An Analysis Of The Hydrochemical Characteristics And Geneses Of The Hot Springs In The Yunlingong Area Of Kangding In Sichuan

Kangding is located in the eastern margin of the Qinghai-Tibet Plateau and belongs to the western Sichuan subtropical zone on the eastern side of the Yunnan-Tibet geothermal zone.Geothermal resource in the Kangding area is abundant,and the geothermal geological background is superior.The Yulingong Hot Spring is located to the south of the city of Kangding.The tectonic activities in the Kangding area were strong,and the large size of granite occur with abundant hydrothermal activities.This paper mainly examines some hot springs near Yulingong,including4 hot springs and 2 geothermal wells,namely the Longtougou Hot Spring,Kuaishuang Hot Spring,Jinjiaheba Hot Spring and Guanding Hot Springs.A total of 11 water samples were collected.Studies of the hydrochemical and isotopic characteristics,genetic model and the influence factors of travertine deposition of these hot springs are helpful in enriching the understanding of geothermics and provide scientific basis for the reasonable utilization and development of the Yulingong hot springs.Fractured-type geothermal reservoirs occur in the study area,and the distribution of the hot springs are controlled by the Xianshuihe fault.The temperature of hot springs in the study area ranges from 43.2 to 87.1?,TDS from 60.4 to 2610 mg/L,p H from 6.1 to 8.1,Eh from-356 to271 m V,and the hydrochemical types are of HCO₃-Na type or HCO₃·Cl-Na type.The main components in the water samples include Na⁺,K⁺,Ca²⁺,Mg²⁺,SO₄^2-,HCO₃^-and Cl^-.The trace elements mainly include Li,Rb,Cs,Sr,Ba,etc.The REE distribution pattern of the water samples shows a slight increasing trend with upward fluctuation.The?REE contents range from 0.014 to0.295?g/L,showing the characteristics of the deficiency of light rare earth elemets,the enrichment of heavy rare earth,and positive Eu anomaly and negative Ce anomaly.The reverse simulation is carried out by using the PHREEQC software,and the results show that the minerals such as albite and potassium feldspar are dissolving and the minerals such as calcite and dolomite are precipitating in the process of deep circulation of the thermal groundwater.The characteristics of stable hydrogen and oxygen isotope show that the Yulingong Hot Spring is of meteoric origin.The altitude of the recharge areas of the hot spring is estimated as5200 to 6200 m,which are located in the eastern and western snow mountains,and the temperature of the recharge areas is from-5 to-10?.By applying the geothermometers and the silicon enthalpy equation method,the temperature of the geothermal reservoirs of the hot spring ranges from 150 to 190?,and the proportion of cold water mixing in some spring vents exceeds 60%.Some vents of the hot springs are depositing travertine with morphologies of slope,tower and cone.The factors affecting the deposition of travertine are identified by analyzing the physical and chemical parameters of the hot spring water.The results show that CO₂,P_CO2,p H,TDS and concentrations of Ca²⁺,HCO₃^-and?Ca/?HCO₃ of the hot spring water cannot be used to judge whether the hot spring travertine deposits.By analyzing the relationship between the different ion pairs concentration of Ca²⁺and SI in the Guanding hot springs,it is found that the change of concentration of ion pairs Ca CO₃⁰ is consistent with the change of SI,indicating that Ca CO₃⁰concentration may directly affect the deposition of travertine,and the approximate exponential relationship between Ca CO₃⁰ and SI is given.The genetic mode of the Yulingong Hot Spring in the study area can be summarized as follows:the melting water of snow and ice(meteoric origin)in the snow mountains with an elevation of more than 5000 m on the eastern and western sides infiltrates the groundwater,it undergoes deep circulation along the faults,and is heated by deep heat flow to form fissured-type thermal groundwater,which may mix with deep magmatic water.When the hot water flows upward,and rise to the surface to form hot springs,it mixes with shallow cold groundwater,and silicate and carbonate minerals in the surrounding rocks dissolve.As the pressure drops,dissolved CO₂ escapes from the hot water,resulting in precipitation of carbonate minerals to form travertines.