Characteristics of geothermal geology and genetic model of the Anning hot spring in Yunnan Province

The Anning hot spring,reputed as "the most wonderful hot spring in the world", is an ascending spring group.The hydrochemical type of the thermal water is HCO3—Ca·Mg or HCO3—Ca type.Horizontally,the geothermal field is characterized by a high temperature center at "the most wonderful hot spring in the world".In the vertical direction the characteristics change with depth.The welltemperature curves can be grouped into four types,i.e.,the temperature-increasing type,the constant-temperature type,the suddenly increasing-decreasing type and the temperature-increasing-temperature-decreasing type.The thermal reservoirs are composed of multivariate structures.The currently-used thermal water originates from some superficial thermal reservoirs.The discharge of the hot spring is closely related to supply of rainfall,being an open supply pattern.The circulation period of thermal water is over 21 years.The analysis results show that heat source of the Anning hot spring originates from the regional high heat flow background and its water resource from atmospheric precipitation.The Tanglangchuan fault is a passage through which water and heat transmit.Therefore, the geological genetic model of the Anning hot spring is a deep-fault circulation geothermal system with an open supply pattern.