Genesis And Prospecting Prognosis Of Zhongba Superlarge Graphite Deposit In Panzhihua

By means of optical thin section identification,fluid inclusion temperature analysis,U-Pb dating of wall rock zircon and carbon isotope testing,the geological characteristics and genesis of the Zhongba Graphite Deposit in Panzhihua City are analyzed,and the prospecting direction of the Graphite Deposit in the future is speculated.Zhongba graphite mining area is located in the western margin of the middle section of Kangdian geoaxis and the western wing of Datian anticline.The deposit occurs in the Datian Formation of the Huili Group of the Pre-Sinian,and the ore-bearing rock series distributes in the mixed granite as residual body.The ore-bearing lithology is mica quartz schist series.The ore minerals are graphite,gangue minerals are mainly quartz and mica with 90%content,and other minerals are less.According to the analysis of inclusion temperature measurement data,the hydrothermal fluids of Zhongba graphite deposit are mainly metamorphic fluids with low temperature and salinity,with the addition of atmospheric water and basin brine.The analysis of fluid inclusion composition shows that the main gas component in the inclusion is CH4.This indicates that the fluid carries considerable organic carbon during the mineralization process.The results also show that the main source of carbon in Zhongba graphite deposit is organic carbon.Zircon 206Pb/238U age of wall rock migmatite shows that the intrusion time of migmatite is 700-800 million years ago,suggesting that the metallogenic age of Zhongba graphite deposit should be in Neoproterozoic era.The value of carbon isotope of graphite ore is in the range of-24.1‰-28.5‰.The distribution of the delta?¹³C values of the samples is relatively concentrated,with a weak difference,which is consistent with the world average level of organic matter?-26±7?.Compared with the graphite samples from other areas,it shows the value of organic carbon as delta 13C.It can be seen that the carbon of Zhongba graphite ore mainly comes from deposited organic carbon.Based on the analysis of geological characteristics,there are no carbonate rocks and metamorphic rocks around Zhongba graphite mining area.This paper considers that the original rocks of graphite mineralization in this area are mainly argillaceous sandstone and silty shale rich in organic matter,and graphite ore is formed through a series of metamorphism.Carbon in graphite ore mainly comes from organic carbon,and there may be a small amount of inorganic carbon added.Under the condition of regional metamorphism,the carbon gradually changes to form crystalline graphite with fine particle size.With the superimposition of migmatization,thermal metamorphism and carbon-rich fluid geology caused by later magmatic intrusion.With the deepening of the degree of graphite metamorphism,the size of crystals increases,resulting in the formation of large scale graphite deposits.The measured data of plane and depth by geophysical spontaneous potential method show that the area located in Zhongba graphite mining area is about 900 m north-east of the plane,and the control depth of the spontaneous potential method for deep graphite ore is 700 m,while the control depth of boreholes for Zhongba graphite ore is 1000 m before,so we think that the future prospecting targets for graphite ore in Zhongba area should focus on these two aspects.Direction:the area of 900 m in NE direction and the deep area of 300-400 m below the current ore-controlling depth of the mining area.