Petrography & Geochemistry of the lower Konkiep Terrane, Namibia

The study was carried out on the Kumbis and Kairab Formations of the Sinclair Supergroup in the Konkiep terrane, southern Namibia. There is little geochemical data available for the Kumbis Formation as compared to its correlate the Kairab Formation. The project generated reveals some relationships between the two formations on the basis of petrography and geochemistry. Petrography shows that Kumbis Formation mostly has felsic units that are intruded by mafic dykes, whereas, Kairab Formation has mostly mafic rocks intruded by felsic dykes. Intermediate rocks were rarely encountered and intrusive rocks in both formations range from gabbro through granite-granodiorite. Spider plots by REE chondrite-normalization for both felsic and mafic rocks shows a depleted pattern. Geochemical discrimination plot of Yb ¿ Th/Ta and the Th-Hf-Ta-Zr-Nb system shows a continental arc tectonic setting. Geochemical data shows that the tectonic setting of the area is more of a convergent plate margin then a rift tectonic setting proposed by some authors.