EVOLUTION OF DEFORMATION DURING OROGENY: VORTICITY AND FABRIC ANALYSES IN THE MENDERES MASSIF, SW TURKEY

Orogenic crust flows laterally or vertically in response to stress gradients that may be significantly influenced by upper crustal and surface processes. Metamorphic core complexes are excellent places to study crustal flow patterns and kinematics in relation to driving forces, including brittle upper crustal extension. The Menderes Massif of W Turkey is a large (200 x 300 km) core complex with a long tectonic history (Pan-African to Alpine). Despite its complex history, the well exposed orthogneiss core of the S Menderes submassif is a spectacular site for investigating kinematics and conditions of flow through time. The overall structure of the orthogneiss core is a series of 1-10 km wide, N-S trending antiforms and synforms. C-axis fabrics of coarse-grained qz ribbons record an early top-to-N deformation that is probably contractional. Extension overprinted this fabric, and is shown by ä and ó-type recrystallization tails on feldspar augen, S-C and S-C' fabrics. These suggest bivergent extension about an ENE-WSW kinematic hinge with top-to-N motion in the N sector of the submassif and top-to-S in the S. Subparallel contraction and initial extension created a penetrative foliation and N-S mineral lineation. Fabrics involving qz and fspar suggest amphibolite facies conditions, consistent with previous studies. Quartz c-axes and Flinn plots of augen shapes both suggest constrictional strain, and the majority of augens plot in the 1