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

24 reputedly averaged 6700 ppm Pb including 2% Pb for the sample from 432433 depth (ca 131.8 m, but see the NTGS reassay below); the other had up to 950 ppm Zn over 0.3 m at 10271028 (ca 313 m) depth (Grainger 1968b, Shaw and Warren 1975). During 19691970, Utah Development Company (1970) targeted the area for Zambianstyle s t r a t i f o r m cu m i n e r a l i s a t i o n . Wo r k w a s f o c u s e d n e a r mo l l i e Bl u f f a n d o n t h e r e d u c e d h o s t r o c k s a t t h e mo u n t sk i n n e r prospect, where three areas were sampled on a 15 x 61 m g r i d , u s i n g s o i l , r o c k c h i p a n d a u g e r s a m p l e s . a t o t a l o f 8865 assays for Cu, Pb, Zn, Co and Ni were undertaken. ro c k c h i p s o f t h e t a r g e t h o r i z o n r a r e l y y i e l d e d i n e x c e s s o f 3 0 0 p p m a n d e v e n t h e b e s t a s s a y s w e r e l e s s t h a n p e r c e n t l e v e l . ex p l o r a t i o n d i d n o t a d v a n c e t o d r i l l i n g . ce n t a m i n b e c a m e o p e r a t o r s o f t h e mo u n t sk i n n e r a r e a i n 1970. They contracted Compagnie Gnrale de Gophysique (1971) to undertake 195 km of refraction seismic, 158 line k m o f r e s i s t i v i t y a n d 3 1 x 3 0 0 m - s p a c e d e l e c t r i c a l r e a d i n g s . Four targets identified by the geophysical survey were tested by cored drillholes (CMS1 to 4), totalling 1780 m. The last t h r e e t e r m i n a t e d i n c r y s t a l l i n e b a s e m e n t . on l y s e l e c t e d i n t e r v a l s w e r e a n a l y s e d a n d n o e c o n o m i c m i n e r a l i s a t i o n was discovered (Cotton 1972, Chuck 1982). al c o a t a r g e t e d s y n g e n e t i c - e x h a l a t i v e s e d i m e n t - h o s t e d b a s e m e t a l m i n e r a l i s a t i o n b e l o w t h e ce n t r a l mo u n t st u a r t Formation. They flew a 500 mspaced magnetic survey (Ashley in Chuck 1982) and reanalysed selected intervals o f t h e ce n t a m i n c o r e s b y e d g e g r i n d , a t o m i c a b s o r p t i o n s p e c t r o s c o p y (aas) a n d in d u c t i v e l y co u p l e d Pl a s m a ma s s sp e c t r o m e t r y (icPms). ge n e r a l l y t h e s e r e t u r n e d l e s s e n c o u r a g i n g cu r e s u l t s t h a n t h e ce n t a m i n a s s a y s . in particular, CMS1 was significantly downgraded. However, t h i n i n t e r v a l s o f a n o m a l o u s zn d o o c c u r i n a l l h o l e s a n d t h e interval 251.4254.5 m depth in CMS4 averages 0.4% Pb. Alcoa defined a drilling target, but the company withdrew f r o m b a s e m e t a l s e x p l o r a t i o n b e f o r e i t c o u l d b e t e s t e d (Chuck 1983). During the early to mid1990s, CRA explored for s t r a t a b o u n d cu i n t h e ce n t r a l mo u n t st u a r t Fo r m a t i o n i n BarroW creek a n d alcoota. th e y i n s p e c t e d t h e Mount Skinner prospect and assayed the open file core for 25 elements (Menzies and Louwrens 1995). The results were not released, but generally confirmed that the reduced h o s t r o c k s c o n t a i n 2 3 t i m e s b a c k g r o u n d cu a n d l o c a l l y e l e v a t e d ag , as , co , mo , ni , Pb a n d zn (me n z i e s a n d Louwrens 1995). Soil and stream sediment sampling were u n a b l e t o a c c u r a t e l y l o c a t e o u t c r o p p i n g m i n e r a l i s a t i o n , because of low Cu tenor and flatlying strata. Spectral a n a l y s i s o f la n d s a t tm d a t a f a i l e d t o u n a m b i g u o u s l y m a p t h e h o s t r e d u c e d l i t h o f a c i e s o f t h e ce n t r a l mo u n t st u a r t Formation (Menzies and Louwrens 1995). re c e n t w o r k b y ntgs (du n s t e r et al 2 0 0 7 ) r e c o g n i s e d p r e v i o u s l y u n r e p o r t e d v i s i b l e e p i g e n e t i c g a l e n a f r o m 251256 m depth in the Elyuah Formation in CMS4. to p r o v i d e m o r e m e a n i n g f u l a s s a y s t h a n p r e v i o u s c o m p a n y e d g e g r i n d s , m u l t i e l e m e n t a n a l y s e s o f c a 3 0 c m q u a r t e r - c o r e c o m p o s i t e s w e r e u n d e r t a k e n (Appendix2). All composites from 251.76254.20 m depth returned >2000 pm Pb, including 0.92 m at >0.5%. A lower interval at 2 5 5 .4 2 2 5 5 .7 3 m , c o n t a i n i n g p r e v i o u s l y u n r e p o r t e d v i s i b l e galena, pyrite, chalcopyrite and fluorite, assayed 339 ppm cu , 2 5 5 5 p p m Pb a n d 2 4 0 p p m zn . Pe r c e n t l e v e l s o f Pb , p r e v i o u s l y r e p o r t e d f r o m mo u n t sk i n n e r 3 , c o u l d n o t b e d u p l i c a t e d b y q u a r t e r - c o r e s a m p l i n g . th r e e c o m p o s i t e samples over 131.67132.13 m depth returned a maximum o f o n l y 2 1 p p m Pb (Appendix2). T antalu m, n iobi u m, t in, bi s mu th ta n t a l i t e a n d c a s s i t e r i t e o c c u r a t t h r e e s m a l l p r o s p e c t s , c o l l e c t i v e l y k n o w n a s ut o p i a , 1 0 k m w e s t o f ut o p i a c o m m u n i t y (Powell 1981, Frater 2005). Shaw (1968) described the host r o c k a s a t o u r m a l i n e - m u s c o v i t e - f e l d s p a r - q u a r t z p e g m a t i t e , i n t r u d e d p a r a l l e l t o t h e f o l i a t i o n o f t h e m u s c o v i t e - b i o t i t e g n e i s s c o u n t r y r o c k . so m e o f t h e m i n e r a l i s a t i o n c o n t a i n s bismuth and is weakly radioactive (Daly and Dyson 1963). Old workings occur in two areas approximately 1.8 km a p a r t , r e f e r r e d t o a s ut o p i a 1 a n d ut o p i a 3 . an a d d i t i o n a l p r o s p e c t , ut o p i a 2 , o c c u r s i n t h e v i c i n i t y o f ut o p i a 1 a n d i s n o t d e s c r i b e d f u r t h e r h e r e . ut o p i a 1 i s t h e s o u t h e r n m o s t a n d s m a l l e r o f t h e t w o w o r k i n g s , a n d c o n t a i n s m i n o r t a n t a l i t e a n d q u a r t z w i t h r a r e n a t i v e b i s m u t h a n d b i s m u t h i n i t e , w i t h n o e v i d e n c e of radioactivity (Daly and Dyson 1963). The workings c o n s i s t o f a s i n g l e s h a l l o w p i t , 2 x 5 m i n p l a n , g o u g e d o u t o f a s t e e p l y d i p p i n g , m a s s i v e q u a r t z b l o w , 4 m w i d e a n d t r e n d i n g 0 7 0 . th e q u a r t z v e i n l o c a l l y c o n t a i n s l a r g e s a l m o n - c o l o u r e d k- f e l d s p a r u p t o 1 0 c m i n s i z e . a f e l d s p a r - q u a r t z (- t o u r m a l i n e ) p e g m a t i t e a b u t s t h e v e i n q u a r t z o n t h e n o r t h e r n s i d e a n d t o t h e e a s t , w h e r e t h e q u a r t z v e i n s p l i t s a n d n a r r o w s i n t o t w o l i m b s . th e r e i s n o g r e i s e n d e v e l o p e d , a n d o n l y a t r a c e o f w h i t e m i c a i n t h e p e g m a t i t e . Utopia 3, located 1.8 km northwest of Utopia 1, is the m a i n p r o s p e c t i n t h e a r e a . sh a l l o w w o r k i n g s o c c u r i n a n a r e a c o n t a i n i n g s e v e r a l p e g m a t i t e s a t t h e n o r t h e r n e n d o f a p e g m a t i t e b e l t t h a t e x t e n d s t o ut o p i a 1 i n t h e s o u t h (sh a w 1968). Although there is no record of production, several p i t s a n d c o s t e a n s i n e l u v i a l d e p o s i t s a n d t w o o p e n c u t s i n the outcrop indicate smallscale mining prior to 1949 (Daly and Dyson 1963). Utopia 3 consists of numerous pegmatite o u t c r o p s , r a n g i n g f r o m v e i n s t o d y k e s o f c o n s i d e r a b l e s i z e , w i t h t w o s m a l l o p e n c u t s i n a n o r t h w e s t - t r e n d i n g p e g m a t i t e d y k e . ta n t a l i t e , b i o t i t e , t o u r m a l i n e , m a g n e t i t e , b e r y l a n d b i s m u t h m i n e r a l s h a v e b e e n r e c o r d e d f r o m t h i s prospect (Daly and Dyson 1963, Shaw 1968). Shaw (1968) c o m m e n t e d t h a t t a n t a l i t e w a s m o r e p r e v a l e n t i n e l u v i u m t h a n i n t h e p e g m a t i t e i t s e l f . a 3 m - d e e p p i t h a s b e e n c u t i n t o a c o m p l e x p e g m a t i t e - g r e i s e n - q u a r t z v e i n . Wo r k i n t h e s h a f t a p p e a r s t o h a v e b e e n c o n c e n t r a t e d a t t h e v e i n q u a r t z - p e g m a t i t e c o n t a c t . no s y s t e m a t i c i n t e r n a l p e g m a t i t e z o n i n g w a s a p p a r e n t f r o m t h e o b s e r v e d e x p o s u r e . sm a l l p i t s a n d e x c a v a t e d r u b b l e t r a c e t h e p e g m a t i t e o v e r a n a r e a o f 1 5 x 1 0 0 m . a p r o m i n e n t q u a r t z v e i n i n t h e s h a f t t r e n d s 0 1 5 a n d d i p s v e r t i c a l l y , b u t t h e o v e r a l l t r e n d o f t h e p e g m a t i t e i s 1 5 0 . a q u a r t z - b i o t i t e - m u s c o v i t e p s a m m i t e o c c u r s a t t h e c o u n t r y r o c k c o n t a c t . th e w o r k i n g s t e r m i n a t e w h e r e t h e p e g m a t i t e p a s s e s u n d e r s a n d c o v e r t o t h e n o r t h . H o w e v e r , a p e g m a t i t e w i t h a s s o c i a t e d g r e i s e n a n d v e i n q u a r t z r e a p p e a r s 400 m to the north (444300mE 7542800mN; Utopia North), w h e r e i t i s e x p o s e d o v e r a 2 0 0 m s t r i k e l e n g t h a n d a w i d t h o f 4 0 m . re c e n t g e o c h e m i c a l a n a l y s i s s u g g e s t s t h a t ut o p i a 3 contains elevated Ta (eg 300 ppm and 390 ppm) and Nb


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