Chemical composition of rocks and minerals from the Weddell Sea

Studied samples represent bedrock occurrences rather than products of transportation by floating ice. Two regions were distinguished: the East Antarctic margin (submarine Maud Ridge) characterized by intensive destruction and oceanization of the continental crust, and the northwestern part of the Weddell Sea (Powell Basin), where spreading processes are superimposed on the weakly destructed continental crust. Volcanic rocks of the Maud Ridge derive from an enriched mantle source. The following geologic section was observed: young fresh porous basaltic porphyrites underlain by older massive basaltic porphyrites metamorphosed under greenschist-facies conditions. Presence of granulite-facies rocks suggests continental origin for these rocks. Mineralogical and geochemical features of magmatic rocks collected from various areas of the Weddell Sea floor may indicate contribution of deep fluids. We believe that the magmatic replacement of the Precambrian granite-metamorphic complex of the continental basement by basic-ultrabasic mantle material played the main role in transformation of the continental crust into the secondary oceanic crust. This process occurred under significant contribution of fluid flows and uneven activity of geologic processes, in contrast to formation of the primary oceanic crust because of seafloor spreading. Our results suggest that the basement of the Weddell Sea is of continental origin and has experienced extensive destruction.