Thermal Geochemical Characteristics Of Typical Geothermal Fields In Jizhong Depression

The geothermal exploitation potential of Jizhong Depression is huge,and numerous researches have been carried out in the past few decades.However,the exploration of deep geothermal resources still relies heavily on geothermal drilling and geophysical exploration,and there are some problems such as high drilling cost and uncertain geophysical interpretation.The combined exploration of geochemistry,geothermal drilling and geophysics is one of the development directions to reduce the cost and improve the accuracy of interpretation.This paper applies geochemical methods,geothermal geophysical methods,rock radiogeochemical methods,and in-depth studies the regional soil front halo elements,the water radon,shallow geothermal field,and thermophysical properties of rocks,in order to provide theoretical guarantee and data support for the exploitation and utilization of geothermal resources in study area.The main conclusion for this paper is as follows:The soil front halo elements such as As,Bi,Sb,Hg,Be,As,Li,Cu,Zn,Mn,Co,Cs,Sc,Ni,Pb,Rb,Sn,Mo,W are significantly correlated and enriched in different degrees.The contents and outliers of the front halo elements of Niutuozhen Uplift in the south of the study area are higher than those in Daxing Uplift,indicating that deep and large faults such as Daxing Fault and Niudong Fault are closely related to these elements.The area with high value of radioactive element ²¹⁰Po and the water radon is located near Niutuozhen.The contents of the front halo elements such as As,Sb and Bi in the rock are lower than those in the soil and there is little relationship between them.The enrichment of geothermal-related elements in the soil is related to the upwelling of deep hydrothermal fluids along deep and large faults.The geothermal field of 4?5m shallow layers in the study area is distributed in a concave-convex banded pattern,low in the sag area and high in the uplift area.There is a geothermal temperature of 5m>4m near the southern Niutuozhen,indicating that the southern Niutuozhen has better geothermal resources than other areas in the study area.The geothermal temperature of 5m and 4m has no obvious correlation with the anomalous distribution of the soil front halo elements.The thermal conductivity of limestone and dolomite in the study area is high,with an average value of 3.92W/m K and 5.75W/m K,respectively.The low radiogenic heat generation rate,with an average value of 0.75?W/m³ and 0.19?W/m³,respectively,indicates that the rock strata are beneficial to the conduction of deep heat flow,which is of great significance to the formation of heat reservoir.The overburden mudstone and conglomerate have large thickness,good water permeability,and low thermal conductivity(the average value is 2.35W/m K and 3.24W/m K),which are good capping beds for deep heat reservoir.The thermal conductivity of deep gneiss is low(2.59W/m K on average),but the radiogenic heat generation rate is high(1.26?W/m³ on average),which is beneficial to thermal reservoir insulation.Geothermal formation in the study area is established,the paper calculates the contribution of crustal heat flow in the heat flow is 36.91%?48.37%,the contribution of crustal heat flow is less than 50%,belong to the typical"hot mantle cold crust"ithospheric thermal structure,in the study area is the main heat source from deep mantle heat conduction,and thermal lithosphere thickness is 90?138 km,east west thick thin characteristics,related to the eastern north China Craton destruction.In summary,the study area has very favorable conditions in heat source,heat storage,cap rock,hot fluid channel and other elements,and has a great prospect of development and application.