Timing and hydrothermal fluid evolution of the Tenglongling gold deposit, North Tianshan, NW China

• The Tenglongling gold deposit was formed younger than 114 ± 1.2 Ma. • The ore-forming fluids are metamorphic origin with an input of meteoric water. • Both an increase in pH and a decrease of LogƒS 2 facilitate the precipitation of Au. The Tianshan Orogenic Belt (TOB), which lies in the southwestern part of the Central Asian Orogenic Belt (CAOB), represents a significant gold ore cluster. The Tenglongling gold deposit was recently found in the Bogda-Harlik Belt in the TOB. However, the timing and mechanism of gold mineralization remain unclear. Gold orebodies in Tenglongling occurred in the Carboniferous Shiqiantan Formation and diorite dykes, controlled by regional shear zone. The hydrothermal paragenesis can be divided into (Ⅰ) quartz-pyrite stage, (II) quartz-stibnite-arsenopyrite-gold stage, and (III) quartz-stibnite stage. The age of 114 ± 1.2 Ma, determined by SIMS zircon U-Pb of the Tenglongling diorite, provides a minimum age constraint on gold mineralization. Fluid inclusions hosted by quartz suggest that the ore-forming fluids are characterized by medium temperatures, low salinities, and CO 2 -CH 4 -rich compositions. Coexisting LR-type and VR-type FIs with comparable homogenization temperatures (T h ) suggest fluid immiscibility during the hydrothermal fluid evolution. The δ 18 O H2O (−3.7 ‰ to +9.2 ‰) and δD (−110 ‰ to −95 ‰) for ore-forming fluids indicate a metamorphic origin. Fluid immiscibility, accompanied by elevated pH (pH > 8) and decreased LogƒS 2 (LogƒS 2 = −11 to −17), contribute to a significant reduction in gold solubilities, ultimately generate the deposition of gold. Combined with geological and geochemical characteristics, the Tenglongling deposit is classified as an orogenic-type gold deposit, providing new insights into late Mesozoic gold mineralization in the Bogda-Harlik Belt.