| In recent years,the discovery of Weilasituo tin polymetallic deposit is a big breakthrough in the ore belt of Da Hinggan Mountains in the middle of the southern section,and has an important theoretical significance.The deep tin polymetallic deposit in relationship of porphyritic alkali feldspar granite and the shallow vein zinc copper polymetallic deposit constitute a metallogenic system of magmatic hydrothermal evolution.To strengthen the research on this metallogenic system,has an important theoretical value to reveal the regional magmatic evolution and mineralization mechanism.Metallogenic magmatite hidden in the deep of the Northwest Mining Area,which is not completedly uncovered by drilling now.Through the microscopic identification,it's named porphyritic alkali feldspar granite.The rock mass with high silicon,aluminum,potassium,sodium,and low magnesium,calcium,iron,belong to peraluminous high-k calc-alkaline rock,and is formed from highdifferentiation of magma.Through the study,it is also found that rock mass is a kind of A type granite,which is formed by the fractional crystallization.The rock mass has good ore-bearing property,the geochemical characteristics of which is very similar to typical A-type metallogenic granite in the ore belt of Da Hinggan Mountains in late Jurassic to Early Cretaceous.So it has huge metallogenic potential.Through the study of the Weilasituo tin polymetallic deposit and zinc copper polymetallic ore,the magmatic hydrothermal metallogenic system is divided into three main metallogenic stages:the first stage of mineralization mainly formed cassiterite and sphalerite,which are the productions of medium-high temperature hydrothermal mineralization in the top of rock mass;the second stage of mineralization mainly formed arsenopyrite,chalcopyrite and sphalerite,which are the productions of medium-low temperature hydrothermal mineralization.They are distributed in structural fissures;the third stage of mineralization mainly formed arsenopyrite,chalcopyrite and sphalerite,which are the productions of the late metallogenic after the fragmentation.By LA-ICP-MS,The data of trace elements in sulfides of different mineralization stages are obtained.The results indicate that the ore-forming material of Weilasituo polymetallic deposit may be from the contribution of the surrounding rock strata,and the later ore-forming fluid is involved in meteoric water or formation water.Based on the trace elements of minerals,the results of the temperature measurement show that the forming temperature of tin polymetallic deposit is in the 281?~288?,and the forming temperature of zinc copper polymetallic deposit is in 204?~257?,which confirmed the change of the temperature gradient of magmatic hydrothermal system during the mineralization fluid evolution.In addition,by comparing with the characteristics of trace elements in different types of deposits in China and abroad,it is confirmed that the Weilasituo deposit belongs to magmatic hydrothermal deposit. |
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