Tectonic history of continental crustal wedge constrained by EBSD measurements of garnet inclusion trails and thermodynamic modeling

摘要: Inclusion trails in garnets represent an important but underused tool of structural geology to examine non-coaxial or polyphase coaxial deformation histories orogens. Garnet growth with respect during prograde and retrograde orogenic evolution a continental crustal wedge was constrained by EBSD measurements internal garnet fabrics petrological record from mid-crustal rocks the Śnieznik Massif (Western Sudetes). Textural position metamorphic minerals thermodynamic modeling document three main stages tectonic evolution. Few cores show MnO zoning coeval formation earliest foliation which is only rarely observed field. The major occurs synchronously second steep S2 fabric under still conditions as shown appearance staurolite kyanite (peak at 6,5kbar/600°C). Oppositely, retrogression associated development sillimanite later andalusite indicates pressure decrease ca. 3 kbar for late flat pervasive S3 macroscopic recumbent folding foliation. Electron back-scatter diffraction on ilmenites platelets included help determining their crystallographic preferred orientation. Ilmenites a[100] axes define planar structures that are interpreted foliations. Consequently, microscopic observations intersection (FIA) allow distinguish between two different records. Only few (prograde) yield information orientation presumed first whereas most foliations straight, correspond relics originally fabric. Importantly, this attitude persistent both F3 fold hinge limb zones well complete transposition into S3.