Regional structural controls on a hydrothermal geothermal system in the eastern Pingdingshan coalfield, China: A comprehensive review

The Cambrian limestone of the Pingdingshan coalfield in central China possesses substantial geothermal waters. The efficient extraction and utilization of these mine geothermal resources are crucial for the reduction of carbon emissions, thereby enhancing the sustainability of energy management in this coalfield. In this work, we collected data on geothermal waters in the eastern Pingdingshan coalfield, analyzed the chemical characteristics of geothermal water, and identified the control of regional structure on the geothermal system. Geochemical results show that the main type of Cambrian geothermal water in the eastern Pingdingshan coalfield is Na-CaHCO3-SO4, which is classified as a peripheral water source and is predominantly a product of water-rock interactions. The mean temperature of the Cambrian thermal reservoir is 68.6 degrees C, with an average geothermal water circulation depth of 1441 m within the Cambrian limestone. Isotopic data (518O and 5D) indicate that atmospheric precipitation is the principal source of geothermal water, forming hydrothermal geothermal resources through the heating of high-temperature rock during seepage. A slight positive 518O shift suggests minimal water-rock interaction with the surrounding rock, categorizing it as a low-temperature geothermal resource. Heat flow measurements in the eastern Pingdingshan coalfield range from 65 to 80 mW/m2, with an average geothermal gradient of 36.3 degrees C/km, characteristic of a high geothermal region. A distinct jump at the base of the PBR1 temperature curve points to the presence of a high-temperature Proterozoic thermal reservoir beneath the Cambrian limestone. The dual tectonic heat accumulation model determines the occurrence environment of the hydrothermal system in the eastern Pingdingshan coalfield. The geothermal system here is governed by the spatial configuration of regional structures and rock thermal conductivity, where extensional faults dictate the spatial morphology of hydrothermal systems, and variations in rock thermal conductivity influence heat conduction pathways.