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Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa

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Junge, Malte and Oberthür, Thomas and Kraemer, Dennis and Melcher, Frank and Piña García, Rubén and Derrey, Insa T. and Manyeruke, Tawanda and Strauss, Harald (2019) Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa. Mineralium Deposita, 54 (6). pp. 885-912. ISSN 0026-4598, ESSN: 1432-1866

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Official URL: https://link.springer.com/article/10.1007%2Fs00126-018-0848-7


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Abstract

The Platreef of the Bushveld Complex is currently the largest PGE open pit deposit. In order to investigate the behavior of PGE during weathering, three boreholes covering a sequence of oxidized and pristine Platreef ore from the Mogalakwena mine were studied. Further, sulfides and platinum-group minerals (PGM) at various locations along the strike of the Platreef, at Townlands, Tweefontein and Nonnenwerth were compared to those of the Mogalakwena mine (Overysel, Sandsloot). In the pristine ore, PGE generally occur as PGM, or in solid solution within sulfides. PGM are usually associated with sulfide and mainly comprise (Pt,Pd)-bismuthotellurides, cooperite-braggite, and sperrylite. Electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) indicate concentrations of Pd in pentlandite (up to 185 ppm), whereas pyrrhotite contains up to 15 ppm of Os, Ir, and Ru, and chalcopyrite is usually devoid of PGE. Two compositionally different groups of pyrite differing in Ni, Co, and Pt contents were identified. Sulfur isotope data indicate different degrees of assimilation from the country rocks. Near-surface, oxidized PGE ores have a large economic potential. However, attempts to extract the PGE have proven unfeasible due to low PGE recoveries (< 30%) achieved by conventional metallurgical methods. In the oxidized ores, rare relict PGM are present. EPMA and LA-ICP-MS measurements demonstrated that secondary iron oxides/hydroxides and secondary silicates contain erratically distributed concentrations of Rh, Pt, and Pd (up to several 100 ppm). The polymodal distribution of PGE in the weathered PGE ores explains the low recovery rates by conventional flotation processing.


Item Type:Article
Subjects:Sciences > Geology > Geochemistry
Sciences > Geology > Mineralogy
ID Code:56419
Deposited On:19 Jul 2019 10:52
Last Modified:19 Jul 2019 10:52

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