Geological Characteristics And Genesis Of Polymetallic Copper Deposit Of Jiama, Tibet

Copper polymetal deposit of Tibet Jiama is produced in Gangdese epicontinental volcano-magmatic arc, which is located in Mesozoic intra-arc sedimentary basin. It is the typical representatives of skarn-porphyry Copper polymetal deposit in Tibet Gangdese metallogenetic belt. In this article, on the basis of full collecting and carefully studying the previous information, I have done a great deal of field work and synthetically used multidisciplinary theories and methods, such as: structural geology, petrology, mineralogy, gitology, geochemistry, fluid medium and enclosure geology, isotope geology, etc. Mineral ore are mainly distributed in skarn. It is in layers and similar layers, lensing output, located in the Upper Jurassic Duodigou formation and the contacting position of the Lower Cretaceous Linbuzong formation. The primary ore minerals are chalcopyrite, chalcopyrite, bornite, galena, sphalerite, pyrite, molybdenite sulphide, and so on, which is native sulphide. They can totally be accounted for more than 95%. Gangue mineral is main skarn minerals, such as garnet, malacolite, etc. In rock alteration, skarnization, mamorization, silicate and hornfelsing are in the most closely relations to mineralization. In the horizontal and vertical, the phenomenon of alteration zoning is obvious and in strong regularity. The research of hydrogen-oxygen isotope indicated that in the anhydrous skarn stage metallogenic fluid are mainly metamorphic water and magmatic water, precipitation and Organic Water mixed in metallogenic fluid later; In the hydrous skarn stage metallogenic fluid are mainly magmatic water. According to the research of lead isotope, sulfur isotope and rare earth elements, the main ore-forming metals come from the mantle or lower thickening crust.The studies of fluid inclusion show that copper-polymetallic deposit in JIA Ma belongs to medium-high hydrothermal deposit, parts of fluid inclusion have not yet in uniform at more than 500°,fluid inclusions containing daughter minerals are well deve-loped,the fluid has relatively high salinity.The physico-chemieal conditions during the formation of deposits are determined.At last, through the study of the geological and geochemical characteristics, renewedly explain ore genesi. It is expected that the paper can plays important role in theoretical guidance for the future working of prospecting, exploration and forecast in this areas.