DOI: 10.1038/ngeo2344
论文题名: Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life
作者: Heinrich C.A.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2015
卷: 8, 期: 3 起始页码: 206
结束页码: 209
语种: 英语
Scopus关键词: anoxic conditions
; Archean
; burial (geology)
; dissolution
; gold
; hydrothermal fluid
; mobilization
; sedimentation
; South Africa
; Witwatersrand
英文摘要: The Witwatersrand Basin in South Africa is one of the best-preserved records of fluvial sedimentation on an Archaean continent. The basin hosts the worlds biggest gold resource in thin pebble beds, but the process for gold enrichment is debated. Mechanical accumulation of gold particles from flowing river water is the prevailing hypothesis, yet there is evidence for hydrothermal mobilization of gold by fluids invading the metasedimentary rocks after their burial. Earth's atmosphere three billion years ago was oxygen free, but already sustained some of the oldest microbial life on land. Here I use thermodynamic modelling and mass-balance calculations to show that these conditions could have led to the chemical transport and precipitation of gold in anoxic surface waters, reconciling the evidence for fluvial deposition with evidence for hydrothermal-like chemical reactions. I suggest that the release of sulphurous gases from large volcanic eruptions created acid rain that enabled the dissolution and transport of gold in surface waters as sulphur complexes. Precipitation of the richest gold deposits could have been triggered by chemical reduction of the dissolved gold onto organic material in shallow lakes and pools. I conclude that the Witwatersrand gold could have formed only during the Archaean, after the emergence of continental life but before the rise of oxygen in the Earth's atmosphere. © 2015 Macmillan Publishers Limited. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/106206
Appears in Collections: 气候减缓与适应 科学计划与规划
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作者单位: ETH Zurich, Department of Earth Sciences, Clausiusstr. 25, Zurich, Switzerland; Faculty of Mathematics and Natural Science, University of Zurich, Zurich, Switzerland
Recommended Citation:
Heinrich C.A.. Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life[J]. Nature Geoscience,2015-01-01,8(3)