ABSTRACT

The Ordos Basin located in the Western North China Craton (WNCC) has been confirmed to have undergone large-scale lithospheric thinning at the end of the Early Cretaceous (130 ~ 90 Ma), but investigations involving its lithospheric thermal structure in the Mesozoic and Cenozoic are limited. In this study, we employed a 1D, steady-state, heat conduction equation to calculate mantle heat flow and its partitioning, the Moho temperature and the thermal lithospheric thickness of different tectonic units in the Ordos Basin based on an analysis of thermal history reconstruction and crustal layering models. The results suggest that the peak of mantle heat flow at the end of the Early Cretaceous varied between 46.65 mW/m² and 62.97 mW/m², far exceeding 50% of surface heat flow, which shows a typical ‘hot mantle and cold crust’ type of lithospheric thermal structure, and the lithospheric thinning reached a minimum thickness of 50 ~ 75 km. This was followed by a thermal decay phase in the Late Cretaceous, and a significant vertical thickening of lithosphere occurred during this period, during which the lithospheric thickness increased to 78 ~ 133 km by the end of the Late Cretaceous. Since the Cenozoic, the ratio of mantle to surface heat flow gradually declined to less than or close to 50%. At present, the average mantle heat flow in the Ordos Basin ranges from 22.10 mW/m² to 38.76 mW/m², the lithospheric thickness is between 81 ~ 158 km, and the Moho temperature entirely surpasses 600°C. In addition, we discuss potential factors and uncertainties in the thermal structure calculation. Combined with previous studies, we suggest that the lithosphere in the WNCC has been thinned locally due to asthenosphere upwelling.

摘要

位于华北克拉通西部（WNCC）的鄂尔多斯盆地在早白垩世末期（130～90 Ma）已被证实经历了大规模的岩石圈减薄，但涉及中、新生代岩石圈热结构的研究是有限的。在这项研究中，我们采用一维稳态热传导方程来计算鄂尔多斯盆地不同构造单元的地幔热流及其分区、莫霍面温度和热岩石圈厚度，基于热历史重建和地壳分层模型。结果表明早白垩世末期地幔热流峰值在46.65 mW/m ²和62.97 mW/m ^{2 之间变化}，远超过地表热流的50%，呈现出典型的“热地幔冷地壳”型岩石圈热结构，岩石圈减薄厚度最小达到50～75km。紧随其后的是晚白垩世的热衰变阶段，在此期间岩石圈发生显着的垂直增厚，到晚白垩世末岩石圈厚度增至78～133 km。新生代以来，地幔与地表热流之比逐渐下降到小于或接近50%。目前鄂尔多斯盆地平均地幔热流为22.10 mW/m ²～38.76 mW/m ²,岩石圈厚度在81～158km之间，莫霍面温度完全超过600℃。此外，我们讨论了热结构计算中的潜在因素和不确定性。结合之前的研究，我们认为 WNCC 中的岩石圈由于软流圈上升流而局部变薄。