GEOCHEMISTRY OF THE UPPER MANTLE UNDER THE SOUTH RIM OF THE ALDAN SHIELD

Abstract

To ascertain the geochemical specificity of the upper mantle under the south rim of the Aldan shield and the Stanovoy zone, we studied xenoliths from the Tokinskiy Stanovik lava field. The latter is underlain at the surface by Cenozoic alkalic basalts and belongs to the vast Asian belt of alkalic basalt volcanism, which includes the alkalic basalt fields of Vitim, Dzhida, Udokan, Mongolia and Manchuria. This study has revealed the very mixed composition of the material in the subcrustal zone. The particulars of the distribution of petrogenic elements in enriched and depleted spinel lherzolite reflects different degrees of melting of the primitive parent substrate. The geochemical studies have also shown that the upper mantle here consists of primary, undifferentiated material and is similar in composition to the primitive mantle of oceanic islands.