Geologic Features And Genesis Research Of Qingguo Graphite Deposit In Tibet

High quality crystalline graphite is a strategic mineral resource in the modern industry,which has the characteristics of high temperature resistance,conductivity,thermal conductivity,lubricity,chemical stability,plasticity and thermal shock resistance.With the discovery of graphene,carbon nanotubes,graphite alkyne and other carbon materials,it marks the arrival of the new material revolution of graphite,and the human society will enter the "Carbon era" from the "Silicon era".Qingguo is the first large-scale graphite deposit discovered and evaluated in Tibet.However,due to the late start of exploration,the research about the characteristics,genetic types and mineralization of this deposit is relatively backward.On the basis of fully collecting and sorting out regional data and previous research results,combined with the latest exploration results of the deposit,the geological characteristics of the ore body are ascertained according to detailed geological investigation and drilling-hole logging.In addition,microscopy,scanning electron microscopy(SEM),zircon U-Pb isotope dating,rock geochemical analysis and carbon isotope composition are help to determine the time of diagenesis and mineralization,and discuss the genesis and the regional metallogenic prospect and prospecting potential.The graphite ore body of the Qingguo deposit occurs in the monzogranite,and the main ore body is in irregular ellipse shape exposed on the surface,generally inclined to the north-east.SEM shows that the useful minerals in the ore are mainly crystalline graphite,with scale,leaf metamorphic structure and unique spherical,bean and disseminated structure,with typical magmatic-hydrothermal type features.The ore-bearing monzogranite is characterized by high silicon,high aluminum,rich alkali,low iron,and poor calcium.It belongs to the high potassium calc-alkaline peraluminous rock series.The main and trace element composition characteristics indicate that it has undergone complex differentiation during the evolution process.The LA-ICP-MS zircon U-Pb age of ore-bearing intrusion is 244.7 ± 1.3 Ma,forming in the middle Triassic,as the product of the south-west subduction of Lancang ocean.The diagenetic age approximately represents the time of graphite mineralization.The carbon isotopic composition of graphite indicates that the ore-forming material of graphite is derived from organic carbon.The Qingguo deposit is controlled by the middle Triassic intermediate-felsic magmatism and high carbon wall-rocks.The ore body occurs in the contact zone of intrusion.The carbon in the stratum is an important source of ore-forming materials for the graphite deposit.There are good metallogenic conditions and prospecting prospects in the region.14 minimum prediction areas and 4 prospecting prospect areas have been identified.In conclusion,the Qingguo deposit is a typical magmatic hydrothermal type graphite deposit.Its genesis is the remelting of the lower Carboniferous surrounding rock by the Middle Triassic magmatism(monzogranite),which results in the recrystallization of the carbon in the strata to form crystalline graphite.The regional conditions of strata and magmatic rocks,and the discovery of many graphite deposits(mineralized target)indicate that there is a good potential for the exploration of crystalline graphite deposit in Sanjiang area,eastern Tibet,the potential resource of graphite is predicted to exceed 11 million tons in the metallogenic belt.