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[Display omitted] • Mantle volatiles and heat contributions in high sulfidation epithermal Zijinshan deposit. • A progressive dilution of a magmatic-sourced hydrothermal fluid by meteoric water in Cu-Au ore-forming processes. • Leaching by meteoric water contributed to the vertical zoning of Au and Cu at Zijinshan. The giant Zijinshan high-sulfidation epithermal Cu-Au deposit is located in the Zijinshan ore field of southeastern China. A sharp boundary separates the upper Au orebodies from lower Cu orebodies at roughly 650 m below the original pit surface, below which digenite is the predominant Cu-bearing mineral. The current discussion revolves over whether the shallow Au and deep Cu mineralization are cogenetic or reflect independent ore-forming episodes, as well as whether the digenite formation is hydrothermal or supergene. In this contribution, we investigate the He-Ar isotope compositions of ore-related sulfides to decipher the source and history of ore-bearing fluids, and use the systematic variation of Cu isotope in Cu-bearing minerals to reveal the hydrothermal (hypogene and supergene) process. A gradual decrease in fluid 3He/4He and 40Ar/36Ar ratios, as well as a sharp drop in 3He/36Ar ratio, reflects the progressive dilution of a magmatic-sourced hydrothermal fluid by meteoric water. Some pyrites have 3He/4He ratios nearly identical to those of mantle fluid, indicating that the ore-forming fluids were mantle-derived with insignificant crust assimilation. The 3He/heat ratios that are higher than those of mid-oceanic ridges, indicating that the heat was transported by convection of low-temperature fluids with hydrothermal fluids rather than direct magma volatile injection. The copper isotope composition of the sulfides (δ65Cu = -3.59 to 1.33 ‰) increases with depth, which was likely caused by the release and downward transport of heavier copper isotopes near the surface. More than half (14 of 24) of these sulfides have a hypogene origin (δ65Cu = -0.05 ± 0.18 ‰), with 9 of 24 samples are likely of supergene origin. Combining with previous study, we confirm that enriched 65Cu reservoir is absent at Zijinshan. Based on the mass-balance of Cu isotopes and the spatial orebody relationship, we conclude that the leaching by meteoric water contributed to the conversion of low-grade initial hypogene Au mineralization into supergene, friable high-grade ore, resulting in the vertical zoning of Au and Cu at Zijinshan. Furthermore, the 65Cu-rich fluids produced by leaching may have lost to the groundwater, resulting in little exploration potential for 65Cu enrichment zone, while the uniform pattern of Cu isotope in the deep indicates a high exploration potential for hypogene Cu mineralization zone at depth. [ABSTRACT FROM AUTHOR]

• The Halatumiao intrusion was emplaced during early Permian (ca. 292 Ma). • Fractional crystallization and crustal contamination played a significant role. • The Xing'an-Inner Mongolia region have the potential to form Ni-Cu sulfide deposits. The recently discovered Halatumiao magmatic Ni-Cu sulfide deposit is located in the western part of the Baolidao terrane, which represents the middle-eastern segment of the Central Asian Orogenic Belt (CAOB), Inner Mongolia, NE China. This deposit is an important case of a magmatic sulfide deposit related to Early Permian subduction magmatism in an arc setting. In this contribution, we report in-situ zircon U-Pb ages, whole-rock major and trace element and PGE data, and Os and S isotope compositions from the Halatumiao ore-bearing intrusion to constrain its genesis and relationship to the Early Permian subduction-related magmatism. The Halatumiao mafic-ultramafic intrusion is composed of wehrlite, olivine websterite and gabbro. Semi-massive and disseminated sulfide mineralization with a pentlandite + pyrrhotite + chalcopyrite assemblage occurs in both mafic and ultramafic rocks of the intrusion. In-situ dating of magmatic zircon grains separated from an ultramafic rock sample yielded a U-Pb age of 292.3 ± 1.5 Ma. This age is very close to the age of the Erbutu Ni-Cu sulfide deposit (294.2 ± 2.7 Ma) located in the western part of the northern margin of the North China craton. The high Ni/Cu ratios (6.7 in average, except one sample) of ore samples indicate that the parental magma to the Halatumiao deposit was a primitive basalt. The good positive correlation between IPGEs (Ir vs. Os, Ru and Rh) indicates that fractional crystallization of MSS is the key factor for the PGE tenors. The positive γOs(t) values (from +46 to +68) and mantle-like S isotopic compositions (δ34S mostly between −1.5 and 0.5‰), The trace element characteristics show that a minor to moderate degree of crustal contamination (5–10%) has occurred in the magma. Fractional crystallization and crustal contamination were likely the key factors for sulfide saturation in the Halatumiao mafic magma. The relatively high Ni tenors of sulfides (avg. 6.4 wt%) indicate that the Late Paleozoic mafic-ultramafic intrusions abounding in the Xing'an-Inner Mongolia region have a good potential for hosting economic Ni-Cu sulfide mineralization. [ABSTRACT FROM AUTHOR]