Petrogenesis of the Swaziland and Northern Natal Rhyolites of the Lebombo Rifted Volcanic Margin, South East Africa

The Jozini and Mbuluzi rhyolites and Oribi Beds of the southern Lebombo Monocline, southeastern Africa, have geochemical characteristics that indicate they were derived by partial melting of a mixture of high-Ti/Zr and low-Ti/Zr Sabie River Basalt Formation types. Compositional variations within the...

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Bibliographic Details
Published in:Journal of petrology 2007-01, Vol.48 (1), p.185-218
Main Authors: Miller, Jodie A., Harris, Chris
Format: Article
Language:English
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Summary:The Jozini and Mbuluzi rhyolites and Oribi Beds of the southern Lebombo Monocline, southeastern Africa, have geochemical characteristics that indicate they were derived by partial melting of a mixture of high-Ti/Zr and low-Ti/Zr Sabie River Basalt Formation types. Compositional variations within the different rhyolite types can largely be explained by subsequent fractional crystallization. The Sr- and Nd-isotope composition of the rhyolites is unique amongst Gondwana silicic large igneous provinces, having ɛNd values close to Bulk Earth (−0·94 to 0·35) and low, but more variable, initial 87Sr/86Sr ratios (0·7034-0·7080). Quartz phenocryst δ18O values indicate that the rhyolite magmas had δ18O values between 5·3 and 6·7‰, consistent with derivation from a basaltic protolith with δ18O values between 4·8 and 6·2‰. The low-δ18O rhyolites (
ISSN:0022-3530
1460-2415
DOI:10.1093/petrology/egl061