裂谷盆地构造-热演化模拟中几个问题的讨论  

Discussion on several problems in tectono-thermal modeling of rift basins

作　　者：刘琼颖[1,2] 何丽娟[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院大学,北京100049

出　　处：《地球物理学报》2015年第2期601-612,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金重大研究计划(91114202)资助

摘　　要：裂谷盆地的构造-热演化模拟是在岩石圈尺度计算裂谷盆地形成演化过程中的热历史和沉降史.拉张模型实现了构造和热的完美结合,在描述裂谷盆地沉降和热流演化方面取得了很大的成功.本文使用二维运动学模型,通过有限元方法,在拉格朗日坐标系下进行拉张背景下的构造热演化模拟,探讨了拉张模型中初始地壳、岩石圈厚度、软流圈对流、模型上边界对构造热演化的影响,以及载水和载沉积物两种情况下盆地侧翼抬升的差异.Tectono-thermal modeling of rift basins is to calculate the thermal and subsidence history of a rift basin during its formation and evolution on a lithosphere scale,which links tectonic and thermal developments perfectly.However,most extension models have the following problems：assuming the lithosphere to be 125 km thick initially,considering heat conduction in the asthenosphere only,controversial setting of the upper boundary and rarely including thermal effects of sediments.Some effects on the tectono-thermal modeling are discussed,including the initial crustal and lithosphere thicknesses,the convection of asthenosphere and the upper boundary of the model.We also calculate the differences of rift flank uplift between water and sediment loading models. The tectono-thermal modeling is based on a two-dimensional non-instantaneous extension model using the finite element algorithm in the Lagrangian system.By solving the heat conduction equation,the thermal history and tectonic subsidence history of the basin are modeled simultaneously. The results are as follows：（1）Initial crustal and lithospheric thicknesses have great influence on tectono-thermal modeling,especially on the tectonic subsidence.（2）Compared to the model considering heat conduction in the asthenosphere only,the heat convection model has slower tectonic subsidence and thermal decay rates,and temperature from lower crust to the bottom of the model is significantly higher.（3）The fixed or moving upper boundary during themodeling affects the calculated heat flow and tectonic subsidence in the thermal subsidence phase,and has remarkable influence on the temperature field.The effect increases with the increasing of the stretching factor.（4）Rift flank uplift of the water loading model would disappear within 200 Ma while the uplift would be stable at a certain value for the sediment loading model. If the initial crustal and lithospheric thicknesses are uncertain in the modeling,sets of initial thicknesses should be given.The optimum ini

关 键 词：裂谷盆地 构造-热演化模拟 拉张模型 热流 构造沉降 温度场 

分 类 号：P314[天文地球—固体地球物理学]