Ore Genesis Studies Of The Cu-Ni-Pt Deposit Related To The Basic Complex, Jidong, Heilongjiang Province

Wuxing Deposit is located in the south-eastern magmatic belt of Xiaoxing'anling-laoyeling, the north of Mesozoic magmatic NNE tectonic uplift belt of Pacific Ridge, the ea-stern edge of Xing'anling Mongolian orogenic belt of the eastern side of the volcanic magmatic tectonic belt, Dunmi deep fault pass through the northern part of study area.Theoldest exposed strata of the region is huangsong group of upper proterozonic erathem yangmu group (Pt3y) and yanwangdian group (Pt3yn); the region has strong tectonic magmatic activity and more magmatic rocks. There are mainly Yanshan stage, Indo-Chinese Epoch and Cenozoic intrusive rock. There are also have large areas of alkaline basalt because of Dunmi faults in Cenozoic era. This research show that the relate between the cenozoic basic ultrabasic rocks and mineralization is most closely .The studies on Geological characteristics of the mining area prove that Wuxing deposit is a copper nickel sulphides and platinum palladium complex type deposits. The deposit is composed of copper nickel sulphide and platinum palladium orebody.The mineralizations are mainly conce- ntrated in the contact of diopside rock lithofacies and olivehui lithofacies, but tend to the side of diopside lithofacies. There are a few distributed in olivehui lithofacies, which is showed lenticular and constitute two mines. Copper nickel mineralization occurs mainly in olive hornblende pyroxenite lithofacies, while platinum palladium mineralization occurred both in the hornblende peridotite pyroxenite and hornblende pyroxenite. Platinum palladium mineralization and copper nickel sulphide orebody are accompanied, which partly consistent with the scope of the minerali- zation. Ore body is mainly distributed in east-west direction near the central rock containing ore belt. The direction of distribution of the ore body broadly in line with the extened direction of the rock, which is shape the direction of NNE and NWW belt such as layered, lentils and layer like band. So sulphide ore vein can be seen that exist not only in liquation melt orebody,but vein penetration orebody.In addition, according to the characteristics of the Orebody and wall rock,Wuxing Orebody can be divided into syngenetic disseminated orebody and quasi syngenetic disseminated orebody. The typ- es of wall rock alteration are mainly chloritization, serpentinization, actinolition, sericitization, uraliti- zation, carbonatization and so on, but they are not generally strong. The texture and structure of ore are mainly euhedral and half euhedral granular texture, metasomatic texture, solid solution separation tex- ture; disseminated structure, spongy aerosiderited structure, massive structure and vein structure. The main ore minerals are pyrrhotite, pyrite, chalcopyrite, pentlandite, magnetite and so on. According to the ore fabrics and the relationship between minerals, the mineralization can be divided into four stages: pyrrhotite, pentlandite and linnaeite phase; polymetallic sulfide phase; pentlandite and valleriite phase; the hydrothermal metasomatic metallogenic stage of the hydrothermalore-forming period.By researching on the major elements,trace elements and isotope in ore-bearing rock in this work, the results showed that the intrusive rocks in this region are subalkaline tholeiite, with the characteristics of largeion lithophile elements (Rb, Ba, Sr, etc.) and light rare elements (LREE) enrichment, while the relative loss of HFS (Nb, Ta, Zr, Hf, etc.), which reflects the characteristics of active continental margin igneous rocks. Element geochemical characteristics show its origin in the upper mantle, while in the formation of magma or the evolution of crustal material being subjected to hybridism. Sulfophile,iron group and PGE elements of the research show that the ore rich combination of elements of Ni-Co-Cu and Pt-Pd.Through researching on element geochemistry of ore-bearing rock phase and ore characteristics above mentioned of the study is that the ore-forming materials from the mantle, and mixed by crustal material.Combined with the ore-bearing pyroxenite rock SHRIMP zircon age (37Ma) and the area's geological tectonic background, we believe that the ore-forming environment is: at Cenozoic era, due to the high point of the Pacific plate subduction made Dunmi fault zone into the environment of extension activities which similar to a strong back arc spreading mechanism, while asthenosph- ere was upwelling, lithosphere was delaminating in the lower continent, the occurrence of melting formated the characteristics of mantle derived mafic magma, the magma underplated the overlying crust and provided a heat source, made the earth's crust and molten materials mixing with and thus formed the magma, while temperature and pressure changed, ore-bearing magma formed after hybrid magma fractional crystallizated and melted. Following by tectonic stress acted, the magma emplaced to shallow crust along tectonic fracture, formed the Wuxing ore-bearing rock body.