Woodgreen, Northern Territory : explanatory notes
Northern Territory Geological Survey
E-Publications; E-Books; PublicationNT; Australia 1:100 000 Geological Map Series
2007
Australia 1:100 000 Geological Map Wood 5458; Australia 1:250 000 Geological MapAlcoota SF5310; Australia 1:250 000 Geological MapAlcoota SF5310
1:100 000
Made available via the Publications (Legal Deposit) Act 2004 (NT); Available from GEMIS - Geoscience Exploration and Mining Information System
English
Geology; Georgina Basin; Arunta Region
Northern Territory Government; Northern Territory Government
Darwin
1st ed.
Australia 1:100 000 Geological Map Series
application/pdf
9780724571321
0811-6296
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://creativecommons.org/licenses/by/4.0/
https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81885 [GEMIS]
https://hdl.handle.net/10070/794795
https://hdl.handle.net/10070/794807
3 of t he e a s t e r n A r unt a , w he r e hi gh- gr a de m e t a m or phi c r oc ks ha ve ne opr ot e r oz oi c t o C a m br i a n pr e c ur s or s ( B ui c k et al 2001) . A l l A r unt a re gi on r oc ks i n W oodgreen f or m pa r t of t he A i l e r on P r ovi nc e . T he ol de s t know n r oc ks i n t he A i l e r on P r ovi nc e a r e a w i de s pr e a d s uc c e s s i on of pe l i t e s a nd ps a m m i t e s of t he L a nde r pa c ka ge , de p os i t e d i n t he i nt e r va l 18651820 M a . T he L a nde r pa c ka ge va r i e s i n s e di m e nt a r y f a c i e s f r om s ha l l ow t o de e p m a r i ne , a nd i s m e t a m or phos e d f r om gr e e ns c hi s t t o gr a nul i t e f a c i e s . A younge r , onge va pa c ka ge of s i l i c i c l a s t i c a nd vol c a ni c l a s t i c m e t a s e di m e nt a r y r oc ks oc c ur s i n t he e a s t e r n A r unt a re gi on, a nd ha s de pos i t i ona l a ge s i n t he r a nge 18101800 M a ( S c r i m ge our 200 3 ) . T hi s l a t t e r pa c ka ge i nc l ude s m os t of t he S t r a ngw a ys M e t a m or phi c C om pl e x ( H us s e y et al 200 3 ) , a nd t he B onya S c hi s t a nd a s s oc i a t e d m e t a s e di m e nt a r y r oc ks i n H U C K I T T A ( S c r i m ge our et al 20 01, C l a ou - L ong a nd H oa t s on 2005) . T he A i l e r on P r ovi nc e w a s a f f e c t e d by a num be r of t e c t onot he r m a l e ve nt s dur i ng t he l a t e P a l a e opr ot e r oz oi c t o e a r l y M e s opr ot e r oz o i c , t he m os t i m por t a nt of w hi c h w e r e t he 18101800 M a S t a f f or d eve nt , t he 17801770 M a Y a m ba h eve nt , t he 1 7 3 01700 M a S t r a ngw a ys or oge ny a nd t he 15901570 M a C he w i ngs or oge ny . T he s e e ve nt s w e r e s e pa r a t e d by pe r i ods of s i l i c i c l a s t i c s e di m e nt a t i on, i nc l udi ng t he 1780 M a re ynol ds ra nge gr oup i n t he nor t he r n A r unt a a nd t he 17651740 M a L e da n pa c ka ge i n t he e a s t e r n A r unt a ( M a i dm e nt et al 2005) . T h e ge o r g i n a B a s i n i s t h e l a r g e s t o f t h e i n t r a c r a t o n i c ne o p r o t e r o z o i c P a l a e o z o i c b a s i n s o n t h e no r t h A u s t r a l i a n C r a t o n . T h e b a s i n ' s p r e s e n t e x t e n t o f 3 3 0 0 0 0 k m 2 i s a n e r o s i o n a l r e m n a n t o f a s e r i e s o f i n t e r c o n n e c t e d b a s i n s , t h e e a r l y p h a s e s o f w h i c h a r e i n c l u d e d i n t h e C e n t r a l i a n S u p e r b a s i n ( W a l t e r et al 1 9 9 5 ) . A s e r i e s o f i n t r a p l a t e o r o g e n i c e v e n t s , i n c l u d i n g t h e ed i a c a r a n C a m b r i a n P e t e r m a n n or o g e n y a n d P a l a e o z o i c A l i c e S p r i n g s or o g e n y , l e d t o e x h u m a t i o n o f b a s e m e n t f r o m b e n e a t h t h e s u p e r b a s i n , f o r m i n g t h e s e r i e s o f i s o l a t e d s e d i m e n t a r y b a s i n s ( ng a l i a , ge o r g i n a , A m a d e u s , Officer and Wiso basins and the Irindina Province) seen today. re g i o n a l l y , t h e ge o r g i n a B a s i n h a s a d e p o s i t i o n a l h i s t o r y r a n g i n g f r o m a p p r o x i m a t e l y 8 0 0 M a t o L a t e de v o n i a n ( W a l t e r et al 1 9 9 5 , H a i n e s et al 2 0 0 1 ) , a l t h o u g h o n l y a n i n c o m p l e t e s u c c e s s i o n i s p r e s e r v e d i n W oodgreen. I n e x c e s s o f 1 . 5 k m o f ne o p r o t e r o z o i c s e d i m e n t a r y r o c k s a r e p r e s e r v e d i n d o w n f a u l t e d b l o c k s a n d h a l f - g r a b e n s o n t h e s o u t h e r n m a r g i n o f t h e b a s i n , a n d d e p o c e n t r e s a n d s y n c l i n e s c o n t a i n u p t o 2 . 2 k m o f C a m b r i a n t o de v o n i a n s e c t i o n . P r e v i o u s e s t i m a t e s o f a s m u c h a s 9 k m t o t a l t h i c k n e s s , b a s e d o n m a g n e t i c d e p t h m o d e l l i n g , d i d n o t r e c o g n i s e l o w - m a g n e t i c - i n t e n s i t y g r a n i t e s a n d , h e n c e , h a v e o v e r e s t i m a t e d t h e t h i c k n e s s o f t h e s e d i m e n t a r y b a s i n . I n W oodgreen, t h e m a x i m u m p r e s e r v e d t h i c k n e s s o f t h e ne o p r o t e r o z o i c C a m b r i a n s e c t i o n i s i n t e r p r e t e d t o b e 1 1 2 0 m ( du n s t e r et al 2 0 0 7 ) . A h i g h - g r a d e m e t a m o r p h i c e v e n t ( L a r a p i n t a ev e n t ) a f f e c t e d t h e A r u n t a re g i o n a n d o v e r l y i n g s e d i m e n t s i n t h e H a r t s ra n g e r e g i o n t o t h e s o u t h e a s t o f W oodgreen d u r i n g t h e or d o v i c i a n ( a t 4 8 0 4 6 0 M a ; M a w b y et al 1 9 9 9 , H a n d et al 1 9 9 9 ) . T h e L a r a p i n t a ev e n t i s i n f e r r e d t o h a v e b e e n o f e x t e n s i o n a l n a t u r e , a n d w a s f o l l o w e d b y a p r o l o n g e d p e r i o d o f e p i s o d i c c o n v e r g e n t t e c t o n i c a c t i v i t y , t h e A l i c e S p r i n g s or o g e n y , w h i c h p e a k e d d u r i n g t h e de v o n i a n a n d C a r b o n i f e r o u s ( H a i n e s et al 2 0 0 1 ) . T h i s e v e n t p r o d u c e d r e g i o n a l - s c a l e r e t r o g r e s s i v e s h e a r z o n e s t h r o u g h t h e A r u n t a re g i o n ( S c r i m g e o u r a n d ra i t h 2 0 0 1 ) a n d w a s r e s p o n s i b l e f o r t h e u p l i f t a n d r e m o v a l o f l a r g e a r e a s o f s e d i m e n t a r y c o v e r , a s w e l l a s m o d e r a t e d e f o r m a t i o n i n s u r v i v i n g b a s i n r e g i o n s . T h e A l i c e S p r i n g s or o g e n y w a s a l s o a s s o c i a t e d w i t h w i d e s p r e a d f o r e l a n d d e p o s i t i o n ( H a i n e s et al 2 0 0 1 ) , b u t s u c h d e p o s i t s a r e n o t p r e s e r v e d i n W oodgreen. T h e Dulcie Syncline to the northeast preserves Devonian fluviatile s a n d s t o n e s t h a t p r o b a b l y i n c l u d e d e t r i t u s r e m o v e d f r o m t h e W oodgreen a r e a . T h e r e g i o n p r e s e r v e s l i t t l e r e c o r d o f p o s t - P a l a e o z o i c e v e n t s , a p a r t f r o m l o c a l C e n o z o i c d e p o s i t i o n , s u c h a s t h a t o f t h e T i - T r e e B a s i n . STRATIGRAPHY T he s t r a t i gr a phy of t he A r unt a re gi on, ge or gi na B a s i n a nd C e noz oi c c ove r i n W oodgreen a r e s um m a r i s e d i n Tab les 1 , 2 a nd 3 , r e s pe c t i ve l y . P A L A eoP roT eroZ oI C A rU nT A regI on M apat a G ne is s (LP nm) The Mapata Gneiss is defined to the east of W oodgreen i n deL nY ( S ha w et al 1979) . S e ve r a l out c r ops ne a r t he s out he a s t e r n c or ne r of W oodgreen a r e t e nt a t i ve l y a s s i gne d t o t he M a pa t a gne i s s , ba s e d on t he r e gi ona l m a ppi ng of S ha w a nd W a r r e n ( 1975) . T he s e out c r ops a r e dom i na t e d by bi ot i t e - qua r t z - f e l ds pa r m i gm a t i t e w i t h pt ygm a t i c a l l y f ol de d l e uc os om e s , t oge t he r w i t h l e s s e r bi ot i t e s c hi s t a nd m i nor a m phi bol i t e . I n W oodgreen, t hi s uni t i s i n s he a r e d c ont a c t w i t h t he de l ny M e t a m or phi c s . S ha w a nd W a r r e n ( 1975) a nd S ha w et al ( 1979) a s s i gne d t he M a pa t a gne i s s t o t he S t r a ngw a ys M e t a m or phi c C om pl e x a nd i m pl i e d t ha t t he de l ny M e t a m or phi c s s houl d unc onf or m a bl y ove r l i e t he unit, although there is no definitive field or geochronological e vi de nc e t o s upp or t t hi s . T he uni t i s e s s e nt i a l l y non- m a gne t i c , but i s di s t i nc t l y hi gh i n a l l r a di om e t r i c c ha nne l s . A nira M e tamorph ics (LP an) T he A ni r a M e t a m or phi c s ( ne w na m e ; s e e Appendix 1 ) c om pr i s e s e ve r a l s m a l l out c r ops of gr a nul i t e - f a c i e s m e t a s e di m e nt a r y r oc ks i n t he a r e a nor t hw e s t of A ni r a da m , t he be s t e xpos ur e s be i ng a t a bout 4 3 1985m e 75 3 0881m n. The rocks are dominantly pelitic and preserve well defined pr i m a r y s e di m e nt a r y l a ye r i ng ( Figu re 3 ) . P s a m m i t e l a ye r s r e pr e s e nt 1020% of t he s uc c e s s i on a nd a r e t ypi c a l l y 15 c m t hi c k, w i t h i nt e r na l s e di m e nt a r y l a ye r i ng. M e t a pe l i t i c uni t s ha ve a hi gh vol um e of m e l t a nd a qua r t z - poor c or di e r i t e - , s i l l i m a ni t e - a nd s pi ne l - r i c h m e l a nos om e . L e uc os om e i s usually confined within pelitic layers. Local quartz-poor c or di e r i t e - s i l l i m a ni t e - s pi ne l - bi ot i t e r oc ks a r e i nt e r pr e t e d t o be r e s t i t i c f ol l ow i ng t he e xt r a c t i on of m e l t ( Figu re 4 ) . P s a m m i t e s c ont a i n bi ot i t e a nd ga r ne t , a nd a r e ge ne r a l l y m e l t f r e e ( Figu re 5 ) , a l t hough t he y a r e l oc a l l y i nt r ude d by m e l t t ha t ha s m obi l i s e d f r om pe l i t i c l a ye r s . L oc a l i s e d l a r ge r m e l t a c c um ul a t i ons w i t h t a bul a r K - f e l ds pa r m a y be e qui va l e nt t o t he W oodgr e e n gr a ni t e C om pl e x. T he A ni r a M e t a m or phi c s a r e i nt r ud e d by s e ve r a l s m a l l bodi e s of gr a ni t e , a s s i gne d t o t he W oodgr e e n gr a ni t e C om pl e x, a nd r a f t s of s i m i l a r m e t a s e di m e nt a r y l i t hol ogy t o t he f or m e r uni t a r e pr e s e nt