燕山中部地热流体化学特征及成因OA

The central Yanshan region is characterized by abundant geothermal resources and favorable geothermal geological conditions,exhibiting significant geothermal resource potential.As a representative area,Chengde City's geothermal fluid chemical characteristics and genetic mechanism play a crucial role in guiding regional geothermal resource development and utilization.This study focuses on the distribution of geothermal resources and the chemical characteristics of geothermal fluids in Chengde City.Through field sampling and laboratory testing,we systematically investigated the major-ion composition,iso-topic characteristics,and evolutionary patterns of geothermal fluids,thereby revealing the controlling factors and genetic mechanisms governing their chemical characteristics.The results indicate that water-rock interactions in most geothermal waters of the study area have not reached equilibrium,with dissolution processes still ongoing.Stable isotope analysis of D and 18O demonstrates that the geothermal water originates from atmospheric precipitation and is stored in medium-to low-temperature reservoirs,with recharge elevations ranging from 828.08 to 2 757.70 m.The ¹⁴C dating method was employed to determine the age of the geothermal water in the study area,which ranges from 24.16 to 42.76 ka,most of which is paleo-groundwater.Calculations of the metamorphic,desulfation,and salinization coefficients indicate that the geothermal fluids in the study area are generally in an oxidized environment with poor confinement,exhibiting low concentrations and intense ac-tivity.In the central part of the study area,the temperature of the shallow geothermal reservoir ranges from 56.95 to 149.10℃,while that of the deep geothermal reservoir ranges from 89.40 to 188.10℃.The mixing ratio of cold water ranges from 47%to 84%,and the depth of the thermal circulation ranges from 1 575.19 to 6 757.85 m.Based on these findings,we summarized the genetic mechanism of geothermal resources in the study area,providing a scientific basis for the sustainable development of geothermal resources and hydrogeological research in the central Yanshan region.