The Geochemistry Characteristic of Sidingheishan Mafic-Ultramafic Layered Intrusion, East Tianshan, Xinjiang

The Sidingheishan layered intrusion is located in the eastern of the Huangshan mafic-ultramafic rocks belt,East Tianshan,large-scale,northeast trending,can be divided into north and south intrusion,composes of clinopyroxene peridotite,olivine pyroxenite,olivine norite-gabbro,olivine gabbro,pyroxene amphibolite,gabbro,hornblende gabbro,diorite,and the ultramafic rock phase and gabbro phase often showed a rhythm with interbedded.The petrochemical compositions belong to the tholeiitic series.The chondrite-normalized REE patterns are flat type and positive Eu anomalies,generally enriched in LILE (i.e.,Rb,Ba,U),significant positive anomalies of Sr and Nb,Ta loss.Estimate the MgO and FeO content of the parental magma is 6.23% and 6.60% by the highest Fo values (79.6) of olivine,respectively.The magma experiences olivine,orthopyroxene,clinopyroxene,plagioclase fractionation / cumulate and weakly upper crustal contamination in the parental magma.The high (La/Yb)N ratio (1.550) and (Gd/Yb)N ratio (1.744) indicates that the depth of the magma source may be greater than 90Km; The Th/U ratio characteristic and Th/Yb versus Nb/Yb and La/Ba versus La/Nb diagrams show that the magma source of the Sidingheishan intrusion may be the modified lithosphere mantle by subduction.