LITHOPHILE TRACE ELEMENTS IN MINERALS OF A COMPLEX MANTLE XENOLITH

Abstract

The paper reports on a study of the texture and mineral composition (including the distribution of various trace elements) of a complex mantle xenolith, containing apatite and mica. This xenolith was found in the northern part of Mongolia, in the Shavarin Tsaram volcanic structure, which has already been described in various publications. It is the first apatite find in plutonic xenoliths within Mongolia and the second for the Asian continent as a whole. The main result of this work is that it has revealed the mineral forms in which lithophile trace elements such as tantalum, hafnium, cesium and thorium accumulate in upper mantle rocks. Another, especially noteworthy feature is the demonstrated fact that the phlogopite (a mineral regarded as a typical indicator of mantle metasomatism) of upper mantle metasomatites contains negligible concentrations of REE, and that the principal accumulator minerals of rare-earth and particularly volatile elements in this case are apatite and clinopyroxene.