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Turkish Journal of Earth Sciences

Abstract

Strain analyses and kinematic studies in orogenic belts are essential for understanding their deformation mechanisms. The Chai-Kour brittle-ductile shear zone is located in the central Sanandaj-Sirjan metamorphic belt, southeast of the Zagros orogen. The present study analyzes deformed mylonitic rocks to clarify the deformation kinematics, temperature, and strain geometry of the Chai-Kour shear zone. Previously developed kinematic shear indicators such as S-C shear bands, deformed porphyroclasts, asymmetric boudins, and folds provide an overall top-to-the-southeast sense of shear in the Chai-Kour shear zone. Quartz micro-thermometry confirms that the Chai-Kour rocks were initially affected by a high-temperature (550–650 °C) deformation that was followed by a postsuperimposed low-temperature (380–420 °C) deformation. Rf/ϕ strain measurements reveal a plane-strain deformation geometry. The estimated Wm by the Rigid Grain Net technique ranges from 0.54 to 0.73, suggesting simultaneous contributions of simple (38–54%) and pure (46–62%) shear components. Spatial variation of deformation indicates that the simple shear component increases towards the northeast and southwest boundaries of the shear zone. The present study suggests that this shear zone experienced a 55–75% shortening perpendicular to its boundaries. These deformation characteristics in the Chai-Kour shear zone have been influenced primarily by a transpressive tectonic regime with lateral extrusion, resulting from the continuing oblique convergence of the Afro-Arabian plate with the continental crust of central Iran. This tectonic evolution resembles that experienced in other collisional zones, such as the Alpine and Himalayan orogens.

Author ORCID Identifier

SAEEDE KESHAVARZ: 0000-0002-6176-7833

SAEED ZAREI: 0000-0001-6130-2748

MAJID SHAHPASANDZADEH: 0000-0002-8856-4630

SOUMYAJIT MUKHERJEE: 0000-0003-2247-8526

DOI

10.55730/1300-0985.1996

Keywords

Microstructures, ductile shearing, deformation temperature, strain portioning, Zagros, Chai-Kour shear zone

First Page

824

Last Page

844

Publisher

The Scientific and Technological Research Council of Türkiye (TÜBİTAK)

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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