Superposition of gold mineralisation on pre-existing carbonate alteration: structural evidence from the Mulgarrie gold deposit, Yilgarn Craton

Davis, B.K., Hickey, K.A., and Rose, S. (2001) Superposition of gold mineralisation on pre-existing carbonate alteration: structural evidence from the Mulgarrie gold deposit, Yilgarn Craton. Australian Journal of Earth Sciences, 48 (1). pp. 131-149.

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Abstract

Carbonate alteration at the Mulgarrie gold mine in the Eastern Goldfields of Western Australia, is represented by porphyroblasts, veins and pervasive, texturally destructive, carbonatisation. Two foliations, S1M and S2M, were produced by two separate deformation events at the mine-scale, D1M and D2M. D1M and D2M both occurred in response to regional D2 tectonism. Carbonate alteration was the product of two separate episodes of fluid ingress: the earlier produced magnesite and the latter Fe-dolomite. Both periods of carbonate alteration occurred pre- to early syn-D2M, when mafic to ultramafic komatiitic rocks reacted with fluids that moved along regional faults and pre-date the alteration associated with regional peak metamorphism. Gold at Mulgarrie overprints pre- and late syn-D2 quartz veins in zones of massive carbonate alteration, suggesting it has a late- to post-D2 timing. This late timing agrees with the generally accepted syn-D3 (and younger) age for gold mineralisation in the Eastern Goldfields. We suggest that carbonate alteration at Mulgarrie is not a product of the hydrothermal event responsible for the gold mineralisation. Rather, the different relative timing of magnesite, Fe-dolomite and gold indicates there were two carbonate-producing fluid systems and a fluid transporting the gold overprinted these. Similarly, early carbonate alteration may play a role in localising auriferous vein deposits throughout the Yilgarn and other Archaean cratons.

Item ID: 13102
Item Type: Article (Refereed Research - C1)
Keywords: carbonates; deformation history; gold; mineralisation; structure
ISSN: 0812-0099
Date Deposited: 04 Dec 2010 13:15
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040312 Structural Geology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840105 Precious (Noble) Metal Ore Exploration @ 100%
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