Geology,geochemistry And Genesis Of Gaogangshan Porphyry Molybdenum Deposit In Heilongjiang

Xiaoxing’anling- Zhangguangcailing metallogenic belt is one of the important molybdenum metallogenic belt of China,and its main deposit type is Skarn-porphyry copper-molybdenum polymetallic deposits, the metallogenesis is associated with the subduction of Paleo-Pacific in Early Yanshanian. The Gaogangshan deposit is the first discovered Early Triassic porphyry molybdenum deposit in the Xiaoxing’anling-Zhangguangcailing metallogenic belt, and its research level is low. This study is based on field survey combining with research on microscopic identification,geochemical analysis and testing of fluid inclusion, using multiple theories and methods such as mineralogy, petrologymineral deposit and geochemical. And established the genesis of the deposit by these research.The ore-bearing rocks of Gaogangshan molybdenum deposit are little stocks of late Permian. The deposit possesses the characteristics of typical Porphyry molybdenum deposit because it is restricted by ignious rocks, strata lithology structural conditions and Wall rock alteration. The intrusive rock main are granitic porphyry, porphyritic granite and granodiorite, which are metaluminous peraluminous, olive dolerite series,S-type granites. The ore-bearing strata are mainly granitic porphyry,which provide advantageous wall-rock conditions. The wall-rock alterations dominated by potassic alteration and silicification control the spatial distribution of ore types and mineralization strength.Ore structures contain porphyritic structure, porphyaceous structure, annulus structure. Ore textures contain gneissic texture, vein-like structure, disseminated texture, veinlets disseminated texture, star-shaped texture, brecciated texture and so on. Mineralization process of Gaogangshan molybdenum deposit have ecperienced four mineralization stages from early to late:(Ⅰ)Quartz– feldspar stage;(Ⅱ)Quartz- pyrite- pyrrhotite ± molybdenite stage;(Ⅲ)Quartz- pyrite- molybdenite stage;and(Ⅳ)Quartz- calcite ± fluorite stage.The results of geochemistry indicate the mineralization rocks in the deposit area formed in a continental collision environment. Its geodynamic may related to continental collion between Jiamusi-Mongolia block and the eastern segment of the northern margin of the North China Plate. The results of fluid inclusions of Gaogangshan molybdenum deposit indicate the deposite was produced in shallow-seated to middle-deep environment, ore-forming fluids belong middle-high temperature, middle to low salinity and medium density. During mineralization, metallogenic pressure, depth, homogenization temperature and salt content are lowering continuously, and metallogenic density increasing slightly. There are some boiling inclusions group in quartz,it is suggested that fluid boiling was the leading factor of the precipitation of metal sulfides like molybdenite and pyrite.fluid boiling cause precipitation of metal sulfides like molybdenite and pyrite.Ore characteristics, minerals coexisting relationship and ore textures of Gaogangshan molybdenum deposit suggest that the deposit is a typical Porphyry molybdenum deposit.