Journal article
Origin of Witwatersrand gold: A metamorphic devolatilisation-hydrothermal replacement model
G Neil Phillips, R Powell
Transactions of the Institutions of Mining and Metallurgy Section B Applied Earth Science | Published : 2012
Abstract
Goldfields extend for 300 km around the margin of the Archaean Witwatersrand Basin of South Africa associated with regional greenschist facies metamorphism and deformation. Metamorphic mineral assemblages involving pyrophyllite-chloritoid are associated with gold in all goldfields, reflecting low pressure and 300 to 400°C conditions, and indicating high geothermal gradients. The origin of Witwatersrand gold can be explained by metamorphic devolatilisation to generate auriferous fluids beneath and outside the Witwatersrand Basin, followed by passage of these fluids along large structures and into the Basin. In this model, generation of the fluid is a consequence of the transition to amphiboli..
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Awarded by Australian Research Council
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Funding Acknowledgements
The work would not have been possible without mine access and research projects involving 40 Witwatersrand gold mines. Many people have debated and refined our ideas on Witwatersrand gold genesis; and Russell Myers, Jonathan Law and Andy Barnicoat are thanked especially for sharing their insights into the roles of the thrust faults, gold grains, quartzites and sedimentology. MartinHughes is thanked for his significant input to our understanding of Palaeozoic slate belt and gold placer systems; and Iain Pitcairn for his comments on the manuscript. Figures are taken from geology of gold courses with permission. Metamorphic and alteration studies were supported by the Richard Ward Endowment Fund from University of Witwatersrand, Key Centre for Economic Geology in Townsville, Gencor Mining Corporation, Great Central Mines Ltd, and CSIRO. NP acknowledges support from Australian Research Council grant A39030663, and RP from ARC DP0451770 and DP0987731.