TY - JOUR A1 - Korges, Maximilian A1 - Junge, Malte A1 - Borg, Gregor A1 - Oberthür, Thomas T1 - Supergene mobilization and redistribution of platinum-group elements in the Merensky Reef, eastern Bushveld Complex, South Africa JF - The Canadian mineralogist N2 - Near-surface supergene ores of the Merensky Reef in the Bushveld Complex, South Africa, contain economic grades of platinum-group elements, however, these are currently uneconomic due to low recovery rates. This is the first study that investigates the variation in platinum-group elements in pristine and supergene samples of the Merensky Reef from five drill cores from the eastern Bushveld. The samples from the Richmond and Twickenham farms show different degrees of weathering. The whole-rock platinum-group element distribution was studied by inductively coupled plasma-mass spectrometry and the platinum-group minerals were investigated by reflected-light microscopy, scanning electron microscopy, and electron microprobe analysis.
In pristine ("fresh") Merensky Reef samples, platinum-group elements occur mainly as discrete platinum-group minerals, such as platinum-group element-sulfides (cooperite-braggite) and laurite as well as subordinate platinum-group elementbismuthotellurides and platinum-group element-arsenides, and also in solid solution in sulfides (especially Pd in pentlandite). During weathering, Pd and S were removed, resulting in a platinum-group mineral mineralogy in the supergene Merensky Reef that mainly consists of relict platinum-group minerals, Pt-Fe alloys, and Pt-oxides/hydroxides. Additional proportions of platinum-group elements are hosted by Fe-hydroxides and secondary hydrosilicates (e.g., serpentine group minerals and chlorite).
In supergene ores, only low recovery rates (ca. 40%) are achieved due to the polymodal and complex platinum-group element distribution. To achieve higher recovery rates for the platinum-group elements, hydrometallurgical or pyrometallurgical processing of the bulk ore would be required, which is not economically viable with existing technology. KW - Bushveld Complex KW - Merensky Reef KW - PGE KW - PGM KW - supergene ores KW - weathering Y1 - 2021 U6 - https://doi.org/10.3749/canmin.2100023 SN - 1499-1276 VL - 59 IS - 6 SP - 1381 EP - 1396 PB - Mineralogical Association of Canada CY - Ottawa ER - TY - JOUR A1 - Genderjahn, Steffi A1 - Lewin, Simon A1 - Horn, Fabian A1 - Schleicher, Anja M. A1 - Mangelsdorf, Kai A1 - Wagner, Dirk T1 - Living lithic and sublithic bacterial communities in Namibian drylands JF - Microorganisms : open access journal N2 - Dryland xeric conditions exert a deterministic effect on microbial communities, forcing life into refuge niches. Deposited rocks can form a lithic niche for microorganisms in desert regions. Mineral weathering is a key process in soil formation and the importance of microbial-driven mineral weathering for nutrient extraction is increasingly accepted. Advances in geobiology provide insight into the interactions between microorganisms and minerals that play an important role in weathering processes. In this study, we present the examination of the microbial diversity in dryland rocks from the Tsauchab River banks in Namibia. We paired culture-independent 16S rRNA gene amplicon sequencing with culture-dependent (isolation of bacteria) techniques to assess the community structure and diversity patterns. Bacteria isolated from dryland rocks are typical of xeric environments and are described as being involved in rock weathering processes. For the first time, we extracted extra- and intracellular DNA from rocks to enhance our understanding of potentially rock-weathering microorganisms. We compared the microbial community structure in different rock types (limestone, quartz-rich sandstone and quartz-rich shale) with adjacent soils below the rocks. Our results indicate differences in the living lithic and sublithic microbial communities. KW - lithobiont KW - intracellular DNA KW - extracellular DNA KW - weathering KW - dryland KW - rock Y1 - 2021 U6 - https://doi.org/10.3390/microorganisms9020235 SN - 2076-2607 VL - 9 IS - 2 PB - MDPI CY - Basel ER -