAustralia Geological Survey, pp. 20.

Occhipinti, S.A., Sheppard, S., 2001. Geology of the Glenburgh1:100,000 sheet, Geological Series Explanatory Notes. WesternAustralia Geological Survey, pp. 37.

Occhipinti, S.A., Sheppard, S., Nelson, D.R., Myers, J.S., Tyler,I.M., 1998a. Syntectonic granite in the southern margin of thePalaeoproterozoic Capricorn Orogen, Western Australia. Aust.J. Earth Sci. 45, 509–512.

Occhipinti, S.A., Swager, C.P., Pirajno, F., 1998b. Structural-meta-morphic evolution of the Palaeoproterozoic Bryah and PadburyGroups during the Capricorn Orogeny, Western Australia.Precambrian Res. 90, 141–158.

Occhipinti, S.A., Sheppard, S., Tyler, I.M., 1999a. The Palaeopro-terozoic tectonic evolution of the southern margin of theCapricorn Orogen, Western Australia. Geol. Soc. Aust. Abstr.53, 173–174.

Occhipinti, S.A., Sheppard, S., Tyler, I.M., Nelson, D.R., 1999b.Deformation and metamorphism during the c. 2000 Ma Glen-burgh Orogeny and c. 1800 Ma Capricorn Orogeny. In: Watt,G.R., Evans, D.A.D. (Eds.), Two Billion Years of Tectonicsand Mineralisation. Geol. Soc. Aust. Perth Abstr. 56, 26–29.

Occhipinti, S.A., Sheppard, S., Myers, J.S., Tyler, I.M., Nelson,D.R., 2001. Archaean and Palaeoproterozoic Geology of theNarryer Terrane (Yilgarn Craton) and the Southern GascoyneComplex (Capricorn Orogen)—A Field Guide, Record 2001/8.Western Australia Geological Survey, Perth, 70 pp.

Pirajno, F., Occhipinti, S.A., 2000. Three Palaeoproterozoicbasins—Yerrida, Bryah and Padbury—Capricorn Orogen,Western Australia. Aust. J. Earth Sci. 47, 675–688.

Pirajno, F., Occhipinti, S.A., Swager, C.P., 1998. Geology andtectonic evolution of the Palaeoproterozoic Bryah, Padbury, andYerrida Basins (formerly Glengarry Basin), Western Australia—implications for the history of the south-central CapricornOrogen. Precambrian Res. 90, 119–140.

Pirajno, F., Occhipinti, S.A., Swager, C.P., 2000. Geology andmineralization of the Palaeoproterozoic Bryah and PadburyBasins, Western Australia, Report 59. Geological Survey ofWestern Australia, 52 pp.

Pirajno, F., Jones, J.A., Hocking, R.M., Halilovic, J., 2004.Geology and tectonic Evolution of Palaeoproterozoic Basins ofthe Eastern Capricorn Orogen, Western Australia. PrecambrianRes. 128, 315–342.

Reddy, S.M., Occhipinti, S.A., 2004. High-strain zone deformationin the southern capricorn orogen, Western Australia:Kinematics and age constraints. Precambrian Res. 128, 295–314.

Sheppard, S., Occhipinti, S.A., 2000. Geology of the Errabiddyand Landor 1:100,000 sheets, Geological Series ExplanatoryNotes. Western Australia Geological Survey, pp. 37.

Sheppard, S., Swager, C.P., 1999. Geology of the Marquis1:100,000 sheet, Geological Series Explanatory Notes. WesternAustralia Geological Survey, pp. 21.

Sheppard, S., Occhipinti, S.A., Nelson, D.R., Tyler, I.M., 1999.The significance of c. 2.0 Ga crust along the southern marginof the Gascoyne Complex, Annual Review 1998–1999. WesternAustralia Geological Survey, pp. 56–61.

Sheppard, S., Occhipinti, S.A., Tyler, I.M., 2001a. The tectonicsetting of granites in the southern Gascoyne Complex. GSWA2001 extended abstracts: New geological data for WA explorers,Records 2001/5. Western Australia Geological Survey, pp. 3–4.

Sheppard, S., Occhipinti, S.A., Tyler, I.M., 2001b. Linksbetween regional-scale deformation and granite generation: theYarlarweelor gneiss complex, Western Australia. In: Davidson,G., Pongratz, J. (Eds.), 2000: A Structural Odyssey. Geol. Soc.Aust. Tasmania Abstr. 64, 172–173.

Sheppard, S., Occhipinti, S.A., Tyler, I. M., 2004. A 2005–1970Ma Andean-type batholith, in the Southern Gascoyne Complex,Western Australia. Precambrian Res. 128, 257–277.

Sheppard, S., Occhipinti, S.A., Tyler, I.M., 2003. The relationshipbetween the tectonism and composition of granite magmas,Yarlarweelor Gneiss Complex, Western Australia. Lithos. 66,133–154.

S.A. Occhipinti et al. / Precambrian Research 128 (2004) 237–255 255

Tyler, I.M., Thorne, A.M., 1990. The northern margin of theCapricorn Orogen, Western Australia—an example of anearly Proterozoic collision zone. J. Struct. Geol. 12, 685–701.

Williams, S.J., 1986. Geology of the Gascoyne Province, WesternAustralia, Report 15. Western Australia Geological Survey,Perth, pp. 85.

Windh, J., 1992. Tectonic Evolution and Metallogenesis ofthe Early Proterozoic Glengarry Basin, Western Australia.Unpublished Ph.D. Thesis. University of Western Australia.

Wyborn, L.A.I., Wyborn, D., Warren, R.G., Drummond, B.J.,1992. Proterozoic granite types in Australia: implications forlower crust composition, structure and evolution. Trans. R. Soc.Edinburgh: Earth Sci. 83, 201–209.