超高压榴辉岩中绿辉石组构测定及其流变学意义

FABRIC MEASUREMENTS OF OMPHACITE FROM ULTRAHIGH PRESSURE ECLOGITE AND ITS RHEOLOGICAL SIGNIFICANCE

绿辉石高温变形特征在很大程度上决定了榴辉岩流变学表象．绿辉石变形显微构造和晶格优选方位（ＬＰＯ）的研究是认识榴辉岩变形机制和动力学背景参数（应变、应力、应变速率）的重要途径之一．详细介绍了绿辉石ＬＰＯ测定方法和步骤，报道了潜山县双河地区超高压榴辉岩中绿辉石组构初步研究成果及流变学意义．ＬＰＯ测量成果表明：双河榴辉岩中绿辉石组构［００１］极密位于页理面附近，并近于平行线理Ｌ，［０１０］环带垂直于Ｌ，［００１］极密相对Ｓ和Ｌ偏离８°左右，它反映了该区绿辉石事实上经历高温塑性变形，与绿辉石形态方位密切相关的Ｌ型组构显示区域性伸张线理发育，并经历了局部简单剪切非共轴变形．

The understanding of deformation mechanism from ultrahigh pressure eclogite is crucial for the construction of geodynamic models of orogenic belt. The characters of high temperature deformation of omphacite to a great extent depend on rheological properties of eclogite. The study on deformed microstructure and lattice preferred orientation (LPO) is an important approach to understanding dynamic parameters of deformation mechanism from eclogite (strain, stress and strain rate). The main objectives of the present paper are: (1)to introduce in details method and procedure of LPO measurement for omphacite; (2)to report preliminary result of omphacite fabric from Shuanghe eclogite and its rehological significances. LPO measurements reveal that omphacite fabric has a dominant concentration paralled to lineation L while has a great circle normal to lineation L. concentration is roughly asymmetrically arranged with respect to L and S, which suggests that the omphacite in this area has undergone high temperature plastic deformation, and that L-type fabric, closely associated with shape orientation of omphacite, shows regional development of extensional lineation and local non co-axes deformation of single shearing.