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New Data for Malanite and Cuprorhodsite from Chromitites of the Bushveld Complex, South Africa

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Abstract

The 3D-mineralogical technology was used to study a representative selection of grains of thiospineles from three 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). The statistics for this selection of grains have resulted in the following formulas: for malanite, (Сu2+,Fe2+)(Pt3+Rh3+,Ir3+,Co3+,Ni3+Fe3+)2S4 and for cuprorhodsite, (Сu2+,Fe2+)(Rh3+,Pt3+,Ir3+,Fe3+)2S4. According to morphological properties and their relationship with platinum-group minerals (PGMs) and base metal sulfides, thiospinel can be attributed to the earliest primary PGMs 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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Notes

  1. The considered thiospineles were not found among PGMs of two broadly studied samples from the Merensky reef (from the western and eastern parts of the Bushveld Complex).

  2. ECD is the equivalent diameter of a circle whose area is equal to the area of the cross-section of the grain.

  3. The amount of sulfides in flotation concentrates is higher than in primary chromitites, while the ratio of sulfides practically does not change.

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ACKNOWLEDGMENTS

The authors are sincerely grateful to Dr. T. Oberthür and Dr. I.V. Veksler for the samples from Bushveld chromitites presented for research.

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  1. CNT Instruments, LLC, St. Petersburg, Russia

    N. S. Rudashevsky & V. N. Rudashevsky

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Rudashevsky, N.S., Rudashevsky, V.N. New Data for Malanite and Cuprorhodsite from Chromitites of the Bushveld Complex, South Africa. Geol. Ore Deposits 62, 796–802 (2020). https://doi.org/10.1134/S1075701520080139

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