Study On Geological And Geochemical Features Of The Tellurium Deposit In Dashuigou, Shimian, Sichuan Province

Based on large geological investigations in the field and a lot of analytical data gained in the laboratory, the author researched the regional geological-geochemical background and the geological features by studying the element geochemistry, the isotope of Pb, S in ores, and the isotope of H, O of fluid inclusions of different stages of mineralization, in order to discuss the ore-forming environment, the sources of materials and the sources of the ore-forming fluid. The result showed that:1. The Dashuigou tellurium deposit is formed in the site where the plates splice, the structure with deep fracture, and the magma intense activity. Multiple stages of the deep fracture provide passages for the latter magma. Minerals react fully and precipitation in the fragmentation zone which caused by plate collision. This is conducive to the formation of tellurium deposit.2. The Dashuigou tellurium deposit is located in area with regional geochemical background of polymetallic ore enrichment. It is the polymetallic ore enrichment area of Cu, Au, Ag, and so on. Lying in the geochemical field with barren Te, the enrichment of the Te (up to 7-8 orders of magnitude) in partial geologic bodies where the whole area is poor of Te in the geological environment indicated that the Te may source from the deep.3. The deposit is formed in the Triassic metabasic volcano rock of Tonghua group of Silurian in the Dashuigou thermal dome, and under the control of NNE group of brittle rupture zones with equal interval. The thermal dome structure provided favorable storage place for the development of Te deposit. The later development of brittle structure made the ore bed crash fully, which greatly increased the surface area of reaction between the ore-forming hydrothermal and it, provided passage and reaction field for ore-forming materials so that they reacted adequately and enriched into deposit in the Dashuigou thermal dome.4.The features of the trace elements showed that the origin of the metamorphic wall rocks are continental tholeiite. The redox environment of the deposit and the wall rocks are very different which is conducive to mineralization. The granite exposed in the area is rich of Bi and Ag, which has the trace element characteristics of continental crust-type granites. The limestone of Tonghua group of Silurian is obviously erosion of magmatism which is enrichment of Co, Ni, Sc, In, Ga. The ore-forming elements of Te and Bi are rich in metamorphic rocks, especially in slate, schist, fine - banded marble and rocks with low metamorphic degree.5.The features of isotopes show that Te and its mineralizer, ore-bearing fluid mainly come from the deep magmatic hydrothermal. The environment of ore-forming is isolated with the outside.In summary, it is believed that the form of Gashuigou Te deposit is closely related with tectonic-magmatic activities, dynamic metamorphism, Dashuigou thermal dome structure and brittle substructure, chemical differences between ore-hosting wall-rocks and ore-forming materials. It indicates this deposit has the features of dynamic metamorphic magmatic mineralization.