New data on malanite and cuprorhodsite from chromitites of the Bushveld Complex, South Africa

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Abstract

The 3D mineralogical technology was used to study the representative selection of grains of thiospineles from 3 groups of chromitite horizons (lower LG6, middle MG1/MG2 and upper UG2): 46 grains of malanite (4—42 μm) and 34 grains of cuprorhodsite (9—42 μm). Their microprobe analysis was performed (n = 61). Statistics for this selection have resulted in following formulae: for malanite — (Сu2+,Fe2+)(Pt3+,Rh3+,Ir3+,Co3+,Ni3+Fe3+)2S4, for cuprorhodsite — (Сu2+,Fe2+) ∙ ∙ (Rh3+,Pt3+,Ir3+,Fe3+)2S4. According to morphological properties and their relationship with platinum-group minerals (PGM) and base metal sulphides, thiospinel can be attributed as the earliest primary PGM in chromitites. The distribution of cuprorhodsite and malanite in chromitites was controlled by the Rayleigh fractionation of the primary sulfide melt in the process of formation of Bushveld chromitite horizons.

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Nikolay Semenovich Rudashevsky

LLC, CNT Instruments

Author for correspondence.
Email: nrudash@list.ru
Scopus Author ID: 6602557468

Doctor of Geological and Mineralogical Sciences

Russian Federation, Saint-Petersburg

Vladimir Nikolaevich Rudashevsky

LLC, CNT Instruments

Email: vlad.rudashevsky@gmail.com
SPIN-code: 6834-4770

Candidate of Geological and Mineralogical Sciences

Saint-Petersburg

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2. Fig. 1. Grains of malanite and cuprorhodsite from chromitites of the Bushveld complex. Polished sections of heavy mineral HS concentrates.

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3. Fig. 2. Triple diagrams Rh—Pt—Ir (a) and Rh—Pt—(Ni + Co + Fe) (б) for compositions of malanite and cuprorhodsite from Bushveld chromitites. Sample BD-11/2 (1, UG2), Sample S (2, LG6) and Sample T (3, 2MG1/ MG 2).

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4. Fig. 3. Charts of number of intergrowths (%) between PGM and pentlandite (pn), chalcopyrite (cp), and pyrite (py) in various groups of Bushveld chromitite horizons.

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