The Characteristics And Origin Of The Dikes In Jinchuan Cu-Ni(PGE) Sulfide Deposits,Gansu Province

Located in the western of North China,Jinchuan Cu-Ni sulfide deposits are hosted in the mafic-ultramafic rocks,which is the world's third largest copper-nickel sulfide deposits.The occurrence of five hundred million tons of copper-nickel sulfide deposits,Jinchuan deposits are the largest Ni,Cu,PGE resource suppliers.The grade of Ni is 1.2%,and the grade of Cu is 0.7%.A dike is an important record of magmatic evolution.Temporal and spatial relations of the dikes and the ore body and rock mass are close,so the research of dikes can help know the genetic types of ore deposits and the tectonic setting.In this paper,Jinchuan dikes were researched through petrography,mineralogy and geochemistry,etc.It classified the dikes of the Jinchuan deposits.There is a preliminary discussion on the petrogenesis and tectonic setting of the dikes.The main research results are as follows:1.Jinchuan Cu-Ni(PGE)sulfide deposits are hosted in the mafic-ultramafic rocks,The main dike types are diabase and diorite porphyrite.The diabase mainly composed of pyroxene and plagioclase,and diorite porphyrite composed of plagioclase,potassium feldspar and hornblende.By electron probe test,we can see the pyroxenes of the dikes are diopside,augite,enstatitie and the feldspars are andesine and labradorite.Pyroxene and amphibole occur chloritization;2.The dikes in the region overall has the characteristics of the high of Mg,Fe,low of Na2O + K20.Dikes in LREE and LILE enrichment,HREE ratios losses,the Eu anomaly is not obvious;3.Magma experienced fractional crystallization of olivine and orthopyroxene during magma evolution.The tectonic setting of dikes' origin is the intraplate environment.The geochemical features suggest that the dikes have the characteristics of OIB.Therefore,it is speculated that the dikes in Jinchuan deposits were produced by the cause of mantle plumes in continential rift environment.4.Platinum group elements of dikes are depleted,which indicates that the parent magma of dikes is residual magma after the segregation of sulfide liquid.