PLATINUM-GROUP MINERALS IN THE SELUKWE SUBCHAMBER, GREAT DYKE, ZIMBABWE - IMPLICATIONS FOR PGE COLLECTION MECHANISMS AND POST-FORMATIONAL REDISTRIBUTION
Bm. Coghill et Ah. Wilson, PLATINUM-GROUP MINERALS IN THE SELUKWE SUBCHAMBER, GREAT DYKE, ZIMBABWE - IMPLICATIONS FOR PGE COLLECTION MECHANISMS AND POST-FORMATIONAL REDISTRIBUTION, Mineralogical Magazine, 57(389), 1993, pp. 613-633
This paper presents the results of microprobe investigations of the Pl
atinum-Group Elements (PGE) of the Serukwe Subchamber, Great Dyke, Zim
babwe. The PGE are associated with base metal sulphides in the uppermo
st pyroxenites of the Ultramafic Sequence of the Great Dyke. The follo
wing minerals have been indentified: bismuthotellurides (moncheite, ma
skovite, michenerite, kotulskite and polarite); arsenides (sperrylite)
; and sulphides and sulpharsenides (cooperite, laurite, braggite and h
ollingworthite). Platinum Group Minerals (PGM) occur in three distinct
textural environments: (I) at the boundary of sulphides and silicates
/hydrosilicates, (2) entirely enclosed within sulphides, and (3) entir
ely enclosed within silicate or hydrosilicate minerals. The stratigrap
hic distribution, environments and textures of the PGM have important
genetic implications, and cannot be explained by a single process. A m
ulti-process model for the petrogenesis of the PGE mineralisation in t
erms of complexation and intermediate compound formation is proposed.
The primary mineralising events were due to orthomagmatic processes, b
ut the observed textures are the result of microscale remobilisation o
f PGM components by trapped interstitial fluids (hydromagmatic process
es).