The temperature dependence of thermal conductivity for lherzolites from the North China Craton and the associated constraints on the thermodynamic thickness of the lithosphere

Abstract

In this study, the authors aimed to compute the lithospheric thickness beneath the North China Craton (NCC) by combining the measurement of the thermophysical properties of lherzolite xenoliths from the Cenozoic basalts in North China with the corresponding geothermal data, thus providing geothermal constraints for the lithospheric thinning beneath the NCC. Based on the precise measurement of the thermal diffusivity, specific heat capacity at high temperatures, and density at room temperature for lherzolites from the NCC, the temperature dependence of lattice thermal conductivity for lherzolites was obtained. Combining with the surface heat flow, heat production of rocks and other relevant conditions, the average thickness of the lithosphere beneath the NCC and the lithospheric thickness of secondary massifs were computed, and we identified the relationship between depth and temperature beneath the NCC and each secondary massif. The computed lithospheric thickness is highly consistent with the results of geophysical observations. The computation results of this study indicate that the average lithospheric thickness of the current NCC and the average thickness of the eastern NCC were 101 and 75 km, the lithospheric thickness of the Ordos block increases from 110 km in the east to approximately 200 km in the west, and the average thickness is 141 km, that were thinner than that in the Archean era (200 km) by approximately 100, 125 and 60 km. These results reveal that, in addition to eastern NCC, the Taihang orogenic belt and Ordos block have also experienced varying degrees of thinning with a thinning centre oriented in the north–south direction, consistent with the direction of the thinning centre along the Tanlu fault zone beneath the east NCC.