Authors / CoAuthors
Fu, B. | Mernagh, T.P. | Fairmaid, A. | Phillips, D. | Kendrick, M.A.
Abstract
The Maldon gold deposit in central Victoria lies within the contact aureole of the Harcourt Granite and associated granitic dykes. The ore-bearing fluids are characterised by the presence of CH4-rich fluids, which exhibit complex freezing and heating behaviour, as well as mixed CO2-low-salinity aqueous fluids. Raman analysis indicates that the CH4-rich inclusions from Maldon contain 30 to >70 mol.% CH4 (and <40 mol.% N2) and have highly variable ratios of CH4/CO2, ranging from 0.12 to 15.6. The presence of graphite in the CH4-rich inclusions indicates either accidental trapping of the solid phase at high temperature or post-trapping changes (i.e. incomplete reactions). Higher-salinity brine inclusions only occur locally. The Harcourt Granite is a moderately reduced, I-type granite and the reduced fluids are believed to have formed within (or in close proximity to) thermal aureoles of the dykes or granites during contact metamorphism. We conclude that the Maldon deposit is an 'orogenic' gold deposit that was metamorphosed and/or remobilised during the emplacement of post-orogenic intrusions/dykes. The late-stage magmatic fluids and retrograde metamorphic fluids have produced many of the features associated with other well documented reduced intrusion-related gold systems. This suggests that some 'orogenic' gold deposits may have been completely overprinted by later magmatic/metamorphic events and are now only evident as reduced intrusion-related gold systems.
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nonGeographicDataset
eCat Id
73301
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- External PublicationAbstract
- ( Theme )
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- economic geology
- ( Theme )
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- fluid inclusions
- ( Theme )
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- geochemistry
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2012-01-01T00:00:00
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