Tectonics of the Southern Ocean passive margins in the Africa – East Antarctica region

Based on geological and geophysical data for the conjugate margins of Africa – East Antarctica, the peculiarities of preparation of the breakup central Gondwana supercontinent are discussed. When using the historical approach, a significant inheritance of the Middle-Upper Jurassic tectono-magmatic development from the preceding time is shown. The first location of tectono-magmatic activity in zones of weakness on the proximal margin, its subsequent migration to distal margins and further oceanic opening is established. The geochemical features of magmas of the region and their sources are under discussion. Evidence for the decisive influence of the Karoo-Mod plume on the development of magmatism is presented. A significant feature of the plume manifestation is considered: the presence of high-magnesian ferruginous picrites , formed by melting of a pyroxenite source with specific composition, coinciding with the central part of the plume and corresponding to the earliest eruptions. We determined the source of magmatism at the initial stage could have been the substance of a rising plume, and magmas reached the surface through existing fractures without interacting with the lithosphere. In the course of evolution, the admixture of pyroxenites in the source decreased and the melts acquired the features of the melting lithospheric mantle, which was reflected in the isotopic characteristics of the melts with a predominance of the enriched EM II component. The structure and magmatism of the Southern Ocean and South Atlantic are compared. Also discussed the locations of the Mesozoic Karoo-Maud and Tristan plumes, as well as the zones of the subsequent breakup of Gondwana, above the margin of the African superplume, indicating a relationship between surface and deep-seated events, is discussed.

Regularities in variations of the pume volcanics composition in the Southern Atlantic and at the African plate

The action of the African Superplume provided input and accumulation of the volatile, alkaline and some others elements at the base of continental lithosphere. Transformation and interaction of these components with mantle peridotites took place under the African continental plate of the great thickness. Generation of low silica and rich in CO2 melts occurs at the great depth: this is the family of kimberlites, melilitites and carbonatites. At the shallower levels of the lithospheric plate the melts of basalts originated; they are more rich in SiO2 and poor in volatiles. The origin of deep generated volcanics was controlled by the pressure of CO2 in the fluids. The melting of basalts is connected mainly with tectonic position.