Skip to Main Content
Book Chapter

The Witwatersrand Gold Fields: Part II. An Origin for Witwatersrand Gold during Metamorphism and Associated Alteration

By
G. N. Phillips
G. N. Phillips
Geology Department, University of the Witwatersrand, Wits, 2050, South Africa
Search for other works by this author on:
R. E. Myers
R. E. Myers
Geology Department, University of the Witwatersrand, Wits, 2050, South Africa
Search for other works by this author on:
Published:
January 01, 1989

Abstract

An epigenetic replacement model is proposed for Witwatersrand gold mineralization. In this model, unconformities that developed during deposition of the Upper Witwatersrand sediments were sites of selective accumulation of iron pisolites-ferricretes and carbon seams. These Fe-C-bearing intervals are part of 1- to 2-m-thick reef packages that were preferred channelways for Au-S-bearing metamorphic fluids because of their lithologic heterogeneity and preferential accommodation of strain during deformation. It is suggested that the metamorphic fluids were associated with a high-strain, cleavage-forming event recorded in the Witwatersrand, Venters-dorp, and Transvaal successions.

Selective replacement of Fe-C-bearing phases by Au-S-bearing metamorphic fluids accounts for the secondary nature of the Witwatersrand mineralogy, apparent structural control on gold mineralization, the secondary texture of gold, and the presence of replacement textures involving pyrite and uraninite. Most importantly, the model also accounts for the close relationship of gold distribution to sedimentary features. If the present distribution of Fe and C approximates original sedimentary patterns, any epigenetic gold precipitated by interaction with Fe and/or C must also reflect sedimentary features.

This replacement model obviates the requirements imposed by the placer model for Witwatersrand gold for a more reducing Precambrian atmosphere, for a particularly enriched source terrane, or for an unusually efficient sorting mechanism to concentrate gold in a diverse range of rock types.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

Economic Geology Monograph Series

The Geology of Gold Deposits: The Perspective in 1988

Reid R. Keays
Reid R. Keays
Search for other works by this author on:
W. R. H. Ramsay
W. R. H. Ramsay
Search for other works by this author on:
David I. Groves
David I. Groves
Search for other works by this author on:
Society of Economic Geologists
ISBN electronic:
9781629490014
Publication date:
January 01, 1989

GeoRef

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal