Provenance Analysis Of Xiqin Geothermal Field,in Lazi County,Tibet

This project selects the Xiqin geothermal field in Lazi County,Tibet as the research object,comprehensively analyzes the Regional geological background,hydrogeological conditions and other achievements,systematically analyzes the geothermal geological conditions in the Xiqin area;on this basis,carries out systematic geological survey and collects geothermal Fluid and water chemical analysis and isotope analysis,combined with geophysical exploration data,construction exploration and logging data,pumping test and dynamic monitoring data,and other comprehensive exploration techniques,Identification of the distribution,recharge,runoff and excretion of geothermal resources in the Xiqin area.research and analysis of the"store","stratum","aisle"and"source"of geothermal water,and explore its genetic model.Comprehensive evaluation of geothermal resource reserves and geothermal fluid quality,To provide a basis for the scientific and rational use of geothermal resources.The Xiqin geothermal display area is structurally located in the south extension of the Shenzha-Xietongmen north-south active tectonic belt and is a typical representative of neotectonic activities in the area.It consists of a series of active faults,strip-shaped fault basins(fracture belts)and fault block mountains(bumps)and associated hydrothermal(hot springs)and seismic activities,which are decisive control for heat storage patterns.The area is located in the Sakya Chongqu Valley,with a large Quaternary river alluvium.The geotectonic location of this area is in the Yarlung Zangbo suture tape.The tectonic activity is strong,the rock fissures develop,and the atmospheric precipitation is easy to infiltrate and runoff.It is another geothermal area discovered after the Naqu-Nimu land tropics.The high-temperature underground hot water in the area is mainly HCO3-Na·Ca water.The average thermal storage temperature range is 66.3-96.6°C by the SiO2 geochemical temperature scale in the display area,which is the medium-low temperature geothermal display area.There may be different proportions of cold water mixed in the underground hot water.The p H of the hot water is between 7.08 and 7.39,which belongs to neutral and HCO3-Na·Ca type fresh hot water.The substantial negative correlation between SiO2,F,Sr and Cl may indicate different degrees of mixing of cold water.According to the?D and?¹⁸O values of atmospheric precipitation,it is mainly used to analyze the recharge of hot water from local atmospheric precipitation.The water-rock isotope exchange rate of groundwater at a lower temperature is extremely slow,with a slight ¹⁸O drift.It is further estimated that the elevation of the recharge zone is 4100-4608m,and the average temperature is 8.7°C.Compared with other well-known hot spots in Tibet,the Xiqin Hot Spring belongs to the medium-low temperature geothermal system.At the same time,the calculation results of different geothermal temperature scales are analyzed.The relationship between SiO2,Na/K,K/Mg and 1000/T in the study area can be seen.The water falls below the Na/K balance line,indicating that the underground hot water is mixed with cold water of varying proportions,affecting the water-rock reaction that does not reach full equilibrium.Therefore,the thermal storage temperature of the Silica temperature standard method is estimated to be 96.6°C.Analysis of heat source,water source,thermal reservoir and migration channel of the Xiqin geothermal fluid,The heat source of the Xiqin Hot Spring may originate from the condensed and positioned magma melt in the deep crust of the northwest side,replenishing atmospheric precipitation and snow and ice in the base rock mountain area on the northwest side of the field,Mainly along the deep EW to the large fault F1,is the structural belt in the area,the infiltration into the ground,along the fault runoff,through the deep circulation to the base heat source heating,the combined effect of hot water in hydrostatic pressure and heat convection into upward movement.Then,along the next-stage NNW,the F2 heat-control structure channel is uplifted to form a thermal reservoir.The F2 fault is both a deep-flow path for groundwater and a thermal reservoir in the middle and deep layers.Supported by the F4 reverse fault is located in the piedmont area on the south side of the river valley.At the same time,hot water is mixed with cold water to varying degrees during the upwelling and water-rock reactions occur underground,which changes the chemical composition of the initial hot water ion in the underground.The form reveals the surface.