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Alteration patterns linked to high-grade gold mineralization at the Wattle Dam deposit, Western Australia

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Abstract
Sharp physio-chemical gradients occur in Archean gold systems, yet they are often poorly defined. These physio-chemical gradients can provide windows into fluids that deposit high-grade gold mineralization. Recognizing different alteration styles and fluid-types in mineral systems helps define processes that led to the deposition of high-grade gold. Here we report on the architecture and chemical gradients across the komatiite-hosted Wattle Dam gold deposit in the eastern Yilgarn Craton, Western Australia, which is one of Australia’s highest grade-gold deposits. The deposit notably contains millimeter- to centimeter-thick gold-only veins with an absence of quartz. Whole rock geochemistry shows that high-grade gold veins are hosted in komatiite flow-margins facies with olivine orthocumulate komatiites in the footwall, interbedded graphitic shale close to the lode and komatiite basalt in the hangingwall. The komatiite flow-margin facies that hosts high-grade gold veins have been pervasively altered by stage 1 biotite-actinolite. Stage 2 gold veins cross-cut the biotite-actinolite altered komatiite and these veins contain thin (2O-CO2 fluids, commonly linked with Archean gold systems. The generation of carbonate-undersaturated alkaline fluids in the high-grade core of the Wattle Dam deposit, may be explained by phase-separation or a CO2-poor alkaline fluid source. Either way these alkaline fluids played a critical role in mobilizing and concentrating very high amounts of gold into veins.
Item Type: | Article |
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Authors/Creators: | Bath, AB and Walshe, JL and Cloutier, J and Rotherham, J and Hutchison, R and Hollebeck, E and Verrall, M and Schmitt, L |
Keywords: | Archean, gold, alkaline, metasomatism |
Journal or Publication Title: | Ore Geology Reviews |
Publisher: | Elsevier Science Bv |
ISSN: | 0169-1368 |
DOI / ID Number: | 10.1016/j.oregeorev.2020.103471 |
Copyright Information: | Copyright 2020 Elsevier B.V. |
Item Statistics: | View statistics for this item |
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