Element mapping the Merensky Reef of the Bushveld Complex

Geoscience Frontiers

Wolfgang Maier¹  Gareth Moorhead²  David Reid³  William Smith⁴  Stephen Barnes⁴  Bartosz Karykowski⁵ 

[1] Corresponding author.;CSIRO Mineral Resources, Perth 6160, Australia;CSIRO, Clayton, Victoria, Australia;School of Earth and Ocean Sciences, Cardiff University, Cardiff CF240DE, United Kingdom;University of Cape Town, South Africa;

关键词: Merensky Reef;    Bushveld Complex;    Magmatic sulphide;    Platinum-group elements;    PGE;    Anorthosite;   

DOI  :  

来源: DOAJ

【 摘 要 】

The 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 and in situ growth. 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.

【 授权许可】

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