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标题：Element mapping the Merensky Reef of the Bushveld Complex
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作者：William Smith ; Wolfgang Maier ; Stephen Barnes 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2021
卷号：12
期号：3
页码：1-20
DOI：10.1016/j.gsf.2020.11.001
语种：English
出版社：Elsevier
摘要：AbstractThe Merensky Reef hosts one of the largest PGE resources globally. It has been exploited for nearly 100 years, yet its origin remains unresolved. In the present study, we characterised eight samples of the reef at four localities in the western Bushveld Complex using micro-X-ray fluorescence and field emission scanning electron microscopy. Our results indicate that the Merensky Reef formed through a range of diverse processes. Textures exhibited by chromite grains at the base of the reef are consistent with supercooling andin situgrowth. The local thickening of the Merensky chromitite layers within troughs in the floor rocks is most readily explained by granular flow. Annealing and deformation textures in pyroxenes of the Merensky pegmatoid bear testament to recrystallisation and deformation. The footwall rocks to the reef contain disseminations of PGE rich sulphides as well as olivine grains with peritectic reaction rims along their upper margins suggesting reactive downward flow of silicate and sulphide melts. Olivine-hosted melt inclusions containing Cl-rich apatite, sodic plagioclase, and phlogopite suggest the presence of highly evolved, volatile-rich melts. Pervasive reverse zonation of cumulus plagioclase in the footwall of the reef indicates dissolution or partial melting of plagioclase, possibly triggered by flux of heat, acidic fluids, or hydrous melt. Together, these data suggest that the reef formed through a combination of magmatic, hydrodynamic and hydromagmatic processes.Graphical abstractDisplay OmittedHighlights•High-resolution element mapping of the Merensky Reef.•Micro-textural characteristics of chromite grains.•Distribution of sulphides and Pt-PGM across the reef lithologies.•Petrogenetic constraints on the formation of the Merensky Reef.
关键词：KeywordsMerensky ReefBushveld ComplexMagmatic sulphidePlatinum-group elementsPGEAnorthosite