High-silica(SiO2＞70 wt.％)granites(HSGs)are the main source of W,Sn,and rare metals.However,abun-dant HSGs,temporally,spatially,and genetically associated with Pb-Zn mineralization,in the Lhasa ter-rane(LT),provided an ideal opportunity to study the key factors responsible for Pb-Zn enrichment,instead of W-Sn enrichment.Here we contribute to this topic through U-Pb dating of zircon and garnet,and whole-rock and Sr-Nd-Hf isotopic geochemistry of ore-related quartz porphyries in the Bangbule deposit and compared these results with published data from large and giant Pb-Zn and W deposits in the LT.The magmatism-alteration-mineralization event in the Bangbule deposit was recorded by robust zircon U-Pb ages of 77.3±0.9 Ma and hydrothermal garnet U-Pb ages of 75.7±4.8 Ma,which is 10-15 Ma earlier than the main Paleocene metallogenic event and the first record of late Cretaceous Pb-Zn polymetallic mineralization in the LT.The late Cretaceous-Paleocene magmatism and mineralization events are a response to the subduction of Neotethyan oceanic lithosphere,which occurred as a result of the collision of the Indian and Asian plates.These HSGs related to Pb-Zn mineralization,with high total-alkalis and low magnesian contents,are enriched in Ba,Th,and Rb,but depleted in Ti,Eu,Sr,and P.They belong to either the S-type,or I-type granites.The Sr-Nd-Hf isotopic compositions of the Pb-Zn mineral-ized granites demonstrate that they were generated by the partial melting of Proterozoic basement with or without mantle-derived melt input.This was consistent with the postulated source of W enrichment in the LT.The Pb-Zn and W related granites have similar zircon-Ti-saturation temperatures,comparable low whole-rock Fe2O3/FeO ratios,and zircon oxygen fugacity.This indicated that the Pb-Zn-W enrichment in the high-silica magma system could be attributed to a relatively reduced magma.The Pb-Zn related HSGs,abundant quartz and feldspar phenocrysts,and weak fractionation of twin-elements in whole-rock analysis,can be used to reconstruct a model of the magma reservoir.We postulate that these features could be reproduced by silica-rich crystal accumulation in a magma reservoir,with a loss of magmatic flu-ids.The magma associated with W mineralization exhibited a higher level of differentiation compared to the Pb-Zn related magma;however,different groups of zircon texture with varying rare earth elements and concomitance of rare earth elements tetrad effect and high fractionation of twin-elements in whole-rock are formed by a magmatic-hydrothermal transition in highly evolved system.As the source and oxy-gen fugacities of the Pb-Zn and W related magmas are similar,the absence of a giant W-Sn deposit in the LT may indicate that parent magmas with a low degree of evolution and magmatic-hydrothermal transition are not conducive to their formation.This implies that the rocks that originated as highly evolved silicate-rich parent magmas,with a high degree of magmatic-hydrothermal alteration,would need to be targeted for W-Sn mineral exploration in the LT.In summary,our results emphasize that variations in chemical dif-ferentiation and the evolution of high-silica magmatic-hydrothermal systems can lead to differences in Pb-Zn and W enrichment.This has implications for the evaluation of the mineral potential of high-silica granites and hence their attractiveness as targets for mineral exploration.

Shunbao Gao;Xin Chen;Youye Zheng;Nan Chao;Shunli Zheng;Hao Lin;Xiaojia Jiang;Song Wu

Institute of Geological Survey,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Resources,China University of Geosciences,Wuhan 430074,China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China

地学前缘（英文版）

[1]Shunbao Gao;Xin Chen;Youye Zheng;Nan Chao;Shunli Zheng;Hao Lin;Xiaojia Jiang;Song Wu-.Discrepant chemical differentiation and magmatic-hydrothermal evolution of high-silica magmatism associated with Pb-Zn and W mineralization in the Lhasa terrane)[J].地学前缘（英文版）,2022(05):32-49

Discrepant,HSGs,rane,Bangbule,Neotethyan,magnesian,phenocrysts,concomitance,tetrad,fugacities

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