Regional Metallogenic Model And Regularity Of Copper Deposits In Shannan,Tibet

Shannan,in Tibet, located in southernpart of eastern Gangdise,in this area,there are great ore mineralization and exploration potential but the lack of sysricmatic and synthetic study. In this Paper, based on a number of literature reading, combined with the completefield geological investigation and the research work, the writer states the geological, geochemical feature and chronology of deposits three different types.According to the predecessor research and the composite analysis of most deposits here, the writer discusses the regional metallogenic model and regularity. It has been finally reached the following conclusions:The deposits fall into three categories:porphyry type, skarn type and porphyry-skarn type.The skarn deposits associated with Mamuxia Group of Lower Cretaceous(K1m) and Bima Group of Lower Cretaceous(J3K1b); both of skarn and porphyry deposits are associated with medium-acid intrusive rocks, such as quartz monzodiorite, granodiorite and monzonite granite.Metallogenic age of Mingze deposit is about 30 Ma, and the deposit responded to the Oligocene late-collision,metallogenic age of Shuangbujiere deposit is about 51.5Ma, and the deposit responded to Eocene main-collision, metallogenic age of Panan deposit is about 86 Ma, and the deposit responded to the late Cretaceous Neo-tethys subduction.It is special in Gangdise metallogenic belt diagenetic and metallogenic age of deposits in Shannan include all four stages: subduction stage, main-collision stage, late-collision stage and post-collision stage.The metallogenic model of deposits in Shannan fall into three types:(1)During the Neo-tethys subduction, the fluid produced by the dehydration of slab upwelled and melted the lower crust and lithosphere, then the mixing magma invaded to the stratums resulted in mineralization.(2)During the main-collision, upwell asthenosphere caused by subduction slab melted the lithosphere and lower crust, then caused the magmatic activity and mineralization.(3)During the late collision, the thickened crust delamination caused the upwelling of asthenosphere and the mineralization.The strongest and most extensive mineralization in Shannan area is Late-collisional of Oligocene, secondly by Neo-Tethys 'Subduction of Late Cretaceous, then main collision of Paleocene and Eocene. The NWW direction and NEE direction fault zone controlled the most deposits in Shannan area. The pull type conversion structure in south of east Gangdise controlled the formation of early skarn copper deposit, the push type conversion structure controlled the porphyry ones. In Shannan, deposit?s distribution has the characteristics of?along both side of the Yaluzangbu river, equidistant occurencedand with piecewise concentrated ?.