The Metallogenic Age of Tangge Skarn-Type Copper-Lead-Zinc Deposit in Xizang:Constraints from Garnet U-Pb Geochronology
Huang Qian
Wu Song
Liu Xiaofeng
Shen Yahui
Danzeng Awang
Ci Qiong
Chen Lie
Wei Shoucai
Abstract：In-situ U-Pb dating of garnet is a newly developed isotope dating method for low-U minerals recently,which has been widely used in skarn deposits study.In this paper,the LA-ICP-MS U-Pb age and trace element compositions of garnet are reported for the first time in the Tangge skarn-type copper-lead-zinc deposit in Xizang.Combining with the results of zircon U-Pb dating of quartz porphyry,this study investigates the timing of magmatism and related mineralization and the ore-forming processes of the Tangge deposit.The garnet U-Pb age is 65.5±3.9 Ma,and the zircon U-Pb age of quartz porphyry is 68.1±0.9 Ma.These ages indicate both the granitic rocks and mineralization of the Tangge deposit were formed at Late Cretaceous-Palaeocene.The rare earth distribution patterns of garnet show an enrichment in light rare earth elements and depleted in heavy rare earth elements in the Tangge deposit with a LREE/HREE ratio is 0.01 to 12.68.Thegarnet can be further divided into two stages(Grt I and Grt II).The different Eu anomalies and average U contents in Grt Ⅰ and Grt Ⅱ indicate that the oxygen fugacity increases at first and then decreases.The average contents of Hf and Ta in the core of the first-stage garnet(GrtI-1)(8.84×10-6 and 0.52×10-6)are higher than those in the rim(GrtI-2:1.60×10-6 and 0.23×10-6),and in the second-stage garnet(GrtII:1.47×10-6 and 0.37×10-6),indicating that the metallogenic environment changes from a relatively closed system to an open and oscillating one.The ore-forming age of the skarn-type deposits in the syn-collisional Gangdese metallogenic belt is gradually getting older from east to west,which reveals the diachronous volcanic activity and reflects the characteristics of uneven collision between the Indian continent and the Asia continent.The Tangge deposit is a newly discovered syn-collisional skarn-type copper polymetallic deposit in the South Gangdese,which will provide a new direction for mineral prospecting in the Zhunuo ore concentration area and its surrounding areas,and even in the entire South Gangdese.
Keywords：GarnetU-Pb datingskarn depositTanggeGangdesegeochemistry
Publication Date：2025-02-14
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：18( 621-638 )