Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Khalil Sarkarinejad, Saeede Keshavarz, Ali Faghih

Kinematics of the Sirjan mylonite nappe, Zagros Orogenic Belt: insights from strain and vorticity analyses

Journal of Geosciences, volume 60 (2015), issue 3, 189 - 202

DOI: http://doi.org/10.3190/jgeosci.198

The Sirjan mylonite nappe is part of the HP-LT Sanandaj-Sirjan Metamorphic Belt (Zagros Orogenic Belt, Iran). This nappe was emplaced in a transpressional regime during oblique convergence between the Afro-Arabian Continent and Central Iranian Microcontinent. In order to investigate the type of flow, fabrics from deformed quartz and K-feldspar porphyroclasts were analyzed. Quantitative finite strain (R_XZ = 1.9-3.8) and mean kinematic vorticity number (W_m = 0.60-0.85) analyses revealed that both the strain ratio and the simple shear component of deformation increase towards SE along a 2 km long NW-SE-oriented transect. Analysis of quartz and K-feldspar textures suggests shearing at c. 400-650 °C. We also conclude that deformation in the Sirjan mylonite nappe began with nearly pure shear flow but became a more simple-shear flow in character as strain accelerated.