| The west slope of Daxing’anling is an important Ag-Cu-Pb-Zn polymetallic metallogenic belt in China. In 2014, extra Sn mineralization has been found both in the peripheral and the deep part of the Weilasituo Ag-Cu-Pb-Zn mine. Currently, the proven resource of Sn(332+333)comes up to 83700 t, which can be considered as a large-scaled deposit. Apparently, this discovery is a milestone in Sn-polymetal prospecting within the west slope of the Daxinganling region.The paper selects Weilasituo Sn polymetal deposit in Inner Mongolia for the study,mainly discusses the geological and geochemical characteristics and genesis of deposit in Weilasituo Sn polymetal deposit based on strengthening mine geology and geological characteristics analysis according to the petrology, mineral petrographic,rock geochemistry,geochronology and fluid inclusion petrography research.The main achievements and recognize for the paper are as follows:1. Based on the detail research of ore-body characteristics, ore type, mineral relations in Weilasituo Sn polymetal deposit, and combined with petrology, mineralogy and electron probe microscopy observation, the Weilasituo Sn polymetal deposit is divided into 3 metallization epochsl, six mineralization stages.2. The geochemical characteristics indicated that quartz-porphyry which is associated with mineralization have silicon-rich, rich base, potassium, calcium depleted, over aluminum, high-specific features.The evolution of quartz porphyry is high, it belongs to the high-K calc-alkaline granites. Rocks are strongly depleted in Ba, Sr, Ti, P, and enrichment of Rb and La, Ce, Pr, Nd, Sm,Th, U; The REE distribution patterns show a "V", a strong negative Eu anomalies, with the typical characteristics of alkaline feldspar granites. The weighted average age of LA-ICP-MS zircon U-Pb in quartz porphyry is 136.25±0.68Ma; Molybdenite Re-Os isotope isochron age in ore is 116.6±1.8Ma. The ore-forming age and metallogenic epoch in Weilasituo Sn polymetal deposits belong to early Cretaceous period.3. The main types of fluid inclusions in Weilasituo Sn polmetal deposit is gas-liquid two-phase inclusions. The range of completely homogeneous temperature of ore-forming fluids in main mineralization stage is 220 ~ 321 ℃.The initial ore-forming fluids belongs to the H2O-NaCl system with high temperatures, medium-low salinity, the ore-forming fluids in early and middle metallogenic stage belong to the H2O-NaCl-system with high temperatures, medium-low salinity, and the ore-forming fluids in late stage of mineralization belong to the H2O-NaCl-system with low-pressure temperatures, medium-low salinity. The Weilasituo Sn-polymetal mine was identified as a meso-hypothermal magmatic-hydrothermal deposit. |
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