Petrogenesis and magma fertility of the Heishishan skarn deposit, East Kunlun, NW China: Insights from geochronology, mineralogy, geochemistry, and Sr-Nd-Hf isotopes

•Redefining the ore-forming rock of the Heishishan skarn deposit as monzogranite (241.7±1.0 Ma).•Ore-forming monzogranite has the characteristics of adakitic rock, derived from crust-mantle magma mixing.•Ore-forming magma has high oxygen fugacity, high water, SO3 and Cl contents, showing strong metallogenic ability.•Using the SO3 and Cl contents of apatite to estimate magma fertility should consider the influence of fluid exsolution.