Orchid Basin East Thrust Nappe Tectonic Characteristics And Its Ore-controlling Role

The eastern area of the Lanping basin, which is the section between Lanping and Jianchuan, is located at the compound position of the east branch of giant tectonic system of Indonesia, Eurasian plate and the NS-trending structural system of the three rivers(Jinsha river, Nu river and Lancing river). The main exposure strata in the study area consists of Shanglan formation, Waigucun formation, Sanhedong formation, Waluba formation and MaizhuQing formation of the Trias, Huakaizuo formation and Bazhulu formation of the Jurassic, Jingxing formation, Nanxin formation and Hutousi formation of the Cretaceous. The Magmatite in this area contains the Yanshanian trachyte and Himalayan granodiorite, granite and so on.Based on the field geologic survey,, there are four fault zones along SN direction nearly in the study area, which are Bijiang fault zone, Xuebangshan-Yunling fault zone, Mishahe fault zone and Shizhongshan fault zone from west to east. The Xuebangshan-Yunling fault zone has a series of the thrust nappe structures, which is over thrust eastwards and westwards. The main fault surface and the strata of the footwall in the nappes have been eroded, and then several klippe windows are constructed.The thrust nappe structure system in the eastern area of the Lanping basin consists of a series of imbricate thrust faults along SN direction nearly with different sizes, structural rock masses between thrust faults and imbricate thrust folds overlaid with various folds and related to thrust faults. Under the control of the stress field due to the tectonic compression in the WE direction and Tectonic process deeply in the area, the formation mechanism of the thrust nappe structure system is closely related to the suture after the collision between Indonesia and Eurasian plate. Therefore it was formed in the Eocene Epoch.Through the research on ore-controlling of the thrust nappe structure in the several metal deposits, the article points out that the difference surface of physical properties in the upper and lower plate of thrust nappe fault and the collapse space provide an ore space. According to the ore-controlling regularity of the thrust nappe structure, the Ore-controlling analysis of the typical ore-controlling structures, field investigation results, remote sensing data, geophysical and geochemical data in the study area to predict several ore-finding prospects, which are Jinding ore deposit, Baijizushankou ore deposit, Shuijingpo ore deposit, Laojunshan ore deposit, Chufeng ore deposit respectively. The five prospecting areas for Pb-Zn polymetallic ore deposits provide the basis for the further exploration and plan.