Analysis of geothermal resources in the northeast margin of the Pamir plateau

The northeastern margin of the Pamir Plateau in China is situated in the northwestern Tibetan Plateau, proximity to the Indo-Asian subduction zone. The region is characterized by intense tectonic activity, high terrestrial heat and abundant groundwater, contributing to the formation of an extremely promising high-temperature geothermal system. By integrating various data sources, including water chemistry, isotopes, volatile gases, and radiogenic element analysis, with regional structural and geological data, a local geothermal genetic model is proposed. The snowmelt water and atmospheric precipitation infiltrated along the deep fault are mixed with the deep magmatic water, and heated by the magma, granite radioactive elements, fracture friction and a small amount of mantle heat flow to form the deep parent material thermal fluid (370 °C). The parent material thermal fluid continues to expand and rise, dissolves the surrounding rock minerals, and forms multiple shallow and deep thermal reservoirs (111.68 °C-260.96 °C). The fluid in the geothermal reservoir rises again under the driving of pressure difference, and forms Group A high temperature hot water after adiabatic cooling. As the hot water migrates upward and laterally flows into the secondary fault, mixed cooling and conduction cooling occur, resulting in the formation of Group B and C medium and low temperature water. In the study area, medium and low temperature hot water of Groups B and C are formed. Due to the different degree of mixed cold water, Group C hot water shows relatively higher content of Ca²⁺ and HCO^3- ions and lower outcrop temperature compared with Group B. The recharge height of the geothermal water is inferred to be 3810–5540 m, and the recharge sources are mainly snowmelt water and atmospheric precipitation. These findings suggest a multi-faceted heat source regime, encompassing crustal radioactive heat generation, molten magma heat, tectonic frictional heat, and mantle heat flow.