The Study On Mineralzaion And Metailogenic Background Of Da’anhe Gold Deposit In Yichun, Heilongjiang Province

Da’anhe gold deposit is located in the north of Tie Li, Yi Chun. Considered withgeotectonic view, it is located in yichun-yanshou structure-magma belt.It is the tipicalskarn type deposit in Heilongjiang Province. Based on previous research results, we makea study on deposit geology, fluid inclusion, Chronology and Geochemistry that can drawthe following conclusions:The deposit geology suggests that orebody is mainly hosted in the skarn which thecontact zone of gabbro and metamorphic Tumenling Group quartz sandstone.Mineralization is related to skarn.Orebody is mainly hosted in NE and NW tensionalfracture.The ore body occur in veins and lens. The ore granular is mainly allotriomorphicgranular and the others are subhedral-granular, idiomorphic-granular, metasomatic textureand including granular. The structure of ore are mainly disseminated and cstaclastic and theothers are breccia structure, residual structure and veinlet-disseminated structure. Themain metallic minerals are chalcopyrite, pyrrhotite, arsenopyrite, magnetite, magneticpyrite and natural gold.The gangue minerals are garnet, tremolite, actinolite, chlorite,calcite and quartz. The wall rock alterations are skarnization, silicification, epidotization,sericitization, chloritization, carbonatization, zeolitization and tremolition.Study on mineralography and fluid inclusion show that the types of fluid inclusions ofmainly for gas phase inclusion,liquid phase inclusion, gas-liquid two-phase inclusion andcrystal mineral inclusion.The size of gas phase inclusions are between4and10microns.The size of gas-liquid two-phase inclusions are between4and10microns.The size ofliquid phase inclusions are between1and4microns.Metallogenic process haveexperienced several mineralization stages.They are garnet-diopside stage, tremolite- actinolite stage, magnetite stage, quartz-sulfide stage and quartz-calcite stage. Garnet-diopside stage has a ore-forming temperature of177℃to600℃,salinity from6.38%to8.97％and11.13%to12.97t％, density from0.25g/cm~3to0.27g/cm~3and0.44g/cm~3to0.87g/cm~3. Quartz-sulfide stage with ore-forming temperature of147℃to455℃,salinityfrom1.05%to4.17％, density from0.46g/cm~3to0.93g/cm~3.Quartz-calcite stageore-forming temperature of137℃to247℃,salinity from0.88%to2.07％, density from0.63g/cm~3to2g/cm~3. Ore-forming fluid generally belong to K+, Na+, SO42-, Cl-, H2O,CO2, CO, CH4system.The overall characteristics are in accordance with the domestictypical skarn ore deposits.We can judge it as a skarn type gold deposit.Zircon LA-ICPMS U-Pb dating of gabbro that associated with mineralization is189±3Ma.So that can be thought of magma crystallization time occurred in210Ma to182Ma (about28Ma). Skarnization should be began at the time of crystallization of zircon(189±3Ma）. Mineralization occurred in the extension of middle Early Jurassic.Fluid isotopic and lithogeochemical characteristics of vein rocks show that ore-forming fluid is derived from magmatic water and join with atmospheric precipitation,ore-forming materials are derived from crust-mantle mixed.The study are belongs tovolcanic island ate and syn-collision circumstances.Mineralization is related to thecollision event of Jiamusi massif to Songnen massif and the subduction of Pacific plate atthe time of Jurassic.