Skip to Main Content
Book Chapter

Origin of hydrothermal fluids and gold mineralization associated with the Ventersdorp Contact Reef, Witwatersrand Basin, South Africa: Constraints from S, O, and H isotopes

By
B. Zhao
B. Zhao
Department of Geology, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa
Search for other works by this author on:
L.J. Robb
L.J. Robb
EGRI, School of Geosciences, University of the Witwatersrand, Johannesburg, Private Bag X3, Wits 2050, South Africa
Search for other works by this author on:
C. Harris
C. Harris
Department of Geological Sciences, University of Cape Town, Private Bag, Rondebosch 7700, South Africa
Search for other works by this author on:
L.J. Jordaan
L.J. Jordaan
Council for Geoscience, Private Bag X112, Pretoria 0001, South Africa
Search for other works by this author on:
Published:
January 01, 2006

The Ventersdorp Contact Reef, one of the major gold-bearing conglomerate horizons in the Witwatersrand Basin, occurs as a distinct horizon between the overlying Klipriviersberg Group lavas (2714 Ma) and the underlying Central Rand Group rocks (<2894 to >2714 Ma). The Ventersdorp Contact Reef has been metamorphosed and hydrothermally altered under greenschist facies conditions (290–350 °C and 0.2–0.3 GPa). A study of S, O, and H isotopes was carried out to constrain the sources of hydrothermal fluids and gold mineralization in the Ventersdorp Contact Reef. A narrow range of δ34S values (−1.5‰ to +1.8‰) for authigenic pyrite, pyrrhotite, chalcopyrite, sphalerite, and galena from the Ventersdorp Contact Reef and its hanging-wall and footwall lithologies suggests a reconstitution of detrital sulfides during fluid circulation at peak metamorphic conditions. The δ18O values of authigenic quartz and calcite range from +8.9‰ to +11.3‰, and the δ18O and δD values of muscovite separates are between +7.2‰ and +8.4‰ and −62‰ and −31‰ respectively. The estimated δ18O (+4.8‰ to +6.1‰) and δD (−27‰ to −39‰) values of the fluids in equilibrium with these minerals under the relevant P-T conditions suggest a metamorphic origin for the fluid. It is concluded that the metamorphic fluids involved were probably derived from the Basin itself, and allogenic sulfides in the Ventersdorp Contact Reef were reconstituted during fluid circulation at peak metamorphic conditions. Accordingly, gold appears to have been locally remobilized and possibly derived from pre-existing placer concentrations.

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

Figures & Tables

Contents

GSA Special Papers

Processes on the Early Earth

Wolf Uwe Reimold
Wolf Uwe Reimold
Search for other works by this author on:
Roger L. Gibson
Roger L. Gibson
Search for other works by this author on:
Geological Society of America
Volume
405
ISBN print:
9780813724058
Publication date:
January 01, 2006

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Related Articles
Related Book Content
This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now