Zircon Hf Isotope Characteristics and Source of Mafic-ultramafic Intrusions in Huangshan Region, Xinjiang

Huangshandong, Xiangshan and Tudun plutons are multiple-phase intrusive complexs, which show clear intrusive contact boundaries with wall rock. These intrusions are mainly composed of peridotite and gabbro. Peridotite has orthopyroxene or plagioclase, while clinopyroxene is augite or diopside. The Huangshandong, Xiangshan and Tudun plutons are mainly tholeiitic in composition, and some of them show calc-alkaline and alkaline characteristics. Chondrite-normalized rare earth element patterns show flat feature or slight enrichment in LREE. Zircon Hf isotopic compositions indicate that the Huangshandong, Xiangshan and Tudun intrusive complexes are derived from the depleted mantle source.Huangshandong, Xiangshan and Tudun plutons are not the remnants of subducted oceanic crust or Alaska-type rocks, but they are formed by the underplating of depleted mantle source.