Tectonics
Babak Samani
Abstract
The use of spatial orientation of structural elements provides a great help to understand the geometry of shear zones. Investigating the indices of non-axial deformable flow in two areas of shape preferred orientation (SPO) and lattice preferred orientation (LPO) of quartz in the deformed rocks of Koli ...
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The use of spatial orientation of structural elements provides a great help to understand the geometry of shear zones. Investigating the indices of non-axial deformable flow in two areas of shape preferred orientation (SPO) and lattice preferred orientation (LPO) of quartz in the deformed rocks of Koli Kosh complex in the Sanandaj-Sirjan metamorphic belt at the north of Fars province show the dextral shear component. Quartz c-axis preferred orientation indicates the dominance of bulging and sub-grain rotation recrystallization in the thermal range of 379±50 to 448±50 degrees Celsius and pressure of 3 to 3.5 kbar. According to stereography projection of pole of foliation and lineation the plane of vorticity normal section was estimated as N15W/45SW. Assuming the compatibility of the north and south thrust systems with the boundary of the shear zones, the rake angle of the boundary of the shear zone and the vorticity normal section was calculated equal to 19 degrees. Therefore, it is possible to consider the oblique transpiration model with triclinic geometry as the structural evolution model of this shear zone.
Tectonics
Babak Samani
Abstract
In this research, using deformed chert nodules in the calcareous units of Sarvak Formation in Pyun anticline, quantitative strain values in different parts of this anticline have been investigated. In a perpendicular fold axis survey, the anticline was divided into seven different areas. At least 40 ...
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In this research, using deformed chert nodules in the calcareous units of Sarvak Formation in Pyun anticline, quantitative strain values in different parts of this anticline have been investigated. In a perpendicular fold axis survey, the anticline was divided into seven different areas. At least 40 nodules were measured in each area and finite strain analysis was carried out using Rf/Ø and polar methods. The results of strain studies show an increase mode in strain values from the fold limbs (Rs = 1.7) to the fold hinge (Rs = 2.9). Kinematic vorticity analysis shows the range between 0.68<Wk<0.91 and the effect of both simple and pure shear strain components and the occurrence of the strain partitioning in the Pyun anticline. The amounts of kinematic vorticity number indicate the increase of pure shear strain components in the hinge of anticline and the predominance of simple shear strain components in the limbs of the Pyun anticline. According to the results of strain analyses the amounts of bulk shortening was estimated about 47- 50 percent in the Pyun anticline.
Petrology
Behnaz Bakhtiari; Nahid Shabanian-Broujeni; Alireza Davoudian-Dehkordi; Hossein Azizi
Abstract
The Muteh–Golpayegan Metamorphic Complex is located within the center of the Sanandaj-Sirjan Metamorphic Zone. The strain parameter measurements by the strain ellipsoid including strain ratio in the XZ principal plane, strain ellipsoid (RXZ), strain ellipsoid shape (K), and strain intensity (D) ...
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The Muteh–Golpayegan Metamorphic Complex is located within the center of the Sanandaj-Sirjan Metamorphic Zone. The strain parameter measurements by the strain ellipsoid including strain ratio in the XZ principal plane, strain ellipsoid (RXZ), strain ellipsoid shape (K), and strain intensity (D) exhibit prolate shape for the amphibole mineral for the deformed amphibolitic rocks in the Muteh–Golpayegan Metamorphic Complex. Several kinematic shear sense indicators consist of the asymmetric fold, kink fold, boudin, S/C fabrics, oblique grain shape, and mineral fishes show a dextral shear sense. The quantitative kinematic analyses highlight that Wk varies between 0.6 and 0.93, implying a general shear flow with 42% < simple shear <74% and 26% < pure shear <58%.
Tectonics
MohammadAmir Alimi
Abstract
The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain ...
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The Bahlgerd shear zone in the northern margin of Bagheran Mountain is separated Eocene flysch from the Cretaceous ophiolite sequence and Quaternary sediments by southern Birjand and Bahlgerd faults. In the deformation evaluation , sigmoidal array arrays located in sandstone units have been used as strain markers. Based on the geometry of these arrays, the mathematical equations and R-θ' diagrams of the strain parameters were estimated. The mean values of shear strain (γ), volume change (∆) and convergence across the zone (K) are 0.45, -0.26 and 0.85, respectively. The plotting strain ellipses on the logarithmic Flinn diagram are in the field of flattening, which indicates the simultaneous simple shear and compaction in the region and show a volume reduction of up to 30%. Also, in the Bahlgerd shear zone, the value of θ'> 45 ° and cleavages are created in the direction perpendicular to the opening of the veins, which conforms to the characteristics of the compactional simple shear model. The horizontal strain parameters in the transpression model have similar values the compactional simple shear model. Based on the calculated convergence parameter (0.39), Behlgard shear zone is in the category of slightly convergence zones in which the amount of shortening
Tectonics
mohammadreza sheikholeslami; Shirin Elyasi; Mohamad Reza Ghasemi
Abstract
The Mohr circle is a well-known method for two-dimensional strain analysis. Due to the formation of the boudins during two stages of the progressive deformation (D1 and D4) in cherty marbles, from north Golpaygan metamorphic complex, they have been analyzed for strain in two-dimension. This analysis ...
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The Mohr circle is a well-known method for two-dimensional strain analysis. Due to the formation of the boudins during two stages of the progressive deformation (D1 and D4) in cherty marbles, from north Golpaygan metamorphic complex, they have been analyzed for strain in two-dimension. This analysis is based on estimating of the initial length of the boudins before deformation, and measuring the current length of the boudins, after deformation. Calculation of the longitudinal parameters of the strain and drawing Mohr circles show that the strain ratio varies between 1.06 to 2.35 for D1 stage, and between 1.10 to 2.84 for D4 stage. The mean shear angle for the D1 stage is 22 ° and for the D4 stage is 24 °.
S. Dashti Chandanagh; M. R. Sheikholeslami; J. Taheri
Abstract
This study was conducted to determine the deformation pattern of the Mashhad metamorphic rocks which results from the convergence between Turan and Central Iran plates and closure of Paleotethys Ocean during Early Cimmerian event. The results of 2D and 3D strain analysis show that the maximum deformation ...
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This study was conducted to determine the deformation pattern of the Mashhad metamorphic rocks which results from the convergence between Turan and Central Iran plates and closure of Paleotethys Ocean during Early Cimmerian event. The results of 2D and 3D strain analysis show that the maximum deformation is concentrated in the central part of the study area and most strain shape parameters (K) obtained from oriented samples are located within the flattening part of the Flinn diagram. Strain intensity parameter in most cases is less than 0.5 and a maximum strain occurred in the central part which is reduced towards the margins. This is the most characteristic of the typical shear zones in which, the maximum strain is concentrated on the central part. Calculated vorticity numbers is ranged between 0.2 to 1 indicating the presence of both pure shear and simple shear during a transpressional regional deformation.
