Geology and mineral resources of the Northern Territory

Ahmad M and Munson TJ (compilers)

Northern Territory Geological Survey Special Publication 5

Chapter 26: Basin

BIBLIOGRAPHIC REFERENCE: Dunster JN and Ahmad M, 2013. Chapter 26: Victoria Basin: in Ahmad M and Munson TJ (compilers). ‘Geology and mineral resources of the Northern Territory’. Northern Territory Geological Survey, Special Publication 5.

Disclaimer While all care has been taken to ensure that information contained in this publication is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of its information. The Northern Territory of gives no warranty or assurance, and makes no representation as to the accuracy of any information or advice contained in this publication, or that it is suitable for your intended use. You should not rely upon information in this publication for the purpose of making any serious business or investment decisions without obtaining independent and/or professional advice in relation to your particular situation. The Northern Territory of Australia disclaims any liability or responsibility or duty of care towards any person for loss or damage caused by any use of, or reliance on the information contained in this publication. Victoria Basin Current as of March 2010 Chapter 26: VICTORIA BASIN JN Dunster and M Ahmad

INTRODUCTION estimate of the age of the group. The minimum age of the succession is constrained by an inferred age of about The Neoproterozoic Victoria Basin is exposed in the Victoria 635 Ma or younger for the Moonlight Valley Tillite of River area of the northwestern NT, where it unconformably the overlying Wolfe Basin, based on correlations of this overlies the Palaeo–Mesoproterozoic Birrindudu Basin unit with the Olympic and Elatina formations from the (Figure 26.1). Previous workers (eg Blake et al 1975, Sweet Amadeus Basin and Adelaide Belt, respectively 1977) recognised the Birrindudu and overlying Victoria (Grey and Corkeron 1998, see Centralian Superbasin). basins as being distinct depositional basins separated by The most current references for the Auvergne Group are an unconformity, but there was no consensus as to which Sweet et al (1974) and Dunster et al (2000) and the following of several unconformities within the overall succession 128° 129° 130° 131° 132° marked the break. Dunster et al (2000) and Cutovinos et al 12° (2002) used the unconformity at the base of the Wattie DARWIN Money *URXSWRVHSDUDWHWKHEDVLQVEXWWKLVSXEOLFDWLRQUHGH¿QHV Shoal Basin the basins by positioning the break at the unconformity Daly Basin WESTERN NORTHERN between the Tijunna and Auvergne groups, so that only 13° AUSTRALIA TERRITORY Pine Creek the Auvergne Group is assigned to the Victoria Basin. This Orogen is supported by the presence of detrital zircons within the

7LMXQQD*URXSWKDWKDYHJUHDWHUDI¿QLWLHVZLWKWKRVHRIWKH Fitzmaurice underlying strata than with those of the Auvergne Group Basin &DUVRQ 7KHUHGH¿QHG9LFWRULD%DVLQRXWFURSVRYHU 14° an area of >32 500 km2 within the NT, although its total Bastian Daly Basin Basin extent under younger covering rocks is somewhat greater. Bonaparte It spans the Western Australian–Northern Territory border, Basin Carr-Boyd Basin but is much more widely distributed in the latter. 15° The Auvergne Group contains seven formations (Table 26.1) that were initially deposited in a northeast- Wyndham trending intracratonic sag basin in southwestern AUVERGNE1 and western WATERLOO (Figure 26.2). Wolfe Kununurra Basin In ascending order, these are the Jasper Gorge Sandstone, 16° Angalarri Siltstone, Saddle Creek Formation, Pinkerton Bonaparte Sandstone, Lloyd Creek Formation, Spencer Sandstone Basin and Shoal Reach Formation. The succession attains a Halls Creek thickness of 950 m and forms most of the Pinkerton, Orogen Spencer, Yambarra and Newcastle Ranges. It is best 17° exposed in AUVERGNE, but extends to all the adjacent NT mapsheets (Figure 26.1). The Victoria River Ord Birrindudu Zone limits its present northwestern distribution. In Basin Basin drillhole Bullo River-1 (Figure 26.2), the Auvergne Group 18° directly overlies basement. This demonstrates that the Birrindudu Basin is not present beneath the Victoria Wiso Basin Basin in the northwest. Wolfe TANAMI Basin 7KHUH DUH QR GH¿QLWLYH FKURQRVWUDWLJUDSKLF DJHV REGION A09-242.ai from the Auvergne Group, but it is believed to have 19° OLWKRVWUDWLJUDSKLFDI¿QLWLHVZLWKWKH1HRSURWHUR]RLF location of Mesozoic–Cenozoic Supersequence 1 of the Centralian A Superbasin (Walter Figure 26.2 et al 1995, see Centralian Superbasin), which includes the Neoproterozoic–Palaeozoic Victoria Basin Amadeus, Ngalia, Murraba, Wolfe and Georgina basins in early Cambrian Kalkarindji Province road the Northern Territory. SHRIMP U-Pb dating of detrital zircons from the basal Jasper Gorge Sandstone have given Palaeo–Mesoproterozoic basins railway Wyndham a conservative maximum deposition age of 1322 ± 22 Ma, Palaeo–Mesoproterozoic orogens locality 0 100 200 km with two isolated younger grains at ca 1243 Ma and Archaean 1171 Ma (Carson 2010). A poorly constrained Rb-Sr wholerock age of 838 ± 80 Ma has been obtained for the Figure 26.1. of Victoria Basin in NT and WA. Angalarri Siltstone from the lower part of the Auvergne NT geological regions from NTGS 1:2.5M geological regions GIS Group (Webb and Page 1977), and this is the best existing GDWDVHW:$JHRORJLFDOUHJLRQVVLPSOL¿HGDQGVOLJKWO\PRGL¿HG from Tyler and Hocking (2001); some small outliers/inliers 1 Names of 1:250 000 mapsheets are shown in large capital letters RPLWWHG([WHQWRI.DONDULQGML3URYLQFHLQ:$VOLJKWO\PRGL¿HG eg AUVERGNE. from Glass and Phillips (2006).

Geology and mineral resources of the Northern Territory 26:1 Special publication 5 Victoria Basin

PORT KEATS Giants Reef Fault FERGUSSON RIVER Pine Birrindudu Creek Basin Daly Basin Orogen Bonaparte Basin

Zone

Fitzmaurice Basin

Fault

AUVERGNE DELAMERE

River Bullo River-1 Carpentaria Victoria Basin Halls Basin Creek Fault Victoria

Spencer Pinkerton Range Fault Range Fault

WATERLOO Wolfe VICTORIA RIVER DOWNS Basin

Kalkarindji Province

Kalkarindji Province

Carpentaria LIMBUNYA WAVE HILL Basin Ord Basin

Negri Fault

Limbunya FaultBirrindudu Basin Wiso Basin

A09-243.ai ?Mesoproterozoic–?late Neoproterozoic Mesozoic–Cenozoic Shoal Reach Formation

Neoproterozoic–Palaeozoic Spencer Sandstone drillhole

early Cambrian Kalkarindji Province Lloyd Creek Formation fault Pinkerton Sandstone Palaeo–Mesoproterozoic basins DELAMERE Saddle Creek Formation 1:250 000 mapsheet Palaeo–Mesoproterozoic orogens Angalarri Siltstone 0 50 km Jasper Gorge Sandstone

Figure 26.2. Exposure of the seven formations that constitute the Auvergne Group in the NT, showing major faults, derived from GA 1:1M and NTGS 1:250K GIS datasets. NT geological regions from NTGS 1:2.5M geological regions GIS dataset.

Geology and mineral resources of the Northern Territory 26:2 Special publication 5 Victoria Basin discussion is based on those works, with only minor platform. Sedimentary structures indicate a nearshore amendments. marine environment. The Angalarri Siltstone is apparently conformable ?MESOPROTEROZOIC–?LATE NEOPROTEROZOIC on the Jasper Gorge Sandstone and forms a 25 km-wide northeast-trending belt that underlies the Whirlwind Plain. Auvergne Group It is generally very poorly exposed, but a complete section of 753 m was intersected in cored drillhole Bullo River-1 The Jasper Gorge Sandstone is spectacularly exposed in (52K 567666mE 8275746mN, Figure 26.2). On a regional Jasper Gorge in Gregory National Park in DELAMERE scale, the Angalarri Siltstone shows some lateral lithological and as the escarpment above Timber Creek township variation. In DELAMERE, FERGUSSON RIVER and in AUVERGNE, where mesas and ranges are scenic northeast AUVERGNE, it is almost entirely recessive and is attractions (Figure 26.3). The formation is typically GRPLQDWHGE\PLFDFHRXV¿VVLOHVLOWVWRQHPXGVWRQHZKHUHDV 50 m to 70 m thick, but it ranges up to 130 m locally. It more resistant siltstone and sandstone are exposed in the overlies the Timber Creek and Skull Creek Formations southwest. Smaller-scale lateral and vertical variations of the Birrindudu Basin with a low-angle unconformity. include dolomitic, glauconitic, pyritic and carbonaceous A 6 m-thick basal conglomerate is present 24 km facies (Figure 26.4). Various ripple morphologies, including southeast of Auvergne homestead, where the sandstone oscillation ripples, are common on exposed pavements. is 130 m thick. Around Timber Creek, the Jasper Gorge Overall, the Angalarri Siltstone is interpreted as a moderately Sandstone contains decimetre-thick basal pebble deep-water shelf deposit, deposited mostly below fair- ODJV DQG LV W\SLFDOO\ ௘±௘P WKLFN (OVHZKHUH LQ AUVERGNE, the contact is less obviously erosional and the basal conglomerate is lacking; however, thin conglomerate beds are present at stratigraphically higher levels in the formation. Mud clasts, now weathered to moulds, are common throughout the lower portion of the formation. In thin section, the rock is an orthoquartzite. Up to 10% of the quartz grains were derived from volcanic or metamorphic sources within the surrounding Palaeoproterozoic orogens. This is consistent with a SHRIMP U-Pb detrital zircon study by Carson (2010), who reported that the sandstone contains almost no detritus older than ca 1800 Ma, a ubiquitous age population present in the underlying sedimentary rocks. Carson obtained a conservative maximum depositional age of 1332 ± 22 Ma for the Jasper Gorge Sandstone. The Figure 26.3. Cliff-forming Jasper Gorge Sandstone caps the ranges distribution and petrology of the unit indicate that it was looking north from the escarpment near the township of Timber deposited as a mature sand on a stable, broad continental Creek (AUVERGNE, 52K 656434mE 8269641mN).

UNIT, THICKNESS LITHOLOGY DEPOSITIONAL STRATIGRAPHIC RELATIONS ENVIRONMENT Shoal Reach Formation Quartzose and silty dolostone, 0L[HGFDUERQDWHVLOLFLFODVWLFSODWIRUP Conformable on Spencer Sandstone, <100 m, thins to northeast dololutite, dolarenite, dolostone, gradational contact sandstone, minor siltstone and shale Spencer Sandstone Quartz sandstone, silty sandstone, Shallow marine with periods of Conformable on Lloyd Creek 7\SLFDOO\௘±P dolomitic sandstone subaerial exposure Formation Lloyd Creek Formation Dolostone (oolitic and microbial), 6KDOORZPDULQHPL[HGFDUERQDWH Conformable on Pinkerton Sandstone Typically <90 m, quartzose and silty dolostone, siliciclastic with wave action, up to 162 m locally dololutite, dolarenite, dolomitic storm deposits and brine-logging of siltstone, quartz sandstone sediment Pinkerton Sandstone Silica cemented quartz sandstone, Marine transgression, rare periods of Conformable on Saddle Creek 7\SLFDOO\±PXSWR minor siltstone and mudstone brine-logging Formation 375 m locally Saddle Creek Formation Basal sandstone, upper siltstone Very shallow to emergent, high- Regionally conformable on Angalarri Typically <160 m, and minor oolitic dolostone and energy clastic phases with brine- 6LOWVWRQHGLVXQFRQIRUPDEOHDWWZR >222 m locally, dolarenite logging, ooid shoals, argillaceous locations upper siltstone thins to northeast phases are slightly deeper water Angalarri Siltstone Siltstone and shale, minor Relatively deep water, hummocky Conformable on Jasper Gorge >300 m in outcrop, dolostone and sandstone, more FURVVVWUDWL¿FDWLRQEHORZVWRUPZDYH Sandstone 753 m Bullo River 1 arenaceous in southwest base Jasper Gorge Sandstone Silica cemented quartz sandstone, Near-shore marine on broad platform Unconformable on Timber Creek 7\SLFDOO\௘±P siltstone and basal conglomerate and Skull Creek Formations (Bullita up to 130 m locally Group)

Table 26.1. Lithostratigraphic succession of the Auvergne Group in AUVERGNE.

Geology and mineral resources of the Northern Territory 26:3 Special publication 5 Victoria Basin weather wave base, but at least partly above storm wave AUVERGNE (Dunster et al 2000). The formation contains EDVHRQWKHEDVLVRIPLFURKXPPRFN\FURVVVWUDWL¿FDWLRQ a basal sandstone usually less than 10 m thick, overlain FRPPRQÀXWHFDVWVDQGZHOOGH¿QHGODPLQDWLRQDQGGHHS E\ VLOWVWRQH RROLWLF GRORVWRQH VLOLFDFHPHQWHG TXDUW] water ripple morphologies. Webb and Page (1977) obtained sandstone, dolarenite and minor shale. An ooid grainstone a Rb-Sr poorly constrained whole-rock age of 838 ± 80 Ma RUD¿QHWRPHGLXPJUDLQHGGRODUHQLWHRFFXUVVRPHWHQV for this unit. of metres below the top of the formation. Sedimentary The Saddle Creek Formation appears to be regionally structures in the basal sandstone include cross-bedding, conformable on the Angalarri Siltstone, but locally, the FRQYROXWHEHGGLQJÀDPHVWUXFWXUHVVHYHUDOW\SHVRIULSSOH contact can be erosional and an angular unconformity morphologies, mudcracks, synaeresis cracks in ripple of about 10º has been documented in AUVERGNE swales, pseudomorphs and casts after halite, sole marks ()LJXUH). Its overall thickness is typically less than and current lineations. The Saddle Creek Formation was 160 m, but a maximum of 222 m has been measured in deposited in very shallow to emergent conditions, initially with intermittent high-energy clastic phases and brine- a logging of the sediment. The siltstone represents slightly deeper, stable conditions and the oolitic dolostone was probably deposited in higher energy shoals. The Pinkerton Sandstone conformably overlies the Saddle Creek Formation and forms a resistant capping on the main escarpments and dissected plateaux of the Pinkerton and Yambarra ranges. It also outcrops in Spencer Range and forms a prominent hogback ridge along the southeastern side of the Victoria River Fault Zone. A basal medium- JUDLQHGVLOLFDFHPHQWHGTXDUW]VDQGVWRQHXSWRPWKLFNLV RYHUODLQE\PXGVWRQHVLOWVWRQHDQG¿QHJUDLQHGVDQGVWRQH 7KLVLVRYHUODLQE\DVHFRQGFOLIIIRUPLQJ¿QHJUDLQHG sandstone and siltstone up to 30 m thick that contains DEXQGDQWPRXOGVDIWHUPXGÀDNHVDQGZHOOH[SRVHGULSSOH pavements (Figure 26.6 $¿QHWRPHGLXPJUDLQHG VLOLFDFHPHQWHGTXDUW]VDQGVWRQHLVWKHXSSHUPRVWIDFLHV exposed. Dolomitic phases, and rare cm-scale cubic casts after halite, which are associated with various ripple morphologies, are also present. The Pinkerton Sandstone UDQJHVXSWRPWKLFNEXW௘±PLVPRUHW\SLFDO The Pinkerton Sandstone probably represents a marine transgression with high-energy nearshore conditions and more terrigenous clastic input than the formations above or below. Sparse outcrops of the Lloyd Creek Formation are characterised by oolitic (Figure 26.7) and stromatolitic GRORVWRQHLQWHUEHGGHGZLWKGRODUHQLWHTXDUW]RVHGRORVWRQH DQG ULSSOHG TXDUW] VDQGVWRQH 5DUH JODXFRQLWH JUDLQV DUH present in the carbonate rocks. Subordinate lithologies include laminated dolostone, dolomitic siltstone and imbricated plate breccia. Recessive intervals may be of b

Figure 26.4. Angalarri Siltstone (after Perring and Jones 1991). (a) A09-244.ai Grey-green siltstone underlying darker carbonaceous shale. Cliff is )LJXUH. Probable unconformable contact (shown) between about 10 m high. (b) Limonite, probably after pyrite, occurring as Angalarri Siltstone (below) and Saddle Creek Formation (AUVERGNE, thin laminae in Angalarri Siltstone in Koolendong Valley. 52K 570730mE 8253670mN, after Dunster et al ¿JXUH 

Geology and mineral resources of the Northern Territory 26:4 Special publication 5 Victoria Basin dolomitic shale. Pseudomorphs of swallow-tail gypsum The Spencer Sandstone is conformable on the Lloyd twins, and casts of pagoda halite and of halite hoppers up Creek Formation and typically ranges between 140 m to 4 cm across indicate an evaporitic overprint. Pinolitic and 165 m in thickness. In most areas, the basal Spencer prisms of ferroan carbonate are interpreted as a diagenetic 6DQGVWRQH LV D WKLQO\ EHGGHG ¿QH RU PHGLXPJUDLQHG RYHUSULQWDVVRFLDWHGZLWKODWHUEULQHÀXVKLQJDQGQRWDV sandstone up to 15 m thick. It contains abundant small- pseudomorphs of primary evaporite. The formation is scale cross-lamination and ripple marks. Moulds after mud conformable on Pinkerton Sandstone and is typically less ÀDNHV DUH FRPPRQ 7KH RYHUO\LQJ XQLWV DUH FRPPRQO\ than 90 m thick, but ranges up to 162 m. A shallow-marine UHFHVVLYHH[FHSWIRUWKLQEHGVRIPHGLXPWR¿QHJUDLQHG mixed carbonate/siliciclastic environment of deposition, sandstone and friable quartzose siltstone. Mudcracks, ripple characterised by wave action and occasional brine-logging marks, cross-beds and thin pebble lags are common. The of the sediment, is postulated. Imbricated plate breccias are uppermost Spencer Sandstone is typically dolomitic. Halite interpreted as storm deposits. casts and pseudomorphs up to several centimetres across occur in swales between ripples. The Spencer Sandstone was probably deposited in a shallow-marine environment with periods of subaerial exposure. The Shoal Reach Formation conformably overlies the Spencer Sandstone and the contact is gradational. The formation is poorly exposed, apart from low benches and ground-level outcrops of quartzose and silty dolostone, dololutite, dolarenite, siltstone and sandstone, and intraformational conglomerate in places. It is probably between 70 m and 100 m thick over most of its distribution, but thins to the northeast. The Shoal Reach Formation was deposited on a mixed carbonate-siliciclastic marine shelf. $Q DVVRFLDWLRQ RI GRORVWRQH ZLWK ¿QHVFDOH FURVVEHGV ripple marks and graded beds indicates a shallow protected environment above fair-weather wave base.

STRUCTURE, METAMORPHISM AND IGNEOUS ACTIVITY

The rocks of the Victoria Basin are unmetamorphosed and DUHJHQHUDOO\ÀDWO\LQJWRJHQWO\GLSSLQJQRUWKZHVW7KHUH is no known evidence of igneous activity. In contrast to the underlying Birrindudu Basin, there is little evidence of syndepositional fault activity or uplift during the Victoria Basin’s depositional history, other than possible differential uplift prior to the deposition of the Saddle Creek Formation. However, subsequent locally intense deformation is associated with major faults. The greatest fault movements probably occurred prior to the Cambrian, but some reactivation postdates the early Cambrian Antrim Figure 26.6. Ripples in Pinkerton Sandstone in Pinkerton Range Plateau Volcanics. (AUVERGNE, 52K 569700mE 8256100mN, after Dunster et al The Victoria River Fault Zone (Figure 26.2) is a 1 km- ¿JXUH  wide belt of intense deformation affecting the Auvergne Group. There were several periods of movement in the fault zone and it includes a major strike-slip component. Sweet (1977) and Slade (1987) interpreted the present FRQ¿JXUDWLRQDVDORZDQJOHWKUXVWUHVXOWLQJIURPQRUWK± south compression. A major left-lateral component was also inferred. This is consistent with a continuation of the Victoria River Fault Zone into the Halls Creek Fault to the south, as interpreted by Thorne and Tyler (1996). However, a right-lateral sense is more consistent with a possible extension of the Victoria River Fault Zone into the Giants Reef Fault to the north. Rocks within the Victoria River Fault Zone are steeply dipping and overturned by up to 75° from vertical. Shear zones that are tens of metres wide indicate both near-vertical and strike-slip components to the Figure 26.73DUWLDOO\VLOLFL¿HGRRLGJUDLQVWRQHLQ/OR\G&UHHN)RUPDWLRQ latest fault movements. Conspicuous quartz blows occur in (AUVERGNE, 52K 569700mE 8256100mN, after Dunster 1998). dilational zones, and areas of isoclinal folding are present.

Geology and mineral resources of the Northern Territory 26:5 Special publication 5 Victoria Basin

Several major faults parallel to the Victoria River Fault Zone Petroleum offset the Auvergne Group to varying extents. An unnamed fault parallels the Newcastle Range and is conspicuous on The Proterozoic rocks in and around AUVERGNE were air-photos, where it can be traced over 50 km, but there is LQYHVWLJDWHGEULHÀ\IRUWKHLURLOSRWHQWLDOE\2ZHQ   little apparent vertical displacement. Laing and Allen (1956) and Laing (1982), who followed The Pinkerton Range and Spencer Range faults are up 1890s reports of bitumen in water wells and petroleum parallel, separated by 7 km, and extend discontinuously seeps in the Spencer Range. The Angalarri Siltstone was southwest for over 100 km from the Victoria River into believed to be the source of a water sample from a spring WATERLOO. There appears to be varying vertical near the Bullo River access road that contained 2.3 ppm displacements associated with their component faults. of hydrocarbons (Laing and Webby 1982). A fully-cored The maximum offset on the Pinkerton Range Fault is 970 m petroleum well, Bullo River-1, was drilled by along Lloyds Creek where the Pinkerton and Spencer Queensland Petroleum during 1984. It intersected the sandstones are juxtaposed. This indicates an apparent Auvergne Group, from the Saddle Creek Formation to the vertical displacement of 120 m. The Spencer Range Fault Jasper Gorge Sandstone, and was terminated in granite has a maximum throw of 500 m and there is a narrow band basement. No shows were reported and there has been no of intense deformation on its northwest side. This fault further exploration since then. has been interpreted as either a steeply dipping normal fault with two episodes of movement and collapse on the Uranium northwestern side, or as a low-angle reverse fault (Sweet 1977). The north side of the Spencer Range Fault has a The Auvergne Group in the Spencer and Pinkerton ranges VWUXFWXUDOFRQ¿JXUDWLRQVLPLODUWRWKDWRIWKH9LFWRULD was explored for uranium by Broken Hill Proprietary Co Ltd River Fault Zone and they probably share a common in the late 1960s. Scintillometer and magnetometer surveys history. ZHUHÀRZQDQGVRPHJURXQGLQVSHFWLRQVXQGHUWDNHQ7KH Northeast trending faults are cut by numerous shorter UHVXOWVZHUHGLVDSSRLQWLQJDQGWKHDUHDZDVUHOLQTXLVKHGLQ orthogonal faults. These are nearly vertical and are 1970 (Gunn 1970). This area was again under exploration generally downthrown to the southwest by less than 200 m licence by several companies in the mid 2000s uranium (Sweet et al 1974). Some appear to have a similar lateral boom, but little work was undertaken. displacement. A series of northeast-trending anticlines and synclines, and relatively more intense faults occur in the Diamonds area surrounding the junction of the Victoria River Fault Zone and Halls Creek Fault. Synclines and anticlines, tens Early exploration for diamonds in the Victoria Basin was of kilometres long, are developed along the southeastern focused in the vicinity of the Victoria River Fault Zone side of the Victoria River Fault Zone. Examples at Paperbark (Geopeko Ltd) and Pinkerton Ranges (BHP, Aberfoyle Creek and west of Koolendong Valley are associated with Resources Ltd). More regional programs were undertaken bends in the fault zone. An area east of Koolendong Valley by Ashton Mining NL and Stockdale Prospecting Ltd. contains several broad synclines and anticlines, and a basin- Collectively, these surveys provided at least reconnaissance shaped syncline, 15 km across, is present in the southeast of stream sediment coverage over most of the Victoria Basin. AUVERGNE. However, later work focused on the older Birrindudu Basin after the discovery of the Timber Creek kimberlite pipes. MINERAL RESOURCES Industrial minerals Base metals Pods and veins of barite occur in the Angalarri Siltstone Carbonate and shale units of the Auvergne Group are and Saddle Creek Formation. Barite veins up to 30 cm prospective for base metals. The earliest mineral exploration wide have been reported in the Angalarri Siltstone in the in the basin related to conceptual targeting for stratiform southern Koolendong Valley (Perring and Jones 1991). A copper and this theme was revisited when a BHP Minerals lens of barite 6 m long and 2 m wide occurs as part of a Pty Ltd–Carnegie Minerals NL joint venture investigated fault blow near the highway 1.5 km northwest of Saddle the potential for sediment-hosted copper mineralisation in Creek (Pontifex and Sweet 1972). This, and other nearby the Auvergne Group along the Victoria River Fault Zone, occurrences have been mapped, costeaned, drilled and using semi-detailed stream sediment sampling (Stephens sampled (Willis and Newton 1975), but no commercial 1997). The Angalarri Siltstone is known to contain pyritic exploitation has been reported. shale units and may be prospective for stratiform sediment- hosted base metals mineralisation, but exploration to date REFERENCES has been unsuccessful. This unit has not been explored systematically, because so much of it is under cover. As part Blake DH, Hodgson IM and Smith PA, 1975. Geology of the of an exploration program for diamonds and base metals, Birrindudu and Tanami 1:250 000 sheet areas, Northern BHP drilled six shallow (6–60 m) percussion holes in the Territory. Bureau of Mineral Resources, Australia, Angalarri Siltstone on Whirlwind Plain (Taylor 1981). Report 174. Although the holes were targeted on magnetic anomalies, Carson CJ, 2010. The Victoria and Birrindudu basins: A QRVLJQL¿FDQWEDVHPHWDOVZHUHLQWHUVHFWHG U-Pb SHRIMP study and review of resource potential: in

Geology and mineral resources of the Northern Territory 26:6 Special publication 5 Victoria Basin

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