The Musgrave Province, Central Australia

Unravelling the tectonic framework of the Musgrave Province, central Australia

Benjamin P. Wade, B.Sc (Hons)

Geology and Geophysics School of Earth and Environmental Sciences The University of Adelaide

This thesis is submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in the Faculty of Science, University of Adelaide

September 2006 Chapter 1

Introduction

1.1 Project Overview and Aims 1995; Myers et al., 1996; Scott et al., 2000; Cawood and Tyler, 2004; Giles et al., 2004; Occhipinti et The 1.60-1.08 Ga Musgrave Province in central al., 2004; Tyler, 2005; Betts and Giles, 2006; Wade southern Australia occupies a vast area (~120,000 et al., 2006). The Musgrave Province is km2) (Figure 1.1), however it comprises the least geographically central to, and younger than, these known Proterozoic terrain in Australia. The accreted Archaean-Palaeoproterozoic fragments construction of a cohesive and data-rich geological (Figure 1.2). This makes it a key element in the framework for the evolution of the Musgrave assembly of Proterozoic Australia, and therefore Province has been hampered by two factors. any models that attempt to describe the evolution of Proterozoic Australia require a sound framework 1) There is a paucity of outcrop beyond the for the geologic evolution of the Musgrave Province. main topographic ranges of the Province; The aim of this thesis was to develop a framework 2) Approximately 80% of the land in the for the protracted geological evolution of the Musgrave Province falls within the traditional Musgrave Province, starting from its earliest history Anangu Pitjantjatjara, Yankunytjatjara and (early Mesoproteorozic), to its latest (early Ngaanyatjarra lands, creating significant difficultly Cambrian) (Figure 1.3). Also of interest was in obtaining access to regions. determining the timing of the final amalgamation of Proterozoic Australia. This was conducted Due to a range of studies over the past decade, utilising geochemical, isotopic, and it is now generally accepted that convergent plate geochronological means. In order to achieve this margin processes played an important role in the aim a five-module program was constructed that assembly of the various Archaean-Proterozoic involved: fragments of Australia (e.g. Zhao and McCulloch,

129°00 132°00 N

25°00 Petermann Ranges Amadeus Basin W oo dro f fe Mt

Aloysius Hinckley Ranges Mulga Park Mann Domain Cohn Ranges Kulgera N.T. Hill ° Area 26 00 T Ma omkinson nn Champ De S.A. Ranges H T Mars inc Deering hru kle Amata st y F Hills ault F Mt ault ? ? West Musgrave Ranges ? Fregon Levinger Ferdinand Fault Domain Graben

Moorilyanna W inti ginna Fault Graben 27°00 Indulkana Lindsay Fault Range Fault Birksgate Range Eromanga Everard Basin Officer Basin Ranges Thrust 0 50 100 km W.A.

Inferred Basement ca. 1.2-1.05 Ga granite Neoprot-Camb sediments

Amphibolite facies ca. 1.3 Ga orthogneiss ca. 1.08-1.04 Ga and granite volcanics/sediments Granulite facies ca. 1.4-1.36 Ga Giles mafic-ultramafic intrusions metasediments 1600-1540 Ma

Figure 1.1 Location map of the Musgrave Province indicating main areas of fieldwork undertaken in this study and areas of interest. 1

Chapter 1 Introduction Musgrave Province (Figure 1.3) has prohibited a 3. The genesis and tectonic significance of the coherent region-wide evaluation of the mechanisms layered intrusions of the mafic-ultramafic Giles involved in the formation of the Musgrave Province. Complex;

1.2 Outline and organisation of thesis 4. The genesis of the intracratonic Petermann Orogeny as it is recorded in the sediments of the This thesis is organised in a manner that Officer Basin. systematically provides geochemical and isotopic constraints to address a number of elements 5. The genesis of the granitic gneiss of the relating to the tectonic environment pertaining to Coompana Block, and the subsequent implications the formation of various lithologies within the for Proterozoic reconstructions of Australia. Musgrave Province, and also the boundaries with other tectonic domains. These elements are: Chapter 2 summarises the regional geological framework of the Musgrave Province. Despite the 1. The origin of the ca. 1.60-1.54 Musgravian fact that it occupies a large portion of central Gneiss of the Musgrave Province, and the Australia, the Musgrave Province represents one implications for the timing of reconstruction models of the least studied terranes of Proterozoic Australia. involving fragments of Proterozoic Australia; An attempted summary of the results and interpretations of published papers and Ph.D 2. The source of metasediments in the eastern theses, as well as results recorded by State Musgrave Province, and the subsequent Geological surveys is presented in the paper. The implications for pre-Rodinia palaeogeographic chapter is divided into a description of the individual reconstructions involving Australia; lithological units, structural framework, metamorphic

Musgrave Province Time (Ma) Mulga Park Domain Fregon Domain

D7 ? ? D7 550 D6 PETERMANN OROGENY D6

D5 ? ? D5 D4 ? ? D4 800 Amata Dyke Swarm Felsic volcanics

Mafic intrusive

1000 Unnamed olivine dolerites Layered Mafic Intrusion

Tjauwata Group Giles Tollu Group Post 1.3 Ga Rocks D3 D3 Felsic intrusive Alcurra Dykes ? ? Complex Alcurra Dykes 1100 ? Unconformity Pitjantjatjara Pitjantjatjara Supersuite Supersuite D2 MUSGRAVE D2 Protolith 1200 OROGENY Volcanic

Mafic-intermediate intrusive Un-named 1300 D1 ? ? Orthogneiss D1 ? Metasedimentary ???? Felsic intrusive 1400 ? ? Un-named Pre 1.2 Ga Gneissic Rocks Metasediments Metamorphism/ Deformation ??????? 1500 Pre-D1?

Olia Birksgate Gneiss Complex 1600

Figure 1.3 Musgrave Province lithostratigraphic sequence

3 Chapter 1 Introduction

A B

C D

E F

G H

Amata Dyke

FIgure 1.4 (A) Felsic gneiss of the Birksgate Complex, Deering Hills; (B) Mafic gneiss of the Birksgate Complex, Deering Hills; (C) Weathered metapelitic rock of the Birksgate Complex, Deering Hills; (D) Folded quartzite of the Deering Hills; (E) Calc- silicate of the Birksgate Complex, Deering Hills; (F) Example of Pitjantjatjara Supersuite Granite, eastern Musgraves; (G) Example of magmatic layering within the Giles Complex, Caroline intrusion; and, (H) Example of Amata Dyke cross-cutting felsic and mafic gneiss of the Birksgate Complex, Deering Hills.

4 Chapter 1 Introduction record, and possible tectonic significance of the Chapter 7 investigates the age and petrogenetic Musgrave Province. origin of a granitic gneiss located to the west of the Gawler Craton under cover, in what is termed Chapter 3 describes the geochemistry and Nd the Coompana Block. This module was conducted isotopic characteristics of a suite of ca. 1.60-1.54 following the interpretation of results from Chapter Ga felsic orthogneisses that comprise the basement 4, primarily to locate potential sources of zircons in the northern Musgrave Province. This study within the metasedimentary rocks of the eastern provides the first detailed geochemical and isotopic Musgrave Province. analysis of this magmatic event. Limited geochemical work on equivalent felsic rocks in the The thesis is concluded in Chapter 8 with a western Musgrave Province conclude a possible summary of the implications derived from the plate margin origin (e.g. Glikson et al., 1996; Wade results of this study. This section summarises the et al., 2006). By discriminating the tectonic origin findings of the thesis and investigates the of these felsic orthogneisses through geochemical implications of these results for reconstructions of and isotopic means, it allows us to place constraints Proterozoic Australia. on the evolution of the Musgrave Province during the early Mesoproterozoic. Several parts of this thesis have been published or submitted in varying forms to international Chapter 4 reports U-Pb SHRIMP and U-Pb LA- journals. Chapter 2 has been submitted as a ICPMS geochronological and Nd isotope data on review paper to a special volume of Precambrian metasedimentary rocks from the eastern Musgrave Research concentrated on Proterozoic Australia. Province. Originally mapped as part of the ca. Chapter 3 has been published in the Journal of 1.60-1.54 Ga basement Musgravian Gneiss (Conor, Geology, and Chapter 4 has been submitted to 1987), detrital zircon geochronology was and is in review in Geology. Chapter 5 has been undertaken to ascertain possible source regions submitted and in review at the Journal of Petrology. to aid in reconstructions of Proterozoic Australia. Chapter 6 is published in the Journal of the Geological Society of London, and Chapter 7 has Chapter 5 presents geochemical and radiogenic been submitted and is in review at the Australian isotopic data (Nd-Sr) of sample traverses over Journal of Earth Sciences. Appendix 5 has been three intrusions of the mafic-ultramafic Giles submitted to and is in review at Computers and Complex within the western Musgrave Province Geosciences. I have also been involved in a of South Australia. Detailed mapping and sampling number of related projects that are in submission of the Kalka, Ewarara, and Gosse Pile intrusions in international peer reviewed journals. As the has been previously undertaken during the early structure of this project has been focussed on 1970s (e.g. Goode, 1970; Moore, 1970); however, producing each chapter as a stand-alone detailed geochemical and isotopic analysis has manuscript, there is some repetition in the not been applied. The aim is to understand the geological background sections of each chapter. petrogenesis of the mafic magmatism, by characterising the magmatic processes that were in operation during their formation. Furthermore, characteristics of the possible mantle source for the Giles Complex is proposed. These characteristics form the basis for proposing models on the lithospheric evolution of the Musgrave Province and provide information for crust-mantle interactions in this part of Proterozoic Australia. Chapter 6 investigates the geochemical and isotopic effects of the early Cambrian (ca. 550 Ma) Petermann Orogeny of the Musgrave Province on the basin fill sediments of the Officer Basin in southern central Australia. Detailed isotopic and geochemical analysis was undertaken through the stratigraphy of the Officer Basin, starting in the basal Neoproterozoic units through to upper units of late Cambrian age. By recognising the initial large influx of Musgrave derived material in the geochemical and isotopic signatures of the Officer Basin, we are able to place constraints on the duration of the intracratonic Petermann Orogeny.

CHAPTER 2

The Musgrave Province; Terra Anonymous?

This chapter is accepted to a Special Volume of Precambrian Research focussing on Proterozoic Australia as: Wade, B.P., Kelsey, D.E., Hand, M., Barovich, K.M. (2006) The Musgrave Province; Stitching North, West and South Australia. Precambrian Research. See appendix for full article.

Wade, B.P., Kelsey, D.E., Hand, M., Barovich, K.M. (2006) The Musgrave Province; Stitching North, West and South Australia. Precambrian Research, special volume

NOTE: This publication is included on pages 6 – 23 in the print copy of the thesis held in the University of Adelaide Library.

It is also available online to authorised users at:

http://dx.doi.org/10.1016/j.precamres.2007.05.007

6 CHAPTER 3

Evidence for early Mesoproterozoic arc magmatism in the Musgrave Block, central Australia: implications for Proterozoic crustal growth and tectonic reconstructions of Australia

This chapter is published as: Wade, B.P., Barovich, K.M., Hand, M., Scrimgeour, I.R., Close, D.F. (2006) Evidence for early Mesoproterozoic arc magmatism in the Musgrave Block, central Australia: implications for Proterozoic crustal growth and tectonic reconstructions of Australia. Journal of Geology, 114, 43-63. See appendix for full article.

Wade, B.P., Barovich, K.M., Hand, M., Scrimgeour, I.R. and Close D.F. (2006) Evidence for early Mesoproterozoic arc magmatism in the Musgrave Block, central Australia: implications for Proterozoic crustal growth and tectonic reconstructions of Australia. Journal of Geology, v. 114 (1), pp. 43-63, January 2006

NOTE: This publication is included on pages 24 – 36 in the print copy of the thesis held in the University of Adelaide Library.

It is also available online to authorised users at:

http://dx.doi.org/10.1086/498099

24 CHAPTER 4

The Musgrave province, central Australia: cinching the Belt Supergroup down under?

This chapter is submitted as: Wade, B.P., Barovich, K.M., Hand, M., Maidment D. (2006) The Musgrave province, central Australia: cinching the Belt Supergroup down under? Terra Nova. See appendix for full article.

Wade, B.P., Barovich, K.M., Hand, M., Maidment D. (2006) The Musgrave province, central Australia: cinching the Belt Supergroup down under? Terra Nova

NOTE: This publication is included on pages 37 – 46 in the print copy of the thesis held in the University of Adelaide Library.

37 CHAPTER 5

Petrogenesis of the isotopicaly evolved layered ultramafic-mafic intrusions, Musgrave Block, Australia: modified mangle or crustal contamination?

This chapter has been submitted to the Journal of Petrology as: Wade, B.P., Barovich, K.M., Hand, M. (2006). Petrogenesis of the isotopicaly evolved layered ultramafic-mafic intrusions, Musgrave Block, central Australia: modified mantle or crustal contamination?. Journal of Petrology. See appendix for full article.

Wade, B.P., Barovich, K.M., Hand, M. (2006) Petrogenesis of the isotopicaly evolved layered ultramafic-mafic intrusions, Musgrave Block, central Australia: modified mantle or crustal contamination? Journal of Petrology.

NOTE: This publication is included on pages 47 – 66 in the print copy of the thesis held in the University of Adelaide Library.

47 CHAPTER 6

Nd isotopic and geochemical constraints on provenance of sedimentary rocks in the eastern Officer Basin, Australia: Implications for the duration of the intracratonic Petermann Orogeny

This chapter is published as: Wade, B.P., Hand, M., Barovich, K.M. (2005) Nd isotopic and geochemical constraints on provenance of sedimentary rocks in the eastern Officer Basin, Australia: implications for the duration of the intracratonic Petermann Orogeny. Journal of the Geological Society, London. 162, 1-18. See appendix for full article.

Wade, B.P., Hand, M., Barovich, K.M. (2005) Nd isotopic and geochemical constraints on provenance of sedimentary rocks in the eastern Officer Basin, Australia: implications for the duration of the intracratonic Petermann Orogeny. Journal of the Geological Society, v.162 (3), 2005, pp. 513-530

NOTE: This publication is included on pages 67 - 83 in the print copy of the thesis held in the University of Adelaide Library.

It is also available online to authorised users at:

http://dx.doi.org/10.1144/0016-764904-001

67 Chapter 7 Filling the magmatic gap of Proterozoic Australia

Abstract The Coompana Block represents an essentially unknown basement province that separates the Gawler Craton of South Australian from the Yilgarn Province of Western Australia. Previously geochronologically, geochemically, and isotopically uncharacterised granitic gneiss intersected by deep drilling of the Coompana Block represents an important period of within-plate magmatism during a time of relative magmatic quiescence in the Australian Proterozoic. Samples of granitic gneiss from Mallabie 1 drill hole are metaluminous and dominantly granodioritic in composition. They have distinctive A-type chemistry characterised by high contents of Zr, Nb, Y, Ga, LREE with low Mg#, Sr, CaO and HREE. U-Pb LA-ICPMS dating of magmatic zircons provides an age of 1505±7.2 Ma, interpreted as the crystallisation age of the granite protolith. eNd values are high with respect to exposed crust of the Musgrave Province and Gawler Craton, and range from +1.2 to +3.3 at 1.5 Ga. The genetic relationship of the granitic gneiss represents a fractionated melt of a mantle derived melt parent. The tectonic environment into which the precursor granite was emplaced is also unclear; however, one possibility is emplacement within an extensional environment. Regardless, the granitic gneiss intersected in Mallabie 1 represents magmatic activity during the Australian magmatic gap of ca. 1.50-1.35 Ga, and is a possible source for detrital ca. 1.50 zircons found within sedimentary rocks of Tasmania and Antarctica, and metasedimentary rocks of the eastern Musgrave Province. Keywords: Proterozoic Australia; A-type, Nd-isotopes; Coompana Block; Geochemistry

7.1 Introduction Albany-Fraser Complex (ca. 1.33-1.14 Ga granites of the Nornalup Complex (e.g. Myers, 1995; Nelson The magmatic history of Proterozoic Australia is et al., 1995). punctuated by intervals of relative quiescence in magmatic activity, the two main periods being ca. This apparent paucity of magmatism during the 2.0-1.9 Ga and ca. 1.50-1.35 Ga. These periods interval of ca. 1.50-1.35 Ga has provided problems may represent a time of reduced activity in mantle for many provenance studies that have identified dynamics, a preservation problem, or a sampling detrital zircons falling within this time period (e.g. problem. Much like the ca. 1.60-1.54 Ga North Goodge et al., 2002; Black et al., 2004; Chapter American magmatic gap of Laurentia (Van Schmus 4: this study). In all cases the authors have cited et al., 1993), the only two felsic magmatic events sources exotic to Australia, such as the voluminous of any note occur around ca. 1.50-1.35 Ga. These A-type granitoids suites of southern Laurentia include the ca. 1.51 Ga Spilsby Suite Granite of (Anderson and Bender, 1989; Van Schmus et al., the Gawler Craton, the outcrop of which is restricted 1993). Following this, the presence of ca. 1.50- to Spilsby Island (Fanning, 1997), and the 1.52- 1.35 Ga detrital zircons has led to palaeogeographic 1.50 Ga Williams Supersuite of the eastern Mt Isa reconstructions involving Australia and Laurentia Inlier (Page and Sun, 1996; Wyborn, 1998) (Fig. (e.g. Goodge et al., 2002; Chapter 4: this study). 7.1). Prior to this from ca. 1.60-1.54 Ga we have The gross tectonic elements of Proterozoic voluminous magmatism throughout much of the Australia, namely the North, South, and West North Australian and South Australian Cratons Australian cratons (Fig. 7.1), are separated by (NAC and SAC) associated with the Hiltaba Suite deep and aerially extensive sedimentary basins, and Gawler Range Volcanics in the Gawler Craton of which the underlying basement geology is either (Fanning et al., 1988), the voluminous S-type poorly or totally unknown. It is beneath these granites in the Curnamona Province (Page et al., sedimentary basins in which the potential lies to 2003), and the meta-igneous rocks of the Mt Isa discover magmatic belts of ages that would fill the and Yambo inliers of north Queensland (Blewett ca. 1.50-1.35 Ga time gap in the geological record. et al., 1998) (Fig. 7.1). Post 1.35 Ga is the emplacement of voluminous granitoids in both the The Coompana Block separates the West Musgrave Province (ca.1.30 Ga orthogneiss (White Australian Craton (WAC) from the SAC (Figs. 7.1 et al., 1999); and ca. 1.20-1.14 Ga granites of the and 7.2), and represents an area in which the voluminous Pitjantjatjara Supersuite (e.g. Camacho underlying basement is shallow enough to be and Fanning, 1995; Edgoose et al., 2004)), and sampled by drillcore. Its geographical position is 84 Chapter 7 Filling the magmatic gap key in deciphering what may underlie the Officer (qtz + k-feld) and mafic-rich bands (bt+hbd+plag) Basin in South and Western Australia. at the cm scale, and a less segregated foliated Here we present U-Pb LA-ICPMS data, Sm-Nd lithology of identical mineralogy (qtz+k- isotopes, and geochemistry on granitic gneiss of feld+bt+hbdplag) (Fig. 7.3). Previous the Coompana Block located in South Australia geochronology on the granitic gneiss consists of (Figs. 1 and 2, Appendix 5: Tables 1,2 and 3). The K-Ar geochronology on biotite and hornblende, data indicate that the precursor to the granitic and provided ages of 1159 Ma and 1185 Ma gneiss cored in Mallabie 1 represents a previously respectively (Webb et al., 1982). These ages unrecognised ca. 1.50 Ga A-type magmatic suite, represent the only geochronological analyses for raising the possibility of undiscovered rock suites the entire Coompana Block. These ages have beneath the Officer Basin of an age within the been interpreted to represent a Musgrave Orogeny Australian magmatic gap. overprint (Drexel et al., 1993), raising the possibility of Musgrave Orogeny deformation extending from 7.2 Geology of the Coompana Block the Albany-Fraser Orogen in W.A. as far east as the western edge of the Gawler Craton in S.A. The Coompana Block represents a suite of rocks (Fig. 7.1). of unknown extent totally concealed beneath the Phanerozoic cover of the Eucla basin (Figs. 7.1 Interlayered arenaceous sediments and basic and 7.2). Lithologies intersected in the drillhole volcanics are interpreted to overlie the granitic Mallabie 1 (Fig. 7.2) comprise a basement granitic gneiss. The age of this sequence is unknown, gneiss intruded by dolerite-gabbro dykes, and however correlations have been proposed with the overlain by flat-lying interlayered basic volcanics Roopena Volcanics of the GRV (Thompson, 1970), and arenaceous sediments (Drexel et al., 1993). Neoproterozoic volcanics of the Adelaide Rift The limited number and depth of drillholes within Complex, and the Cambrian Kulyong volcanics of the Coompana Block prevents a detailed the Officer Basin (Scott and Spear, 1969). Mafic examination of its geology, and given its size gabbroic intrusives, and small satellite gabbroic (>200x200 km from TMI interp), there exists the bodies have also been intersected in drillhole (Fig. potential for a further complexity in its lithologies. 7.2), again the age of which are unknown. Numerous north-northwest trending mafic dykes The granitic gneiss intersected in Mallabie 1, which have been interpreted from TMI, which probably is the focus of this study, consists of an intensely correlate with those of the Gairdner Dyke Swarm foliated lithology of interlayered quartzofeldspathic (Drexel et al., 1993).

Darwin

NORTH AUSTRALIAN CRATON

Mount Isa Arunta Inlier

Region Alice Springs Figure 7.1 Map of tectonic elements of Proterozoic Musgrave Australia including the North, West, and South Australian WEST AUSTRALIAN Cratons. Inset: represents CRATON area displayed in Fig. 7.2 Fig. 7.2 Gawler Craton Curnamona Province

Albany-Fraser SOUTH AUSTRALIAN CRATON Mesoproterozoic 'Grenville-age' 1000 km orogenic belts Palaeo-Mesoproterozoic Archaean Sedimentary Basin Sedimentary Basin Block/Inlier Block/Inlier

Chapter 7 Filling the magmatic gap moderately foliated samples from the EOH 1493.5- composition were evaporated in HF/HNO3 1495.6 m cored intersection. The two samples of overnight, digested in hot HF/HNO3 in sealed Teflon intensely foliated granitic gneiss (658669 and bombs for five days, then evaporated to dryness 658670), contain mafic (dominantly bt-hbd-plag) in HF/HNO3. Samples were subsequently and quartzofeldspathic bands (qtz-kfeld-plag) (Fig. evaporated in 6M HCl then bombed with 6M HCl 7.3). overnight. Nd and Sm concentrations were calculated by isotope dilution, with Nd isotope All five samples were analysed for major and trace ratios measured by thermal ionisation mass elements (Appendix 5: Table 1), one sample dated spectrometry on a Finnigan MAT 262 mass by U-Pb LA-ICPMS (Appendix 5: Table 2), and spectrometer, and Sm isotope ratios measured on three analysed for Sm-Nd isotopes (Appendix 5: a Finnigan MAT 261 mass spectrometer. The Table 3). Whole rock samples of granitic gneiss 143Nd/144Nd ratio is normalised to 146Nd/144Nd = were crushed and powdered in a tungsten carbide 0.721903. The single Nd blank carried out during mill. An aliquot was taken for isotopic analysis the course of the analyses was 85 pg. The and whole rock geochemistry. The remaining 143Nd/144Nd ratio of the in-house standard crushate was retained for zircon separation by (Johnson Matthey) at the Adelaide University standard Frantz and heavy liquid separation laboratory during the course of the analyses was techniques, followed by hand picking of zircons. 0.511597 ± 0.000006 (1s, no. of analyses = 2). Running average for La Jolla over the year is For analysis of major elements a 0.1 g sub-sample 0.511838 ± 0.000008 (1s, no. of analyses = 6). of the analytical pulp was fused with lithium metaborate followed by dissolution in nitric acid solution to give a "total solution" ready for ICPMS 7.4 Age of the Mallabie 1 Granitic Gneiss analysis. Analysis of trace and REE elements was achieved by digestion of up to 0.5 g of the analytical One sample of foliated granitic gneiss (658673) pulp in a HF/multi acid solution and presented to was dated by LA-ICPMS. The data is presented an ICPMS for the quantification of the elements of in Table 2 (Appendix 5). Transmitted light and CL interest. All dissolution and element analysis were images of typical zircons are displayed in Figure carried out at Amdel Laboratories in Adelaide. 7.4, while conventional U-Pb concordia and a 207Pb/206Pb histogram of the ages are presented U-Pb analysis of zircons from sample 658673 in Figure 7.5. All zircons were clear to pale pink (foliated granitic gneiss) was conducted by LA- in colour, ranged in morphology from acicular to ICPMS at the University of Adelaide. Zircon grains stubby prisms, and were generally greater than were imaged using standard BSE and CL imaging 100um in length. Most zircons contained inclusions techniques on a Phillips XL20 SEM with attached of apatite and hornblende (Fig. 7.4). All zircons Gatan CL (Fig. 7.4). Equipment and operating analysed display oscillatory zoning under CL conditions are identical to those reported by Payne luminescence, attributed to a magmatic genesis et al. (2006). Ages were calculated using the (Fig. 7.4). GEMOC GJ-1 zircon standard to correct for U-Pb fractionation, and the GLITTER software for data Thirty-three zircons were analysed, all of which reduction (Van Achterbergh et al., 2001). provided excellent data with minimal to no common Fractionation of U-Pb was corrected using the Pb (Appendix 5: Table 2). On a conventional U- GEMOC GJ-1 zircon standard (TIMS normalisation Pb concordia diagram the data are slightly data 207Pb/206Pb = 608.3 Ma, 206Pb/238U= 600.7 discordant, and when a Model 2 fit line is regressed Ma and 207Pb/235U= 602.2 Ma, Jackson et al. 2004). through the points gives an intercept age of Accuracy was monitored by repeat analyses of 1502±4.3 Ma (Fig. 7.5). The slightly high MSWD the in-house internal standards comprising of a Sri of 2.1 indicates some scatter about the mean. Lankan zircon standard (BJWP-1, ca. 727 Ma). The weighted average of the 207Pb/206Pb ages Over the duration of this study the reported average (1505±7.2 Ma) provides an age indistinguishable normalised ages for GJ-1 are 608.9±7.3, 600.6±2.0 from that of the concordia intercept, however its and 602.3±1.7 Ma for the 207Pb/206Pb, 206Pb/238U more acceptable MSWD of 0.25 suggests that it and 207Pb/235U ratios, respectively (n = 37). Due may be a more reliable age. Hence we suggest to the LA-ICPMS inability to measure common Pb, that the 207Pb/206Pb weighted average age of correction was carried out using the CommPbcorr 1505±7.2 Ma represents the crystallisation age of macro (Andersen, 2002). Negligible (<0.5% 206Pb) the precursor to the Mallabie granitic gneiss. common Pb was detected in all of the analyses when the 3D concordia method employed by CommPbcorr was used.

Whole rock samples analysed for Sm-Nd isotopic

87 Chapter 7 Filling the magmatic gap

Spot 27 1505±21 Ma

Ap Figure 7.4 Transmitted light photograph of typical zircon from the granitic gneiss displaying inclusions of apatite and possible hornblende. CL images of 100 um typical zircons also shown displaying magmatic zoning Hbd and spot location and 207Pb/206Pb age. Spot 17 1495±19 Ma

50 um 100 um 7.5 Geochemistry of the Mallabie 1 Granitic 7.5.2 Trace and Rare Earth Elements Gneiss For consistency, foliated and intensely foliated 7.5.1 Major elements samples defined in the previous section have been adopted here. All samples display a relatively Major element analyses are summarised in Table restricted range in trace element compositions; 1 (Appendix 5), along with average values of A-, however, there are subtle differences between I-, and S- type granitoids of Whalen et al. (1987). both groups (Appendix 5: Table 1). Trace and SiO2 values for the samples are intermediate, REE spidergrams are normalised to Primitive ranging from ~59-64% (Appendix 5: Table 1). The Mantle (McDonough and Sun, 1995) and REE samples have been split into two groups according Chrondritic values (Taylor and McLennan, 1985) to the intensity of their gneissic fabric. Samples 658671, 658672, and 658673 are comparitively weakly deformed, whereas samples 658669 and 0.29 1600 658670 are intensely deformed (Appendix 5: Table 0.28 1). Foliated samples have lower SiO2 (58.9-61.7 1560 wt%), higher Al2O3 (15.2-16.1 wt%), TiO2 (1.04- 0.27 U

1.32 wt%), and P2O5 (0.41-0.51 wt%) than those 238 0.26 of the intensely foliated samples which conversely Pb/ 1460 have higher SiO2 (63.5-64.3 wt%), with lower 206 0.25 Al2O3 (14.6-15.0 wt%), TiO2 (0.92-0.96 wt%), and 1400 P2O5 (0.24-0.27 wt%) (Appendix 5: Table 1). Major 0.24 Upper intercept at 1502 ± 4.3 Ma element oxides generally show linear trends on MSWD = 2.1 0.23 Harker diagrams with an increase in K2O, and a 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 systematic decrease of Al2O3, CaO, FeOt, P2O5, 207Pb/235U Na2O and TiO2 with increasing SiO2 content (Fig. n=33 7.6). All samples are metaluminous with ASI<1; Wght. Avg. (95% conf.) 20 1505 ± 7.2 Ma however, the foliated samples display slightly MSWD = 0.25 increased metaluminous characteristics when Relative probability compared to the intensely foliated samples 15 (Appendix 5: Table 1, Fig. 7.7). 10 On a CIPW normative Ab-An-Or classification Number diagram, the samples plot as dominantly 5 granodioritic, with one sample of the intensely 0 foliated granitic gneiss plotting in the tonalitic field 1400 1440 1480 1520 1560 1600 1640 (Fig. 7.8a). All samples fall within the calc-alkaline 207Pb/206Pb field defined in AFM, clustering near the Figure 7.5 Conventional U-Pb concordia diagram displaying tholeiitic/calc-alkaline boundary (Fig. 7.8b). upper intercept age of ca. 1.50 Ga. Also shown is 207Pb/206Pb age histogram and probability density curve displaying weighted average of ca. 1.50 Ga.

88 Chapter 7 Filling the magmatic gap

16.0 Al O3 Na2O 2 4.5

A 15.0 4.0

I S 3.5 14.0

I 3.0

13.0 2.5 A S 5.0 CaO P2O5 0.5

4.0 0.4 I

3.0 0.3 S 0.2 2.0 S I 0.1 1.0 A A K O A 4.5 2 TiO2 1.2

4.0 S 3.5 0.8

3.0 I S I 2.5 0.4

A S FeOt I MgO 6.0 1.5

5.0

1.0 4.0 S

0.5 3.0 A A I

55 60 65 70 75 55 60 65 70 75 SiO2 SiO2 Figure 7.6 Harker variation diagrams for samples of granitic gneiss. Open triangles represent samples of foliated granitic gneiss, while open circles represent samples of intensely foliated granitic gneiss. Also plotted for comparison are average I-, S-, and A- type of Whalen et al. (1987)

(Figs. 7.9a,b). Samples from the intensely foliated group display flat to slightly positive Eu anomalies ((Eu/Eu*)N = The REE patterns for the foliated and intensely 0.99-1.04), and less steep REE ((La/Yb)N = 6.01- foliated samples differ (Fig. 7.9a). Samples from 6.58) and HREE profiles ((Gd/Yb)N = 1.68-1.80) the foliated group have marked positive Eu than those of the foliated group (Appendix 5: Table anomalies ((Eu/Eu*)N = 1.27-1.38), steep REE 1, Fig. 7.9a). ((La/Yb)N = 10.05-12.21) and HREE ((Gd/Yb)N = 2.48-2.60) patterns (Appendix 5: Table 1, Fig. 7.9a). When normalised to Primitive Mantle, differences 89 Chapter 7 Filling the magmatic gap

Metaluminous Peraluminous 3

A/NK 2 I S

1 A Peralkaline

0 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 A/CNK Figure 7.7 A/NK vs A/CNK plot of Shand (1943) displaying the metaluminous characteristic of the granitic gneiss. Symbols as per Figure 7.6

M A An (b)

Calc-alkaline I A (a) S

Tonalite Grano- Tholeiite diorite Quartz I Monzonite S Quartz Syenite

Trondhjemite F Granite Ab A Or

Figure 7.8 (a) CIPW normative Ab-An-Or ternary diagram displaying granodioritic composition of granitic gneiss. (b) AFM diagram of Irvine and Baragar (1971) displaying calc-alkaline characteristic of granitic gneiss samples. Symbols as per Figure 7.6

1000 1000 (a) (b) Sample/Primitive Mantle

100 100

10 10 Sample/Chondrite

1 1 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Rb BaTh U Nb Ta K LaCe Pr Sr P Nd SmZr Hf Eu Ti GdTb Dy Y Er Yb Lu Figure 7.9 (a) Chondrite normalised REE plot of foliated and intensely foliated sampes of granitic gneiss. (b) Primitive Mantle normalised trace element plot of foliated and intensely foliated samples of granitic gneiss. Symbols as per Figure 7.6

90 Chapter 7 Filling the magmatic gap 10 DM

5 2% 20% 40% 5% Depleted Mantle 60% 5 10% 80% Average Musgrave 0 Nd Province Evolution

e MP 20%

eNd 0 40% -5 60% 80% GC

-5 Average Gawler Craton Evolution

-10 1.0 1.2 1.4 1.6 1.8 2.0 Age (Ga) Figure 7.10 eNd evolution diagram displaying the juvenile nature of the granitic gneiss in Mallabie 1 when compared to the surrounding basement of the Musgrave Province and Gawler Craton, which comprise the nearest Proterozoic basement provinces. See text for references of isotopic evolution fields of the Musgrave Province and Gawler Craton. Inset: Mixing calculations displaying percentage of GC or MP contaminant required to be added to the Depleted Mantle to attain range of eNd values seen for Mallabie 1 granitic gneiss. Symbols as per Figure 7.6 can be observed in LILE and HFSE concentrations Gawler Craton to the east of the Coompana Block between both groups (Fig. 7.9b). The foliated (Fig. 7.1), are also shown in Figure 7.10 (Gawler samples display enrichment of Ba, Sr, and P, and Craton: Stewart, 1992; Turner et al., 1993; Creaser, depletion of Rb, Th, and U when compared to the 1995; Schaefer, 1998; Musgrave Province: This intensely foliated samples (Appendix 5: Table 1, study). Samples exhibit marked positive initial eNd Fig. 7.9b). The HFSE Nb, Zr, and Ti are all enriched values of +1.2 to +3.3 (Appendix 5: Table 3, Fig. in the foliated samples compared to the intensely 7.10). Although a limited number of samples were foliated samples. analysed, there appears no correlation of the two groups with eNd values (Appendix 5: Table 3, Fig. 7.5.3 Sm-Nd systematics 7.10). Table 3 displays the eNd values for three samples 7.6 Petrogenetic Origin of the Mallabie 1 Granitic analysed, one intensely foliated and two foliated Gneiss granitic gneisses. Values have been calculated at 1.50 Ga, which is the interpreted age of 7.6.1 A-type affinity of the granitic gneiss emplacement. The classification of the Mallabie granitic gneiss The single sample of intensely foliated granitic as A-type is clearly distinguished on Nb vs gneiss has a slightly higher isotopic Sm/Nd ratio 10000xGa/Al and Ga/Al vs Zr+Nb+Ce+Y plots of of 0.1284 when compared to those of the foliated Whalen et al. (1987) (Fig. 7.11). The granodioritic samples (0.1151 and 0.1153) (Appendix 5: Table composition of these samples are comparable to 3). However, measured 143Nd/144Nd values show that from other A-type granitoids worldwide (e.g. no grouping, ranging from 0.511894 to 0.512051 Smith et al., 1999; Volkert et al., 2000; Mushkin et (Appendix 5: Table 3). al., 2003).

Nd isotopic data expressed as eNd is plotted Despite differences between the two groups, the against age in Figure 7.10. Average crustal overall high Ba content in all samples suggests evolution lines for proximal basement terrains, the samples represent relatively unfractionated A- including the Musgrave Province to the north, and type melts (Appendix 5: Table 1, Fig. 7.9, King et

91 Chapter 7 Filling the magmatic gap al. 1997). Unfractionated A-types are distinguished Hussain et al., 2004; Perini et al., 2004). from felsic I-type granites by a greater abundance of high-field-strength elements, such as Zr (Whalen 7.6.2 Tectono-magmatic affinity et al., 1987; King et al., 1997; Mushkin et al., 2003). Strongly fractionated I-types do contain elevated The general position of all samples lie within the HFSE, REE and Ga, but these melts usually have within-plate granite field of the Rb vs Y+Nb and high silica values coupled with high Rb and low Sr Nb vs Y Pearce plot (Pearce et al., 1984; Fig. and Ba values (King et al., 1997), which are not 7.12)., which is not unexpected given the evident in the samples of this study. Thus it can petrogenetic nature of A-type granitoids (e.g. Eby, be confidently concluded that these samples 1992). When plotted on Nb-Y-3xGa and Nb-Y-Ce represent A-type melts. plots of Eby (1992) (Fig. 7.13), all samples lie within the A2 field defined as an apparent crustal source Some fractionation of the primary melt is evident that is not metasedimentary in origin. Despite this upon consideration of the increase in SiO2 content it is not unknown for A2 granitoids to still have a from the foliated granitic gneiss to the intensely mantle origin (Eby, 1992). A2 granitoids can be foliated granitic gneiss (Appendix 5: Table 1). The emplaced within a variety of tectonic settings, higher SiO2 content of the intensely foliated including post-collisional and true anorogenic samples may be indicating that they represent a environments (Eby, 1992). This makes it difficult more fractionated melt phase than that of the to make any definite conclusions on the tectonic foliated samples. The samples show typical origin of A2 granitoids, however generally these fractionation trends of decreasing Ba,Sr, Zr, Nb magmas were generated from crust that has been and LREE with increasing Rb (e.g. Whalen et al., through a cycle of subduction zone or continent- 1987; King et al., 1997; Mushkin et al., 2003), continent collision processes (Eby, 1992). moving from the less fractionated foliated samples to the increasingly fractionated intensely foliated A-type granitoids often occur in bimodal association samples. The chemical variations seen in the with intermediate to mafic rocks such as mafic granitic gneiss of Mallabie 1 can be explained by dykes and gabbros (e.g. Turner et al., 1992; partial melting of a source followed by fractional Mushkin et al., 2003), and in some cases their crystallisation. The coupled decrease of Al2O3, genesis is related fractionation of associated mafic CaO, Sr and Ba with a shift of Eu/Eu* anomalies magmas (e.g. Chazot and Bertrand, 1995; Volkert from strongly positive to flat, and inverse et al., 2000). Unfortunately, at this stage the lack concentration relationship between Ba and Rb of drillholes intersecting basement lithologies of indicate the removal of feldspars (e.g. Bea, 1996; the Coompana Block prevents a conclusive answer. Roberts et al., 2000; Perini et al., 2004). However it remains likely that the precursor Increasingly negative P and FeOt contents from granitoids were emplaced within an extensional the foliated to intensely foliated samples may setting. represent fractionation and removal of apatite and Fe-Ti oxides respectively from the source (e.g. Droux and Delaloye, 1996; Whalen et al., 1999;

1000 Nb Ga/Al 500 A-type A-type 10

100 5 50

A A Fractionated 10 S Granite I S I & S I 2 5 type Other Granite Type

1 1 12 510 50 100 200 500 1000 10000*Ga/Al Zr+Nb+Ce+Y Figure 7.11 Nb vs 10000xGa/Al and Ga/Al vs Zr+Nb+Ce+Y plots of Whalen et al. (1987) displaying A-type characteristics of the granitic gneiss. Symbols as per Figure 7.6

92 Chapter 7 Filling the magmatic gap

Upper Crustal Melts Syn-Collisional Granites 500 500 Within Plate Granites Within Plate S A Granites I 50 Rb 50 A Nb

S I Ocean Ridge Volcanic Arc Granites/ Ocean Ridge 5 Granites Volcanic Arc Granites/ Granites 5 Post Collisional Granites Post Collisional Granites

1 1

1 5 10 50 500 1 5 10 50 500 Y Y+Nb Figure 7.12 Tectonic discrimination diagrams of Pearce et al. (1984) displaying within-plate tectnonic character of the samples of granitic gneiss from Mallabie 1. Symbols as per Figure 7.6

Ce Y Nb A2 Crustal Source -not medasedimentary

A1 Figure 7.13 Nb-Y-3xGa and Nb-Y-Ce ternary plots of Eby, (1982) displaying A2 A1 Mantle Origin Mantle Origin classification for samples of granitic gneiss. This implies a non-metsedimentary crustal source. Symbols as per Figure 7.6

A2 Crustal Source -not medasedimentary Nb Y 3*Ga

7.6.3 Sm-Nd systematics Musgrave Province: this study). The Nd concentration of potential mantle derived melts is The eNd evolution of the three samples are not known. However, attempts at characterization markedly more juvenile than the evolution fields of N-MORB sources have been carried out by of crustal material that comprises the currently various workers using a Nd concentration of 5 ppm exposed adjoining lithosphere (Gawler Craton and suggested for a depleted mantle melt (e.g. Musgrave Province; Fig. 7.10). This suggests Hofmann, 1988; Hart et al., 1999). Subsequently, either limited older crustal contamination, or a more a Nd concentration of 5 ppm is used in this study. juvenile pre-existing lithosphere underneath the Coompana Block with respect to the enclosing The mixing calculations argue for addition of only regions. Sample 658672 has an eNd value of ~5-10% of Gawler Craton or 40-80% of Musgrave +3.3, suggesting some mantle component for at Province crustal material to a N-MORB like depleted least part of the Mallabie 1 granitic gneiss. mantle melt in order to attain the Nd isotopic signature of the Mallabie 1 granitic gneisses. The Inset to Figure 7.10 shows the amount of mixing relatively mafic nature of the Mallabie 1 granitic of both Gawler Craton and Musgrave Province gneisses would preclude the amount of mixing material with depleted mantle that would be required required using a Musgrave Province end-member, to produce the range of eNd values calculated for given the felsic nature of the Musgrave Province the Mallabie 1 granitic rocks at 1.50 Ga. Nd crust. Thus the Gawler Craton is seen as a concentration estimations for the Gawler Craton preferable contaminant, if indeed the isotopic and Musgrave Province in the mixing calculations signature of the Mallabie 1 granitic gneisses are are 30 ppm (Gawler Craton: Stewart, 1992; Turner reflecting contamination of a mantle melt by crustal et al., 1993; Creaser, 1995; Schaefer, 1998; material. 93 Chapter 7 Filling the magmatic gap Unfortunately no isotopic data on exists on the HREE. U-Pb LA-ICPMS dating on separated gabbroic rocks of the Coompana Block. This magmatic zircons has provided an age of ca. 1.50 makes it impossible to consider the genetic Ga, interpreted as the crystallisation age of the relationship between the Mallabie 1 granitic granite. The intersection of intensely foliated gneisses and the mafic rocks that they may granitic gneiss further up-section of the Mallabie plausibly be derived from. 1 drillhole appears to represent a slightly more fractionated melt than that of the foliated granitic 7.7 Implications for the source of detrital zircons gneiss intersected further down the hole. Nd whose age falls within the Australian magmatic isotopic analysis provide juvenile values ranging gap from +1.2 to +3.3 at 1.50 Ga. This could plausibly be explained by derivation from a mantle melt with U-Pb detrital zircon provenance studies in Tasmania minor contamination. The gabbros of the (Black et al., 2004), Antarctica (Goodge et al., Coompana Block may be related to the genesis of 2002), and the eastern Musgrave Province (Chapter the Mallabie 1 granitic gneiss, raising the possibility 4: this study), have identified zircons whose age that they are of an equivalent age. that are difficult to reconcile with Australian sources. These ages range from ca. 1.50-1.35 Ga and fall The identification of granitic A-type magmatism in the Australian magmatic gap, which represents that falls within the Australian magmatic gap of a period of relative magmatic quiescence in the Proterozoic Australia has implications for Australian Proterozoic, with only two recognised reconstruction models citing non-Australian sources felsic magmatic events occuring around this age for detrital zircons falling within the age bracket of range over the whole North and South Australian ca. 1.52-1.35 Ga, possibly allowing for a more Proterozoic (SAC: Spilsby Suite Granite, ca. 1.51 proximal source to be proposed. However, at this Ga. Fanning, 1997; NAC: Williams Supersuite, ca. stage this is just one intersection of granitic gneiss 1.52-1.49 Ga; Page and Sun, 1996; Wyborn, 1998). in a single drillhole, the age of which fills just part Conversely, this period marks a time of voluminous of the magmatic gap. Despite this, the identification magmatic activity in southern Laurentia such as of granitic magmatism of this age under the extensive A-type magmatic suites throughout Neoproterozoic-Cambrian cover of the eastern the Yavapai and Mazatzal terranes (Anderson and Officer Basin raises the possibility that underlying Bender, 1989; Van Schmus et al., 1993). As a the Officer Basin in S.A. and W.A. separating the result, Laurentian sources for zircons of this age Gawler Craton from the Yilgarn Block is an found within Australian sequences have generally expansive belt of rocks of an age unusual to been proposed (Goodge et al., 2002; Black et al., Proterozoic Australia, and that indeed Australias 2004; Chapter 4: this study), and used as a basis magmatic gap may be hiding under cover. for broad palaeogeographic correlations. The age of the Mallabie 1 granitic gneiss (ca. 1.50 Ga) is similar to that of the Spilsby Suite Granite (ca. 1.51 Ga) in the eastern Gawler Craton, and the granites of the Williams Supersuite (ca. 1.52-1.50 Ga) in the eastern Mt. Isa Inlier. Ca. 1.50-1.49 Ga detrital zircons found in Tasmania Black et al., 2004), Antarctica (Goodge et al., 2002), and the eastern Musgrave Province (Chapter 4: this study), could therefore plausibly be sourced from these magmatic suites. However, there still remains the question of the source of detrital zircons with ages ranging from ca. 1.49-1.35 Ga found in sedimentary sequences of Antarctica, Tasmania, and the eastern Musgrave Province. At this stage sources exotic to Australia would still have to be proposed.

7.8 Summary and Conclusions

The granitic gneiss intersected in Mallabie 1 drillhole exhibit petrological and geochemical characteristics typical of A-type granites. The Mallabie 1 granitic gneiss is characterised by distinctive major and trace element compositions such as high contents of Zr, Nb, Y, Ga, LREE with low Mg#, Sr, CaO and 94 Chapter 8 The Musgrave Province; terra incognito no longer?

8.1 Introduction The findings of the four modules will be discussed in chronological order; The aims of this thesis were to develop a tectonic framework for the evolution of the Musgrave 1) ca. 1.60-1.54 Ga Musgravian Gneiss; Province, by applying a number of geochemical and geochronological techniques on various 2) ca. 1.40 Ga unnamed metasedimentary rocks; lithological units ranging in age from earliest Mesoproterozoic to Cambrian. It was envisaged 3) ca. 1.08 Ga mafic-ultramafic rocks of the Giles that by increasing our knowledge of the tectonic Complex; and processes involved in the formation of the Musgrave Province, we could better constrain reconstruction 4) ca. 0.56 Ga deformation associated with the models of Proterozoic Australia. As such a five- Petermann Orogeny. module programme was undertaken that involved: 5) Petreogenesis of the Coompana Block · establishing the tectonic environment involved in the formation of the oldest rocks of the Musgrave A generalised geological history of the Musgrave Province, the ca. 1.60-1.54 Ga felsic and mafic Province is presented in Table 8.1. Musgravian Gneisses, through application of geochemistry and Sm-Nd isotopes; 8.2 ca. 1.60-1.54 Ga Musgravian Gneiss · examining detrital input to metasedimentary 8.2.1 Historical views on crustal formation (or lack rocks through U-Pb SHRIMP, U-Pb LA-ICMPS and thereof?) during the Australian Proterozoic Nd istopes, and what it can tell us about the Musgrave Provinces geographic position at the Historically, crustal growth mechanisms of late time of their formation; Archaean to early Mesoproterozoic Australia have been dominated by the assumption that the · investigating the petrogenesis and crust-mantle Australian lithosphere was a single stabilised mass relationships involved in the formation of layered by the late Archaean (e.g. Rutland, 1973; Gee, mafic-ultramafic intrusions of the Giles Complex 1979; Etheridge et al., 1987; Wyborn et al., 1988; utilising geochemistry and Nd-Sr isotopes; and Oliver et al., 1991). These models invoke processes such as vertical accretion involving underplating, · constraining the timing of the Petermann Orogeny and extensional tectonism driven by mantle plumes through geochemical and Sm-Nd isotopic analysis and delamination as the primary crust forming of sedimentary rocks from the Officer Basin. processes. This view of a contiguous late Archaean to Proterozoic Australia envisages all tectonic and · examining the nature of the basement rocks that magmatic activity to be intracratonic, independent separate the gross tectonic elements of Proterozoic of plate-boundary elements involving driving forces Australia, namely the NAC, SAC, and WAC. This such as subduction zones, with little or no new was done by geochemical, Nd-isotopic, and U-Pb crustal growth. age analysis of granitic lithologies in the Coompana Block. Recently, detailed geochemical and isotopic studies within Australian terrains such as the Arunta Region The observations and interpretations presented in and Capricorn Orogen are recognising evidence the previous chapters suggests that both plate of accreted fragments along convergent plate margin and within-plate processes played important margins (e.g. Zhao, 1994; Zhao and McCulloch, roles in crustal formation and reworking within the 1995; Scrimgeour et al., 1999; Cawood and Tyler, Musgrave Province. One of the findings from this 2004; Occhipinti et al., 2004). These datasets study highlights the importance of recognising have been used by a number of workers to propose rocks that have formed through plate margin that the evolution of Proterozoic Australia involved processes, as their origin has important implications important accretionary and collisional events (e.g. for all reconstruction models of Proterozoic Myers et al., 1996; Scott et al., 2000; Betts et al., Australia. 2002; Giles et al., 2002; Giles et al., 2004; Tyler, 2005). 95 Chapter 8 Terra incognito? 3 ?msihpromatemseicafetilobihmareppuhtiwdetaicossanoitasitamgiM 0 1 , 9 noitasitamgimybdeinapmoccamsihpromatemseicafetilunarG 21,01 )C°058~=Tsrabk6~=P(msihpromatemseicafetilunarG srabk6~taC°057ot°0511morfgnilooccirabosiraeN snoitidnoccihpromateM 1 2 M M etiztrauqdna,setacilisclac,sessiengcitilepdnacifamronim- seidobdereyalcifamartlu-cifamsuoremunfotnemecalpme- raehserupevitartenepyltsom,gnidloftnebmucerlanilcosi- nigirocinaclovdnacitinargfosessiengci s ekyd pu noisseccustfi or setilepatemsuonimulademannU s shtworgrevodnasniargcihpromatemsuotiuqibu- G a ssiengohtrocislefdemannU ulloTe ylir )ynegorOevargsuM( etiusrepuSarajtajtnajtiP noitailoflellarapreyal,sdloflanilcosidenilcer- amirps ssienG ssiengohtronishtwor ssiengohtronishtworgrevocihpromatem- tnevE/ygolohtiL 4 r 1, h sdiotinargfotnemecalpmesuonimulov- t skcortnemesabfognitlemlatsurcartni- 31 atawuajTehtfonoisurtxe- f 3 tnevEseliG osci tl ? xelpmoCetagskriBdnas 1 01 naivargs e DerP 1 ?sevargsuMnretsewnidesilacol- ?sevargsuMnretsewnidesilacol- ?sevargsu m D 5 n 7 citi ?yrtsimehcdetalernoitcudbus- a se cl nar ov galbme u l gro 01 M ad 2 M omi D nim ssatg-ll nret grevocihpromatem- beht fo kcolBevargsuMehtfostnevednaseigolohtilfoyrammuS- s slefyltnanimod- aenide t nem fo i s- s iengailO- d noisu e c-dlef-ztq c si al lacol- pme- r txe- kraPagl kraPagluMdnanogerF kraPagluMdnanogerF kraPagluMdnanogerF kraPagluM niamoD nogerF nogerF nogerF uMd nan o ge r F 1 1, 1 9, 2, 8,4 3 41 1, 4,3,2,1 9, , , 8,4 3 9 8 3 ,2 1, 692.1-423.1.ac 213.1-423.1.ac , ,1 ega.peD.xaM 2 4 ,1 51.1-32.1 45.1- 40.1-80.1.ac 41.1-2.1.ac )aG(e 6 3 65.1.ac 04.1.ac 0 8.1elbaT 6 . 1.ac . gA ac

96 Chapter 8 Terra incognito? noisorednatfilpuhtiw.cossanoisserpmocedlamrehtosi-raen- ni( 9 d 1,01 xelpmoCseliGfotnemecalpmeoteudgnidaolcitatsohtil- e ;2991notarehSdnanuS h s ilb C°057-007~=Tsrabk31-11~=P:setinolymlatsurcpeeDscir u pn unuSu 02,41,31,01 s neh C°007-056~=Tsrabk11-8~=P S 61 3 4 8 0 ; M M 1 ;7891,ronoC 39 seicafetilobihpma-tsihcsneerG 91, 41,31 h c ol srabk5-4~=P 3002,.lateesolC lu CcMdn 7 ;b,a5002,.lateedaW aoa 3 3 h DylraE DetaL Z 51 12 ; ;1991,llewoPdnaekralC 69 9 1, .l 6 ;6002,.lateedaW aten otdetcirtserecnivorPevargsuMnretsae/nrehtuosnistceffe- ehtot nretsew-htronehtdekrowerni ?sevargsuMnretsewnidesilacoltnempolevedetinolym- bafcitinolymlatsurcpeednitnedive,ecnivorPevargsuM uS 41 t ; necajda 6 99 )ynegorOnnamreteP( 1 mrawSekyDarruc sekyDenivilOde , 02 .l 5 t a )tnevEseliG( ;9991esolcdnaruoegmircS 51 ;4002,.lateesoogdE nempolevedet ?xelpmoCseliGehtotsredeefstnanmer- t etireloDatamA etireloDarruclA enoskil 0 1 setirelodciti 5-4 ?sevargsuMnret G D e senozniarts-hgihlacitrevraen- 31 gadN-mSdeniartsnocylroop- ; 0 lAotralimisyllacimehcoeg- 1 etinargaG70.1.acedurtni- 20 mannU il artslaixaoc-nonevisavrep- 3 91,01 raehselpmisevitartenep- yhca D 0 2 ielohtfotnemecalpme- , 7-6 .l t od 4 a D ;7991,ohcamaC teeti e tsurhTeffordooW s uspd e deviredemulp- w 9 hW 1 o ;2991,.lateokobaM td n 21 ae e ;5 si ti lac 0 no 0 lym 2,.l ol 3 ;1991,.lateokobaM - at kraPagluMdnanogerF kraPagluMdnanoge kraPagluMdnanogerF kraPagluMdnanogerF e yll e K 81 11 nogerF nogerF ;4991,.lateoahZ ; 59 9 1,.l 2 a ;5991,gninnaFdnaohcamaC teekr r F al 7 1 C 01 ;)6991,.latenoskilG ; 41 9 99 .dtnoc- ,3 1, 81 1, 9 ,3 01 1,.l 1, 60.1-80.1.ac 0 01, 71,61 1 a 65.0?-8.0? 3, 5 teetihW 1 1 6 1 65.0.ac 80.1.ac 28.0.ac 8.1e 0.1.ac l baT 1 9

97 Chapter 8 Terra incognito? (a) ca.1.60-1.595 Ga (b) Gawler Range Volcanics Direction of - initiation of island arc (proto-Musgraves) outboard of Archaean Gawler movement? - Rhyolites, dacites, and basalts of the GRV intrude and extrude the Gawler - GRV is extensional inboard expression of outboard south-dipping subduction Kimberley Craton NAC Georgetown ~1.55 Ga Voluminous Felsic Archaean Island-arc Inlier Extrusives Gawler -proto-Musgraves metm1. ~1.54 Ga A B NAC Isan3 Rollback ~1.59-1.56 Ga ~1.59 Ga Mawson Arunta Nth. Australian + Continent Region Craton Pilbara Chewings4 Olarian2 Craton WAC Curnamona B Province Basalts

q q q q q q q q q q ca.1.595-1.58 Ga q q ~1.56-1.54q Ga q q Hiltaba Event/Musgraves northernq Gawler A ?1.60-1.54 Ga - Hiltaba event becomes compressional inboard expression of south-dipping subduction Craton5 - back-stepping of island-arc ? q Yilgarn Craton q SAC q Compressional ? metamorphism at Island-arc Compressional Compressional q ca.1.58 Ga (Hiltaba) -proto-Musgraves metamorphism at metamorphism at Archaean ca.1.595-1.57 Ga (Chewings) ca.1.585 Ga ? q Mawson A Gawler (Early Isan) B q Rollback q Continent ? Mawson Arunta Nth. Australian q Continent Region Craton ?q

Cratons Voluminous Felsic 1000 km Inrusives (Hiltaba) <1.58 Ga Early Proterozoic Mobile Belts Compressional Intraoceanic Arc Closure deformation - closure of ocean - compression and accretion of arc chains between Gawler Craton Middle Proterozoic Mobile Belts and Arunta Region Subduction zone qqqqq -intraoceanic-arc Closure and accretion Compressional Middle Proterozoic Basins Metamorphism at Archaean of island-arcs ca.1.55 Ga Compressional Gawler metamorphism at A ca.1.595-1.57 Ga (Chewings) B Figure 8.1 (a) Reconstrucion of Australia involving an active Mawson Arunta Nth. Australian margin between the NAC and SAC (b) Cross-section along Continent Region Craton A-B displaying possible evolution of the margin 8.2.2 Do the oldest rocks of the Musgrave Province dipping plate margin setting between the NAC and record the amalgamation of Proterozoic Australia? SAC (Figure 8.1a). Ongoing activity along the margin and resultant collision of these two crustal The Musgrave Block is considered here to represent framgents may explain approximately coeval a critical link in understanding the process and deformation and magmatism within the SAC, and timing of the suturing of the North Australian Craton broadly N-S compressional deformation within (NAC) with the South Australian Craton (SAC) large parts of the NAC (Figure 8.1b). (Figure 8.1a) as part of the larger Mawson Continent (e.g. Fanning et al., 1996), as it lies on If this conclusion is correct, models involving plate the interface between the two aforementioned reconstrucions of Australia will now have to crustal elements incorporate the formation of the Musgrave Province, where previously it has been markedly absent. Existing models of the amalgamation of Proterozoic Australia have suggested that the Albany-Fraser 8.3 ca. 1.40 Ga unnamed metasedimentary Orogeny, coincident with the Musgrave Orogeny, rocks reflects the collision of the North Australian Craton (NAC) with the South Australian Craton (SAC) 8.3.1 Where does Australia fit within the (Figure 8.1a) during the assembly of Rodinia at supercontinent Rodinia? ~1.30-1.10 Ga (e.g. Pidgeon, 1990; Black et al., 1992; Myers, 1993; Myers et al., 1996; Clark et All late Mesoproterozoic reconstructions of Rodinia al., 1999; White et al., 1999; Clark et al., 2000). involve an unidentified continent residing outboard Alternatively, Sener et al. (2005) have proposed of the western margin of Laurentia (e.g. Dalziel, suturing of the NAC with the SAC much earlier at 1991; Moores, 1991; Karlstrom et al., 2001; Sears ca. 1.73 Ga, with similar suturing of the continents and Price, 2000; Wingate et al. 2002; Li et al., between 1.8-1.5 Ga proposed by Giles et al. (2004). 2002). Current models have involved both South China (e.g. Li et al., 2002) and Siberia (Sears and Contrary to these reconstructions, the results from Price, 2000) as the rifted companion continent. this study suggest that the docking of the NAC Despite this, for approximately 15 years Australia with the SAC occurred sometime during the interval has featured prominently in models that invoke a of 1.60-1.54 Ga. The isotopic and geochemical collision-rift setting with the western margin of results of this study suggest that the protolith to Laurentia (e.g. Dalziel, 1991; Moores, 1991; the ca. 1.60-1.54 Ga Musgravian Gneiss was Karlstrom et al., 2001; Wingate et al. 2002). formed in an arc setting, developed in a south- 98 Chapter 8 Terra incognito? The initial reconstruction involving a Laurentia- been called the AUSMEX configuration (Wingate Australia connection is referred to as the south- et al. 2002). Despite this, owing to the sparseness west U.S-East Antarctica (SWEAT) model, and of reliable Mesoproterozoic palaeopoles, the relative was first proposed on the basis of apparent tectonic configuration and proximity of both Australia and similarities between parts of Australia, southern Laurentia before 1.2 Ga is not well known. Laurentia and Antarctica (e.g. Dalziel, 1991; Moores, 1991). Subsequent to this, an increase 8.3.2 Does the Musgrave Province contain a vital in palaeomagnetic evidence and the recognition piercing point in Rodinian reconstructions? of inferred continental piercing points led to a revision of this continental arrangement and was Two key lines of evidence have been used in the developed into the AUSWUS arrangement. This past to support a connection between Australia places eastern Australia adjacent to western US and Laurentia. The first is the presence of ca. (e.g. Karlstrom et al., 2001). AUSWUS places 1.60-1.54 Ga detrital zircons located in lower parts importance on correlation of orogenic belts across of the ca. 1.47-1.4 Ga Belt Basin in western the rifted Laurentia-Australia margin, and on late Laurentia (Ross et al., 1992; Ross and Villeneuve, Mesoproterozoic and early Neoproterozoic 2003). Source rocks for zircons of this age are palaeopoles, the reliability of which has recently extremely rare within Laurentia, and lie within what been questioned (Wingate et al. 2002). Recent is termed the ca. 1.60-1.50 Ga North American acquisition of precise latest Mesoproterozoic Magmatic Gap (Van Schmus et al., 1993). palaeopoles have led others to the conclusion that Conversely, source rocks of this age within Australia Australia was separate from Laurentia at 1.2 Ga are widespread, which led the authors to suggest (Pisarevsky et al., 2003), and that the two probably some derivation of the lower Belt Basin rocks from only came together at ca. 1.07 Ga in what has sources such as the Gawler Craton (e.g. Ross and

Figure 8.2 (a) Probability density plots for samples of ca. 1.47-1.45 Ga (b) Derivation of parts of lower Belt sequences from Musgrave material metasedimentary rock analysed by SHRIMP and LA- ICPMS (b) Postulated Mesoproterozoic reconstructions C of Australia and Laurentia

I G HEARNE A n dso Hu - YAV/ M s MO/GE AG MB? GC? n

a MAZ? r

T (a) Gaw CP SUPERIOR PROVINCE 13.3% 12.2%24.5% 42.9% 3.1% 4.1% WYOMING

Yavapai/ (a) SHRIMP Data Mojave Mazatzal Ant Metm. Detrital n=98 Grains Grains

ca. 1.42 - 1.4 Ga Deposition of Musgrave metasediments from dominantly Yavapai/ Mohave provinces

C Relative Probability I G HEARNE A n dso Hu - M s

a r

T Gaw CP SUPERIOR PROVINCE WYOMING

Yavapai/ Mojave Mazatzal Ant AG YAV/ MB? GC? MO/GE MAZ? 48.6%4.8% 16.4% 25.3% 2.7% 2.1% (b) LA-ICPMS Data ca. <1.4 Ga Metm. Detrital Rifting and breakup cutting off n=135 sediment supply, passive margin Grains Grains sedimentation

HEARNE G n A I dso Hu - M s n

a r

T SUPERIOR Gaw CP PROVINCE WYOMING

Yavapai/ Relative Probability Mojave Mazatzal Ant

0 2000 km

Avg. Crustal Model Ages Direction of sediment >1.8-1.6 Ga transport (thickness proportional to amount of contribution)

2.0-1.8 Ga 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 >2.0 Ga Belt Basin Passive sediments margin seds. MESOPROTEROZOIC PALAEOPROTEROZOIC ARCHAEAN

99 Chapter 8 Terra incognito? Villeneuve, 2003). The second piece of data that 2000). Early models on interaction between mafic may allude to an Australia-Laurentia connection is magmas and crustal rocks were tested using data the presence of ca. 1.49-1.40 Ga detrital zircons from layered intrusions, with most initial models in rocks located in both Tasmania and Antarctica involved simple bulk assimilation of crustal rocks (Goodge et al., 2002; Black et al., 2004). Similar into a mafic magma (e.g. Gray et al., 1981; Zindler to the magmatic gap of North America, this time et al., 1981). Following this, a number of more span marks a period of quiescence in magmatism complex models were applied involving combined within Australia, and could be termed the Australian assimilation and fractional crystallisation (AFC) Magmatic Gap. This led the authors to conclude (Depaolo, 1981) to layered intrusions such as the derivation of the ca. 1.49-1.40 Ga zircons from Kiglapait and Skaergard bodies (Depaolo, 1985; Laurentian sources such as the voluminous A-type Stewart and Depaolo, 1990), and the refilling, granite suites located in southern Laurentia (e.g. tapping, fractionation, assimilation (RFTA) models Anderson, 1989; Van Schmus et al., 1993). to mafic complexes in Italy and France (O'Hara, 1977; Poitrasson et al., 1994; Voshage et al., Results presented in this study of U-Pb detrital 1990). However, magmas may also obtain their zircon and Sm-Nd isotopic analyses of enriched isotopic and trace element signature metasedimentary rocks located in the eastern through mantle enrichment in subduction regimes, Musgrave Province suggest a piercing point either through subduction of slab sediment, mantle between the eastern margin of central Australia metasomatism, or some combination of both (e.g. and the Laurentian Belt-Purcell Group during the Amelin et al., 1996; Halama et al., 2003; Lambert late Mesoproterozoic. Detrital zircon ages range et al., 1994; Mazzucchelli et al., 1995). In some from Palaeoproterozoic to late Mesoproterozoic cases, both crustal assimilation and prior mantle (Figure 8.2a), constraining the maximum enrichment may have contributed to the enriched depositional age of the metasediments to isotopic signature (Amelin et al., 1996; Amelin and approximately 1.42-1.36 Ga, similar to that of the Semenov, 1996). The multiplicity of possible Belt Supergroup. The 1.49-1.36 Ga detrital zircons processes in operation during magma generation, in the Musgrave metasediments are interpreted to ascent, and crystallisation makes every layered have been derived from the voluminous A-type intrusion unique, which probably accounts for the suites of Laurentia. numerous petrogenetic models proposed.

Most metasedimentary rocks exhibit eNd(1.40 Ga) Kalka 8.0 N-MORB (a) values ranging from 5.1 to +0.9, inconsistent with Ewarara derivationsoley from Australian sources, which are Gosse Pile Depleted Continental more isotopically evolved. The detrital zircon ages 4.0 Tholeiite Primitve Alcurra and Sm-Nd isotopic characteristics are consistent Dyke 0.0 Primitve Picritic with derivation from a mixture of both Australian Basalt CHUR and Laurentian sources (Figure 8.2b). This -4.0

interpretation supports palaeogeographic [email protected] Ga

e Avg. Juvenile reconstructions between Australia and Laurentia Crust during the Mesoproterozoic. -8.0 Avg. Crust -12.0 Basement to the Musgravian metasedimentary Avg. Evolved Crust CHUR rocks includes ca. 1.60-1.54 Ga felsic granulites. -50.0 0.0 50.0 100.0 150.0 200.0 Their age and isotopically juvenile characteristics [email protected] Ga make them excellent candidates for the source of 0.5120 the lower Belt Supergroup with its abundant ca. (b) 1.6-1.54 Ga detrital zircons, also supporting N-MORB Australia-Laurentia reconstruction models. 0.5115

143Nd/ CHUR 144 Ndi 8.4 ca. 1.08 Ga Giles Complex r = 0.8

0.9 0.9 0.8 0.5110 0.7 0.5 0.7 0.0 0.5 0.0 8.4.1 Layered intrusions and crust-mantle Avg. Crust interaction r = 0.5

0.5105 CHUR

0.700 0.705 87 86 0.710 0.715 Geochemical and isotopic studies in layered mafic- Sr/ Sri ultramafic intrusions can provide important Figure 8.3 (a) eNdi vs eSri plot displaying various information on the nature of an ascending mafic magma composition and contaminant endmembers magma and its interaction with the surrounding (b) Example of AFC mixture model involving a picritic crustal rocks (e.g. Amelin et al., 2000; Amelin et source composition and average Musgrave crust as al., 1996; Amelin and Semenov, 1996; Maier et al., the contaminant 100 Chapter 8 Terra incognito? 8.4.2 The Giles Complex; crustal contamination (Hoskins and Lemon, 1995; Moussavi-Harami and or modified lithospheric mantle? Gravestock, 1995; Walter et al., 1995; Lindsay and Leven, 1996). The exhumation of the Musgrave The Giles Complex represents part of the erosional Province marks the initiation of the Petermann remnants of the Warakurna LIP, proposed to have Orogeny and forms the northern margin of the covered much of central and western Australia Officer Basin. On its southern margin, the Officer between ca.1.078 and 1.07 Ga (Wingate et al., Basin is bordered by the Archaean- 2004). The geochemical and isotopic signature Palaeoproterozoic Gawler Craton. recorded in the coeval ca. 1.08 Ga high-Mg low- Ti tholeiites of the Alcurra Dyke Swarm of the The timing and duration of this uplift has been the Musgrave Province have been interpreted as subject of some debate, with two general models recording modification of the sub-continental proposed. The first suggests that the Petermann lithospheric mantle by subduction processes during Orogeny began at around 0.65 Ga and continued the Proterozoic (Zhao and McCulloch, 1993). to approximately 0.53 Ga (Shaw, 1991; Calver and In addition to this, petrographic and geochemical Lindsay, 1998). The second model suggests that studies on Giles Complex intrusions located in the Petermann Orogeny was a relatively short- Western Australia have concluded that they were lived event, spanning ~ 0. 58-0.54 Ga (e.g. Hoskins derived from an enriched source, probably involving and Lemon, 1995; Lindsay and Leven, 1996; the subcontinental lithospheric mantle (Glikson et Camacho and McDougall, 2000). al., 1995; Glikson et al., 1996). Thermochronological data on the Petermann In opposition to this are the findings from this study Orogeny from within the Musgrave Province is which imply that the isotopic and geochemical restricted to Sm-Nd dating of garnets (Scrimgeour signature of the Giles Complex can be explained and Close, 1999; Camacho and McDougall, 2000), through crustal contamination of a primitive picritic and K-Ar dating of micas (Maboko et al., 1992; mantle source. Careful isotopic (Sm-Nd and Rb- Camacho and McDougall, 2000). However these Sr) and geochemical modelling was carried out dates are restricted by the closure temperature of using a variety of possible source magma the minerals being analysed. Geochemical and Nd compositions and contaminants (Figure 8.3a). isotope analyses of sedimentary rocks within the The enriched isotopic signature of the Giles Officer Basin should determine the time at which Complex intrusions is best explained by addition the erosion of the Musgrave Block began to of ~10% average Musgrave crust to a magma of dominate the basin input, signifying initial unroofing picritic composition (Figure 8.3b). Shallow of the Musgrave Block during the Petermann decompressional melting of an asthenospheric Orogeny plume source beneath thinned Musgravian lithosphere is envisaged as a source for the parental 8.5.2 When was the initiation of the Petermann picritic magma. The contamination of the magma Orogeny? is inferred to have occurred during ascent through the feeder conduits, during which time the magma Sm-Nd isotopic and geochemical data from reached suplhur saturation. This has important Neoproterozoic to Cambrian sedimentary rocks in implications for exploration of magmatic Ni-Cu-Co the intracratonic eastern Officer Basin in central sulphides within the Giles Complex, implying that Australia highlight the evolving provenance roles exploration should be concentrated on locating of the basement complexes that underlie and bound these feeder dyke systems. This exploration the basin (Figure 8.1a). Initial eNd values of around method has been successful in both W.A. (Nebo- 12.0 for the basal units indicate both were largely Babel prospect, WMC) and S.A. (Harcus prospect, derived from the late Archaean to Mesoproterozoic PepinNini). Gawler Craton, which bounds the basin to the south (Figure 8.1a). At approximately 0.72 Ga an 8.5 ca. 0.56 Ga Petermann Orogeny influx of juvenile, glacially derived sediment indicates partial uplift of the Mesoproterozoic Musgrave 8.5.1 Petermann Orogeny; look in the basin not Block along the basins northern margin, in a regime the mountain belt? interpreted to be broadly extensional (Figure 8.1a). At around 0.60 Ga, synchronous with the The Neoproterozoic to mid-Palaeozoic intracratonic development of a foreland architecture, was a large Officer Basin in central Australia is one of a number influx of Musgrave Block-derived sediments (Figure of basins that together formerly comprised the 8.1a). This is interpreted to mark the onset of the Centralian Superbasin (Walter et al., 1995), which intracratonic Petermann Orogeny, which was a was subsequently dissected into a southern long-lived event or series of events, spanning more fragment (Officer Basin) through uplift of the than 70 million years. Subsequent to ~0.60 Ga, Musgrave Province during the Petermann Orogeny the Nd isotopic composition of sequences within 101 Chapter 8 Terra incognito?

Transport of e Amadeus Basin sediment from (Nd) Levinger Moorilyanna Mann Fault system -24 -20 -16 -12 -8 -4 0 4

Graben Graben

p Possible extent

p 400 p

p N.T. of foreland basin

p p p

p Erosion of Stratigraphic

p STAGE p

Mann p S.A. source regions Column Fault Indulkana Shale

4 Mt Chandler Sst

Musgrave Blockq

q Tasman Line q

q 500

q q q Apamurra Fmtn Trainor Hill Sst 3 Arcoeillinna Sst Obs. Hill Fmtn Relief Sst

Mena Mudstone Mbr Tanana Fmtn 2 Dey Dey Mdst Eastern Murnaroo Fmtn Officer Meramangye Fmtn Tarlina Sst 600 Basin

Gawler Bonney Craton Sandstone Chambers Bluff Tillite 700 TIME (Ma)

(b) Adelaide Geosyncline Alinya Fmtn Pindyin Sst 800 0 300 km 1 Cadlareena Volc. Coominaree Dolm.

Figure 8.4 (a) eNd vs time plot of the Officer Avg. Archaean Gawler Avg. Mesoprot. Gawler Musgrave Block Basin units highlighting the evolving roles of the 900 bounding basement complexes (b) Possible Gawler C Craton H U sediment transport directions during the (a) R Petermann Orogeny. 1000 the Officer Basin indicates an increasing (NAC and SAC) associated with the Hiltaba Suite contribution from the Gawler Craton despite up to and Gawler Range Volcanics in the Gawler Craton 45 km of denudation of part of the Musgrave Block (Fanning et al., 1988), the voluminous S-type at ca. 0.56 Ga (Figure 8.1a). This suggests that granites in the Curnamona Province (Page et al., the majority of sediment derived from the 2003), and the meta-igneous rocks of the Mt Isa Petermann Orogen bypassed the eastern Officer and Yambo inliers of north Queensland (Blewett Basin for much of the history of the Petermann et al., 1998) (Fig. 7.1). Post 1.35 Ga is the Orogeny. This may reflect the existence of a long- emplacement of voluminous granitoids in both the lived tectonic barrier such as the presence of an Musgrave Province (ca.1.30 Ga orthogneiss (White axial river system within the foreland basin, a filled et al., 1999); and ca. 1.20-1.14 Ga granites of the foreland basin, and/or the development of an voluminous Pitjantjatjara Supersuite (e.g. Camacho efficient means of transporting sediment along the and Fanning, 1995; Edgoose et al., 2004)), and axis of the orogenic belt (Figure 8.2a). Albany-Fraser Complex (ca. 1.33-1.14 Ga granites of the Nornalup Complex (e.g. Myers, 1995; Nelson 8.6 Filling the Australian magmatic gap; the et al., 1995). Coompana Block This apparent paucity of magmatism during the 8.6.1 Why is the Coompana Block so important? interval of ca. 1.50-1.35 Ga has provided problems for many provenance studies that have identified The magmatic history of Proterozoic Australia is detrital zircons falling within this time period (e.g. punctuated by intervals of relative quiescence in Goodge et al., 2002; Black et al., 2004; Chapter magmatic activity, the two main periods being ca. 4: this study). In all cases the authors have cited 2.0-1.9 Ga and ca. 1.50-1.35 Ga. These periods sources exotic to Australia, such as the voluminous may represent a time of reduced activity in mantle A-type granitoids suites of southern Laurentia dynamics, a preservation problem, or a sampling (Anderson and Bender, 1989; Van Schmus et al., problem. Much like the ca. 1.60-1.54 Ga North 1993). Following this, the presence of ca. 1.50- American magmatic gap of Laurentia (Van Schmus 1.35 Ga detrital zircons has led to palaeogeographic et al., 1993), the only two felsic magmatic events reconstructions involving Australia and Laurentia of any note occur around ca. 1.50-1.35 Ga. These (e.g. Goodge et al., 2002; Chapter 4: this study). include the ca. 1.51 Ga Spilsby Suite Granite of The gross tectonic elements of Proterozoic the Gawler Craton, the outcrop of which is restricted Australia, namely the North, South, and West to Spilsby Island (Fanning, 1997), and the 1.52- Australian cratons, are separated by deep and 1.50 Ga Williams Supersuite of the eastern Mt Isa aerially extensive sedimentary basins, of which Inlier (Page and Sun, 1996; Wyborn, 1998) (Fig. the underlying basement geology is either poorly 7.1). Prior to this from ca. 1.60-1.54 Ga we have or totally unknown. It is beneath these sedimentary voluminous magmatism throughout much of the basins in which the potential lies to discover North Australian and South Australian Cratons magmatic belts of ages that would fill the ca. 1.50-

102 Chapter 8 Terra incognito?

1000 Nb 0.29 500 (a) (b) 1600 A-type 0.28 1560 0.27 100 U 238 50 0.26

Pb/ 1460 A 206 0.25 S 1400 10 I 0.24 I & S Upper intercept at 1502 ± 4.3 Ma 5 MSWD = 2.1 type 0.23 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 207Pb/235U 1 12 510 n=33 (c) Wght. Avg. (95% conf.) 10000*Ga/Al 20 1505 ± 7.2 Ma MSWD = 0.25 Relative probability

Figure 8.5 (a) Nb vs 10000xGa/Al and Ga/Al 15 vs Zr+Nb+Ce+Y plots of Whalen et al. (1987) displaying A-type characteristics of the granitic 10

gneiss (b) Conventional U-Pb concordia diagram Number displaying upper intercept age of ca. 1.50 Ga 5 (c) 207Pb/206Pb age histogram and probability density curve displaying weighted average of 0 ca. 1.50 Ga. 1400 1440 1480 1520 1560 1600 1640 207Pb/206Pb

1.35 Ga time gap in the geological record. The ca. 1.50-1.35 Ga, possibly allowing for a more Coompana Block separates the WAC from the proximal source to be proposed. However, at this SAC, and represents one such area in which the stage this is just one intersection of granitic gneiss underlying basement is shallow enough to be in a single drillhole, the age of which fills just part sampled by drillcore. Its geographical position is of the magmatic gap. Despite this, the identification key in deciphering what may underlie the Officer of granitic magmatism of this age under Basin in South and Western Australia. Neoproterozoic-Cambrian cover raises the possibility that underlying the Officer Basin in S.A. 8.6.2 What impact does the genesis of the ca. and W.A. separating the Gawler Craton from the 1.50 Ga granitic gneiss have on reconstruction Yilgarn Block is an expansive belt of rocks of an models? age unusual to Proterozoic Australia, and that indeed Australias magmatic gap may be hiding The granitic gneiss intersected in Mallabie 1 drillhole under cover. exhibit petrological and geochemical characteristics typical of A-type granites (Fig. 8.5a). The Mallabie 8.7 Conclusions 1 granitic gneiss is characterised by distinctive major and trace element compositions such as This study has clearly shown that the Musgrave high contents of Zr, Nb, Y, Ga, LREE with low Mg#, Province has undergone a complex tectonic Sr, CaO and HREE. U-Pb LA-ICPMS dating on evolution spanning a period of approximately 1.0 separated magmatic zircons has provided an age Ga. Understanding the early history of the of 1505±7.2 Ma (Fig. 8.5b,c), interpreted as the Musgrave Province is key to reconstructions of crystallisation age of the granite. Nd isotopes Proterozoic Australia. The key findings of this provide juvenile values ranging from +1.2 to +3.3 study are: at 1.50 Ga. This could plausibly be explained by derivation from a mantle melt with minor (1) The oldest rocks of the Musgrave Province contamination. record a pre-history of plate margin activity. The protolith of these ca. 1.60-1.54 Ga mafic and felsic The identification of granitic A-type magmatism orthogneisses is interpreted to have been arc that falls within the Australian magmatic gap of magmas generated in an island arc setting between Proterozoic Australia has implications for the NAC and SAC. The subsequent closure of reconstruction models citing non-Australian sources this arc and collision of the NAC with the SAC is for detrital zircons falling within the age bracket of viewed to be expressed as widespread

103 Chapter 8 Terra incognito? compressional deformation throughout much of the NAC and SAC.

(2) Metasedimentary rocks of the eastern Musgrave Province record evidence of a pre-Rodinia connection between Australia and Laurentia. Detrital zircon ages and Nd isotopes are irreconcilable with derivation from soley Australian sources. Basement ca. 1.60-1.54 Ga felsic orthogneisses of the Musgrave Province also provide a better isotopic and age match for the dominant detrital zircon peak of ca. 1.60-1.54 Ga found in the basal sequences of the Belt-Purcell Basin in North America/Southern Canada. Combined, this evidence strongly suggests a link between Australia and Laurentia pre-1.40 Ga.

(3) The mafic-ultramafic rocks of the ca. 1.08 Ga Giles Complex record a period of large scale melting of the asthenospheric mantle associated with the genesis of the Warakurna LIP. Isotopic and geochemical modelling suggests crustal contamination of a picritic magma source is the most likely process responsible for the geochemical signatures recorded in the cumulate rocks of the Giles Complex. This makes the Giles Complex extremely prospective for Ni-Cu-Co sulphide deposits. (4) Sedimentary rocks of the Officer Basin record the ongoing evolution and denudation of the Musgrave Province during the ca. 0.60-0.55 Ga Petermann Orogeny. The isotopic record preserved in units of the Officer Basin indicates initial unroofing of the Musgrave Province and thus initiation of the Petermann Orogeny at ca. 0.60 Ga, which continued to ca. 0.55 Ga. (5) A-type granitic magmatism recorded in the Coompana Block occured at a time of unusual quiescence in the magmatic history of Proterozoic Australia. Its discovery raises the possibility of the presence of large belts of ca. 1.50-1.35 Ga granitoids underneath the cover of the Officer Basin, in what otherwise is a magmatic gap in the history of Proterozoic Australia. An underlying theme throughout this thesis has been the need for detailed isotopic and geochemical studies within the vastly understudied Musgrave Province. The Musgrave Province is central to the Australian continent, and central to understanding the final amalgamation of the various elements of Proterozoic Australia.

104