South Africa - Inkaba.org

Rich Ultramafic Pegmatite replacement bodies, Bafokeng
Investigation of the Merensky Reef and the associated Iron
Rasimone Platinum Mine, Rustenburg, South Africa
Olaotse Shadi 1 , D. Reid 2
1. Department of Geological Sciences, University of Cape Town, South Africa. shdola001@uct.ac.za
2. Department of Geological Sciences, University of Cape Town, South Africa. David.reid@uct.ac.za
ABSTRACT
Iron Rich Ultramafic Pegmatite replacement bodies (IRUP) are abundantly distributed throughout the Rustenburg
layered mafic sequence of the Bushveld Complex and have been encountered at Bafokeng Rasimone Platinum
Mine (BRPM) during underground operations. In the NW sector of BRPM North Shaft, extensive IRUP
replacement of the Merensky Reef and underlying footwall norites cause physical displacement and redistribution
of the PGE.
The current study focuses on the replacement phenomena observed in the Merensky Reef sequence adjacent to a
large IRUP pipe with the aim to track the mineralogical and geochemical changes associated with the
transformation. In addition the study also address structural implications linked to the replacement bodies observed
at the mine.
A sample traverse was conducted from unreplaced reef, through a zone of mixing into the centre of the IRUP pipe.
Field characteristics shows that IRUPs preferentially replaces leucocratic lithologies and they occur in close
proximity to areas marked by extensive faulting and folding. Systematic chemical analysis conducted along the
transition shows that the IRUP is more evolved with a higher Fe content whilst depleted in Mg relative to the
norites.
KEYWORDS: IRUP; Merensky reef; mineralogical; geochemical; textural; characterization
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