The geochemistry of mafic and ultramafic rocks in the Wami River granulite complex, central coastal Tanzania

Abstract

The geochemistry of mafic and ultramafic rocks in the Wami River granulite complex of the central part of the coastal region, Tanzania, suggests that their protolith consisted of basaltic rocks with a calc-alkaline differentiation trend. Some of the ultramafic rocks show primitive chemical characteristics including high (Mg/Mg + Fe_tot) ratios and high Ni contents. These primary magmas later evolved mainly by olivine fractionation to yield the parent magmas which cooled to form the protolith of the bulk of the mafic granulites. The effect of the granulite facies metamorphism on the geochemistry of the rocks is restricted to depletion of Nb and Rb and possibly the enrichment of Ba.