New Mössbauer measurements of Fe3+/ΣFe ratios in chromites from the early Proterozoic Bushveld Complex, South Africa
作者： Jacob Adetunji , Simon Everitt , Hugh Rollinson
DOI: 10.1016/J.PRECAMRES.2013.01.007
关键词: Magma 、 Chromite 、 Critical zone 、 Narrow range 、 Redox 、 Geology 、 Proterozoic 、 Mössbauer spectroscopy 、 Oxidation state 、 Geochemistry
摘要: Abstract New Mossbauer measurements of Fe 3+ /ΣFe ratios from chromites in the Upper Critical Zone Rustenberg Layered Suite Bushveld Complex, South Africa vary between 0.139 and 0.232 (mean = 0.185 ± 0.025 (1 σ )). A more oxidised group have range 0.766–0.738. Textural studies indicate that these samples experienced post-magmatic oxidation during brecciation. The chromitites a narrow cr# (0.618–0.671) are Fe-rich. There is some variability with stratigraphic height implying variation composition parental magmas. Variation within less attributed to variations state parent magma, which turn thought reflect different degrees mixing magmatic sources differing states. Comparison geologically recent similar suggests upper mantle redox conditions remained unchanged since 2.06 Ga.
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