Witwatersrand gold particle chemistry matches model of metamorphosed, hydrothermally altered placer deposits |
| |
Authors: | H. E. Frimmel V. H. Gartz |
| |
Affiliation: | (1) Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa, ZA |
| |
Abstract: | Analyses of gold particles from the Ventersdorp Contact Reef in the Klerksdorp and Carletonville goldfields of the Late Archaean Witwatersrand Basin reveal a wide range in Au, Ag and Hg concentrations of 80.9 to 92.9, 6.0 to 17.6, and 0.6 to 5.8 wt.%, respectively. However, individual gold particles are generally homogeneous. This observation is predicted by modelling of Ag and Hg diffusion through gold at the peak metamorphic temperature of about 300 °C. The only exception is gold in hydrothermal quartz veins, the formation of which can be ascribed to the mobilisation of originally detrital gold particles during a chloritisation event that was triggered by tectonically expelled fluids, as a consequence of the 2023 Ma Vredefort meteorite impact event. Inter-particle homogenisation on a hand-sample scale was generally not achieved. The mean gold composition for the same reef in different mines (kilometre scale) can vary drastically. These results confirm the model of a metamorphosed and hydrothermally altered placer deposit. Furthermore they indicate that, in spite of a significant post-depositional modification of the composition of individual gold particles, the mean gold composition at a given reef locality may be used to distinguish different source areas of the originally detrital particles. Received: 3 December 1996 / Accepted: 19 May 1997 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|