The newly discovered Tiantangshan tin polymetallic deposit is located in the southeast Nanling Range, Cathaysia block, Southeast China. The tin orebodies are mainly hosted in the greisen and the fractured alteration zones of the tufflava and trachydacite. However, the genetic relationship between the hidden alkali-feldspar granite and volcanic rocks and the tin mineralization remains poorly understood. This paper presents SHRIMP zircon U–Pb dating, whole-rock major and trace element analyses, as well as Nd isotopic data of the trachydacite and alkali-feldspar granite. The SHRIMP zircon U–Pb dating of the alkali-feldspar granite and trachydacite yields weight mean ²⁰⁶Pb/²³⁸U ages of 138.4 ± 1.2, and 136.2 ± 1.2 Ma, respectively. These granitic rocks have high levels of SiO₂ (64.2–75.4 wt%, mostly > 68 wt%), alkalis (K₂O + Na₂O > 8.3 wt%), REE (except for Eu), HFSE (Zr + Nb + Ce + Y > 350 ppm) and Ga/Al ratios (10,000 × Ga/Al > 2.6), suggesting that they belong to the A-type granite. According to the high Y/Nb and Yb/Ta ratios, they can be further classified into A₁ subtype. Their ε_Nd (T) range from −3.8 to −6.5. They were likely generated by the assimilation-fractional crystallization (AFC) of the coeval oceanic island basalts -like basaltic magma. This study suggests that the A₁ type granite is also a potential candidate for the exploration of tin deposits.

The Laoliwan Ag-Pb-Zn deposit is situated in the southern margin of the North China Craton and represents the first large-scale Ag-Pb-Zn ore deposit discovered in the Xiaoshan District. Ag-Pb-Zn orebodies are structurally controlled by NW- and NNW-trending faults and primarily hosted within early Cretaceous granite porphyry intrusions. In this study, sulfide Rb-Sr isotope dating and C-H-O-S-Pb multiple isotope compositions were conducted to constrain the ore genesis of this deposit. The Rb-Sr isotopic data of sulfides yield a weighted mean isochron age of 132.8 ± 9.5 Ma and an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.7115 ± 0.00016, indicating that mineralization occurred during the early Cretaceous and the ore-forming materials were derived from a crust–mantle mixed reservoir. The δ¹³ C (−1.3‰ to 0.7‰), δD (−96.3‰ to −86.7‰) and δ¹⁸O_H2O (0.3‰ to 5.6‰) values suggest that the ore-forming fluids were mainly derived from magmatic water with a contribution of meteoric water during mineralization. The δ³⁴S values of sulfides (+2.0‰ to +5.8‰) indicate a magmatic source. The Pb isotope data (²⁰⁶Pb/²⁰⁴Pb = 17.301–17.892, ²⁰⁷Pb/²⁰⁴Pb = 15.498–15.560, ²⁰⁸Pb/²⁰⁴Pb = 37.873–38.029) also reveal that the ore-forming materials originated from the lower crust with a small amount from the mantle source. By integrating geochronological and geochemical data, this study proposes that the Laoliwan Ag-Pb-Zn deposit is characterized as an epithermal deposit, with potential for the discovery of concealed porphyry Cu-Mo mineralization at depth. It is inferred to be related to tectonic–magmatic–fluid activities in the context of early Cretaceous lithospheric thinning along the southern margin of the North China Craton.