Paleostress regime reconstruction based on brittle structure analysis in the Shekarab Mountain, Eastern Iran

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.