Neutron Texture Analysis of Omphacite in Eclogites

The microstructural and textural analysis, especially of omphacite in eclogite, provides important information on the deformation of high-pressure rocks at high-pressure metamorphic conditions, and along the exhumation path. The evaluation of crystallographic preferred orientations combined with microstructural studies is the most important tool to get information on the deformational behaviour and the rheology of tectonites, and of deformation and recrystallization mechanisms operating in naturally deformed rocks.Temperature is one important factor that controls the microtructural and textural evolution of omphacite. Moreover, the CPO development of omphacite also highly depends on the deformation geometry . At flattening strain, the crystallographic c-axes [001] generally show a girdle distribution within the foliation plane, while the b-axes [010] show well defined clusters perpendicular to the foliation plane (Godard and van Roermund 1995) (S- type of Helmstedt et al. 1972). At constrictional strain, the c-axes show well defined clusters near the stretching lineation, and the b-axes show a girdle distribution perpendicular to the foliation plane. Hence, crystallographic preferred orientations, combined with microstructural and shape fabric analysis, are an important tool to determine the strain geometry during deformation of rocks at HP metamorphic conditions. Additional studies on omphacite CPOs within eclogites from different tectonic units of the Alps shall provide add not assigned GG: Forschungszentrum Jülich; Universität Bonn