• 标题：Genesis of the Mingsai Au deposit, southern Tibet: Constraints from geology, flfluid inclusions, 40Ar/39Ar geochronology, H–O isotopes, and in situ sulfur isotope compositions of pyrite
• 关键词：Geology,Fluid inclusions,H–O–S isotopes 40Ar/39Ar geochronology,Mingsai Au deposit
• 作者：Zhi Zhang, Guang-ming Li, Lin-kui Zhang, Cheng-shi Qing, Yong Huang, Wei Liang,Hua-wen Cao, Yi-yun Wang, Sui-liang Dong, Liu Lu, Zuo-wen Dai

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Mingsai is a newly discovered Au deposit located in the eastern part of the Tethys Himalayan Au–Sb polymetallic metallogenic belt. The stratiform and lenticular orebodies are hosted within Middle Jurassic metamorphic tuffff and quartz-sericite veins and controlled by an interlayer-gliding fracture zone with extensive hydrothermal alteration. In this study, at least three alteration/mineralization stages of the deposit were recognized as follows: (1) pre-ore stage (Stage Ⅰ), forming mainly ore-barren fifine quartz veins without sulfifides; (2) main ore stage (Stage Ⅱ), forming mainly thick quartz veins with abundant coarse-grained or fifine-grained euhedral and subhedral Au-bearing pyrite, arsenopyrite and sericite; and (3) post-ore stage (Stage III), which is characterized by formation of thick barren quartz–calcite veins with few sulfifides. Three types of flfluid inclusions were identifified as follows: (1) pure carbonic (V-type) inclusions, (2) aqueous-carbonic (C-type, including three-phase C1-type and two-phase C2-type) inclusions and (3) aqueous (L-type) inclusions. Fluid inclusions during the pre-ore stage are mainly C1-type, C2-type and V-type. The main ore stage contains mainly C1-type, C2-type, L-type and limited Vtype, whereas the post-ore stage contains mainly L-type (with limited C2-type) flfluid inclusions. From stages Ⅰ to III, microthermometric data show homogenization temperatures of 292–362 °C (mean = 309 °C), 247–320 °C (mean = 285 °C), and 206–272 °C (mean = 244 °C), respectively, and flfluids with salinities of 0.2–8.3 (mean = 2.8) wt% NaCl equiv., 0.2–13.1 (mean = 5.8) wt% NaCl equiv., and 0.8–15.2 (mean = 8.3) wt% NaCl equiv., respectively. The δD values of the flfluids from stages I to III range from −129.1‰ to −131.8‰, −137.5‰ to −137.4‰, and −143.6‰ to −138.6‰, respectively. The δ18OH2O values of the flfluids from stages Ⅰ to III range from 13.3‰ to 13.6‰, 13.0‰ to 13.2‰, and 11.0‰ to 11.9‰, respectively. The δD and δ18OH2O values may reflflect meteoric water involvement in ore-forming flfluids sourced from either crustal metamorphism or mantle devolatilization. Fluid mixing is the crucial mechanism that controlled the deposition of the Aubearing sulfifides. In situ δ34S values of the Au-bearing pyrite range from 1.06‰ to 2.41‰, whereas δ34S values of the barren pyrite from the slate range from 8.19‰ to 15.86‰, indicating that sulfur of the Au-bearing pyrite has a deep source. The 40Ar–39Ar plateau age of hydrothermal ore-bearing sericite from the main ore stage is 16.03 ± 0.31 Ma, indicating that the mineralization time of the deposit is Miocene, which is difffferent from other major gold deposits (Eocene) in the Tethys Himalayan Au–Sb polymetallic metallogenic belt. Consequently, taking the data together, it is suggested that the Mingsai is an orogenic-type Au deposit in the