鄂尔多斯盆地石炭纪中央古隆起形成机制

将鄂尔多斯盆地简化为受南北挤压的等厚各向同性弹性薄板模型进行应力—应变场数值模拟,力图揭示鄂尔多斯地区石炭纪出现的细腰状中央古隆起的形成机制。模拟中Z轴方向应变(εz)正值区对应于盆地内部的隆起区,zε正等值线形态对应于隆起形态;单轴挤压条件下,εz正等值线总会呈现沿应力轴方向延伸的细腰状形态;点作用力产生的zε正等值线范围局限,而线作用力产生的εz正值区分布较广。模拟结果表明鄂尔多斯盆地石炭纪细腰状隆起是在南北边界受挤压条件下,应力—应变在盆地内部传递过程中所必然出现的结果,南北向点作用力比南北向线作用力产生的zε等值线形态更接近于鄂尔多斯盆地中央古隆起形态;点作用力可能代表了石炭纪微板块间的点碰撞或者弧—陆碰撞。

Formation Mechanism of Carboniferous Central Paleouplift of Ordos Basin

To reveal the formation mechanism of the Carboniferous slender-waist-shaped central paleouplift in Ordos Basin,a series of stress-strain simulations were carried out,in which the basin was simplified into an isopachic,isotropic and elastic shell model and loaded with the NS trending extrusion.The positive strain along Z axis(ε_(z)) corresponded to the uplift,and the shape of positive ε_(z) isoline_()represented that of the uplift.Repeated simulations showed that the outline of positive ε_(z) isoline always appeared slender-waist shape along the maximum stress axis,which approved that the central uplift resulted from stress transfer in the Ordos Basin under the NS trending extrusion.(More-)(over),the shape of the positive ε_(z) isoline caused by the point force was narrow,while that by the linear pressure was relatively wide in the simulations.Since the shapes of ε_(z) isoline induced by the linear pressure was less analogical to the geological uplift in the Ordos Basin,the linear pressure was less reasonable than the point force,which may represented the point collision between microplates or arc-continent collision during Carboniferous.