TY - JOUR

T1 - Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa

AU - Junge, Malte

AU - Oberthür, Thomas

AU - Kraemer, Dennis

AU - Melcher, Frank

AU - Piña, Ruben

AU - Derrey, Insa Theresa

AU - Manyeruke, Tawanda

AU - Strauss, Harald

N1 - Funding information: Robert Schouwstra, Jacques Roberts, Trust Muzondo and AngloPlatinum are thanked for access to the drill cores samples and their help during sampling. Excellent polished sections were prepared by Donald Henry, electron probe microanalysis was ably performed by Christian Wöhrl and Simon Goldmann, all at the BGR in Hannover. Martin Oeser-Rabe is thanked for his support during LA-ICP-MS measurements at the Leibniz Universität Hannover. Eike Gäbler is specially thanked for his support with the LA-ICP-MS data processing. Mineral liberation analysis was carried out at the Helmholtz Institute in Freiberg by Inga Osbahr. Many thanks for the critical and helpful input of reviewers Judith Kinnaird and Marek Locmelis, which together with the constructive comments of Associated Editor Marco Fiorentini improved the quality and clarity of argumentation of our presentation. This study was supported by the graduate school “Geofluxes” at the Leibniz Universität Hannover.

PY - 2019/8/1

Y1 - 2019/8/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85055887346&partnerID=8YFLogxK

U2 - 10.1007/s00126-018-0848-7

DO - 10.1007/s00126-018-0848-7

M3 - Article

AN - SCOPUS:85055887346

VL - 54

SP - 885

EP - 912

JO - Mineralium deposita

JF - Mineralium deposita

SN - 0026-4598

IS - 6

ER -