FLUORINE AND CHLORINE IN UPPER-MANTLE MIN ERALS FROM THE SOUTHERN TIEN-SHAN

The contents of fluorine and chlorine in mantle micas, amphiboles, and apatite were used to distinguish between two provinces of alkali basa lts: southern Tien Shan and Mongolia. The minerals bear similar conten ts of halogens within the framework of a single fluid-magmatic system, which comprises a range of rocks and minerals from the metasomatized mantle source rocks (xenoliths and megacrysts) to alkali basite melts (phenocrysts and cumulates). All of the minerals in question become pr ogressively enriched in F and depleted in Cl from the spinel to the di amond mantle depth facies as the composition of the main volatile comp onents changes, f(O2) decreases, and the K/Na ratio increases.