Abstract In the internal parts of the Zagros collision zone, several deformation phases have been superimposed. The early deformation phase caused the development of a penetrative foliation. The late‐stage deformation phase was preferentially accommodated within shear zones and caused the generation of shear bands, implying a non‐coaxial component of deformation, the end of this stage deformation was marked by the development of kink‐bands. In the vicinity of Zagros suture zone, the kink angle increased from 40° to 60°, and the kink‐bands was converted to chevron folds. In this region, the external ( α ) and internal ( β ) angular ratio is α/ β ≠ 1 and kink angle increased, and deformation occurred with 10% to 30% volume loss. Farther from the suture zone in the east, α / β = 1; and total volume was constant or increased by 5% to 10%. Kink‐bands kinematic analysis in the study area revealed this structures were sensitive to deformation conditions and components such that, with decreasing distance to the Zagros suture zone, shearing and rotation increased, a high kinematic vorticity dominated, and volume loss occurred during deformation.
Abstract The Salmas geothermal field is located in NW Iran. Subduction of Neo‐Tethys oceanic crust beneath the Iranian microcontinent caused to propagation of the magmatic‐Arc. Fractures and faults in the convergent zone have created path‐ways for the circulation of geothermal fluid. Fracture concentration in the Salmas geothermal field has been characterized using of the fractal method and creation of a fracture density map that shows the highest concentration in the central part of the study area. The permeability of fractures has been evaluated by analyzing their orientation in respect to the paleostress axes. Also, the fractal analyzing result indicates the maximum fractal dimension (1.96) is around the thermal spring outlet. Paleostress analyzing revealed that in the central part of the study area, σ1 axes orientation is S90°W/10° and the σ2 dip is near to the vertical in this stress field, where strike slip faults can be propagated. In the SE part near the recharge of the thermal springs, the σ3 plunge increases to 70° and σ1 orientation is N15°E/20°, in this local tectonic regime thrust fault developed. Fractures have an important role in the circulation of fluid and the fractal dimension increases near the thermal springs in the Salmas geothermal field. Regarding the paleostress data fracture with N‐S direction such as the F1 fault zone (parallel to the σ1 axes), a suitable pathway for deep circulation of geothermal fluid flow has been created.
Fluorite mineralization is controlled by the multiple geological processes such as structural control, geochemical characterization of hydrothermal fluids, temperature and depth.The mineralization associated with the alteration of the host rocks and trapping of fluid in the host rock crystallographic defects.Alteration in the host rocks due to circulation of hydrothermal fluids and several techniques were applied to discriminate the associated alterations in fluorite deposition using the ASTER images.The resulting images indicated that the fluorite mineralization in the studied area accompanied by propylitic and phyllic alterations.The results of micro-thermometry analysis of the fluorite hosted fluid inclusions indicated that the maximum homogenization temperature was 253 °C.These data implies that the temperature of hydrothermal fluids probably had an essential role in the propagation of the alteration zones.The depth versus homogenization temperature diagram for fluorite mineralization in the studied district revealed that the depth of fluorite mineralization varies between 33 to 256 m.Two fluorite generations were distinguishing in the study district.The first generation is characterized by high salinity (18-25 wt.% NaCl) which developed on the deeper level and along the fault zone.The second generation is characterized by low salinity (6-13 wt.% NaCl) on shallow depth and deposited in the fractures.The results revealed that fluorite deposition was not contemporaneous with host rock deformation and deposited in the late-stage deformation phase.
Ductile shear zone recorded valuable data about the progressive deformation and geodynamic setting of the earth crust.Analysis of the strain ratio on the deformed quartz grains in the samples of the Zagros orogenic shear zone indicated generally most of the strain ellipsoids shape are prolate and developed under constructional strain regime.Principal axes of the strain ellipticity ratio varied in the range between 2.04 to 3.12, shear strain magnitude analysis indicated ε s are between 0.6 to 1.3.Strain ellipsoid shape also revealed the propagation of the shear zone could not be coeval with the continental collision because in the collision region expected the ellipsoid shape to be oblate.Flattening strain regime in the Zagros Orogeny contemporaneous with the collisional event (D1 phase) and widespread in the Sanandaj-Sirjan Metamorphic Zone.Constructional conditions and prolate strain ellipsoid could be related to the post-collisional deformation phase (D2 phase).In this event stretching and shearing localized in the ductile shear zone and transtension structures superimposed on the former transpression structures.The deformation followed by third phase and brittle event (D3 phase) and caused to the propagation of veins.These veins somewhere cut the foliation and in the other place are parallel to foliation plane.
'%3e%3cg id='e'%3e%3cg id='c' fill='none' stroke='%23fff' stroke-width='2'%3e%3cpath id='b' d='M0 1h26M1 10V5h8v4h8V5h-5M4 9h2m20 0h-5V5h8m0-5v9h8V0m-4 0v9' transform='scale(1.4)'/%3e%3cpath id='a' d='M0 7h9m1 0h9' transform='scale(2.8)'/%3e%3cuse xlink:href='%23a' y='120'/%3e%3cuse xlink:href='%23b' y='145.2'/%3e%3c/g%3e%3cg id='d'%3e%3cuse xlink:href='%23c' x='56'/%3e%3cuse xlink:href='%23c' x='112'/%3e%3cuse xlink:href='%23c' x='168'/%3e%3c/g%3e%3c/g%3e%3cuse xlink:href='%23d' x='168'/%3e%3cuse xlink:href='%23e' x='392'/%3e%3c/g%3e%3cg fill='%23da0000' transform='matrix(45 0 0 45 315 180)'%3e%3cg id='f'%3e%3cpath d='M-.548.836A.912.912 0 0 0 .329-.722 1 1 0 0 1-.548.836'/%3e%3cpath d='M.618.661A.764.764 0 0 0 .422-.74 1 1 0 0 1 .618.661M0 1l-.05-1L0-.787a.31.31 0 0 0 .118.099V-.1l-.04.993zM-.02-.85 0-.831a.144.144 0 0 0 .252-.137A.136.136 0 0 1 0-.925'/%3e%3c/g%3e%3cuse xlink:href='%23f' transform='scale(-1 1)'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
