Strain pattern and vorticity analysis of deformed conglomerates in the Heneshk area within the Sanandaj–Sirjan Metamorphic Belt, Zagros Mountains, Iran

Abstract

Strain measurements have been carried out, using the Rf/ϕ method on a Jurassic deformed conglomerate, in the Sanandaj–Sirjan Metamorphic Belt, Zagros Mountain of Iran. Estimated finite strain ellipsoids range from general flattening to near plane strain (Flinn parameter K = 0.6–0.9) with strain ratios in the X/Z plane with Rxz = 5.4. Quantitative kinematic analyses were performed on the conglomerates using the rigid clast method. Estimated kinematic vorticity numbers (Wk) varied between 0.43 and 0.63, implying a general shear flow (30% < simple shear < 42% and 58% < pure shear < 70%, i.e., pure shear-dominated non-coaxial flow). Combining strain and vorticity data, we estimated a horizontal shortening of ~ 42–55% measured normal to the walls of the deformation zone. We discuss this pure shear-dominated deformation in terms of convergence between the Afro-Arabian continent and the Central-Iranian microcontinents.