OSMIUM ISOTOPE DETERMINATION ON MANTLE-DERIVED PERIDOTITE XENOLITHS FROM PANSHISHAN WITH N-TIMS

The Os-187/Os-188 ratios of spinel Iherzolite xenoliths from Panshisha n determined with N-TIMS are lower than that of the primitive mantle, which shows depleted mantle characteristics. Their positive correlatio n with Al2O3/MgO suggests that the geochemical behavior of trace eleme nts Re and Os is similar to that of Al2O3 and MgO respectively during the magmatic evolution and Re-Os isotopic system is largely immune to mantle metasomatism. A model age of 2.8-3.4 Ga obtained by Os-187/Os-1 88-Al2O3/MgO correlation might represent the homogeneous age of the ma ntle lithosphere beneath the area.