Dynamic model for the exhumation of the Tutak gneiss dome within a bivergent wedge in the Zagros Thrust System of Iran

Abstract

The Bendenow granite-gneiss batholith is part of the Tutak gneiss dome and was emplaced within a regime characterized by oblique convergence between the Arabian plate and Central Iranian microcontinent. The Tutak gneiss dome consists of metamorphosed Silurian and Devonian strata, granite-gneiss, marble, and schist. Its foliation is related to doming and dips radially outward from the core of the dome; however, lithological contacts dip towards the dome. Four factors controlled the formation of this dome: (1) northeast-southwest horizontal extension; (2) an initial stage of doming caused by the release of strain; (3) northeast-southwest horizontal compression; and (4) the ascent of second stage granite. The dominant factors, therefore, may have been extension, diapirism and compression, respectively. The Tutak gneiss dome contains two dextral shear zones, the Surian and Mazayjan, which are parallel to the Zagros Thrust System and define a crustal-scale antiformal pop-up structure that exhumed the dome within a bivergent wedge. Our data cast doubt on the accepted role of successive movements of a sole thrust fault in creating the gneiss dome and a new dynamic model for the exhumation of the Tutak gneiss dome in the Zagros Thrust System is proposed.