Paleostress regime reconstruction based on brittle structure analysis in the Shekarab Mountain, Eastern Iran
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ORIGINAL PAPER
Paleostress regime reconstruction based on brittle structure analysis in the Shekarab Mountain, Eastern Iran Maryam Ezati 1
&
Ebrahim Gholami 1 & Seyed Morteza Mousavi 1
Received: 1 April 2020 / Accepted: 1 November 2020 # Saudi Society for Geosciences 2020
Abstract Eastern Iran, including the Sistan suture zone, comprises the boundary between Lut block and Afghan block. This research aims to reconstruct the stress regime evolution from the upper Cretaceous to Quaternary based on the brittle tectonic analysis. In this study, three episodic changes in stress regimes were recognized in the Shekarab Mountain using data inversion. In places where conglomerate outcrops are present, the Quaternary stress state is obtained using the youngest slickensides. The Quaternary stress state indicates that the direction of σHmax is close to N026°, which is compatible with the present-day Arabia-Eurasia convergence direction. Reconstruction of stress fields using age and sense of motion of faults shows that the stress regime during the Cretaceous was compressional, which caused the uplift of peridotites and ophiolites in the eastern part of the study area. The state of stress in the upper Eocene and Oligocene was transpressional; in the eastern part of the study area, there is a change from transpression to transtension. The exhumation of igneous rocks in the eastern part of the Shekarab Mountains is due to the local change of the stress regime. According to the results of this study, the first stage of stress state in the Shekarab Mountains was compressive and the average direction of maximum stress axis (σ1) was toward N337°. In Eocene, the tectonic regime was transpressional and the average direction of maximum stress axis (σ1) was toward N003°. In Quaternary, the tectonic regime is strike-slip and the average direction of maximum stress axis (σ1) is toward N026°. This implies that at least 49° clockwise rotation of σ1 happened in the Shekarab Mountain. Keywords Brittle structures . Paleostress . Shekarab Mountain . Eastern Iran
Introduction The present tectonics of Iran is due to the north-south convergence between the Afroarabian and the Eurasia plates (Jackson and Mc Kenzie 1984). This convergence is accommodated across the Iranian Plateau and adjacent deformed zones; the deformation is not uniformly distributed. Much of the deformation is concentrated in the Zagros fold and thrust belt in the southwest, Alborz Thrust Belt is bordering the oceanic crust of the South Caspian depression, Kopeh-Dagh active thin-skinned Fold Belt in the northeast, and the east Responsible editor: François Roure * Maryam Ezati [email protected]; [email protected] 1
Department of Geology, Faculty of Science, University of Birjand, P.O. Box: 97175-615, University Blvd, Birjand, Southern Khorasan, Iran
Iranian ranges (Hollingsworth 2007). Results from a regional GPS network indicate that the total convergence across Iran is 25 mm/year in eastern Iran (Vernant et al. 2004). The late Cretaceous to Tertiary rocks of the Si
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