The Types And Metallogenesis Of Basic-ultrabasic Rocks From Hegenshan Area In Inner Mongolia

Hegenshan ophiolite suite is located in the junction part of Siberian and NorthChina Plate, It is comprised of mutually uncorrelated continous blocks such asHegenshan、chaogenshan、zhu’erhengou (wuzinihei)、songgenwula (chonggenshan)、xiaobaliang and so on. Hegenshan ophiolite suite is one of the important Metallogenicbelt Central Asian Orogenic Belt, because of complex geological structure, platesubduction, frequent collision, and developed deep faults. A comprehensive study hasbeen carried out on the describing and discussing the petrography, geochemistry,mineralization of mafic-ultramafic rocks and Hegenshan ophiolite.The mainacheievements obtained in this paper are follows:Firstly, the study on petrography and rock geochemistry indicate that:mafic-ultramafic rocks are the lower part of Hegenshan ophiolite in Songgenwula area,while partial ultramafic rocks are metamorphic peridotite in Zhu’erhengou area. Bothof them have the characteristics of mantle residue.Secondly, we found accumulation complex rocks with Cu-Ni mineralization inZhu’erhengou area, which is the magmatic origin at the first time.Thirdly, Chromite mineralization is mainly produced in the dunite, pyroxeneperidotite, which is closely related to ophiolite suite. That is the product of mantlepartial melting in study area. Cu-Ni sulphide mineralization is mainly produced inpyroxene peridotite with baering olivine structure which suggests it is magmaticorigin in Zhuerhengou area,That is the product of magam through liquation、crystallization differentiation,which come form partial melting of the primitivemantle.Fourthly, the gechemistry analysis and the previous research on ore-bearingbasalt and diabase suggest that Cu-Au deposits formed in Mid-ocean ridge, which isthe product of magmatism and hydrothermal activity in Xiaobaliang mine area.Fifthly, Songgenwula area, Zhu’erhengou area and Xiaobaliang area are belong toone part of Hegenshan ophiolite suite: Songgenwula area represents the mantleperiodite residue of lower part of ophiolite;Most rocks represent upper gabbro wall segment and pillow basalt series. In addition to the existence of mantle residue inZhu’erhengou area; Diabase and basalt in Xiaobaliang area are the Diabase and basaltseries of upper Hegenshan ophiolite.Sixthly, Comprehensive analysis on formation environment, geochronology andtectonic evolution characteristics of Hegenshan ophiolite indicate that Hegenshanophiolite is produced in back-arc basin environment on a subduction belt (SSZ-type)and emplaced in the late Permian or early Triassic. It can be concluded that the finalcollision between the Siberian and the North China plate happened in Hegenshan.