Hydrothermal activity characteristics, types of hydrothermal alteration and exploration direction in Gudui high temperature geothermal field, Tibet

The Qinghai-Tibet Plateau, located in the world-famous Mediterranean-Himalayan tropics, is the most intensely tectonically active region of the Cenozoic in mainland China. Accompanied with a large amount of hydrothermal activity and energy generation, this region had the greatest potential and concentration of high-temperature geothermal resources in mainland China. The Gudui geothermal field, located in the central Cone-oiga rift, is a shallow buried high-temperature geothermal field with the greatest power generation potential. In order to analyze the types and distribution characteristics of sinter and hydrothermal alteration, the favorable exploration direction and heat-controlling structure of Gudui geothermal field, the geothermal geological investigation, microscopic identification, and scanning electron microscope analysis were carried out. The hydrothermal alteration types, such as chloritization, silicification, kaolinization and carbonation, and sinters such as travertine, geyserite and sulphur, were identified. Three groups of faults were developed in the Gudui geothermal field with respect to the heat-controlling structure. The early EW faults are mostly reverse faults, and the later NE or NW secondary faults are mostly extensional faults as the main channels of geothermal fluid.The distribution of hydrothermal alteration is controlled by normal fault, of which alteration center is mainly located at the junctions of faults, and extends along the faults. An obvious hydrothermal alteration zonation was existed in the Gudui geothermal field, which extends from acidic alteration to weak acidic-neutral alteration, and the alteration center is mainly composed of extensively altered silicification or kaolinization zones. The distribution and intensity of hydrothermal alteration implies that the Bushonglanggu and Shagalanga geothermal display area have enormous resource potential. Therefore, geothermal exploration in Gudui geothermal field should focus on the Bushonglanggu and Shagalanga geothermal display area. with respect to hydrothermal deposition, the west area of Gudui geothermal field is dominated by travertine, and the east area is characterized by the coexistence of travertine and siliceous sinter. Furthermore, combined with the dynamic background of Qinghai-Tibet Plateau, an obvious coupling relationship exists between hydrothermal history and the uplift of Qinghai-Tibet Plateau during continent-continent collision and the activity of the Cone-oiga rift.