The Sandaowanzi Gold Telluride Deposit, North Great Xing’an: Geological And Geochronological Characterisation

As an independent gold tellurides deposit, the Sandaowanzi Deposit is a unique example of precious metal deposition in China or even in the world, and its industrial type is Quartz vein type. The wall rocks are volcanic rocks of the Tamulangou Formation. The most important alteration in quartz veins and wall rocks is silicification as well as pyritization, sericitization, kaolinization, chloritization, carbonation and so on, showing multistage and diversities. According to metallic minerals, cutting relationships between quartz veins, mineral symbiotic relationship, and combining with the structural analysis of the ores, three stages of mineralization structures are recognized in the sandaowanzi gold deposit.Timing of mineralization in the Sandaowanzi gold telluride deposit is constrained by the magmatic activities in the area. The gold-bearing quartz veins are developed in the volcanic rocks of the Tamulangou-GuangHua Formation. Meanwhile, a diabase dike without Au mineralization crosscuts the gold-bearing quartz veins. From U-Pb dating of zircons in the two types of volcanic rocks, the gold mineralization occurred during 124.5-117 MaAccording to the geochemical characteristics of volcanic rocks and dikes related to mineralization, it is shown that the volcanic rocks of Tamulangou-GuangHua Formation and syenodiorite and monzogranite-porphyry in Sandaowanzi were derived from lithosphere mantle rich in LILE and water. Fluid inclusions in quartz of Sandaowanzi gold deposit are composed of methane, indicating mantle-derived fluids. Theδ34S value of sulfur isotope is near 0, with the characteristics of mantle sulfur. All of the above imply that the mineralization of the Sandaowanzi gold deposit is attributed to a source region in the lithosphere mantle.Sandaowanzi deposit is a special case of low sulfide gold telluride minerali- zation associated with subalkaline to calc-alkaline magmatism during regional extensionalong the Great Xing’an Range in early Cretaceous. The geodynamic setting is regional extension and upwelling of the asthenosphere resulted from the rollback of the subducting Izanagi plate, and partial melting resulted from the decompression in lower crust and lithosphere mantle. The material of lithosphere mantle intrudes into the shallow crust or erupt to the surface, accompanied by the main mineralization process of open space filling and crack healing.