Various aqueous, carbonic, and hydrocarbon fluid inclusions were recognized in quartz and/or stibnite at the three deposits. These include type 1a one-phase aqueous inclusions, type 1b two-phase aqueous inclusions, type 2a carbonic inclusions, type 2b aqueous-carbonic inclusion, and rare type 3 hydrocarbon inclusions that include two-phase hydrocarbon inclusions (type 3a) and dark one-phase hydrocarbon inclusions (type 3b). The three deposits have the similar low-salinity H2OCO2CH4N2 ore fluids with trace amounts of hydrocarbons. For the Zhemulang, Mazhala, and Shalagang deposits, the salinities of aqueous inclusion range mainly between 3.3 and 6.4 wt.% NaCl equiv., 2.5 and 4.9 wt.% NaCl equiv. and 4.1 and 6.4 wt.% NaCl equiv., respectively. The ore-forming temperatures vary mainly from 180 to 320 掳C, 160 to 300 掳C and 140 to 240 掳C, respectively. The estimated mineralization depths are 4 to 6 km, 3 to 5 km, and 1 to 4 km of the epizonal environment, respectively. The different mineralization temperatures and pressures led to the different element enrichments at the three deposits.
For the Zhemulang, Mazhala and Shalagang deposits, ore fluid isotopic compositions are 未DH2O 鈭?#xA0;107.5 to 鈭?#xA0;36.7鈥?and 未18Ofluid 2.8 to 8.2鈥? 未DH2O 鈭?#xA0;119.0 to 鈭?#xA0;72.7鈥?and 未18Ofluid 7.5 to 16.2鈥? and 未DH2O 鈭?#xA0;173.4 to 鈭?#xA0;139.2鈥?and 未18Ofluid 7.5 to 12.3鈥? respectively; 未13Cfluid values are 鈭?#xA0;11.7 to 鈭?#xA0;9.6鈥? 鈭?#xA0;3.5 to 鈭?#xA0;2.5鈥? and 鈭?#xA0;6.5 to 鈭?#xA0;5.1鈥? respectively; and 未34S values are 鈭?#xA0;4.0 to 鈭?#xA0;1.1鈥? 鈭?#xA0;0.8 to 2.3鈥? and 鈭?#xA0;3.9 to 2.1鈥? respectively. The ore-forming fluids were partly derived from metamorphic devolatilization of immediate or deeper level country rocks, with a deposit's corresponding metamorphic degree controlling the fluid PTX. The ore-forming fluid for Zhemulang, Mazhala, and Shalagang consisted of predominantly metamorphic water with minor involvement of meteoric water, a mixture of metamorphic fluid and meteoric water, and predominantly meteoric water, respectively. Ore metals were derived from country rocks, including synsedimentary Sedex-like sulfide layers in the Jurassic strata observed at the Mazhala AuSb deposit. Among three deposits, the variation of 未13Cfluid and 未34S reflects the fact that the Zhemulang Au deposit formed from a relatively high content of organic carbon and low 茠O2 fluid, the Mazhala AuSb deposit from a relatively low content of organic carbon and high 茠O2 fluid, and the Shalagang Sb deposit from an intermediate content of organic carbon and 茠O2 fluid. Fluid immiscibility was the main mechanism for ore metal precipitation at all three deposits. The vertical zonation of Au, AuSb, and Sb mineralization suggests that additional gold resources may exist below the antimony or gold-antimony orebodies. Stream sediment and soil geochemical surveys and the occurrence of placer gold prospects are effective for identifying areas of orogenic gold and antimony deposits in the Himalayan and other orogens.
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