GEOCHEMICAL HETEROGENEITY OF THE UPPER MANTLE BENEATH THE CENTRAL ASIAN MOBILE BELT

Abstract

Geochemical heterogeneity in the mantle beneath the Central Asian mobile belt was considered for the Tien Shan and Baikal-Mongolian regions. The depletion of ultramafic material and the supply of deep-seated fluids (melts) led to a strong alteration and differentiation of the mantle beneath Tien Shan. In contrast, the lherzolite mantle beneath the Baikal-Mongolian region is characterized by a much less significant reworking. These regions differ in their scale of mantle metasomatism and its fluid, geochemical, and redox conditions. There is a geochemical relation between the compositions of mantle material, magmatic rocks of different ages and generation depths, and the Archean crust within the comparable regions. The geochemical (metallogenic) profile of these regions generally correlates with the rare-element features of mantle-metasomatics and alkaline basalts.