Indian continental crust recovered from Elan Bank, Kerguelen Plateau (ODP Leg 183, Site 1137)

Abstract

At Site 1137 on Elan Bank of the Kerguelen Plateau, a large igneous province in the southern Indian Ocean, a fluvial, volcaniclastic, polymict conglomerate and a fluvial sandstone are intercalated with subaerially erupted tholeiitic basalt flows. Clasts recovered from the conglomerate have highly variable lithologies, including alkali basalt, rhyolite, trachyte, granitoid and gneiss, Major and trace element abundances and whole-rock isotopic data for the sandstones, the conglomerate matrix and representative clasts from the conglomerate are used to infer the origin of these diverse rock types. The gneiss clasts show an affinity to crustal rocks from India, particularly those of the Eastern Ghats Belt and its possible East Antarctic corollary, the Rayner Complex. The felsic volcanic clasts an not genetically related to the intercalated basalt flows, despite being erupted contemporaneously with these basaltic magmas. These felsic volcanic clasts probably formed from partial melting of evolved upper continental crust. The granitoid also probably formed by partial melting of continental crust and could be an intrusive equivalent of the felsic volcanic rocks. In contrast, the alkali basalt clasts have isotopic compositions that are more similar to those of the tholeiitic basalt flows recovered at Site 1137: however, these clasts are highly alkalic (tephrite to phonotephrite) and have a distinct petrogenesis from the tholeiitic basalt flow units.