Genesis analysis of the geothermal water in Dexi Geothermal Field,Baiyu County,western Sichuan——methods from hydrogeochemical and geophysical exploration
Objectives:In order to reveal the genesis mechanism of geothermal water in Dexi Geothermal Field.Methods:This study used techniques including hydrochemistry,isotopes,geothermometers,and audio magnetotelluric to analyze the genesis mechanism of geothermal water based on the hydrochemical data of groups 6 and nearly groups 12 of the geothermal water in Dexi Geothermal Field.Results:Results show that the geothermal water in Dexi Geothermal Field is of the karst type,with the primary heat sources being fault friction heating and geothermal gradients.At 4073～4162 metres above the eastern high mountain,atmospheric precipitation and ice and snow melting water serve as its sources of recharging.The primary hydrochemical processes are the dissolution of carbonate minerals and cation exchange,which are very different from the hydrochemical characteristics of the surrounding geothermal water.The hydrochemical type is mostly HCO3-—Na+·Ca2+type.Controlled by the Zamagang Syncline and the Dexi Village Fault,the geothermal water in Dexi Geothermal Field is situated on the southwest wing of the Zamagang Syncline.The migration of underground geothermal water is facilitated by karst fractures,dissolution holes,and two sets of impermeable strata primarily made of slate and phyllite.The circulation depth of this water is around 1284～1576 metres.The Dexi Village thrust fault on the west side blocks the geothermal water during the migration process.The water is then transmitted upward along the faults and structural fracture zones,such as tension and brittleness,and is enriched in the karst fracture layer between carbonate and clastic rocks.This results in the formation of a thermal reservoir,which has a temperature range of about 75.0～89.6℃.Conclusions:This study may offer a crucial support for the development and utilization of geothermal resources in Baiyu County.
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