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Platinum-group minerals in the Selukwe Subchamber, Great Dyke, Zimbabwe: implications for PGE collection mechanisms and post-formational redistribution

Published online by Cambridge University Press:  05 July 2018

Bronwen M. Coghill  and
Allan H. Wilson
Bronwen M. Coghill
Affiliation:
Department of Geology, University of Natal, P.O. Box 375, Pietermaritzburg 3200, South Africa
Allan H. Wilson
Affiliation:
Department of Geology, University of Natal, P.O. Box 375, Pietermaritzburg 3200, South Africa
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Abstract

This paper presents the results of microprobe investigations of the Platinum-Group Elements (PGE) of the Selukwe Subchamber, Great Dyke, Zimbabwe. The PGE are associated with base metal sulphides in the uppermost pyroxenites of the Ultramafic Sequence of the Great Dyke. The following minerals have been indentified: bismuthotellurides (moncheite, maslovite, michenerite, kotulskite and polarite); arsenides (sperrylite); and sulphides and sulpharsenides (cooperite, laurite, braggite and hollingworthite). Platinum Group Minerals (PGM) occur in three distinct textural environments: (1) at the boundary of sulphides and silicates/hydrosilicates, (2) entirely enclosed within sulphides, and (3) entirely enclosed within silicate or hydrosilicate minerals. The stratigraphic distribution, environments and textures of the PGM have important genetic implications, and cannot be explained by a single process. A multi-process model for the petrogenesis of the PGE mineralisation in terms of complexation and intermediate compound formation is proposed. The primary mineralising events were due to orthomagmatic processes, but the observed textures are the result of microscale remobilisation of PGM components by trapped interstitial fluids (bydromagmatic processes).

Keywords

Platinum Group ElementsZimbabweGreat Dykemicroprobe investigationsAffinity Factor
Type
Mineralogy
Information
Mineralogical Magazine , Volume 57 , Issue 389 , December 1993 , pp. 613 - 633
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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