GEOLOGICAL CHARACTERISTICS OF THE XIJINUOSHAN POLYMETAL ORE FIELD IN HEILONGJIANG PROVINCE

The Xijinuoshan polymetallic mineralization, located in Huzhong area of Daxinganling, occur in Mesozoic secondary volcanic basin of Ergun massif, in the northwest of Derbugan faulted zone. In Xijinuoshan ore field, andesite of Upper Jurassic Tamulangou formation and acidic pyroclastic rock of Lower Cretaceous Shangkuli formation are widely distributed, but only a small amount intrusive rocks outcrop. The host structure of the ore is a NW-trending fracture belt. More than 30 veins of copper, lead, zinc, gold, silver and tungsten have been found in the andesite of Tamulangou formation. The metallic mineral types are mainly galena, chalcopyrite, sphalerite, pyrite and natural gold, with minor chalcocite and ilmenite. The secondary oxidized minerals include azurite, cuprite, cerussite, malachite, anglesite and limonite. The gangue minerals consist of plagioclase, hornblende, quartz, chlorite, calcite and epidote. The ore is in idiomorphic-granular and allotriomorphic-granular textures and dissemination or vein structures. The composition of metallic minerals is mainly metallic sulphide. The wallrock alterations, including propylitization of early period and silicification,chloritization, epidotization and carbonation of late period, are commonly weak. The mineralization is also in two stages,i.e., the one led by volcanic hydrothermal solution of early-medium Tamulangou formation, and that by intruded magmatic hydrothermal solution of Late Cretaceous period. The temperatures of metallogenesis are of 148℃ to 230℃.The source materials of the deposit were derived mainly from volcanic rock of Tamulangou formation. The heat source may be the granite-porphyry at No.897 High in the southeast of Xijinuoshan. The metallogenic epoch is from Late Jurassic to Early Cretaceous.