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 flf
luid inc
lusions were identifified as follows: (1) pure carbonic (V-type) inc
lusions, (2) aqueous-carbonic (C-type, inc
luding three-phase C1-type and two-phase C2-type) inc
lusions and (3) aqueous (L-type) inc
lusions. F
luid inc
lusions 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) flf
luid inc
lusions. 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 flf
luids 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 va
lues of the flf
luids 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 va
lues of the flf
luids 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 va
lues may reflflect meteoric water involvement in ore-forming flf
luids sourced from either crustal metamorphism or mantle devolatilization. F
luid mixing is the crucial mechanism that controlled the deposition of the Aubearing sulfifides. In situ δ34S va
lues of the Au-bearing pyrite range from 1.06‰ to 2.41‰, whereas δ34S va
lues 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
Tethys Himalayan Au–Sb polymetallic metallogenic belt