China’s ‘Double Carbon’ policy (carbon peaking and carbon neutrality goals), means geothermal energy, as a clean renewable energy, has gradually received attention in the energy domain. The thermal conductivity of rock plays an important role in studying the geothermal field and evaluating the amount of geothermal resources, as heat conduction is the main way that the Earth conveys heat to the outside. In order to quantitatively understand the thermal conductivity of rock and the factors influencing it, the thermal conductivity of 135 rock samples were measured by the transient plate heat source method (TPS) and the porosity, density and mineral composition of some selected samples were also measured to provide a dataset for the understanding on the influencing factors of rock thermal conductivity. The results show that the thermal conductivity of volcanic rocks is the lowest, the thermal conductivity of clastic rocks is close to that of intrusive rocks, and the average thermal conductivity of carbonate rocks is the highest, with the thermal conductivity of intrusive rocks, volcanic rocks, clastic rocks and carbonate rocks ranging from 1.62 to 4.00 W/m·K, 1.09 to 2.07 W/m·K, 1.52 to 5.23W/m·K, and 2.34 to 6.55W/m·K respectively. The average thermal conductivity of the four types of rock samples is 2.54±0.53 W/m·K, 1.50±0.24 W/m·K, 2.77±0.83 W/m·K and 4.21±1.28 W/m·K, respectively. There is a close relationship between thermal conductivity and rock fabric. Thermal conductivity of the rock-forming minerals is an important factor affecting rock thermal conductivity. Quartz, the typical mineral with a high thermal conductivity can obviously affect the thermal conductivity of intrusive rocks and clastic rocks, and dolomite content obviously affects the thermal conductivity of carbonate rocks. The thermal conductivity of clastic rocks is negatively correlated with porosity, it decreases with an increase of porosity in a larger porosity range, but the trend is not obvious when the porosity is relatively low. There is a positive correlation between rock thermal conductivity and density. The anisotropy of thermal conductivity is mainly caused by the stratified structure of rocks, that is, there is basically no anisotropy in the thermal conductivity of massive intrusive rocks. The anisotropy coefficients of stratified rocks range from 1.08 to 2.08. A low thermal conductivity cap plays an important role in the accumulation of geothermal resources, which makes the heat from depth accumulate at the bottom of the cap and the top of the basement, resulting in higher temperature distribution in the upper part of the geothermal reservoir.The results provide a reference for understanding the influence of rock fabric on thermal conductivity, the modeling of rock thermophysical parameters in a deep temperature field and geothermal resource evaluation.

The South China Cathaysia block is located in the southeast margin of the Eurasian plate, and is an important mineral and geothermal resource area in China. After several tectonic events, granites of different tectonic stages are widely distributed in the area. Granitoids play a special role in the dynamics and evolution of the Earth and its thermal state, and the heat generated by their radioactive decay is one of the main heat sources on Earth. The high radioactive heat-producing hot dry rock resources are mainly distributed in South China, and the decay heat of radioactive elements is the main heat source, and the lithology is mainly granite. Based on the statistics of granite data in South China, this paper analyzes the heat generation rate of different granite types in different areas of South China, and summarizes the radioactive heat generation characteristics of granite in the study area and the relationship between them and terrestrial heat flow, which has reference value for understanding the main controlling factors of the geothermal field and the macro background of geothermal resource distribution in the study area. Based on the geochemical analysis of 1933 granite samples in South China, the following results are obtained: 1) The heat generation rate of granite ranges from 0.40 to 17.45 μW/m³, with an average heat generation rate of 4.56±2.66 μW/m³, and there is a good correspondence between them according to the distribution of ground heat flow and heat generation rate; 2) The contribution rates of radiothermic elements U, Th and K were 49.45%, 40.16% and 10.39%, respectively. At the same time, the concentrations of U, Th and Th/U varied greatly, and there was no obvious correlation with age; 3) There are differences in the heat generation rate of the three types of granite(Type I、A and S). The average heat generation rate of type I granite (3.86±2.43 μW/m³) is significantly lower than the average heat generation rate of type A and type S granite, which are 5.55±2.91 μW/m³ and 5.0±2.58 μW/m³, respectively; 4) A Monte Carlo method is used to calculate that the average heat yield of the Yanshanian granite in South China is 99.01×10⁵ GJ/a(1 GJ/a=10⁹ J/a), which is converted into standard coal 3.38×10⁵ t/a, and that of Indosinian granite is 63.13×10⁵ GJ/a, which is converted into standard coal 2.15×10⁵ t/a; 5) The calculation of two crustal models shows that granite plays an important role in the contribution of earth heat flow in South China. In the area covered by sedimentary strata, the contribution of Earth’s radioactive heat generation to surface heat flow is 29.13 mW/m², accounting for 41.61% of the total heat flow value. In the area of intrusive rock exposure, the contribution of crustal radioactive heat generation to surface heat flow is 43.85 mW/m², accounting for 51.76% of the total heat flow value.