BARIUM AND STRONTIUM IN THE UPPER MANTLE OF THE PAMIRS AND TIEN SHAN

Abstract

The distribution of Ba and Sr in deep-seated xenoliths, mantle alkaline melts, and their minerals from the Pamirs and Tien Shan and some other regions was considered. In contrast to ordinary magmatic series, the mantle rocks show a correlation of Sr with both Ca and alkalis. The most extensive accumulation of Ba and Sr in the upper mantle occurs during the processes of mantle metasomatism and melting of metasomatized materials. The influx of these elements is probably related to ultradeep plume-type sources. Ba and Sr were transported from the mantle into the crust by both high-temperature alkaline melts and low-temperature hydrothermal solutions. It is supposed that the late Alpine celestite deposits of the huge Sr province of the Mediter-ranean belt are of mantle origin. Geochemical provinces show distinctive concentrations and proportions of Ba and Sr in mantle-derived alkaline basic rocks, metasomatic rocks, and their minerals. The type of Ba-Sr relations is inherited by crustal rocks.