中上扬子区奉节—观音垱剖面深部温度场及热结构特征

Deep temperature and thermal structure along the Fengjie-Guanyindang geotraverse in mid-upper Yangtze area

在大地热流密度分布的基础上,本文基于二维稳态热传导方程,根据研究区热导率、生热率等热物理性质参数,对横穿川东北地区、秭归盆地、黄陵穹窿和江汉盆地等几个构造单元的奉节(FJ)—观音挡(GYD)地学剖面进行了温度场数值模拟研究,获得了其深部热结构认识。模拟结果显示,地幔热流自西向东逐渐升高,变化范围约为25.3~34.7 mW/m^2。莫霍面温度大约在380℃~450℃之间变化。热岩石圈厚度自西向东先稍微增厚,后逐渐变薄,变化范围约为115~171 km。江汉盆地中新生代的伸展作用使其地幔热流稍有升高,"热"岩石圈厚度相对较薄(约116 km);而川东北地区则受到早期的挤压和晚期的抬升剥蚀作用,地幔热流相对较低,其深部"热"岩石圈厚度也相对较厚(约168 km)。

Based on the terrestrial heat flow and the two-dimensional steady-state heat conduction equation, a 2-D geological-geophysical model along the Fengjie-Guanyindang geotraverse in mid-upper Yangtze area was constructed. The profile crosses Chuandongbei regions, Zigui Basin, Huangling Dome and Jianghan Basin. The temperature field was calculated under the constraints of heat production rate, thermal conductivity along the profile. The simulation results show that mantle heat flow along the profile increases gradually from west to east ranging from 24.8 to 35.5 mW/m2. The temperatures at Moho vary from 380 ℃ to 450 ℃. From west to east, thickness of the thermal lithosphere increases slightly then decreases gradually, ranging from 115 km to 171 kin. The extension in Meso-Cenozoic raised the mantle heat flow in Jianghan Basin. While the compressional tectonic background and denudation made mantle heat flow in Chuandongbei regions lower with thick thermal lithosphere.