Geochronology And Geochemical Characteristics Of Ore Bearing Porphyries In The North-Zegulang Ore Segment,jiama Deposit,Tibet

the North-Zegulang Ore Segment is located in the northeast of Jiama mining area,which is an important ore block related to complex rock mass newly discovered in Jiama mining area.Geological survey and borehole logging reveal that the complex rock mass contains many rock types,such as monzonitic granite porphyry,granodiorite porphyry,quartz diorite porphyry and diorite porphyry.Meanwhile,thick porphyry copper molybdenum orebodies are developed.In this paper,zircon La-ICP-MS U-Pb geochronology and whole rock geochemical analysis of different porphyry bodies are carried out in order to find out the diagenetic age and petrogenesis of the complex body in the North-Zegulang Ore Segment,and reveal its coupling relationship with mineralization.The results show that the crystallization ages of monzonitic granite porphyry,granodiorite porphyry,quartz diorite porphyry and diorite porphyry are 15.54±0.13 Ma,15.13±0.17 Ma,15.59±0.19 Ma and 15.05±0.13 Ma,respectively.Among them,monzonitic granite porphyry and granodiorite porphyry emplaced earlier,quartz diorite porphyry and diorite porphyry emplaced later,but they are the products of Miocene magmatism.The geochemical characteristics show that the four types of porphyry belong to calc alkaline high-k calc alkaline series,with quasialuminous weak peraluminous characteristics,enriched in LREE and depleted in Hree,developed weak negative Ce and Eu anomalies,and have adakite characteristics.Their genesis belongs to I-type granite formed by remelting in the mixed source area of lower crust and mantle under the background of post collision.At the same time,alteration and mineralization characteristics show that monzonitic granite porphyry and granodiorite porphyry are important ore bearing porphyry,which are basically consistent with mineralization and alteration time limit,while quartz diorite porphyry and diorite porphyry,as non ore bearing porphyry,are the products of magmatic activity after mineralization.In addition,as an important part of the polycentric composite metallogenic model,the surface geochemical anomalies and deep alteration and mineralization characteristics reveal that the the North-Zegulang Ore Segment has good exploration potention of porphyry skarn hornblende orebody.The follow-up should take ZK832-ZK836 as the center to further carry out detailed investigation and strive to achieve greater prospecting breakthrough.