The Yangbajing geothermal field is situated at the central of the Dangxiong-Yangbajing fault basin, and is wedged between the Nyainqentanglha metamorphic basement to the northwest and the Gangdese magmatic arc to the south. According to differences of the burial depth and the fluid characters among the geothermal reservoirs in the geothermal field, the reservoirs are divided into two types of shallow and deep-seated, both of which are belong to the same hydrothermal system except for different depth and rock composition. The shallow-type reservoirs are formed by lateral-flow supply from deep-seated thermal fluid to the shallow Quaternary pores, buried under the earth surface in a shallow depth, which are composed of Cenozoic alluvial-diluvial sandstone, conglomerate, tillite and weathered granites. The deep-type reservoirs are distributed in north of the field, concentration and migration of the fluid are restricted by regional faults and structural broken belt rigidly that saved most of the thermal fluid in the particular depth and area, the typical thermal reservoir of structural-pores basement. Unlike the shallow-type reservoirs, the deep-seated ones consist of mylonitic granites, granitic mylonites and broken granites that underwent both ductile shear and brittle shear deformation. These reservoirs and the structures are universally developed in the whole basin south the Nyainqentanglha with the Yangbajing field as a typical case that indicates a huge geothermal resource potential area in the basin. Under the background of rapid uplifting of the Nyainqentanglha, an extensional environment formed in the Dangxiong-Yangbajing fault basin and connected the shallow normal faults with the deep-seated ductile strike-slip faults, which brought the anatexis magma of metamorphic complex to the shallow crust that performed as a perfect geothermal channel for the field. Thus the characteristics of geothermal reservoirs and structures enable the south foreland area of the Nyainqentanglha to be the richest area of geothermal resources in Tibet.

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