Study On Metallogenic Geological Characteristics And Regularity Of Gold Deposits In Kangding-Danba Area,Western Sichuan

The Dadu River gold metallogenic belt is located at the north end of north-south structural zone of Kangdian axis.The special tectonic position formed by the intersection of Xianshuihe fault,Longmenshan fault and Panxi rift?During the long process of geological evolution,the area has experienced pre-Sinian crystalline basement formation stage,Sinian-Middle Triassic passive continental margin stage,Late Triassic-Cretaceous collisional orogeny stage and Cenozoic intra-continental orogeny stage,which provide excellent geological background for gold mineralization.Kangding-Danba area in West Sichuan is an important part of the gold metallogenic belt.Typical gold deposits(ore occurrences)such as Huangjinping gold deposit,Jintaizi gold deposit,Erligou gold deposit and Dulanggou gold deposit have been found in this area.The gold metallogenic type of different ore-bearing horizon in the study area are basically the same,mainly quartz vein type and partly altered rock quartz vein type.There are two mafic dikes(bodies)exposed in each mining area,indicating that the formation of Dadu River gold deposit is closely related to the mafic dikes,and the deposit was formed after the mafic dikes(bodies)were in place.All ore bodies are controlled by structures,and the main types of wall rock alteration are the same.The composition of ore mineral is relatively simple,with pyrite as the main metallic mineral and quartz as the main gangue mineral.The gold-bearing minerals are generally pyrite and quartz.The sulfur isotopic peak and content distribution of pyrite in different ore-bearing horizon are similar,the ?34S peak is relatively concentrated,the composition is relatively stable and with high homogenization,which is close to the mantle-derived sulfur,indicating that the source of ore-forming fluid is the same,with the characteristics of mantle sulfur.Before the formation of the metamorphic core complex,a series of thrust nappe ductile shear zones were formed by compressional contraction in the north-south and north-east directions.The ductile deformation makes hydrous mineral dehydrate to form the thermal fluid with H2 O as the main component,induces the change of rock composition,and the activation,differentiation,migration and local concentration ofgold and other ore-forming elements to form the gold-bearing thermal fluid.During the formation of metamorphic core complex,the extensional ductile brittle shear zone formed by structural extension superimposed on the early ductile shear zone,which provided space for gold deposit.The ore-controlling structure of Dadu River gold metallogenic belt in Kang-Dan area is shear zone,and its relationship with mineralization can be divided into pre-mineralization NNE brittle thrust shear zone,mineralization stage NNE ductile brittle extension shear zone and post-mineralization brittle translation shear zone.The shear zone plays a controlling role in the formation of gold deposits,which is a trinity of activation and differentiation,ore guide and ore contain.To sum up,the main controlling factors of gold mineralization in Kang-Dan area are:(1)the NNE trending alteration shear zone is the main structure controlling the gold ore body;(2)the thrust shear zone is superposed by the extensional shear zone to form a closed space,which provides a good space for the mineral precipitation;(3)the bending,occurrence abrupt change and branching complex of mylonite zone are the favorable conditions for the formation of gold ore body.(4)The expanding position and occurrence changing position of quartz vein are favorable for the formation of gold ore body.