| The Kangding-Moxi fault located in the intersection of the Xingshui River and Longmenshan faults in western Sichuan is present complicated structures,secondary faults such as Detuo and Hailuogou faults.Series of hot springs are distributed in N-S direction.Which is consistent with the geological structure line,The tectonic frame is closedly related to the distribution of underground hot water.The hydrogeochemical characteristics of underground hot water are the products of long geological processes in the geothermal formation.These geological effects are reflected by the chemical characteristics of underground hot water and determine the genetic model of underground hot water formation.In this paper,the underground hot water of the Kanding-Moxi fault zone in western Sichuan isregarded as the studying object.Field geological survey and field parameter test were carried out and then water samples are collected for experiments systematically.The hydrogeochemical characteristics were analyzed,the temperature and circulation depth are estimated.The hydrothermal geochemical process of hot water was discussed,and the geothermal geologic structure of hot spring in the study area was proposed,and the genetic model was summarized.The main research results of this paper are presented as follows:(1)The aqueous chemistry types of the underground hot water in the study area are mainly HCO3-Na?HCO3·Cl-Na?SO4·HCO3-Ca·Na,showing enrich in water triplicity and Piper diagram.The chemical types of calcium-type hot water are SO4·HCO3-Ca·Na type,and the chemical types of drilling water are HCO3·Cl-Na.The correlation between the stable isotopes ?D and ?18O in the underground hot water indicates that the underground hot water in the study area is mainly subject to the precipitation of atmospheric precipitation.(2)Different geothermal thermometric scale was used to estimate the thermal storage temperature of underground hot water in the study area.According to the K-Mg temperature scale,the thermal storage temperature of the underground hot water exposed in the natural state of the study area range from 54.7 to 108.2 ?.The mixed model of the silicon-enthalpy curve,the conservative component scatter plot and the Schoellor graph shows that the underground hot water in the study area is mixed with the shallow underground water,and the mixing ratio of the shallow groundwater is higher.Along the fracture zone from north to south mixing ratio is increased,calcium-rich hot water by the mixed effect of the larger sodium-rich hot water.The depth of the hot water exposed in the natural area of the study area vary from 851 to 1923 m.(3)The natural hot water exposed in the study area has the typical characteristics of groundwater formed under rock weathering and filtration,and has experienced long runoff and sufficient water-rock interaction.Hydrogeochemical effects occur in the dissolution of silicate minerals and carbonate minerals,mainly affected by the later.(4)The genetic model of underground hot water in the study area is that under the background of high regional heat flow,the infiltration of infiltration of atmospheric precipitation is carried out,and the crushing zone along the Kangding-Moxi fault is deep,and the migration from the recharge area to the discharge area In the process,underground hot water estracts heat from the rock,"intake" components by leaching out of the rock.In this way,both the heat and aqueous chemical components of the underground hot water in the terrain and head pressure difference in the role of the intersection between main secondary fractures or valley exposed,and varying degrees-degrees mixed with shallow groundwater,forming a low temperature geothermal resources. |
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