The Provenance Analysis Of The Medium-High Temperature Geothermal Fluid In Cona,Tibet

Cona is located in the south of Tibet and the middle of the Himalayas.Its terrain is complex and varies.The study area has the natural geothermal geological conditions and it is rich in geothermal resources.But the energy construction is undeveloped relatively,which results in a series of difficulties to the local residents' production and living,especially heating in winter.It becomes particularly important to develop and utilize the local geothermal resources.In this paper,the hydrothermal characteristics of hot groundwater in the study area were analyzed by water chemistry piper,constant and trace element fingerprint and so on.By analyzing the data of the hot spring gas in the study area,we could summarize the material origin of geothermal fluid.The geothermometer is used to estimate the geothermal reservoir temperature.From geothermal fluid sources,the heat source and thermal storage,geothermal fluid migration channel,we could summarize the genetic model of geothermal field.As a consequence,the conclusion on analysis the thesis will be able to obtain:(1)The cause of Cona thermal field can be summarized as: In the west of the study area,the relief is tall and straight,the bedrock exposed to the surface,a large number of rain and snow melt water along the exposed rock fissure seeped into the deep.In the process of Surface water's migration,the channel may influence its way that move horizontally.During the migration,the groundwater is heated gradually.In the influence of hydrostatic pressure and thermal convection,Along the north of the region,the hot groundwater flow into F1 fault and go upwards,then it flows into the sandstone of Qulongongba group of Triassic upper system in depth of the thickness of 40-60 m,and it forms hot storage layer or warm spring in the low terrain.(2)The high temperature melting layer in the crust of Tibet has high heat and temperature,which provides a good heat source for medium and high temperature geothermal fluid in the study area.The geothermal fluid's migration and storage are controlled by topography and structure.The F1 fault and the F2 fault on the west side of the study area are the migration channels of geothermal fluid.The geothermal fluid is stored in the bedrock during the upward migration along the faults.The Quaternary unconsolidated layers above the bedrock reservoirs form aquiclude,which covers the bedrock.(3)The main chemistry type of surface water in the study area is HCO3-Ca and TDS is very low.The chemistry type of hot groundwater are SO4?HCO3-Na and HCO3?CO3-Na.The range of TDS is 0.32 to 0.40.In the deep heat reservoir,the original type of geothermal water is the HCO3-Na type water,because the hot groundwater is mixed by the cold water in the rise,showing a variety of hot water types.(4)Considering the groundwater is affected by the cold water in the rise,the groundwater have not reached water-rock balance.We utlize the geothermometer of SiO2 to estimate the geothermal reservoir temperature,which combined with temperature standard conditions.It shows the average temperature is 117.(5)By analyzing the data of Cona warm spring gas,we can see that the main component of the gas in the county is N2(about 93.6%),the CO2 and NH3 components are not detected in the gas,the H2 S content is about 16 ppm and the He content is high relatively.Slate and Mudstone are rich in radioactive elements of uranium and thorium.It is the helium component in the hot spring gas source,then it can be determined that the geothermal gas is a mixture of the shell-source component and the atmospheric component.