Territory Stories

Woodgreen, Northern Territory : explanatory notes



Woodgreen, Northern Territory : explanatory notes

Issued by

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

Map scale

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

Publisher name

Northern Territory Government; Northern Territory Government

Place of publication



1st ed.


Australia 1:100 000 Geological Map Series

File type







Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



Related links

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

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4 w i t hi n t he W oodgr e e n gr a ni t e C om pl e x t o t he w e s t ( e g, a t 4 3 12 00m e 75 3 0900m n, 4 3 1000m e 75 3 1800m n) . T h e A ni r a Metamorphics have affinities with the Deep Bore Metamorphics i n H U C K I T T A , w hi c h unde r w e nt hi gh- T , l ow - P m e t a m or phi s m dur i n g t he S t r a ngw a ys or oge ny a t 17 3 0 7 M a ( S c r i m ge our et al 2001) . P r e l i m i na r y S H rI M P U - P b zircon ge oc hr onol ogi c a l da t a ( J C l a oue - L ong, ge oc i e nc e A us t r a l i a ) s ugge s t s t ha t t he A ni r a M e t a m or phi c s ha s a m a xi m um de pos i t i on a ge of a r ound 1785 M a , a nd w a s m e t a m or phos e d dur i ng t he S t r a ngw a ys eve n t . n o c ohe r e nt ge ophys i c a l s i gna t ur e i s a ppa r e nt . D e lny M e tamorph ics (LP dn ) T h e de l n y M e t a m o r p h i c s ( de l n y gn e i s s o f S h a w a n d Warren 1975) are defined in deL nY t o t h e s o u t h e a s t o f W oodgreen, a n d a r e a l i t h o l o g i c a l l y c o m p l e x u n i t comprising fine to medium felsic gneiss, biotite-muscovite s c h i s t , a m p h i b o l i t e , m i n o r q u a r t z i t e a n d r a r e c a l c - s i l i c a t e r o c k . A p a r t f r o m t h e a m p h i b o l i t e s , w h i c h a r e i n t e r p r e t e d as metamorphosed mafic igneous rocks, the bulk of the r e m a i n d e r i s c o n s i d e r e d t o r e p r e s e n t m e t a m o r p h o s e d s i l i c i c l a s t i c s e d i m e n t a r y r o c k s . T a b u l a r a m p h i b o l i t e b o d i e s a r e p r e s e n t o n s e v e r a l s c a l e s , b u t a r e o n l y l a r g e e n o u g h t o d i s t i n g u i s h o n t h e m a p f a c e i n o n e a r e a ( a r o u n d 4 3 4 6 0 0 m e 7 5 1 2 1 0 0 m n) . A c h a r a c t e r i s t i c f e a t u r e o f t h e s c h i s t s a n d s o m e g n e i s s e s i s t h e c o m m o n p r e s e n c e o f c o a r s e c l o t s o f m u s c o v i t e t h a t p o s s i b l y r e p r e s e n t r e t r o g r e s s e d andalusite porphyroblasts. Sillimanite was identified in a h a n d s p e c i m e n f r o m 4 2 9 3 0 0 m e 7 5 1 7 7 0 0 m n, n e a r t h e w e s t e r n l i m i t o f o u t c r o p , a n d t h i s o b s e r v a t i o n s u g g e s t s Tab le 1 . L i t hos t r a t i gr a phy of A r unt a r e gi on i n W oodgreen. 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