The tectonometamorphic evolution of high-pressure low-temperature metamorphic rocks of eastern Crete, Greece: constraints from microfabrics, strain, illite crystallinity and paleodifferential stress

Analysis of strain, paleodifferential stress, illite crystallinity, and microfabrics of quartz and calcite suggest that multiply alternating late Oligocene/early Miocene N-S convergence and N-S extension caused significant vertical discontinuities in the grade of high-pressure/low-temperature metamorphism of the Phyllite-Quartzite unit (PQU) of eastern Crete. Constrictional fabrics and parallelism of D-2 stretching lineations and fold axes are attributed to enhanced slab pull forces at greater depth of subduction. A major D-3 extensional detachment is present in the upper part of the PQU where slates with lowest metamorphic grade (diagenesis/anchizone transition) are resting on top of anchimetamorphic rocks. The highest metamorphic grade (anchi-/epizone transition) has been determined for Skythian rocks on top of pre-Alpine basement. Revived N-S convergence (D-4) led to E-W-trending map-scale folds and top-to-the-S directed brittle thrusts. There is a clear correlation between D-2-related metamorphic grade, finite strain, differential stress, and deformation mechanisms. At the anchi-/epizone transition, solution-precipitation and dislocation creep of quartz and calcite caused maximum finite strains (R-XZ = up to 7) at high strain rates and moderate differential stresses (80-200 MPa). At the diagenesis/anchizone transition, deformation was accommodated by cataclasis, dislocation glide and solution-precipitation creep resulting in relatively low finite strains (R-XZ < 2) at high differential stresses of up to 300 MPa. (C) 2002 Elsevier Science Ltd. All rights reserved.