A comparative study on thermal properties of rocks and their geothermal effects in the Pearl River Delta and surrounding typical areas
The Pearl River Delta is located in the south of the Cathaysia Block.Although several hydrothermal geothermal fields have been found,the geothermal aspect is poorly researched.The study of thermal properties is one of the most fundamental and important tasks in geothermal research.In this study,we measured the density,thermal conductivity,thermal diffusivity of 100 surface rocks,and tested the U,Th,K2O content of 50 magmatic rocks in the Pearl River Delta and its surrounding areas,and calculated the volume heat capacity and radioactive heat production rate(RHPR)respectively.The results indicate that the thermal conductivity of fine sandstone in clastic rocks is the highest(3.94±0.92 W·(m·K)-1),while the shale is the lowest(2.68±0.55 W·(m·K)-1).There is a significant positive correlation between the thermal conductivity and thermal diffusivity.Based on the thickness of strata,a stratigraphic thermal properties column is established,with the Paleogene having the lowest thermal conductivity.The stratigraphic thermal properties are related to the sedimentary environment.The thermal conductivity of basalt in magmatic rocks is the lowest(2.17±0.13 W·(m·K)-1),while the average thermal conductivity of granite is 3.87±0.59 W·(m·K)-1.The RHPR of granite ranges from 0.36 to 14.23 μW·m-3,with an average value of 5.23±3.03 μW·m-3,indicating a high heat production granite.Based on the radioactive element content measurement of previous researchers in this region,it is found that,compared to K2O,U and Th have stronger correlations with RHPR and contributes more to heat production.Compared to granite,basalt has a lower RHPR and its K2O contribution to heat production is higher.The new data provides a new perspective for determining regional heat flow and evaluating geothermal resources.The simulation and calculation results indicate that the sedimentary layers of the Sanshui Basin can accumulate and preserve deep heat,and form high-temperature(＞150 ℃)zones near the basement.The heat flow generated by granite bodies in the upper crust exceeds 45 mW·m-2,accounting for more than half of the average surface heat flow.Both basins and granite bodies have geological conditions for the formation of high-temperature geothermal resources.In addition,the RHPR of felsic magmatic rocks gradually decreases with time,which is related to the mixing effect of basaltic magma from the mantle.
Pearl River DeltaThermal propertiesRadioactive heat productionGeothermal effectGranite
万方数据
维普
