Document Type : Original Research Paper
Authors
1 Professor, Department of Earth Sciences, School of Sciences, Shiraz University, Shiraz, Iran
2 Ph.D. Students, Department of Earth Sciences, School of Sciences, Birjand University, Birjand, Iran
Abstract
The NE oriented Dasht-e-Arjan graben with orientation is located in 65 Km west of ShirazCity. This graben is resulted from the active Kare-e-Bas fault segmentations. This extensional graben system is part of the Zagros Simply Folded Belt and bounded by two boundary fault system perpendicular to the Shahneshin anticline and Salamati anticline. These two boundary faults were named the East-Arjan and West-Arjan faults in this paper. The oriented samples and slabs from slickensides and slickenlines of these two faults were collected in order to reconstruct paleostress orientations for the Dasht-e Arjan graben activities. The paleostress analysis based on the fault-slip inversion method was performed from the striations or the slickenlines data collected from the two faults planes. This showed that the orientations of the maximum principal stress (σ1) of the graben is 70°, N 26° E and the minimum principal stress (σ3) is 25°, S 40°E. Microscopic examination of the oriented thin sections (XY- and XZ- planes) indicated that they consist of the type І and type П calcite e-twins. The measurements of the e- twin and c- axis were carried out using an optical polarizing microscope equipped with 5-axis Universal Stage in order to determine orientations of "Compression"(P) and "Tension" (T) axes. The mean orientation of the sub-vertical maximum principal stress (σ1) is N 35° E ± 11. 72º and mean orientation of the minimum principal stress (σ3) is S 35° E ± 9،32°. The stress field around the boundary faults of the graben is related to the stress field of the Kare-e Bas fault activities.
Keywords
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