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

Bath, AB, Walshe, JL, Cloutier, J ORCID: 0000-0002-9432-9880, Rotherham, J, Hutchison, R, Hollebeck, E, Verrall, M and Schmitt, L 2020 , 'Alteration patterns linked to high-grade gold mineralization at the Wattle Dam deposit, Western Australia' , Ore Geology Reviews, vol. 125 , pp. 1-16 , doi: 10.1016/j.oregeorev.2020.103471.

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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
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.

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