【作者】 何建坤；

【Author】 HE JIANKUN Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

【机构】 中国科学院地质与地球物理研究所；

【摘要】 太行山是我国最大地壳厚度转变带之一.本文从地壳厚度转变带动力学不稳定性出发,应用地壳黏-弹性、幂律流体本构关系开展了二维有限元模拟.结果表明,由于山西高原重力荷载,太行山地壳厚度转变带将发生下地壳黏性流变,下地壳流变将导致盆地区中、下地壳动力学性质脱耦,形成中、下地壳间近水平剪切.这一剪切是诱发上地壳有效水平挤压应力在地壳厚度转变带不断减小、在盆地内不断增大的主要原因.经8.6 Ma后,在3 km高原重力作用下,盆地区上地壳可形成约30 MPa近水平挤压.华北东部盆地北西西-南东东的挤压主要受太行山地壳厚度转变带下地壳流变所造成的动力学制约,与区域板块作用导致的远程应力场可能无直接联系.更多还原

【Abstract】 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.更多还原