Geothermal field and deep thermal structure of the Tianshan‐Altun region

Abstract

AbstractThis paper analyses the characteristics of geothermal gradient and terrestrial heat flow in the Tianshan‐Altun region on the basis of available published data, such as geothermal gradient, measured temperature during oil test producing, rock thermophysics, and heat flow. Based on the steady‐state heat conduction equation, this paper has set up a 3D model by adopting basin modelling method to carry out deep temperature field simulation, with the aim to determine deep thermal structural parameters, the lithospheric thermal thickness, and the crustal contribution rate to the terrestrial heat flow. The geological section of Golmud‐Ejin Banner and the geological section of West Kunlun‐Tarim‐Tianshan were selected to represent the regional temperature and its thermal structure. The results show that the Tianshan‐Altun region has a low temperature geothermal field (averaging temperature gradient 2.2 °C/100 m, heat flow 56.3 mW/m2). The Qaidam Basin has the highest value (averaging 3.2 °C/100 m, 57.4 mW/m2). The lithospheric thermal thickness of the Tianshan‐Altun region is between 110 and 210 km. There are great differences of lithospheric thermal thickness on both sides of the Altun‐Tagh Fault. The west has thicker thermal lithospheric thickness (160–210 km) than the east (110–180 km). The contribution rate of the crust to the terrestrial heat flow decreases in the following order: the Qaidam Basin, the Jiudong Basin, the Jungger Basin, the Tarim Basin, and the Tuha Basin. Sedimentary basins have higher temperature and thinner thermal lithosphere than tectonic orogens when at the same depth. It can be observed that great thermal differences exist on both sides of the Altun‐Tagh Fault. There are relative similarities of low temperature, deeper thermal structure, and thicker lithospheric thermal thickness among the Tarim Basin, the Junggar Basin, and the Yining Basin in a wide geological area because of their shared deep geological basement. The Qaidam Basin and the Hexi Corridor Basin, which are located to the east of Altun‐Tagh Fault, have higher thermal background.