Sequence of crystallisation of pegmatites: the Angola case

Abstract

The Precambrian basement of Angola contains several pegmatite fields, although most of them have not been studied yet. Some of them include pegmatites devoid of rare elements, as those found close to Caxito, about 100 km ENE Luanda. These pegmatites are exploited for the production of industrial minerals. Moreover, some rare element pegmatite fi elds occur close to Namibe, in the desertic part of the southwest of the country. These pegmatites were prospected for Be and Ta in the 1960's. The distribution of the pegmatite types, as well as the exceptional quality of the outcrops, due to lack of weathering or soil cover, allow a complete sampling in order to study the evolution of a pegmatite field, from parental granites to barren pegmatites, beryl-columbite-phosphate pegmatites and spodumene pegmatites. Furthermore, the internal evolution of each pegmatite type has been also studied.