Authors / CoAuthors
Mernagh, T.P. | Wygralak, A.S. | Fraser, G. | Huston, D.L.
Abstract
The Tanami region has become one of Australia?s premier Proterozoic gold provinces, having already produced 122 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 (>5 Moz total resource) located in the Dead Bullock Soak goldfield is currently the largest mine in this region. Fluid inclusion studies indicate that the ore fluids in the Dead Bullock Soak and The Granites goldfields were low to moderate salinity (4 ? 10 wt.% NaCl eq), moderate to high temperature (260 ? 460 ?C) and gas rich. In contrast, ore fluids in the Tanami goldfield were low temperature (120 ? 220 ?C) with only minor CO2. 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. The fluid inclusion data also indicate that the deposits have formed over a range of physico-chemical conditions and depths. Groundrush appears to have formed at the greates depths and has the most reduced (CH4-rich) fluids. The Granites goldfield and the Callie deposit formed at shallower depths. The Granites fluids were CO2-rich but also had variable N2 and CH4. The Callie fluids show only small variations in temperature and salinity and are 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 fluids, although some CO2-bearing fluids have also been detected. Considerable uncertainty surrounds the age of gold mineralisation. The spatial relationship between many of the gold deposits and granitoids has led to proposed genetic links between granite intrusion and mineralisation. These granites have since been dated at between 1825 and 1795 Ma. Preliminary 40Ar/39Ar results from sericite from the Carbine pit in the Tanami goldfield yields a total gas age of 1810 Ma, i.e. similar to the age of the granites. However, 40Ar/39Ar analysis of biotite in mineralised veins from Dead Bullock Soak indicate an age of 1720 ? 1700 Ma. This suggests that mineralisation at Callie may be related to fluid migration driven by the Late Strangways Orogeny that was responsible for widespread deformation and metamorphism in the Arunta Province to the south-east. Results of this study indicate that gold deposits of the Tanami region are surprisingly diverse, with some being basalt and dolerite hosted, some in banded iron formations and some being sediment hosted. Moreover, fluid inclusion data shows that the deposits formed over a range of depths and 40Ar/39Ar dating may indicate the occurrence of more than one mineralising event. Consideration of this diversity from a mineral systems perspective, highlights the likelihood that undiscovered gold deposits in the Tanami region will have a range of characteristics and may occur in a number of different lithologies.
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nonGeographicDataset
eCat Id
39053
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
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2601
Australia
Keywords
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- External PublicationAbstract
- ( Theme )
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- mineral deposits
- ( 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
2002-01-01T00:00:00
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geoscientificInformation
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[-20.0, -19.5, 129.5, 130.0]
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