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Occurrence of zoned uvarovite—grossular garnet in a rodingite from the Vumba Schist Belt, Botswana, Africa: implications for the origin of rodingites

Published online by Cambridge University Press:  05 July 2018

A. Mogessie
Affiliation:
Institute of Mineralogy - Crystallography and Petrology Karl - Franzens University Graz, Universitatsplatz 2, A-8010 Graz, Austria
D. Rammlmair
Affiliation:
Federal Institute for Geosciences and Natural Resources, Stilleweg 2, D-30655 Hannover, Germany

Abstract

Based on petrographic, mineralogical and geochemical data, two groups of rodingites have been documented from the polymetamorphic Vumba Schist Belt of Botswana. Group I rodingites contain relict chromite grains with zoned uvarovite-grossular + clinopyroxene + epidote/zoisite ± quartz, whereas group II rodingites contain no chromite and uvarovite. Although the presence of chromite with Cr/(Cr + Al + Fe3+) ratio > 90, similar to chromites found in komatiites, suggests a possible komatiitic origin of group I rodingites, the major and trace element chemical data of most analysed basic rocks from this belt indicate that the protoliths of both groups of rodingites are related to basalt/gabbro of komatiitic affinity. The rodingites formed during the M3 phase of metamorphism.

Type
Petrology
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1994

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