Fluid inclusions, stable isotopes (H–O–S), and age constraints on the genesis of the Basitielieke polymetallic tungsten deposit in the Altay, Xinjiang, NW China

The Chinese Altay in Northwest China and adjacent regions in the Russian and Mongolian Altay form a tungsten province within the Central Asian Orogenic Belt. Unlike the Russian and Mongolian Altay, almost no tungsten deposits in the Chinese Altay have been reported. The Basitielieke deposit located in the Altay orogenic belt in Xinjiang is a newly discovered polymetallic tungsten deposit hosted in the skarn in the exocontact zone of a granite pluton. Mineralization can be divided into the skarn period and supergene oxidization period, the skarn period can be further divided into a prograde skarn stage (I), a retrograde skarn stage (II), and a quartz–sulphide stage (III). Scheelite mineralization mainly occurred in stage II, and Cu–Zn–Au formed in stage III. The ore‐forming fluid can be divided into a H2O–NaCl systems, including stage I (211 to 480°C and 2.24 to 14.04 wt% NaCl equiv) and stage II (178 to 336°C and 4.96 to 9.47 wt% NaCl equiv), and a H2O–CO2 (±CH4/N2)–NaCl system in stage III (130 to 434°C and 1.40 to 9.60 wt% NaCl equiv). Hydrogen, oxygen, and sulphur isotope compositions indicate that magmatic water participated in the hydrothermal mineralization system in stage I, and meteoric water increased with the process of mineralization. Sulphur was derived from deep‐seated magmas. The Basitielieke deposit is a reduced skarn polymetallic tungsten deposit. The deposit formed by hydrothermal fluid from the granite interacting with strata during the Early Permian, the fluid–rock interaction and fluid mixing (magmatic water and meteoric water) was the main precipitation mechanism of the Basitielieke polymetallic tungsten deposit.