苏胶地体北缘变质构造岩的磁性组构特征

本文介绍了磁性组构的概念和常用的参数,并总结了苏胶地体北缘五个地区20块变质构造岩样品的岩石磁性组构测试分析结果:岩石磁化率各向异性度受不同的因素所控制,变质构造岩的磁各向异性与变质作用过程中的可塑性形变和变质重结晶作用具有相关联系.最大磁化率主轴平行于岩石线理,最小磁化率主轴垂直于岩石面理.同时证明了磁化率各向异性技术作为一种岩石组构因素的研究是有发展前景的,尤其是在应用于缺少常规应变分析标志的地区,更能显示这种方法的优越性.

AMS FEATURES OF METAMORPHIC TECTONITES FROM NORTH SUJIAO TERRAIN

As a new tool, anisotropy of magnetic susceptibility (AMS) is capable of recording finite strain in weakly magnetized rocks. Both AMS and strain are second order tensors geomctrically represented by ellipsoids. Many recent investigations of AMS and strain have establishcd a gencral coincidencc of the principal axes of the magnetic fabric and petrofabric ellipsoids, with the maximum susceptibility axis oriented parallel to pctrographic lineation and the minimum susceptibility axis oriented perpendicular to foliation. Such studies have been carried out in sedimentary rocks, igneous rocks and mctamorphic rocks. This paper discusses the applicability of AMS as a strain indicator in ductilely deformed metamofphic tcctonitcs in north Sujiao terrain. AMS was measured for 20 samples from 5 sitcs in the studied area with the same deformational history, and some conclusions as follows: 1. The result of AMS studies has suggested that it is possible to obtain complete strain ellipsoid data from the magnetic susccptibility, which can be measured rapidly, accurately and economically. 2. AMS of metamorphic tcctonitcs is a reflection of the rocks strain conditions. The shapc of susceptibility ellip soid take oblate as the key, which shows that the metamorphic tcctonitcs had suffered strongly compressing and shearing. 3. The strikes of magnetic foliation can be separated into two direction groups: NE-SW and NW-SE. Dip anglc of magnctic foliation changes in different types of deformed rocks, which reprcsents that the deformed rocks had undergone two stages of tcctonization and folded, and the shape and direction of maximum susceptibility axis has changed with different level since the direction of tectonic strain has taken to transform.