Unusual Perovskite Textural Relationships in Olivine Melilitites from Namaqualand-Bushmanland, South Africa

A. E. Moore*
Department of Geology, University of the Western Cape, Bellville, South Africa
*Present address: Falconbridge Explorations (Botswana), PO Box 1463; Gaborone, Botswana.

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.

Mineralogical Magazine; June 1981 v. 44; no. 334; p. 147-150; DOI: 10.1180/minmag.1981.044.334.04
© 1981, The Mineralogical Society
Mineralogical Society (www.minersoc.org)