Geological Characteristics And Metallogenesis Of Taishanmiao Gold Deposit,Ningshan County

Taishanmiao gold deposit is located in the polymetallic metallogenic belt of South Qinling region, South Qinling region is the gradual product of the interaction between the Yangtze plate and North China plate, its formation and development have experienced a very long geological evolution process. The metallogenic geologic condition is excellent, where rich mineral resources, many large and medium-sized gold deposits have been found.It is an important part of Qinling giant metallogenic belt.The main exposed stratas in mining are Banjiuguan Formation of the upper series of the Ordovician system- the lower boundary of the Silurian and Dafenggou Formation of the mid series of Devonian.The lithology of Banjiuguan Formation is biotite-quartz schist, containing carbon mica-chlorite-quartz schist and bioclastic limestone.The intrusive rocks in the main mining area are the Indo-Sinian granites, including Yanzhiba Pluton and Jinjiashan Pluton. In addition, vein rocks in this area are well-developed, including neutral dike rocks,acid dike rocks, quartz and carbonate dike rocks. Occurrence of the veins are strictly controlled by the tectonic fracture of surrounding rock.The mainly gold orebody in mining is Tizigou AuⅠ-1,which is bedded and stratoid occurrence in the charcoal grey-altered-biotite-quartz schist of Banjiuguan Formation. The direction of gold orebody is approximately east west,which is controlled by F1 and the secondary fault fracture zone with approximate east west direction. large and lenticular orebody appears in the fault crossing.Metallic minerals in Taishanmiao gold deposit are mainly pyrite, pyrrhotite, sphalerite, chalcopyrite,galena,small amount of electrum and bornite;Gangue minerals are mainly quartz,chlorite, muscovite(sericite) and potash feldspar.Major textures of ores are metasomatic texture, cataclastic texture, hypidiomorphic and xenomorphic granular texture, exsolution and colloform.The major structures are vein-stockwork structure,disseminated structure,lumpy structure, brecciated structure and fracture structure, small amount of soil block structure and the membrane structure.The wall rock alterations are mainly silicification, pyritization, magnetic pyrite, limonite, followed by carbonation, sericitization and chloritization, followed by carbonation, sericitization and chloritization.The mineralization can be divided into two periods:the hydrothermal period and supergene period,and the hydrothermal period can be divided into the milky white quartz vein stage, smoky gray quartz vein stage, coarse-grained pyrite quartz vein stage and quartz calcite stage.Mineralization of taishanmiao gold deposit is closely associated withYanzhiba Pluton, orebody mainly exists in fault fracture zone around the rock mass.Geochemical studies indicate that Yanzhiba Pluton is rich silicon, rich alkali, belongs to high-calc-alkaline series and low peraluminous crust source rock.we suggest that the biotite was formed by partial melting of metasedimentary crust, which was induced by fluids from the lower crust or mantle lithosphere, under the condition of high temperature and high pressure.Studies on stable isotopes of S, Pb, H, O indicate that the major metallogenetic matters came from the formation.The mineralization fluids are mainly mixtures of meteoric water and magmatic water of the low temperature liquid or hot springs, the main component is meteoric water. Zircon U-Pb dating for the Yanzhiba Pluton indicates the exact age to be 211-198.4Ma.Combined with geochemical studies, we conclude that background of regional geology should be the tectonic regime transformation stage of collision orogenic periodComprehensive research indicates the genetic types of gold deposits of too mountain temple to be fracture control of magma liquid- hydrothermal(medium to low temperature type gold deposits, formed in the late indosinian collision orogenic the spread of the late tectonic environment.The research demonstrates that the Taishanmiao gold deposit which is controlled by fault and closely related to a middle-low magma liquid- hydrothermal,which lead gold deposit formed in collision orogenic extensional tectonic environment during the late Indocinian stage.