Sangmoladong Ag-Sn deposit, Coqên Co. (Cuoqin Co.), Ngari, Tibet, Chinai

Regional Level Types
Sangmoladong Ag-Sn deposit	Deposit
Coqên Co. (Cuoqin Co.)	County
Ngari	Prefecture
Tibet	Autonomous Region
China	Country

Six ore bodies have been delineated within the volcanic dome complex. They occur as two distinct genetic types: disseminated mineralization and fault-controlled vein-type mineralization. The first style, disseminated tin mineralization, occurs as stratiform and veinlet-hosted bodies within altered granite porphyry and rhyolitic tuff of the Dianzhong Formation. This mineralization is hosted within the tuffaceous rocks, and the surrounding rhyolitic volcanic clastic rocks exhibit intense silicification and chloritization. These ore bodies are 150 – 200 m long and 5 – 7 m thick. Grades range from 0.28% – 0.39% Sn, 0.51% – 1.52% Zn, 0.12% – 0.26% Pb, and 4.12 – 17.5 g/t Ag. The second style consists of tin mineralization in extensional fault zones. These ore bodies are controlled by near east–west trending regional faults. They are characterized by strong silicification along the fault structures, with a broader halo of chloritic alteration in the surrounding tuffs. Although the ore bodies are structurally controlled, their geometry is complex, with branching and composite veins that extend beyond the main fault zones. They are 150 – 200 m long but are significantly thinner than the disseminated bodies, averaging 1 – 2 m in thickness. Tin grades are substantially higher (1.63% – 2.76% Sn), whereas the associated Cu, Pb, Zn, and Ag concentrations are low. The SMLD deposit has a preliminary resource estimate of 10,206 t of Sn metal and 4,100 t of associated Zn metal.
Two principal ore types are identified at SMLD, distinguished by their mineralogy and texture. The first type is a disseminated sulfide ore. This ore is characterized by intense silicification and chloritization and contains a complex assemblage of Sn-Cu-Pb-Zn sulfide minerals. The second type is a tourmaline-quartz vein system. These veins contain cassiterite associated with abundant fluorine- and boron-rich gangue minerals, including tourmaline, fluorite, and quartz. The veins cut both the granite porphyry and the rhyolitic tuff and exhibit vein-filling and replacement textures.

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