Association of platinum-group elements with chromitite within the Merensky reef, Western Limb, Bushveld Complex: Results of a high resolution mineralogical and geochemical study

作者：Magson Justine; Tredoux Marian; Roelofse Frederick

来源：Journal of African Earth Sciences, 2018, 144: 161-175.

DOI：10.1016/j.jafrearsci.2018.04.014

• Bushveld complex
• Merensky reef
• Pegmatoidal
• Non-pegmatoidal
• Chromitite

We present the results of a high-resolution mineralogical and geochemical study conducted across three intersections of Merenslcy reef at Impala Platinum Mines on the Western Limb of the Bushveld Complex. We studied two intersections of non-pegmatoidal Merensky reef and one intersection of non-pegmatoidal Merensky reef in an attempt to reconstruct the petrogenesis of this economically important ore horizon and in order to establish the relationship between non-pegmatoidal and pegmatoidal reef intersections. Our results indicate a much stronger correlation between PGE and Cr than between PGE and S (or Cu as a proxy for sulfides), which favours a model in which chromite and associated PGEs were introduced from a deeper staging chamber to result in the formation of the chromitite layers of the Merensky reef. The geochemistry of chromite in the Merensky reef is suggestive of the fact that the bottom chromitite layer of the pegmatoidal reef is a lateral correlate of the chromitite of the non-pegmatoidal reef, in which only a single chromitite layer occurs. We propose that the Merensky reef at Impala Platinum Mines is a product of the introduction of chromite-laden basal flows into the Bushveld Complex magma chamber and that the relationship between pegmatoidal and non-pegmatoidal reef intersections is related to non deposition, rather than erosion, as was shown to be the case at other localities within the Western Limb.

• 出版日期2018-8