Territory Stories

Woodgreen, Northern Territory : explanatory notes



Woodgreen, Northern Territory : explanatory notes

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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

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1:100 000


Made available via the Publications (Legal Deposit) Act 2004 (NT); Available from GEMIS - Geoscience Exploration and Mining Information System




Geology; Georgina Basin; Arunta Region

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Northern Territory Government; Northern Territory Government

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1st ed.


Australia 1:100 000 Geological Map Series

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81885 [GEMIS]

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4 within the Woodgreen Granite Complex to the west (eg, at 41200mE 750900mN, 41000mE 751800mN). The Anira Metamorphics have affinities with the Deep Bore Metamorphics in HUCKITTA, which underwent highT, lowP metamorphism during the Strangways Orogeny at 170 7 Ma (Scrimgeour etal 2001). Preliminary SHRIMP UPb zircon geochronological data (J ClaoueLong, Geocience Australia) suggests that the Anira Metamorphics has a maximum deposition age of around 1785 Ma, and was metamorphosed during the Strangways Event. No coherent geophysical signature is apparent. Delny Metamorphics (LPdn) The Delny Metamorphics (Delny Gneiss of Shaw and Warren 1975) are defined in delny to the southeast of Woodgreen, and are a lithologically complex unit comprising fine to medium felsic gneiss, biotitemuscovite schist, amphibolite, minor quartzite and rare calcsilicate rock. Apart from the amphibolites, which are interpreted as metamorphosed mafic igneous rocks, the bulk of the remainder is considered to represent metamorphosed siliciclastic sedimentary rocks. Tabular amphibolite bodies are present on several scales, but are only large enough to distinguish on the mapface in one area (around 44600mE 7512100mN). A characteristic feature of the schists and some gneisses is the common presence of coarse clots of muscovite that possibly represent retrogressed andalusite porphyroblasts. Sillimanite was identified in a hand specimen from 42900mE 7517700mN, near the western limit of outcrop, and this observation suggests table1. Lithostratigraphy of Arunta Region in Woodgreen. Unit, map symbol, age Lithology Distribution Stratigraphic relationships Age uncertain Quartz mylonite, mylonite (qm, m) Undated, most assumed to be Palaeozoic Quartz mylonite (qm) Mylonitised granite and metamorphic rocks (m) Widespread in Arunta Region Along shear zones Quartz breccia (qb) Various ages, most probably Palaeozoic Quartz and chert breccia, often ferruginous Widespread in Arunta Region Along shear and fault zones Pegmatite (peg) Various ages Pegmatite Widespread; most abundant in Delny Metamorphics, Crooked Hole Granite and some undivided granitoids Occurs as dykes, sills and irregular bodies; intrudes faults in Delny Metamorphics; biotite-bearing pegmatite intrudes Crooked Hole Granite Ultramafic intrusive rock (px) Age unknown (post-tectonic) Pyroxenite, partly recrystallised to tremolite One isolated outcrop northeast of Boomerang Bore Intrudes Delny Metamorphics Palaeoproterozoic Undivided granitoid rocks (LPg) Diverse granitoid types; foliated and unfoliated Widespread in Arunta Region Intrude undivided metamorphic rocks and Delny Metamorphics Mollie Granite Complex (PLPgm) Biotite-rich granodiorite, porphyritic and non-porphyritic leucogranite; locally foliated In northeast, trending northwest from around Utopia tantalite prospect Intrudes undivided metamorphic rocks and probably Utopia Quartzite Woodgreen Granite Complex (PLPgw) Diverse granitoid types as below Widespread south of Mount Skinner area PLPgw1 Coarse, porphyritic, garnetbearing biotite granite North of Mount Ida Shear Zone, mostly west of Sandover Highway Sheared contact with PLPgw south of Mount Ida Shear Zone; nature of contact with PLPgw2 uncertain PLPgw2 Gneissic granite and migmatite; garnet-bearing North of Mount Ida Shear Zone, mostly immediately east of Sandover Highway Contacts with PLPgw1 and PLPgw3, but nature uncertain PLPgw3 Fine to medium, mostly equigranular, garnet-bearing biotite granite North of Mount Ida Shear Zone, east of Sandover Highway Sheared contact with PLPgw south of Mount Ida Shear Zone; contacts with PLPgw2, but nature uncertain; intrusive into granulite facies metasedimentary rocks PLPgw4 Coarse, porphyritic granite; locally garnet-bearing; garnet regressed to biotite? South of Mount Ida Shear Zone Sheared contact with PLPgw5; contacts with undivided PLPgw to north, but relationship unclear PLPgw5 Coarse porphyritic granite with dark biotite-rich groundmass, medium biotite granite, medium leucogranite Southern edge of Woodgreen Granite Complex Sheared contact with PLPgw4 and Delny Metamorphics; probably intrusive into Delny Metamorphics Crooked Hole Granite (PLPgc) Strongly foliated biotite granite and granodiorite Extreme southeastern WOODGREEN Intrudes Delny Metamorphics Utopia Quartzite (PLPut) Purple, brown and white quartzite; metasandstone, ironstone Isolated outcrops in northeastern WOODGREEN Relationships to other Arunta Region units not exposed in WOODGREEN Undivided metamorphic rocks (PLPu) Gneiss, schist, amphibolite, calcsilicate rock, epidote gneiss, hornfels Scattered outcrops throughout Arunta Region Relationships to other Arunta Region metamorphic units not exposed; intruded by granites Delny Metamorphics (PLPdn) Muscovite-biotite schist, felsic gneiss, amphibolite, minor quartzite; rare calc-silicate rock Far southeastern WOODGREEN Intruded by Crooked Hole Granite; probably intruded by Woodgreen Granite Complex Anira Metamorphics (PLPLPan) Cordierite-sillimanite-spinel migmatitic metapelite; metapsammite Northwest of Anira Dam Intruded by Woodgreen Granite Complex Mapata Gneiss (PLPLPnm) Quartzofeldspathic gneiss, biotite schist; minor amphibolite Far southeastern WOODGREEN Sheared contact with Delny Metamorphics