GEOCHEMISTRY AND PETROGENESIS OF SPINEL LHERZOLITE XENOLITHS FROM BOEUN, KOREA

Abstract

Geochemical characteristics of spinel lherzolite xenoliths, enclosed in Miocene alkali basalt from Boeun, Korea, provide important clues for understanding the lithosphere composition, equilibrium temperature and pressure conditions, and depletion and enrichment processes of subcontinental lithospheric mantle beneath Boeun. The spinel lherzolite xenoliths with protogranular to porpyroclastic textures were accidentally trapped by the ascending alkali basalt magma. The spinel lherzolite xenoliths originated at depths between 50 and 63km with equilibrium temperatures ranging from 847 to 1030°C. These xenoliths may have undergone small degrees (1–2%) of partial melting and cryptic metasomatism by an alkali basaltic melt. Based on Sr and Nd isotope compositions, the subcontinental lithospheric mantle beneath Boeun was heterogeneous and similar to that beneath East China and Central Mongolia rather than the Japanese Island Arc.