Authors / CoAuthors
Mernagh, T.P. | Wygralak, A.S. | Fraser, G.L. | Huston, D.L.
Abstract
The Tanami region has become one of Australia?s premier Proterozoic gold provinces, having already produced 4.85 Moz (150 t) of gold, and still has high exploration potential. This region contains more than 60 gold occurrences including three established gold fields (Dead Bullock Soak, The Granites and Tanami) as well as several significant gold prospects (Groundrush, Titania, Crusade, Coyote and Kookaburra). The Callie deposit (>4.5 Moz total resource) located in the Dead Bullock Soak goldfield is currently the largest mine in this region. The fluid inclusion data suggests that the deposits have formed over a range of physico-chemical conditions and depths. Groundrush appears to have formed at the greatest depths and has the most reduced (CH4-rich) fluids. The Granites goldfield and the Coyote and Callie deposits formed at shallower depths. The Coyote deposit contained both CO2-rich and CH4-rich fluid inclusions. Fluids at The Granites were CO2-rich but also had variable N2 and CH4. Fluids at Callie are relatively more oxidised with only CO2 and N2 being detected. The Tanami deposits appear to have formed at the shallowest levels and are dominated by low-salinity aqueous fluid inclusions, although some CO2-bearing fluid inclusions have also been detected. Thus, it appears that the ore-bearing fluids in the Tanami region attained temperatures between 120 and 430 ?C and contained variable quantities of CO2 ? other gases which may have formed as a result of fluid/rock interaction. Homogenisation data indicate that the Groundrush and Coyote deposits had the highest temperature fluids (260 ? 430 ?C), while the ore fluids in the Dead Bullock Soak and The Granites goldfields were moderate to high temperature (220 ? 326 ?C). In contrast, the Tanami goldfield, is dominated by low temperature (120 ? 220 ?C) aqueous inclusions. O and H isotopic data are consistent with either a metamorphic or magmatic origin for the ore fluids with some mixing with meteoric fluids evident in the Tanami district. In an effort to evaluate the regional extent of this gold-only mineral system we have carried out re-gional sampling of outcropping quartz veins and extended our fluid inclusion and Ar/Ar studies into the north Arunta region. More than 100 quartz vein clusters located in regions with differing metamorphic grade, were selected for sampling on twelve 1:250K mapsheets. The following types of veining have been observed: ? Epithermal veins with a range of textures including chalcedonic, colloform and comb quartz. ? Mesothermal veins striking mainly E-W. These veins are highly prospective as they are of a similar age to those in the gold deposits and have fluid chemistries similar to the ore-bearing fluids. ? Quartz veins with saccharoidal textures that contain two fluids: a higher temperature (230 ? 330 ?C), gas-rich fluid and a lower temperature (120 ? 230 ?C), saline, aqueous fluid. Acknowledgements This work forms part of the North Australia Project, a collaborative project between Geoscience Australia and the Northern Territory Geological Survey. TPM, GLF, and DLH publish with permission from the CEO of Geoscience Australia.
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nonGeographicDataset
eCat Id
61033
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- External PublicationAbstract
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- economic geology
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- geochemistry
- ( Theme )
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- mineral deposits
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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
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2004-01-01T00:00:00
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