Study On The Ore And Mineral Characteristics And Ore Genesis Of Dazong Copper Deposit In Lanping Basin,Western Yunnan

The Sanjiang composite orogenic and metallogenic belt, located in southeastern part of the Tibetan Plateau, has gotten a lot of attention from geologists worldwide for a long time due to its special tectonic settings, the unique geological structure and richness in mineral resources. Lanping Basin is located in the centre of the Sanjiang orogenic belt. A series of structurally controlled vein-type copper deposit are developed in the the western margin of the basin which is about 150 kilometer and spreading nearly in SN. They are Cu-Pb-Zn-Ag polymetallic metallogenic belt of Orogenic and located in the northeastern margin of the Tibetan Plateau. People have carried out a large number of detailed comprehensive research from the different aspects, such as deposit geology, ore deposit geochemistry and so on. People also had a more profound understanding on the coupling relationship between distribution and collision orogenic, the migration, driving and formation mechanism of ore-forming fluid. Considered that it is related to the evolution of Lanping basin closely and reach a consensus on the structure control of ore deposits, yet also have different opinions about the stratigraphic attribution of ore hosting rocks, the tectonic deformation and order of their formation. Therefore, it is unclear to date the deformation order and its relationship with mineralization, it is more difficult to objectively identify its genetic mechanism and ore controlling factors. Dazong deposit is located in the north central of the copper metallogenic belt, which is a small vein-type copper deposit and discovered recent years. The copper ore bodies are product in volcanic rocks and the volcaniclastic rocks, conglomerate and limestone from the adjacent stratum. It had the basic factors to development the study on the genesis of deposit. As such, we development a field geological investigation and indoor work, focus on the ore characteristics of vein-style copper deposit with volcanic rocks ore-bearing to revel the geological characteristics and the genesis. It would provide a new basis for vein-style copper deposit from Lanping basis and even Sanjiang orogenic belt. The following views are obtained.(1) The exposed stratus of Dazong deposit mainly are the upper Permian, lower-middle Triassic and Oligocene.(2) The main minerals of ores are chalcopyrite, bornite, chalcocite, alpha chalcocite, pyrite and covelline. The main gangue mineral is quartz and calcite.(3) Oxidized copper ore and mixed copper ore are the main ore styles of Dazong. The typical ore textures mainly of crystal texture, metasomatic texture and solid solution separation structure, ore structure are mainly vein structure, mottled structure and disseminated structure with the characteristics of hydrothermal vein-style deposit. According to the characters of mineral composition, the hydrothermal stage is divided into three stages, that are quartz stage, quartz-carbonate-sulfide stage and carbonate vein stage.(4)There are many kinds of fluidinclusions, but the main types are rich-liquid inclusions and rich-gas inclusions, include some of gas inclusions, a small amount of mineral inclusions and have no CO2 inclusions. According to the analysis of the microthermometry and H-O isotopic, The results show that the main metallogenic fluid came from the meteoric water, and have the features of middle-low temperature, low-salinity and high density.(5) Dazong copper deposit is of filling-metasomatic hydrothermal vein-type and relationship with volcanic rocks ore-bearing and controlled by tectonic deformation.