Study On Petroenesis Of The Shitoukengde Nickel-Copper Bearing Mafic-ultramafic Intrusion,the East Kunlun Orogrn

The Shitoukengde Ni-Cu bearing mafic-ultramafic intrusion is located in the eastern Kunlun orogenic belt on the northern margin of the Tibetan Plateau.This intrusion is composed of mafic-ultramafic rocks.The wall rocks are the biotite plagioclase gneiss and marble of the Baishahe Group of the Jinshuikou Formation.There are three mafic-ultramafic intrusive bodies(No.I,II,and III)in the Shitoukengde area.The exposed area of the No.?intrusion is about 2.3 square kilometers.Invasion from south to east in the gabbro in the Middle Silurian.The exposed area of gabbro is about 3.2 square kilometers.The mafic-ultramafic intrusion on the surface is produced by 4 rock plants of varying sizes.High degree of crystallization differentiation.The No.?intrusion Spread east-west The tendency is south-south east.The No.II intrusion is exposed about 1.5 km west of the No.I intrusion.The area of No.II intrusion is about 0.70 square kilometers.The rock are mainly composed of olivine pyroxenite and pyroxenite.Strong mineralization of limonite in surface rocks.It obvious that nickel blooms are seen locally.There are seven ore bodies in the No.?and No.II intrusions.The ore bodies in the intrusions have similar mineral structures.Among them,the main minerals are pyrrhotite,pentlandite,chalcopyrite and a small amount of ilmenite.The ore features posses sponge meteorite structure,,massive structure,and disseminated structure.According to the results of the electronic probes,the Fo of the Shitoukengde mafic-ultramafic intrusion are 83.22?89.12.The Ni content of peridotite olivine in Shitoukengde mafic-ultramafic intrusion is 880?1878?g/g.The component En of orthopyroxene endmembers is 84.8?89.69.The orthopyroxene end member component Wo is 0.43?3.6.The component Fs of orthopyroxene end member is 7.26?11.9.Orthopyroxene is mainly enstatite.Shitoukengde intrusion belongs to mafic-ultramafic rock mass.The rock type belongs a tholeiitic series.The diagrams of rare earth element show that the mafic-ultramfic rocks are enriched with large ionic lithophile elements.The rocks are characterized by enrichment of large ion lithophile elements and light rare earth elements,and relative depletion of high field strength elements.The correlation analysis of the elements in the Harker diagram shows that the magma may have undergone fractional crystallization of olivine,orthopyroxene,clinopyroxene and plagioclase.(Nb/Yb)_PM-(Th/Ta)_PMhas a good positive correlation,showing the existence of assimilation and contamination.The contaminated material of the sample mainly comes from the upper crust.Combining with the regional tectonic evolution,the Shitoukengde intrusion was formed in the late Middle Silurian.It is formed in a post-collision extensional setting.Subduction of oceanic slabs caused slabs to plate uplift fracture.This process gave rise to an upwelling of the asthenosphere.After separation crystallization and assimilation contamination,the Shiokengde mafic-ultramafic was formed.