Sulfur and lead isotopic compositions of Hongtuling and Dahu Au-Mo deposit in the Xiaoqinling district, and implications for the regional metallogeny

　　The Xiaoqinling area on the southern margin of the North China Craton is one of Chinese most important gold‑producing bases, where vein‑type gold deposits are widely developed, with molybdenum mineralization occurring as paragenetic or associated components in similar deposits. The age and genesis of gold mineralization in this region have long been controversial. Taking the representative Hongtuling and Dahu Au‑Mo deposits in the Xiaoqinling area as research subjects, this study systematically conducts sulfur (S) and lead (Pb) isotope analyses of sulfides and gangue minerals in gold and molybdenum orebodies on the basis of detailed field geological surveys and ore microscopy. Combined with published geochronological data on magmatism and mineralization, we discuss the material sources and genetic links of gold and molybdenum mineralization.The results show that sulfides from gold orebodies in the Hongtuling and Dahu deposits have similar sulfur isotope compositions (δ³⁴S = −4.4‰ to −0.2‰), consistent with typical magmatic sulfur. In contrast, sulfides from molybdenum orebodies are markedly enriched in ³²S (δ³⁴S = −10.6‰ to −1.6‰). The distinct sulfur isotope signatures may reflect variations in ore‑forming physicochemical conditions or differences in sulfur sources. For lead isotopes, molybdenum orebodies exhibit compositions similar to those of metamorphic rocks of the Taihua Group, indicating that molybdenum‑forming materials were mainly derived from the crust. Lead isotopes of gold orebodies plot along the lead evolution trend of the North China Craton lithospheric mantle, consistent with Early Cretaceous mantle‑derived mafic dikes, suggesting that gold‑forming materials were predominantly sourced from the lithospheric mantle.
　　Integrating our findings with previous geochronological data, it is concluded that Au and Mo mineralization in the Xiaoqinling area resulted from the spatial superposition of an Early Mesozoic molybdenum metallogenic system and a Late Mesozoic gold metallogenic system, with the two having distinct material sources and tectonic‑metallogenic settings. This understanding bears important theoretical significance for correctly interpreting regional metallogenic geochronology data, establishing regional metallogenic models, and guiding mineral exploration in the area.