Woodgreen, Northern Territory : explanatory notes
Northern Territory Geological Survey
E-Publications; E-Books; PublicationNT; Australia 1:100 000 Geological Map Series
Australia 1:100 000 Geological Map Wood 5458; Australia 1:250 000 Geological MapAlcoota SF5310; Australia 1:250 000 Geological MapAlcoota SF5310
Made available via the Publications (Legal Deposit) Act 2004 (NT); Available from GEMIS - Geoscience Exploration and Mining Information System
Geology; Georgina Basin; Arunta Region
Northern Territory Government; Northern Territory Government
Australia 1:100 000 Geological Map Series
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
iv ABSTRACT WOODGREEN1 is centred 160 km north-northeast of Alice Springs and includes elements of the late Palaeoproterozoic Aileron Province of the Arunta Region, the Neoproterozoic to Palaeozoic Georgina Basin and the Cenozoic Ti-Tree Basin. Exposed basement rocks of the Arunta Region include Palaeoproterozoic metasedimentary rocks that are likely to have been deposited at about 1.841.80 Ga. These are dominated by metapelites that include the lower- to mid-amphibolite-facies Delny Metamorphics and minor granulite-facies rocks now named Anira Metamorphics. The Utopia Quartzite forms part of a cover succession that was deposited at about 1.761.74 Ga. Tectonothermal events affected the region at 1.781.77 Ga (Yambah Event) and 1.731.70 Ga (Strangways Orogeny), and involved the intrusion of voluminous granites that dominate the currently exposed basement. The Woodgreen Granite Complex forms the most extensive outcropping basement unit in WOODGREEN and is likely to have been generated during the Strangways Orogeny, broadly synchronous with localised hightemperature, low-pressure metamorphism and partial melting in metasedimentary rocks. Georgina Basin sedimentary rocks are restricted to the northern half of WOODGREEN and range in age from late Neoproterozoic (0.6 Ga) to Late Cambrian. The record begins with localised non-marine glacigene sediments (Boko Formation and Oorabra Arkose), disconformably overlain by shallow-marine to deltaic siliciclastic and minor carbonate and evaporitic rocks of the Elyuah, Grant Bluff and Central Mount Stuart formations. Following a minor erosional hiatus across the EdiacaranCambrian boundary, deposition continued with shallow-marine siliciclastic sediment of the Early Cambrian Octy Formation. Another erosional hiatus is overlain by a mixed carbonate-siliciclastic succession, tentatively identified as the Upper Cambrian Chabalowe Formation, the youngest Georgina Basin unit exposed in WOODGREEN. The WOODGREEN region underwent prolonged episodic tectonism during the Palaeozoic Alice Springs Orogeny, the major phases of which probably occurred during the Devonian in this area. The region was cut by major west-northwesterly high-angle reverse shear zones, which resulted in exhumation of basement and erosional removal of Georgina Basin rocks across the southern half of WOODGREEN. In the north, Georgina Basin rocks were faulted, tilted and locally folded. During the Cenozoic, silcrete and ferricrete profiles developed over deeply weathered, flat to gently domed basement terrane, whereas fans developed around sandstone ranges in the north. Fluviatile and lacustrine sediments collected in broad palaeochannels that fed northwest into the Ti-Tree Basin. A renewed cycle of erosion, which probably commenced in the Neogene and continues to the present, is responsible for the exposure of fresh granite hills and domes from beneath relicts of the older deeply weathered surface. No economic mineral deposits are known in WOODGREEN. Cupriferous outcrop and float occur discontinuously over 100 km2 in the Tops Member of the Central Mount Stuart Formation in central-northern WOODGREEN. At surface, the mineralised interval is at most a few decimetres thick. Exploration, focused on the Mount Skinner prospect, has shown that surface grades of a few percent Cu do not persist in the subsurface. Drillholes in the same area intersected visible galena in the Elyuah Formation. Tantalite has been reported from veins in pegmatite intruded into undifferentiated amphibolite gneiss at the Utopia prospect, 10 km west of Utopia community. 1 Names of 1:250 000 and 1:100 000 mapsheets are shown in large and small capitals respectively, eg ALCOOTA, WOODGREEN.
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