摘要
The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment.Petrography,geochemistry,and field evidence helped to subdivide the metasediments into paragneiss,mica schist,chlorite schist,and quartzite which were derived from greywacke,shale,quartz arenite,litharenite protoliths.They are immature with some mature samples,moderately weathered and reworked Neo-and Post-Archean metasediments.Rare earth element signatures(Chondrite Eu/Eu^(*)≤1),enrichment of light rare earth elements over the heavy ones,and the La/Sc ratio(>0.7)are compatible with those of the intermediate and felsic sources from the upper continental crust.These metasediments were deposited in the continental arc setting and have evolved during Proterozoic times according to the Wilson cycle to form the West Gondwana including NE Brazil.
