鄂东南铁山不对称骨节状石香肠构造基质层中的应变测量与分析

鄂东南铁山是亚洲首个发现骨节状石香肠构造的地区。以该区不对称骨节状石香肠构造为研究对象,利用惯量椭圆法对其基质层进行有限应变测量,获得真应变差、运动学涡度等相关参数及有限应变椭圆长轴展布方位的分布图。对所获数据资料研究表明:该不对称骨节状石香肠构造基质层的应变受其能干层控制,有限应变值与其离能干层的距离趋于负相关,且与其矿物颗粒粒径呈负相关,在平行于石香肠构造伸展方向上基质层有限应变分布不均;石香肠体附近与之相近规模的变形构造可使其相应基质中的应变分布紊乱;该不对称骨节状石香肠构造是由早期平行于层面简单剪切叠加晚期平行层面伸长、垂直层面压缩的纯剪切作用形成。与不对称鱼嘴状石香肠构造对比研究表明,两者基质层中简单剪切与纯剪切的分布均分别与其相对增厚与减薄区段对应,而两者形态的不同主要与石香肠体不连续处充填物的能干性不同有关,再次表明两者均是较好的岩石流变学标志。

Strain Measurement and Analysis in Matrix of Asymmetric Bong-Shaped Boudinage in Tieshan, Southeast Hubei

Tieshan in southeast Hubei is the first area where bone-shaped boudinage was discovered in Asia.To acquire the distributing diagrams of relating parameters such as true differential strain (ε1-ε2),kinematic vorticity(Wk) and orientations of the major axes of the finite strain ellipse,the finite strain measurement at different positions in the matrix of asymmetric bone-shaped boudinage in this area was carried out by inertia moment ellipse method.It is shown that the finite strain in matrix of the asymmetric bone-shaped boudinage is controlled by its competent layer,namely negatively related to the distance away from the competent layer and to the granularity of minerals in the matrix.The finite strain in matrix also shows larger in its thinned sections than that in thickened sections along direction of its elongation.Other structures around the boudin with similar scale could disrupt the distribution of strain in the study matrix.Besides,the study shows that the asymmetric bone-shaped boudinage in this area was formed by simple shear parallel to the layer during early period and by pure shear with extension parallel to the layer and contraction perpendicular to it later.Comparison between asymmetric bone-shaped boudinage and asymmetric fish-head boudinage of the same area reveals that the pure shear and simple shear in their matrix are corresponding to the relatively thinned sections and thickened sections respectively,and that their differences in shape are mainly related to the difference in competency of minerals filled in their discontinuous sections,which proves that both sorts of boudinages could serve as rheological indicators of rocks.