MECHANICAL INSTABILITY OF THE TAIHANG MOUNTAINS CRUST TRANSITION ZONE AND ITS RELATION TO THE TECTONIC COMPRESSION IN ITS FRONTAL CENOZOIC BASIN
太行山地壳厚度转变带动力学不稳定与前缘盆地构造挤压的关系

The Taihang Mountains is one of the great crust-transition zones (CTZ) in China. To reveal the mechanism of the special deformation,this study makes a numerical modeling based on the viscoelastic properties of crustal rocks. Result indicates that under the gravitational loading of the Shanxi plateau, the crust beneath the Taihang Mountains CTZ is mechanically instable due to initiation of the lower-crust ductile flow. The ductile flow of lower crust causes the mechanic de-coupling between the lower and the upper crust, and favors to induce basal sheer along the brittle-ductile transition belt. Since the ductile flow is from the plateau side to the basin side, this basal shear will weaken the compression in the plateau and enhance the compression in the basin within the middle and upper crust. From the numerical result, it is concluded that the mechanics of tensile-compression coupling in the north China block is probably not initiated by regional stress field associated with plate-boundary interactions, but mainly by local stress variation caused by the crust ductile flow.