Origin of the ore-forming fluids of the Tongchang porphyry Cu-Mo deposit in the Jinshajiang-Red River alkaline igneous belt, SW China: Constraints from He, Ar and S isotopes

► We have determined the He, Ar and S isotopic compositions of the Tongchang deposit. ► The Tongchang deposit has crust-derived and mantle-derived He-Ar compositions. ► The Yulong and Machangqing deposits have more mantle-derived He-Ar compositions. ► Mantle composition is an important factor for forming large porphyry Cu deposits.