Geology and Genesis of the Mafic—Ultramafic Complexes in the Huangshan—Jingerquan（HJ） Belt,East Xinjiang

More than twenty mafic-ultramafic complexes,which host several medium-or large-sized Cu-Ni deposits,occur the Huangshan-Jingerquan(HJ) belt in East Xinjiang. Rock types in these complexes are ptrdominated by peridotite, pyroxene peri-dotite, olivine pyroxenite, gabbronorite, orthopyroxene gabbro, troctolite, gabbro and diorite. The ultramafic rocks are relatively Fe-enriched and are characterized by an as-semblage of olivine+orthopyroxene+clinopyroxene+hornblende±plagioclase without obvious metamorphic textures. Chemically, these complexes are relatively Fe-enriched and show a tholeiitic trend of evolution. The complexes in this blet are intruded under the extensional environment in a Mid-Carboniferous back-arc basin. They can be consid-ered as a new type of mafic-ultramafic complexes in orogenic belts, as designated by the name of the East-Xinjiang-type complexes.