Territory Stories

Woodgreen, Northern Territory : explanatory notes

Details:

Title

Woodgreen, Northern Territory : explanatory notes

Issued by

Northern Territory Geological Survey

Collection

E-Publications; E-Books; PublicationNT; Australia 1:100 000 Geological Map Series

Date

2007

Location

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

Notes

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

Language

English

Subject

Geology; Georgina Basin; Arunta Region

Publisher name

Northern Territory Government; Northern Territory Government

Place of publication

Darwin

Edition

1st ed.

Series

Australia 1:100 000 Geological Map Series

File type

application/pdf

ISBN

9780724571321

ISSN

0811-6296

Use

Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government

License

https://creativecommons.org/licenses/by/4.0/

Related links

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

Parent handle

https://hdl.handle.net/10070/794795

Citation address

https://hdl.handle.net/10070/794807

Page content

7 t ha t t he de l ny M e t a m or phi c s i nc r e a s e i n m e t a m or phi c gr a de t o t h e w e s t . T h e de l n y M e t a m o r p h i c s a r e i n t r u d e d b y t h e s t r o n g l y f o l i a t e d C r o o k e d H o l e gr a n i t e ( e g , a t 4 3 5 0 6 4 m e 7 5 1 1 9 6 1 m n) a n d b o t h u n i t s s h a r e a c o m m o n f a b r i c . A l t h o u g h i t i s a s s u m e d t h a t t h e W o o d g r e e n gr a n i t e C o m p l e x i n t r u d e s t h e de l n y M e t a m o r p h i c s , a l l e x p o s e d c o n t a c t s a p p e a r t o b e t e c t o n i c a n d a r e s t r o n g l y s h e a r e d o r m a r k e d b y a r i d g e o f q u a r t z b r e c c i a f a u l t r o c k . S m a l l b o d i e s o f f o l i a t e d g r a n i t i c r o c k i n t r u d e t h e de l n y M e t a m o r p h i c s a t s e v e r a l l o c a t i o n s ( e g 4 2 9 8 0 0 m e 7 5 1 7 5 0 0 m n, 4 3 4 9 0 0 m e 7 5 1 5 4 0 0 m n) a n d p e g m a t i t e i n t r u s i o n s a r e w i d e s p r e a d . T h e de l n y M e t a m o r p h i c s a r e t y p i c a l l y n o n - m a g n e t i c , t h e e x c e p t i o n b e i n g a m o d e r a t e l y m a g n e t i c f e a t u r e c o n c o r d a n t w i t h t h e l o c a l f o l i a t i o n , c e n t r e d o n 4 3 4 6 0 0 m e 7 5 1 4 3 0 0 m n. I t s r a d i o m e t r i c r e s p o n s e i s l o w , w i t h t h e w e a k s i g n a l t h a t i s p r e s e n t b e i n g d o m i n a t e d b y K . P r e l i m i n a r y S H rI M P U - P b zircon g e o c h r o n o l o g i c a l d a t a ( J C l a o u e - L o n g , ge o c i e n c e A u s t r a l i a ) s u g g e s t s t h a t t h e de l n y M e t a m o r p h i c s h a s a m a x i m u m d e p o s i t i o n a g e o f a b o u t 1 8 2 5 M a . u ndi v ide d m e tamorph ic rocks (LP u ) S e ve r a l s m a l l i s ol a t e d out c r ops of m e t a m or phi c r oc k be l on gi ng t o t he A r unt a re gi on ha ve not be e n a s s i g ne d t o a ny f or m a l uni t s . ne a r t he nor t he r n bounda r y of W oodgreen, a s t r ongl y l i ne a t e d bi ot i t e - m us c ovi t e gne i s s i s i nt r ude d by a bun da nt pe gm a t i t e a t 424500m e 7 564300m n. T hi s out c r op i s a s s oc i a t e d w i t h a m ode r a t e l oc a l m a gne t i c a nom a l y a nd s l i gh t K a nd U a nom a l i s m . da r k gr e e n, w e l l l a ye r e d a nd f ol i a t e d a m ph i bol i t e o ut c r ops a t 444 77 4m e 7 541681m n a nd i s i nt r ude d by gr a n i t e a nd pe gm a t i t e . T he m i ne r a l a s s e m bl a ge i n t he r oc k c om pr i s e s a c t i n ol i t e , e pi dot e , c l i nopyr oxe ne , t i t a ni t e , pl a gi oc l a s e a nd qua r t z , a nd m a y r e pr e s e nt a m e t a s e di m e nt a r y c a l c - s i l i c a t e r oc k . I t l oc a l l y e xh i bi t s w e a k, i s ol a t e d U a nom a l i e s t ha t c ont r a s t w i t h t he m or e K - dom i na t e d s i gna t ur e of t he s ur r o undi ng gr a ni t i c m a t e r i a l . nor t h of M ount H a r pe r , poor l y e xpos e d m u s c ovi t e s c hi s t a nd m i no r a m phi bol i t e out c r op a r ound 398 800m e 7 545 500m n a nd a r e ove r l a i n by t he g r a nt B l uf f F or m a t i on. S e ve r a l s m a l l out c r ops of m e t a s e di m e nt a r y r oc ks a r e a s s oc i a t e d w i t h t he W oodgr e e n gr a ni t e C om pl e x. A s t he out c r ops a r e i s ol a t e d, i t i s unc e r t a i n i f t he s e r e pr e s e nt m a r gi ns t o t h e gr a ni t e or a r e l a r ge r a f t s w i t hi n i t . S uc h o ut c r ops i nc l u de a da r k gr e e n hor nf e l s a t 42 7 800m e 7 529100m n a nd e pi dot e - r i c h r oc ks a r ound 429800m e 7 53 7 000m n. U top ia Q u artz ite (LP u t) S e v e r a l s m a l l o u t c r o p s o f d e f o r m e d , m a s s i v e t o t a b u l a r c l e a n q u a r t z i t e , m e t a s a n d s t o n e a n d i r o n s t o n e i n n o r t h - c e n t r a l W oodgreen h a v e b e e n t e n t a t i v e l y a s s i g n e d t o t h e U t o p i a Q u a r t z i t e . T h e s e h a v e d i s t i n c t l y l o w m a g n e t i c a n d r a d i o m e t r i c r e s p o n s e s . I n t w o l o c a l i t i e s ( 4 2 8 6 2 1 m e 7 5 5 4 9 6 0 m n, 4 3 1 6 5 5 m e 7 5 5 2 2 9 2 m n) , i t i s c l e a r t h a t t h e s e r o c k s a r e u n c o n f o r m a b l y o v e r l a i n b y t h e B o k o F o r m a t i o n a n d oo r a b r a A r k o s e , r e s p e c t i v e l y , a n d w e r e d e f o r m e d p r i o r t o t h e d e p o s i t i o n o f ge o r g i n a B a s i n s e d i m e n t s . T h e r e l a t i o n s h i p b e t w e e n o u t c r o p s o f U t o p i a Q u a r t z i t e a n d n e a r b y g r a n i t e s i s n o t k n o w n , b u t i t i s i n f e r r e d t h a t t h e g r a n i t e s i n t r u d e t h e q u a r t z i t e . The Utopia Quartzite is defined in ad acent U T oP I A , w he r e i t ove r l i e s t he L e da n S c hi s t , w i t h bot h uni t s e xt e ndi ng e a s t w a r d i nt o H U C K I T T A ( S ha w et al 19 7 9) . T he L e da n S c hi s t ha s a l s o be e n r e c ogni s e d i n s out he r n B A rroW C reeK ( H a i ne s et al 1991) and tentatively in ad acent W ooL L A ( S ha w et al 19 7 9) . S H rI M P U - P b da t i ng o f de t r i t a l z i r c ons f r om t he L e da n S c hi s t i n U T oP I A gi ve s a m a xi m um de pos i t i on a ge of c a 1 7 80 M a ( M a i dm e nt et al 2005) , s ugge s t i ng t ha t i t w a s de pos i t e d be t w e e n t he Y a m ba h eve nt a nd S t r a ngw a ys or o ge ny . I n A L C ooT A , qua r t z i t e of t he M e ndi p M e t a m or phi c s ha s a m a xi m um de pos i t i o n a ge of 1 7 60 M a , w a s i nt r ude d b y pe gm a t i t e a t 1 7 30 4 M a a nd ha s m e t a m or phi c z i r c on r i m s w i t h a n a ge of 1 7 23 9 M a ( M a i dm e nt et al 2005) . T he s e uni t s a r e c ons i de r e d t o be pa r t of t he s a m e s e di m e nt a r y pa c ka ge a s t he U t opi a Q ua r t z i t e ( L e da n pa c ka ge of S c r i m ge our 2003) , i n w hi c h c a s e , t he U t opi a Q ua r t z i t e w a s a l s o de pos i t e d i n t he i nt e r va l 1 7 651 7 30 M a . Crooke d H ole G ranite (LP gc ) T he C r ooke d H ol e gr a ni t e i s r e s t r i c t e d t o t he s ou t he a s t e r n c or ne r of W oodgreen a nd i s a l s o pr e s e nt i n t he bor de r regions of the ad oining 1:100 000 sheet areas. The type l oc a l i t y i s s i t ua t e d i n t he l ow hi l l s s ur r oundi ng 43 5000m e 7 512000m n ( S ha w et al 19 7 9) . A t ypi c a l s a m p l e f r om 440453m e 7 515968m n i s a bi ot i t e gr a nodi or i t e w i t h a bunda nt pl a gi oc l a s e ( l a r ge l y r e t r ogr e s s e d t o s e r i c i t e ) a nd a c c e s s or y t i t a ni t e a nd z i r c on. T he uni t i nt r ude s t he de l ny Metamorphics and has a strong foliation defined by biotite. T he c ont a c t w i t h t he de l ny M e t a m or phi c s i s w e l l e xpos e d a t 435064m e 7 51 1961m n, ne a r t he t ype l oc a l i t y , w he r e t he C r ooke d H ol e gr a ni t e c a n be s e e n a s a di s t i nc t l y t a bul a r s i l l - l i ke body w i t hi n t he gne i s s , w hi c h a t t hi s l oc a l i t y , di ps ge nt l y w e s t pa r a l l e l t o l i t hol ogi c a l l a ye r i ng a nd f ol i a t i on ( Figu re 6 ) . P e gm a t i t e s a r e c om m on w i t hi n a n d a r ound t he m a r gi ns of t he gr a ni t e a nd t e nd t o i nt r ude pa r a l l e l t o f ol i a t i on. T he C r ooke d H ol e gr a ni t e i s r e por t e d t o be s i m i l a r t o t he C opi a gr a ni t e , w hi c h out c r ops 20 km e a s t - s ou t he a s t of t he s out he a s t e r n c or ne r of W oodgreen ( S ha w a nd W a r r e n 19 7 5 ) . T he s e gr a ni t e s a r e s yn- or pr e - t e c t oni c a nd a r e l i ke l y t o pr e da t e l e s s de f or m e d gr a ni t e s of t he ne a r by W oodgr e e n gr a ni t e C om pl e x. A l t hough t he C r ooke d H ol e gr a ni t e ha s not be e n da t e d, i t i s l i ke l y t o be c ont e m por a ne ous w i t h ot he r de f or m e d gr a ni t e s t ha t i nt r ude d a t 1 7 801 77 0 M a i n H U C K I T T A ( Z ha o a nd B e nne t t 1995) . T he C r ooke d H ol e gr a ni t e ha s a r e l a t i ve l y l ow r a di om e t r i c r e s pons e i n c om pa r i s on t o o t he r gr a ni t e s i n W oodgreen, a nd i s non- t o m ode r a t e l y m a gne t i c ( s us c e pt i bi l i t i e s up t o 822 x 10 - 5 S I were recorded in the field). Portions of the intrusion (such a s a r ound 43 7 500m e 7 513200m n) ha ve a ppa r e n t l y be e n sub ect to magnetite-destructive alteration. W oodgr e e n G ranite Compl e x ( LP gw ) T h e W o o d g r e e n gr a n i t e C o m p l e x c o m p r i s e s a d i v e r s i t y o f g r a n i t i c a n d m i n o r m i g m a t i t i c r o c k s t h a t o u t c r o p o v e r a w i d e a r e a i n c e n t r a l a n d s o u t h e r n W oodgreen. S h a w a n d W a r r e n ( 1 9 7 5 ) n o m i n a t e d a t y p e a r e a a r o u n d 4 3 3 0 0 0 m e 7 5 1 9 0 0 0 m n, s o u t h w e s t o f di x o n B o r e , b u t i n v i e w o f t h e l i t h o l o g i c a l v a r i e t y a c r o s s t h e c o m p l e x , a n u m b e r o f a d d i t i o n a l r e f e r e n c e a r e a s f o r m a p p a b l e s u b u n i t s a r e