Genesis of Late Cretaceous Sn deposits and magmatism in the Yidun Terrane, China: Further northward extension of the Southeast Asian Tin Belt and implication for exploration

The Yidun Terrane in China is located in the north of the world-renowned Southeast Asian Tin Belt (SATB) and is characterized by large numbers of Sn–Pb–Zn–Ag and Cu–Mo–W deposits. Understanding the spatiotemporal and genetic links between proximal Sn and distal Pb‒Zn‒Ag mineralization is hampered by the poorly defined Sn mineralization age. Additionally, it is still debatable if the Sn mineralization in the Yidun Terrane belong to the northward extension of the SATB. Newly obtained garnet and cassiterite U‒Pb ages (99–97 Ma) from the representative Gongjuelong Sn deposit are consistent with the ages of adjacent Pb‒Zn‒Ag deposits and new zircon U-Pb ages (∼98 Ma) of the causative Haizishan granites. The whole-rock geochemistry, zircon trace elements and negative ε_Hf(t) values reveal that the Haizishan granites are reduced and highly-fractionated A-type granites, with the magmas mainly derived from the partial melting of old basement crust. The ore-forming fluids are of the H₂O-NaCl-CO₂ ± CH₄ system, and the H–O isotopes of the fluids indicate that the initial ore-forming fluids were of magmatic origin with increasing input of meteoric water over time. The S-Pb isotope values of sulfides from the Gongjuelong Sn deposit resemble those of both Late Cretaceous granites and sulfides in the Pb‒Zn‒Ag deposits. These geochronological, fluid inclusion and isotopic data suggest that the diverse styles of mineralization in the Yidun Terrane constitute an integrated ore system centered on Late Cretaceous granites, consisting of proximal skarn Sn at depth and distal hydrothermal-vein-type Pb‒Zn‒Ag mineralization above. Furthermore, the Yidun Terrane and SATB underwent similar tectonomagmatic and mineralization histories, suggesting that the Yidun Sn belt can be considered as a northern extension of the SATB. This proposed model highlights the potential existence of concealed Sn deposits beneath the Pb‒Zn‒Ag deposits, as well as Pb‒Zn‒Ag veins and rare metal mineralization around the Sn orebodies and highly-fractionated granites.