The nickel-mineralized Poshi ultramafic intrusion is situated in the southern margin of Baidiwa fault. Sulfide mineralization mainly occurs in the（plagioclase-bearing）wehrlite， lherzolite and dunite. The olivine in Poshi ultramafic rocks show wide range of compositions， with Ni 767×10-6～4 580×10-6 and Fo 76.8～89.6. The Mg#and Cr# in Cr-spinel from Poshi intrusion vary from 13.2 to 43.2 and 48.8 to 64.8，respectively. The variations of Cr2O3 and Al2O3 contents show negative correlations in primitive Cr-spinel，while the relatively small variations of Cr2O3 and Al2O3 in altered Cr-spinel show positive correlations. The stratigraphic variations of olivine compositions indicate Poshi intrusion formed in a much dynamic environment. The replenishment of magma with stable composition， the continuous upward power and the fast crystallization of olivine in upper part，result in different variations of the olivine compositions in different depth. The MgO and FeO contents in estimated magma compositions for Poshi are 14.49％ and 10.01％， respectively. Our modeling results show that the Ni contents in olivine are controlled by both olivine crystallization and sulfide segregation， and the olivine obviously react with sulfide by Fe-Ni exchange. The high Fo in olivine，high MgO in parental magma，mass of plagioclase occurring in ultramafic rocks，high mineral crystallization temperature and arc-like Cr-spinel compositions，indicate that the Poshi parental magma was derived from the previously-modified mantle，and the partial melting of the metasomatized lithospheric mantle is thought to have resulted from heating by mantle plume activity or by upwelling asthenosphere associated with lithosphere delamination.
Xue Shengchao,Qin Kezhang,Tang Dongmei et al. Olivine and Cr-spinel constraints on the petrogenesis，mineralization and source characteristics of nickel-mineralized Poshi intrusion，NE Tarim[J]. Chinese Journal of Geology, 2016, 51(4): 1181-1203.