Microstructural Analysis of the Aghdarband Erosional Window Using Deformational Characteristics of Calcite

The erosional window of Aghdarband, located in NE Iran and SE of Mashhad is a uniqueplace to study of the Eo-Cimmerian event. This event (Late Triassic-Middle Jurassic) resulted from closure of the Paleotethys Ocean and collisionbetween the Iran and Turan plates. In this study, we have tried to analyze the microstructural features of the exposed carbonate units (the Sefid Kuh formation of the Early Triassic age and some Paleozoic units) in the Aghdarband area. The average of ellipticity calculated for the calcite grains is about 0.78 located in the oblate part of the Flinn diagram. The estimated kinematic vorticity number is 0.6 - 0.7. The calcite twining in the carbonate units exposed in the Aghdarband area indicate temperatures of about 180-200˚C and differential stresses of about 180-240 MPa during the main deformational event of the area (Eo-Cimmerian).