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3-D Distribution of Sulphide Minerals in the Merensky Reef (Bushveld Complex, South Africa) and the J-M Reef (Stillwater Complex, USA) and their Relationship to Microstructures Using X-Ray Computed Tomography
Authors:GODEL  BELINDA; BARNES  SARAH-JANE; MAIER  WOLFGANG D
Institution:UNIVERSITÉ DU QUEBEC À CHICOUTIMI, SCIENCES DE LA TERRE, 555, BOULEVARD DE L'UNIVERSITÉ CHICOUTIMI, QC, CANADA, G7H 2B1
Abstract:Large mafic–ultramafic layered intrusions may containlayers enriched in platinum-group elements (PGE). In many cases,the PGE are hosted by disseminated sulphides. We have investigatedthe distribution of the sulphides in three dimensions in twooriented samples of the Merensky Reef and the J-M Reef. Theaim of the study was to test the hypothesis that the sulphidescrystallized from a base metal sulphide liquid that percolatedthrough the cumulate pile during compaction. The distributionof sulphides was quantified using: (1) X-ray computed tomography;(2) microstructural analysis of polished thin sections orientedparallel to the paleovertical; (3) measurement of dihedral anglesbetween sulphides and silicates or oxides. In the Merensky Reefand the J-M Reef, sulphides are connected in three dimensionsand fill paleovertical dilatancies formed during compaction,which facilitated the downward migration of sulphide liquidin the cumulate. In the melanorite of the Merensky Reef, thesulphide content increases from top to bottom, reaching a maximumvalue above the underlying chromitite layer. In the chromititelayers sulphide melt connectivity is negligible. Thus, the chromititemay have acted as a filter, preventing extensive migration ofsulphide melt downwards into the footwall. This could partiallyexplain the enrichment in PGE of the chromitite layer and theobserved paucity of sulphide in the footwall. KEY WORDS: X-ray computed tomography; microstructures; sulphides; Merensky Reef; J-M Reef
Keywords:: X-ray computed tomography  microstructures  sulphides  Merensky Reef  J-M Reef
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