Petrology Characteristics And Ore-bearing Analysis Of Genie Southern Granitoid Of Ganzi Country In Western Sichuan

The Genie granite pluton is located in Litang and Batang county,the western of Sichuan province.Considering the tectonic position,it lies to the middle of the Yidun-Shaluli Island Arc Belt,while the study area belongs to the first-order tectonic unit of the Qiangtang-Sanjiang orogenic system,the secondary unit belongs to the Yidun-litang Arc Basin System,and the third-order tectonic unit is attached to the Yidun-Shaluli Island Arc Belt.Through summarizing the previous research data,it is found that the Genie granite is the kind of complex massif consists of the stage of Yanshan and the phase of Yanshan,and between the two phases of the rock mass are intrusive contact from the north to the South.However,most of the previous studies about the rock body are mainly concentrated in the Himalayan period,there are a lot of research needs to do about the rock mass of the Yanshanian.So,this article is based on the background of the southern granite of Genie,as the Yanshanian period.It needs to discuss its origin,tectonic setting and tectonic-magmatic evolution of granite through the petrographic features,diagenetic age and geochemical characteristics.Based on the relationship between tectono-magmatic evolution and mineralization of the Yanshanian in the Yidun island arc,to analyze and discuss the geotectonic background and the ore-bearing potential of Genie granite.The main lithology of the southern granite of Geni are monzonitic granite,the results of U-Pb geochronology of the two zircons are 91.9±2.9Ma(MSWD=7.9,N=7)and 91.5±1.1Ma(MSWD=2.3,N=12),it turns that the diagenetic age of the rock body is the early Cretaceous period of the late Yanshanian.With the main,trace and rare earth elements test of the rock mass,it is found that SiO2 content ranges from 73.61% to 76.69%,Al2O3 content varies between 12.24% and 14.01%.According to the relation between SiO2 and other main elements,it comes to a decision that the rock belongs to high-k calc-alkaline series and shoshonite series.The aluminum saturation index A/CNK is greater than 1,it is part of the weakly peraluminous rock,while the consolidation index is higher than 1.05,It has features of S granite.The ratio of CaO/Na2 O is under 0.3,which indicates that the source of magma are argillaceous rocks.The trace elements show that the incompatible elements of Rb,Th,U,etc.are enriched,while the large lon lithophile elements of Ba,Sr,P,Ti,etc.are lossed.The average of Nb* which is lower than 1 is 0.37,it is indicated that the source of magma is mixed with material which comes from continental crust or granitic rocks.Also the ratio of Rb/Sr and Rb/Ba can be used to estimate the source of magma.The rare earth elements,?REE ranges from 86.74?g/g to 260.51?g/g,the average is 211.84?g/g,LREE changes from 83.89?g/g to 252.35?g/g,the average is 196.84?g/g,whiles HREE are between 2.85?g/g and 33.42?g/g,the average is 15.01?g/g.The numerial number of ?Eu changes from 0.08 to 0.34,the average of ?Eu is 0.18.With the feature of crustal-derived granitic magma,the loss of Eu element shows a high degree of magmatic crystallization differentiation.While the average of ?Ce is 1.03 with no obvious abnormity,it turns that the granite is crustal anatectic granite,which is S type granite.According to the spider diagram of trace elements,the pattern chart of rare earth elements and the discriminant diagram of tectonic settings,it concludes that the southern granite of Genie is the type of post-orogenic granite which formed in the syn-collisional setting during the late stage of orogeny.The main types of ore deposits that related to yanshanian granite in Yidun Island Arc,has been discovered are skarn,hydrothermal and porphyry.The monzonitic granite and K-feldspar granite are associated with the rare earth minerals,the alkali granite with K2O>Na2O is related to W,Sn,Mo,Bi,Be,and the biotite granite is associated with W,Sn,the two-mica granite is linked to W,Sn,Mo,Bi,Be,and the muscovite-granite is associated with Be,Nb,Li,Ta,Rb.In this paper,it concludes that the ore-bearing potential of the southern granite of Genie is poor,and it has potential prospecting potential for rare and rare earth deposits,through three aspects of the characteristic of major element,the combinations of symbiotic element and the part of geochemical parameters.