Composition and Formation of Walvis Ridge Volcanics

Resumo

Abstract—The paper summarizes material on the chemical composition of Walvis Ridge volcanics. Analysis showed that the formation of the eastern and central parts of the ridge in the Cretaceous and Paleogene was determined primarily by the appearance of fractured decompression centers, which resulted from strike-slip–pull-apart dislocations during the Gondwana breakup. Basalts of the central part of the Walvis Ridge show signs of crustal contamination. Apparently, in the Cretaceous and Paleogene, the Tristan plume indirectly participated in the formation of Walvis Ridge rocks, partially enriching with its material melting centers that occurred in thick (>20 km) deformed crust. The spreading factor manifested itself in the Upper Cretaceous (tholeiitic volcanism of the eastern part of the ridge) and in the Neogene–Quaternary, when the thickness of the newly formed oceanic crust began to decrease. This allowed the “dying” Tristan plume to form a system of volcanic seamounts in the western part of the Walvis Ridge.