Genesis of the Shaquanzi Zn-Pb deposit in the Eastern Tianshan, NW China: Constraints from geology, fluid inclusion and isotope geochemistry

The Shaquanzi Zn-Pb deposit, located in the Central Tianshan Terrane, is mainly hosted by siliceous slates and carbonaceous marbles of the Mesoproterozoic Kawabulake Group, and its mineralization / alteration can be divided into skarn period (I: early skarn stage, II: late skarn stage), quartz-sulfide period (III: early sulfide stage, IV: late sulfide stage and V: quartz-calcite stage) and supergene period (VI: supergene alteration stage). The Wtype fluid inclusions (FIs) were identified in the garnet, chlorite, quartz, and calcite in skarn and quartz-sulfide periods. Detailed fluid inclusion study shows temperature of fluids decreased from Stage I (510-520 degrees C) through, Stage III (481-507 degrees C), Stage IV (248-417 degrees C, peak at 280-400 degrees C) to Stage V (148-260 degrees C, peak at 200-220 degrees C), with salinities of 20.8-22.2 wt% NaCl eqv., 19.8-29.1 wt% NaCl eqv., 10.6-27.8 wt% NaCl eqv. (peaks at 20-23 wt%), and 21.6-29.9 wt% NaCl eqv. (peak at 23-27 wt%), respectively, indicating that the ore-forming fluids consisted of a high-medium salinity and Na-Mg-Fe-Ca-rich fluid system, and may have evolved from highmedium temperature to medium temperature. The H-O isotopic compositions varied from Stage III (delta 18OH2O = 7.7 %o-9.0 %o and delta DH2O = - 105 %o to - 91 %o) through Stage IV (delta 18OH2O = 2.6 %o to 4.3 %o and delta DH2O = 114 %o to - 111 %o) to Stage V (delta 18OH2O = - 4.2 %o to - 3.7 %o and delta DH2O = - 119 %o to - 96 %o), suggesting that the ore-forming fluid sources may have evolved from magmatic fluids to meteoric water. The average delta 34SH2O values of the early sulfide, late sulfide, and quartz-calcite stages are 5.7 %o, 8.5 %o and 14.0 %o, respectively, indicating that the sulfur in the early stage was mainly derived from magmatic hydrothermal sulfur, while the increase of the delta 34SH2O values in the late stages is likely to be sourced from the Kawabulake Group through water-rock reaction. Above all, we propose that the Shaquanzi may have been a skarn-type Zn-Pb deposit.