EBSD analysis of partially-eclogitized rocks from the Marun-Keu Complex, Polar Urals, Russia

• Main Author: Pariskeh Hosseini
• Other Authors: Mary Leech, John Caskey, Karen Grove
• Format: Master Thesis
• Language: English
• Published: San Francisco State University 2011
• Subjects: ural mountains
• Online Access: http://hdl.handle.net/10211.3/116369

The Marun-Keu Complex is a Devonian subduction zone complex in the polar Ural Mountains, Russia, that preserves deep crustal processes during the Uralian Orogeny. Silica-rich fluids locally infiltrated Marun-Keu rocks at eclogite-facies conditions but only rocks adjacent to the resulting veins were eclogitized. Field and microscopic observation of the rocks from this complex show eclogitization took place across sharp, mm- to cm-scale contacts between the host rocks (amphibolite and quartzofeldspathic gneiss) and eclogite-facies rocks. A weak foliation development in Marun-Keu rocks suggests deformation may have also played a role in eclogite-facies metamorphism. This study uses electron backscatter diffraction (EBSD) to analyze crystallographic preferred orientations across these metamorphic fronts from the host rocks (amphibolite and quartzofeldspathic gneiss) to their eclogitized counterparts. Omphacite and amphibole CPOs should record eclogite- and amphibolite-facies fabric development, respectively. The EBSD analysis reveals that weak S- and S-L type fabric development in these rocks is preserved from a prograde, amphibolite-facies fabric. Any deformation during eclogitization took place in a weak stress field, in a stress field perturbed by the presence of high-pressure fluids, or fluid-induced metamorphism outlasted deformation. Fluid infiltration drove eclogitization in Marun-Keu rocks, and deformation did not play a significant role.