Minor and Trace Element Chemistry of Carbonates, Apatites and Magnetites in Some African Carbonatites

J. B. Dawson, I. M. Steele, J. V. Smith and M. L. Rivers
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
Department of Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave, IL 60637, USA
Department of Geophysical Sciences and Consortium for Advanced Radiation Sources, University of Chicago, 5734 S. Ellis Ave, Chicago, IL 60637, USA

Abstract: In calcites and dolomites in seven African carbonatites, SrO, FeO and MnO occur in concentrations from 1 to 2 wt.%, whereas Ce, Y, Cu and Zn occur only at the ppm level. Sr, Ce and Y partition preferentially into calcite relative to co-existing dolomite, whereas Fe and Mn favour dolomite. Sr partitions preferentially into calcite relative to co-exisiting apatite, but the light rare-earth elements partition into apatite. Magnetite from Kerimasi contains up to 13 wt.% MgO and 6 wt.% MnO, extending the known ranges in composition of magnetites from carbonatites.

Keywords: mineral chemistry • carbonatite • carbonate • apatite • magnetite • Africa

Mineralogical Magazine; June 1996 v. 60; no. 400; p. 415-425; DOI: 10.1180/minmag.1996.060.400.03
© 1996, The Mineralogical Society
Mineralogical Society (www.minersoc.org)