Characteristics and Genetic Model of Neogene Geothermal Water In Qabuqia Area, Gonghe Basin

The GongHe Basin, located on the northeastern margin of the Qinghai-Tibet Plateau, is rich in geothermal resources and has a complete range of geothermal resources, including both medium and low temperature hydrothermal type and high temperature dry heat type. However, the research on the correlation between the two is still relatively weak.This paper takes the Neogene geothermal system in the Qiabuqia area of the GongHe Basin as the research objective,and estimates the chemical characteristics , thermal storage temperature and circulation depth of deep underground hot water by analyzing the selected water samples ，so as to infer the genetic model of the Neogene geothermal system in the study area and explore the mutual influence of dry heat and hydrothermal geothermal systems.The analysis results show: (1) The dominant cation of groundwater in this area is Na+, which accounts for more than 90%. The main water chemistry type is Na-Cl·HCO3 type, Na-HCO3·Cl or Na-Cl·HCO3·SO4. The long runoff path and the slower water cycle process have a high degree of water-rock interaction, which belongs to the end of groundwater runoff or excretory area;(2) The Neogene thermal storage temperature in the study area is estimated to be 71~134℃ through the chemical temperature scale, and the circulation depth of underground hot water is 1300~2200m, which is deeper than the buried depth of the top surface of the granite crystalline basement in the study area;(3) The main heat source of the Neogene geothermal system in the study area is the partial molten layer in the deep crust.The groundwater of the Neogene aquifer is heated by the heat conduction of the deep high-temperature granitic rock mass.The Quaternary stratum is the cap layer to ensure that the temperature of the Neogene stratum decreases slowly ,forming a low-temperature geothermal system. This study has deepened the understanding of the influence of hot dry rock geothermal system on shallow hydrothermal geothermal system.