Authors / CoAuthors
Wygralak, A.S. | Mernagh, T.P.
Abstract
Tanami Region, the largest gold province in the Northern Territory, has produced 122 t of gold, has a known remaining resource of 190 t, and has high exploration potential. Most deposits are concentrated in three goldfields - Dead Bullock Soak (DBS), The Granites and Tanami. Significant mineralisation is also located at Groundrush (0.7 Moz Au), Oberon (0.48 Moz Au) and Crusade (0.1 Moz Au) deposits, as well as the Coyote prospect in WA. Gold mineralisation is late in the tectonic cycle, has a spatial assocaition with late orogenic felsic intrusives, and is coincident with late D5 structures. DBS goldfield (remaining resource 23.6 Mt at 5.6 g/t Au) contains stratabound mineralisation in folded greenschist facies siltstone, BIF and chert of the Dead Bullock Formation. At Callie, which is the largest deposit in the Region, mineralisation is in D5 quartz veins associated with fold closures within metasiltstone. It is dominated by free gold (70%) with some auriferous arsenopyrite. The remaining DBS deposits consist of BIF and chert hosted mineralisation associated with arsenopyrite, pyrrhotite and minor pyrite. The Granites goldfield (remaining resource 1.9 Mt at 3.8 g/t Au) comprises stratabound mineralisation within intensly folded amphibolite facies BIF of Dead Bullock Formation. Gold occurs in sulphides (apy, po, py) disseminated in BIF, quartz and quartz-carbonate veins. The Granites goldfield lies in close proximity to Inningarra and The Granites granitic suites (1815?4 and 1795?5 Ma respectively), and is associated with D5 shearing. Tanami goldfield (remaining resource 6.01 Mt at 3.2 g/t Au) comprise auriferous quartz veins in sub-greenschist facies basalt and interbedded sedimentary units of the Mount Charles Formation. Mineralisation is controlled by three sets of D5 faults striking 350-010o, 020-040o, 060-080o and dipping east to southeast. There is a close spatial relationship with the Coomarie and Frankenia granites (1815?4 and 1805?6 Ma respectively). Gold occurs in sulphides (py, apy, po);and vein textures indicate high level mineralisation. Wallrock alteration involves bleaching of basalt and sediments to produce sericite+quartz?pyrite?carbonate assemblages. Groundrush (resource 3.2 Mt at 4.5 g/t Au) comprises auriferous arsenopyrite in quartz veins within dolerite, but structural relations are still not clear. Titania (resource at Oberon 4.1 Mt at 2.6 g/t Au) contains auriferous pyrite and arsenopyrite in D5 quartz veins within detrital and graphitic sediments of the Killi Killi Formation; Minotaur ( resource 1.0 Mt at 2.4 g/t Au) contains auriferous sulphides (apy, po, py) disseminated in lower amphibolite schist of Dead Bullock Formation. Microthermometric and Raman spectroscopic studies of primary fluid inclusions indicate that Callie fluids changed character with time, characterised by decreasing temperature, increasing salinity and changing gas contents. The fluid conditions were 280-400oC and 6-12 wt% NaCl in pre-ore quartz veins; 220-360oC, 8-22 wt% NaCl eq and abundant CO2 in ore-stage quartz veins; 180-320oC and 12-18 wt% NaCl eq in post-ore quartz veins, and 80-160oC and 14-28 wt% NaCl eq in late post-ore carbonate veins. At The Granites goldfield, the main population of ore stage fluid inclusions had a temperatures of 260-312oC and salinity 4-8 wt% NaCl eq. At the Tanami goldfield, the ore fluids had lower temperatures of 120-220oC and salinity below 12 wt% NaCl eq; fluids here were largely degased. At Groundrush, ore fluids had the highest temperatures of 390-430oC and salinity of 4-10 wt% NaCl eq. Groundrush fluids also contained CO2 and exceptionally high CH4. Based on fluid inclusion data, estimated depths of mineralisation were 8.3 to 5.5 km for Groundrush, 7.5 to 3.8 km for The Granites goldfield, 5.8 to 3.2 km for Callie and 1.5 to 0.4 km for the Tanami goldfield.
Product Type
nonGeographicDataset
eCat Id
38088
Contact for the resource
Custodian
Point of contact
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Keywords
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- External PublicationGeological Report
- ( Theme )
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- economic geology
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- AU-NT
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2001-01-01T00:00:00
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unknown
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geoscientificInformation
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Unknown
Parent Information
Extents
[-20.0, -19.5, 129.5, 130.0]
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