Vanadium grossular from the Mozambique metamorphic rocks, south Kenya

Green vanadium grossulars occur as porphyroblasts in calc-silicate-graphite gneiss associated with marble, pelitic-psammitic gneiss and granitoid gneiss in the Mozambique metamorphic belt, south Kenya. Calc-silicate-graphite gneiss contains scapolite, vanadian zoisite, vanadian diopside, vanadian sphene and vanadian magnetite, in addition to vanadium grossular. The vanadium grossular porphyroblasts are mantled by a kelyphitic rim that consists mainly of symplectic intergrowth of fine-grained scapolite, vanadium grossular, vanadian diopside, vanadian sphene, vanadian magnetite, plagioclase, calcite and quartz. Vanadian minerals (vanadian muscovite, vanadian zoisite, vanadian sphene and vanadian rutile) also occur in the marble. The occurrence of scapolite and the enrichment in vanadium suggest that the protolith of calc-silicate-graphite gneiss was evaporite or related sediment. The mode of occurrence of vanadium grossular in Kenya is quite similar to that in the Sør Rondane Mountains, East Antarctica. The vanadium-grossular-bearing gneisses in Kenya might be correlated with those in Antarctica, since the Sør Rondane Mountains had continued from the Mozambique metamorphic belt before the breakup of Gondwanaland.