Structure Of Alteration And Mineralization In Nankeng Ore Segment Of Jiama Copper Polymetallic Deposit,Tibet

The Jiama deposit is one of the most extensive super-large copper polymetallic deposits in the Gangdese metallogenic belt in Tibet.According to the latest exploration results,the Jiama mining area can be subdivided into three main mining segmenst,namely the main mining segment,the Nankeng mining segment and the Zegulang northern mining segment.Among them,the Nankeng ore segment is controlled by the Tongshan slip system,which mainly forms a large skarn ore body occurs in shallow stratum with rich grade.Because of that,the Nankeng ore body has extremely high economic value.Although the Jiama deposit has carried out in-depth theoretical research,the Nankeng mining segment was founded late,which makes the research level relatively weak.The mineralization and alteration structure,especially the controlling factor about this ore body is still unclear.This paper focuses on the basic geological features of the Nankeng ore section.Analysis the mineralization and alteration structure of the Jinma Nankeng ore segment through describe the drilling and microscopic identification.At the same time,reveal the skarn type,the characteristics of the composition,the composition of the original rock,and the distribution law of the ore-forming elements.In order to reveal the key control factors restricting the formation of the Nankeng ore body.The main achievements of the article are as follows:1)Nankeng mining segment is one of the mining segments in Jiama deposit with important economic value.The ore segment mainly occurs in the Tongshan gliding nappe,rich in Cu,Pb,Zn.And controlled by the gliding nappe,diagenetic interface of the marble of the Duodigou Formation and the Linbuzong Formation,and the emplacement of the concealed rock mass in the western part of the ore segment.2)In the ore segment,mineralization is mainly include skarn type's Cu,Pb,Zn mineralization.Skarn is mainly composed of calcareous and external skarn.The mineral composition of skarn is mainly garnet,diopside,wollastonite and a small amount of idocrase,chlorite and epidotite.Metal mineralization include bornite,galena,sphalerite,chalcopyrite,pyrite and a small amount of molybdenite.Among them,the bornite is closely related to the wollastonite-garnet skarn,and the galena and sphalerite are closely symbiotic.3)Recover the rock with strong alteration and deformation in the Nankeng ore segment to the original rock,find that the rock type in the mineralized enrichment zone showes obvious lithologic disorder replacement,which is significantly different from the characteristics of the main ore section..In the Nankeng ore segment,multiple boreholes reveal from shallow to deep.The rocks distribute in chaosm,not strictly controlled by the horizon.At the same time,karst gradual or transitional areas,the skarnization is relatively strong,and the mineralization is also more concentrated.4)The original rock recovery,alteration zoning characteristics and metal element mineralization enrichment trend of the transverse and longitudinal typical sections in the Nankeng ore section reveal that the skarnization strength is positively correlated with mineralization.That is,the stronger the skarnization degree,the more enriched the mineralization.At the same time,the enrichment rules of mineralization in the Nankeng segment further reveals that the segment presents two enrichment centers in the west and northeast,and the mineralization enrichment in the west may be related to the liquid fluid exsolution from the concealed porphyry which was detected.The mineralization and enrichment in the northeastern part may be the production of the concealed porphyry outside the ore segment.In summary,the formation of the ore body in the Nankeng ore segment may be the result caused by a variety of reasons.Such as the large-scale hydrothermal fluid dissolution of the buried porphyry,the lithologic interface of siliceous and calcareous rocks,and the large number of cracks in the front edge of the gliding nappe.