Study On Geological Characteristics And Enrichment Regularities Of Gold Mineralization In Wulaga Gold Deposit, Heilongjiang Province

The Wulaga gold deposit is the main gold deposit in Northeast China. It is located to the North Slop of the Xiao Xing'anling East segment and the middle of Wulaga Rever of Heilongjian water system. It belongs to wulaga town, which is in the south of jiayin county, YiChun, Heilongjiang Province. Geotectonically, the Deposit lies at the joint of Taipinggou upwarping and Jiayin down-warping belt that belongs to the northern Jamusi upheaval belt. The Jamusi upheaval belt is located at Jilin-Heilongjiang geosynclinal system which is in the east segment of Tianshan-Xingmeng Hercynian fold belt. It is affected by the geological developing and evolvement of Central Asia- Mongolia Plate and Pacific Plate. The structure is complicated in the diggings. The nearly EW trend fold and fault are the basement structures. It is formed the NNE trend Wulaga deep-seated fault in Mesozoic era when Pacific Plate subduct to Eurasia Continent.The strata outcropping in the area include lately middle Proterozoic lower Heilongjiang Group, lower Cretaceous Ningyuancun Group(K1n), Taoqihe Group(K1t), upper Cretaceous Yuliangzi Group(K2yl), Cenozoic Neogene Miocene-Pliocene Sunwu Group and Pleistocene-Holocene. The magmatic intruding activities are mainly plagioclase-granite porphyry in the Yanshan period. Orebodies lie in plagioclase-granite porphyry structural breccia belt mostly, others in the porphyry and schist fragmentation alteration belt.NNE trend Wulaga deep-seated fault is the ore-leading and rock-leading structure. It controlled the magmatic activities and hydrothermal fluid movement. NWW trend fault which is sub-structure of Wulaga deep-seated fault is the main ore-controlling structure.The minerals combination is simple in the Wulaga gold deposit, the ore minerals are mainly composed of natural gold, pyrite, marcasite, colloidal pyrite, colloidal marcasite and stibnite; the gangue minerals is mainly colloid calcedony quartz, calcite and kaolin. The texture of the ore bodies are colloidal texture, fine grain-dissemination texture. The main structure of the ore bodies are vein structure, stockwerke structure. There are many types of wall-rock alteration, such as pyrite-beresitization, chloritization, silicification, carbonatization, kaolinization and propylitization. Mineralized silicification is linear distributed and controlled by structure. It is closely related to gold mineralization.According to the study on fluid inclusion of Wulaga gold deposit, Tanan exploration areas and Shisangongli exploration areas, it indicated that the main metallogenic stage ore-forming fluid of the gold deposit is low salinity, low density fluid, the formation temperature is low and ranges from 152℃to 220℃. The average value of pressure is 23.24MPa and the formation depth is about 2.31Km.The ore-forming fluid of Tanan exploration areas is also low salinity, low density fluid, the temperature is low and a normal distribution, the average value of pressure is 23.03MPa and the formation depth is 2.3Km just as the gold deposit. The ore-forming fluid of Shisangongli exploration areas is low salinity, low density fluid too, the homogenization temperature of ore-forming is higher than the gold deposit and Tanan exploration, it ranges from 240 to 300℃with normal distribution, the formation depth is deeper than the gold deposit and Tanan exploration, ranges from 240℃to 300℃with normal distribution, the ore-formation pressure is higher than the gold deposit and Tanan exploration areas, about70 to 75MPa, the depth is about 6.5 to 7.0Km. Through the analyzing of Isotope and Rare-earth Elements, the major ore-forming fluid is atmospheric precipitation and formed at a low temperature environment. Combined with the metallogenic geological characteristics, geochemical characteristics and geophysical characteristics of the gold deposit; Tanan exploration areas and Shisangongli exploration areas, it is recognized that the gold deposit and Tanan exploration areas are belong to epithermal gold deposit, the Shishangongli exploration areas belong to epizonal orogenic gold deposit, through synthesis analysis and comparative study.All the types deposit of Wulaga gold deposit formed a metallogenic series of gold depodit, and this series consist of epithermal deposit and orogenic gold deposit. The orogenic gold deposits were formed during the Early Yanshanian in a compression environment(Shisangongli exploration areas), while the epithermal deposits were usually formed in a extension tectonic setting, Late Yanshanian(the mine district and Tanan exploration areas).The diggings of Wulaga gold deposits and Tanan exploration were formed at the same geodynamic background. Orebodies of the diggings exist basically in the E-W trending structural breccia contact belts of late Yanshanian granite porphyry with the lower subgroup of Heilongjiang Group, while the orebodies of Tanan exploration areas are produced in the alteration-mineralization belt. Diggings and Tanan exploration area were distributed in the north and south of Taipinggou uplift separately. The strata of diggings is the main source bed, the granite porphyry is the favourable conduit ore-bearing wall rocks and provide the necessary thermal power for fluid.The ore bodies in the No.1 vein were the main ore bodies in the diggings. They lie in plagioclase-granite porphyry structural breccia belt mostly. Ore-controlling faults characterized undulating varies in strike and dip. So it will recur between enrichment segment and barren interval. Ore bodies NWW-trend diagonal distributed, and the pitch angle is 7°±. In the dip, orebodies occurred in local extensional place when the ore-controlling fault dip steeper. And there is no orebodies when dips slighter. The zone of convergence controlling the ore deposits is obvious in the alteration zone of Tanan exploration areas.Studying on the ore controlling geological condition and summarizing the mineralization enrichment regularities have important significance for determining the ore-body predictive criterion and direct the prediction of the diggings peripheral and the deep blind orebodies. Through the comparative studying, summarizing the prospecting criteria of geology, geochemistry and geophysical, establishing the prospecting model of Wulaga gold deposit, It is indicated that there are greatly prospecting potentiality in deep exploration of gold-field, Tanan exploration areas and Shisangongli exploration areas.