| The Xishan tungsten-tin deposit and the Gejiu tin-copper polymetallic deposit are located in south of south china tungsten-tin metallogenic province. The study region experienced collision compression because of subduction of the Pacfic plate, extrusion to tension produced by the motion direction of the Pacfic plate, a series of magmatic activities formed by tectonism and accompanied by strong large-scale mineralization.Xishan tungsten-tin deposit in Guangdong province, as the main research object, was compared with Gejiu tin-copper polymetallic deposit in Yunnan in this paper, which is the largest tin polymetallic deposit in the world. Through explaining Xishan tungsten-tin deposit characteristics of geological, orebody, U-Pb isoplot age and comparing the geochemical characteristic of metallogenic rock mass between Xishan tungsten-tin deposit and Gejiu tin-copper polymetallic deposit, to judge if Xishan deposit has potential to be a large deposit from the angle of metallogenic rock mass and to provide a certain basis.Based on the study of Xishan tungsten-tin deposit of geological characteristic, the author considers that the Xishan tungsten-tin deposit is a post-magmatic high-temperature hydrothermal deposit with a close relationship to magma intrusion, ore deposit types are mainly greisen type and quartz vein type, the Xishan tungsten-tin deposit was composed of veined orebody, and mineralization is controlled by fracture and the attitude of stratum. Alterations that closely related with mineralization mainly are silicon greisenization, lithification and hornfels.The weighted average age get from U-Pb isoplot age data of zircon in Xishan granite rock mass is 79.5±1.3Ma, the diagentic ags of Gejiu deposit is about 80 Ma, so both Xishan deposit and Gejiu deposit are belong to late Mesozoic-early late Cretaceous.Through the comparative study of Xishan deposit and Gejiu deposit in geochemical characteristics of major elements, trace elements and rare earth elements, it is can be consided that the lithological of the two deposits are all belong to aluminum-peraluminous, high silicon, calc-alkaline granite series. The sample data on the silicon base figure generally fall into granite area, on the aluminium saturation level discriminant diagrams are falling into a weakly peraluminous- peraluminous scope, the main elements of each Haker graph and the correlation of SiO2 is also similar, reflecting the similar characteristics, evolution in a spider diagram of trace elements and rare earth element distribution diagram, two rock samples show the shallow crust remelting diagenesis and the characteristics of the height of magmatic differentiation.Overall, pitch point show two geochemical characteristics of rock mass is roughly similar, reflect two rock mass are formed crustal remelting, and the mantle material to join the A type granite, and all the high crystallization differentiation, is A product of the late magmatic evolution, and xishan mining area of granite differentiation evolution degree is higher than old granite mining area.Based on two major elements, trace elements and rare earth elements of ore deposits of the comparison of the geochemical characteristics, can be thought of xishan and old both rock lithologic deposit shall be aluminum- peraluminous high silicon calcium alkaline granite series, and the sample data on the silicon base figure generally fall into granite area, on the aluminium saturation level discriminant diagrams are falling into a weakly peraluminous- peraluminous scope, the main elements of each Haker graph and the correlation of SiO2 is also similar, reflecting the similar characteristics, evolution in a spider diagram of trace elements and rare earth element distribution diagram, two rock samples show the shallow crust remelting diagenesis and the characteristics of the height of magmatic differentiation.Overall, pitch point show two geochemical characteristics of rock mass is roughly similar, reflect two rock mass are formed crustal remelting, and the mantle material to join the A type granite, and all the high crystallization differentiation, is A product of the late magmatic evolution, and xishan mining area of granite differentiation evolution degree is higher than old granite mining area.In the tectonic environment discrimination diagram of Xishan mining area rock mass and Gejiu mining area, the the results are almost the same and are all located in the zone of syn-collision granite and within-plate granite, the result reflect the same phase to phase transformation process, combining with the diagenetic age of the two rock masses and tectonic background of southern China, we can speculated that the formation of the two deposits are controlled by the tectonic activity of the Pacific domain, and related to the movement direction of pacfic plate dives to the Eurasian plate,from NW direction change to NEE direction,after 135 Ma in eastern China, and leading to the formation of the two tin deposits.In the light of the illustration and comparsion of the above characteristics, the diagenesis age are the same and the two granite rocks have similar geochemical characteristics, similar sources and a high degree of differentiation evolution process, under the influence of metallogenic tectonic environment of the Pacfic ocean. Thus, the conclusions meet the requirement to next studies for the comparsion between Xishan deposit and Gejiu deposit. |
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