MINOR AND TRACE-ELEMENT CHEMISTRY OF CARBONATES, APATITES AND MAGNETITES IN SOME AFRICAN CARBONATITES

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 in to calcite relative to co-existing dolomite, whereas Fe and Mn favour dolomite. Sr partitions preferentially into calcite relative to co-exi sting apatite, but the light rare-earth elements partition into apatit e. Magnetite from Kerimasi contains up to 13 wt.% MgO and 6 wt.% MnO, extending the known ranges in composition of magnetites from carbonati tes.