Timing and Sulfur Sources of the Baishitai Ag-Polymetallic Deposit, Northern Taihang Mountains, North China

The Baishitai Ag-polymetallic deposit, located in the Northern Taihang Mountains metallogenic belt, is a medium-sized deposit hosting both breccia-type epithermal Pb-Zn and skarn-type Pb-Zn-Ag-Cu mineralization. This study employed LA-ICP-MS U-Pb dating of garnet from the skarn-type Pb-Zn-Ag-Cu mineralization and zircon from microcrystalline albite porphyry breccia fragments within the breccia-type Pb-Zn mineralization to constrain the genetic relationship between the two mineralization styles. Additionally, LA-MC-ICP-MS in situ sulfur isotope analyses of pyrite and chalcopyrite were conducted to constrain the source of ore-forming materials. Garnet U-Pb ages of 132.9 ± 2.0 Ma, 132.8 ± 1.6 Ma, and 130.0 ± 1.7 Ma record the timing of skarn-type Pb-Zn-Ag-Cu mineralization (ca. 130 Ma). Zircon from the microcrystalline albite porphyry yields a U-Pb age of 134.4 ± 0.7 Ma, constraining the timing of the associated albite porphyry and, indirectly, that of the breccia-type mineralization. These ages overlap within error, suggesting that both mineralization styles formed during the same Early Cretaceous magmatic–hydrothermal episode. In situ sulfur isotope data reveal narrow δ34S ranges for both pyrite and chalcopyrite (−0.19‰ to +2.0‰, mean +0.49‰), matching those of typical magmatic–hydrothermal deposits in the Central and Northern Taihang Mountains (predominantly −2‰ to +2‰), collectively indicating a deep-seated source of the ore-forming materials. This sulfur isotope signature also agrees with the δ34S values of regional Mesozoic intrusions, suggesting that mineralization is closely associated with Cretaceous magmatism. This conclusion gains additional support from the geochronological results. These findings provide important geochronological and genetic constraints for further exploration of the Baishitai mining area.