Terrestrial heat flow in the baiyinchagan sag, erlian Basin, northern China

Abstract

The Baiyinchagan Sag of the Erlian Basin is a Mesozoic continental rift basin located in the eastern part of the Central Asian Orogenic Belt between the North China Craton and the Siberian Craton. The sedimentary fill comprises mainly the Cretaceous sandstones and mudstones underlying Cenozoic succession. Knowledge regarding the factors affecting the tectonic evolution of the Baiyinchagan Sag is lacking. The objective of this study is to obtain new terrestrial heat flow measurements in the Baiyinchagan Sag for constraints on its thermotectonic history. We obtained continuous temperature logs from three boreholes, namely Xi24, Xi3-76 and Xi30 with depths of 1230, 1660 and 2160 m, respectively. Additionally, we gauged the thermal conductivity of the lithologic samples of the main sedimentary rocks. Our analysis indicates that subsurface temperatures are affected by the convection of groundwater and subsurface warming. After removing the influence of groundwater and climatic effects, the subsurface temperature gradients of the Cretaceous Duhongmu and Tenggeer Formations range from 40.4 to 42.1 ℃ km−1. We performed water saturation correction for the measured thermal conductivity data. The thermal conductivities of the Saihantala, the Duhongmu, the Tenggeer, and the Aershan Formations were found to be 1.15, 2.13, 1.99, and 2.15 W m-1 K−1, respectively. Vertical Peclet number analysis of the temperature-depth profile of Xi3-76 borehole with a Peclet number of 0.16 indicates that the conductive heat transfer dominates in the component of the vertical heat transfer. The three new heat flow values range from 80.8 to 89.7 mW m-2, with a mean of 84.9 ± 3.4 mW m-2, significantly higher than the global and regional average whereas consistent with its deep thermotectonic regime.