Magmatic-hydrothermal fingerprints in lode gold deposits: A case study of the Liushaogou deposit in the West Qinling Orogen, China

• The ore-forming fluids and materials in the Liushaogou deposit were primarily derived from magmatic sources. • Fluid immiscibility were the critical mechanisms for gold precipitation. • The Liushaogou deposit is predominantly of magmatic-hydrothermal origin. The genesis of gold deposits in the northern belt of the Western Qinling Orogen, hosting numerous world-class gold deposits, remains a contentious issue. The Liushaogou deposit in this region is a quartz vein-style gold deposit, which is strictly controlled by brittle faults, and along with weak silicification and sericitization. Five hydrothermal mineralization stages were identified, including barren quartz (stage I), pyrite-quartz (stage II), quartz-pyrite (stage III), quartz-polymetallic sulfides (stage IV), and quartz-carbonate (stage V). Fluid inclusions within stages I–IV quartz and stage V calcite were studied. Stage I fluids are typified by high temperatures (up to ∼400 °C) and medium to high salinity (8–40 wt% NaCl equiv.), with δ 18 O fluid values of 6.21–8.31 ‰, and δD values of −96.1 to −91.6 ‰, aligning with the characteristics of magmatic fluids. Subsequent stages (II-IV) fluids retain magmatic isotopic signatures, while stage V fluids record a shift toward meteoric water (δ 18 O fluid : −5.44 to −4.84 ‰; δD: −80.1 ‰ to −74.9 ‰), reflecting late-stage meteoric influx. Physicochemical conditions of the mineralization fluids were estimated to be near-neutral, relatively reduced, and H 2 S-rich, favoring the transportation of gold as hydrosulfide complexes. Fluid immiscibility and boiling are the primary mechanisms for gold precipitation. Sulfur isotopes (δ 34 S H2S : 4.9–7.9 ‰) in Liushaogou pyrites closely overlap Triassic magmatic rocks and regional magmatic-hydrothermal deposits, contrasting sharply with heterogeneous δ 34 S values (−28 ‰ to + 47 ‰) of Paleozoic sedimentary/metamorphic rocks. Homogenous Pb isotopic ratios ( 206 Pb/ 204 Pb: 18.225–18.596; 207 Pb/ 204 Pb: 15.623–15.722; 208 Pb/ 204 Pb: 38.368–39.115), which are comparable to those observed in Triassic magmatic rocks, further trace metals to Triassic magmas. The evidence presented here, in conjunction with the spatiotemporal links to Triassic intrusions and coeval Au-Mo-Cu mineralization, collectively point to the magmatic-hydrothermal origin of the Liushaogou deposit. This study emphasizes Triassic magmatism as a significant ore-forming process in the northern belt of the Western Qinling Orogen, with implications for targeting concealed intrusions and associated fault systems in regional exploration.