gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1981.044.334.04 Unusual Perovskite Textural Relationships in Olivine Melilitites from Namaqualand-Bushmanland, South Africa Moore A. E. * Department of Geology, University of the Western Cape, Bellville, South Africa

Present address: Falconbridge Explorations (Botswana), PO Box 1463; Gaborone, Botswana.

 6 1981 44 334 147 150 27 6 1980 Copyright © 1981, The Mineralogical Society 1981 Abstract

Textural relationships shown by oxide phases in olivine melilitites from Namaqualand-Bushmanland, South Africa, indicate early crystallization of picroilmenite from a relatively reduced magma. Evolution of a CO2-rich vapour during magma ascent led to an increase in oxygen activity and liquidus temperatures, causing rapid crystallization of titanomagnetite. Higher oxygen activities, together with the increase in calcium activity following CO2 loss from the magma, resulted in perovskite replacing ilmenite as the stable Ti phase.