مجله زمین ساخت
پیاپی 13 (بهار 1399)

The effect of Shushtar fault in the northern Dezful Embayment cases to several geomorphologic features that can be used to identification of geology and morphotectonic properties of the this fault. The Geomorphic indices including mountain front sinuosity (Smf), valley floor width to valley height ratio (Vf), basin shape index (Bs), stream length–gradient index (SL) and basin asymmetry index (Af) have been calculated for determination of various tectonic activities along the Shushtar fault. The mountain front sinuosity (Smf) index was calculated about 1.007 to 1.584 respectively in the active and inactive parts of the Shushtar fault. The stream length–gradient (SL) index was calculated between 898.11 in the high active tectonic and 242.8 in the low active tectonic parts of the study area. The basin shape (Bs) index has been calculated between 9.62 for the very active parts and, 2.04 for the low active parts of the fault. The amounts of valley floor width to valley height ratio (Vf) index show the range between 1 to 10.5 in the active parts with V shape valley morphology and inactive parts with U shape valley morphology respectively. Also the basin asymmetry index (Af) was calculated between 359.3 in the high active tectonic and 3.7 in the low active tectonic parts of the study area. With application of the GIS techniques and the overlaying the Smf, Bs, Vf, SL and Af data layers the area was divided into three different tectonic zones and quantitative active tectonic zoning map was prepared for the study area. In this active tectonic map, classes 1 to 3 respectively show the highest to lowest tectonic activity along the Shushtar fault. Results reveal that the Shushtar fault in the central and northwestern parts shows the medium tectonic activity and in the southeastern parts shows the low tectonic activity manner. Also results show the high tectonic activity in the some northwestern parts near the Shushtar city.

Tozki volcanic cone located in west of Sistan fold-and-thrust belt in north of Zahedan. In this study morphometric charactristic, field properties and relationship to Neogene strike-slip faults of this cinder-cone have been studied for first time. The composition of the Tuzaki cone lithography is named "Andesite" on the geological map of the ChehelKureh region. However, according to the petrographic studies of this research, its composition includes lava flows, and volcanic agglomera. Tozki volcanic cone and related minor cones emplaced on a branch of Chehelkoureh strike-slip fault related to strike-slip fault system of eastern Iran. Petrology and field properties shows that this cone emplaced into Paleocene-Eocene sedimentary rocks during single intercontinental erupting. Rocks of this cone composed of basaltic lava flow and minor volcanic pumice. In order to calculate Morphometric parameter such as crater diameter, base diameter, cone high, cone volume, ratio of crater cone/base cone, ratio of high/ base diameter and cone angle digital elevation model have been used. These data show the Tozki cone is yang and less eroded with elliptical crater and superelliptical base shape. Estimated  Morphometric age suggest a 0.2  Ma. (Pleistocene) to formation of  this cone.   Another Minor Crater located  at  near  Main Crater show they erupted along the Chehelkureh basement fault but not dislocated by this Neogene fault, Indicates  the activity of these cinder cones occurred after the last activity of the Quaternary faults. These evidences suggest that Tozki is a young monogenetic Quaternary volcanic cone that After the last activity, the main and secondary faults of the region have erupted.

Identification of mineral veins that do not have much data available, due to the importance of vein mines in the economy of the country, is one of the main issues in the explorations. In the eastern region of Iran, the largest magnesite deposits discovered are vein structures located along the strike-slip shear zones. At present, mining of this mineral is confined to the outcrops of veins at the surface. If surface reserves are exhausted, the need for this mineral will only be met by subsurface estimates. This study aimed to evaluate the deep magnesium expansion in the Kuh-e-Sefid mine concerning the geometry of the mineral veins in the Neogene folded conglomerate based on a combination of proposed methods including statistical analysis of the angles related to the intersection of structural elements and fuzzy logic to create a meaningful database before entering data into mineral modeling software. In this method, first all the angles between the structural strikes are weighted two by two based on their intersection. Then, the correlation map of the angles is determined and matched with the shear fractures of the Riedel model. Fuzzy logic is used to create better correlation models, especially in the narrower statistical populations. Field evaluation in the easternmost areas of the mine with the least raw data available confirms the early promising points obtained by this method. Therefore, using these two computational tools, one can convert meaningful data before entering raw data into modeling environments.

To study of relationship between mineralization and brittle structures in Torud area field studies and analysis of more than 170 planar structures (fracture, fault and dyke) were carried out. These studies show relationship between mineralising fluid flow and fractures with special orientation, as well as densely fractured zones (fault damage zones) is clearly visible in form of the precipitation of Cu–bearing minerals in the fractures. Results show preferred orientation of the NE–SW trending fractures, which are mineralized, is related to strike–slip stress field with NE–SW trending shortening axis. Also, these results show the mineralization is controlled not only by fractures as a function of local stress field but also is controlled by fault damage zones.

Qorveh area is located in SE-Kurdistan province, in NW- Sanandaj-Sirjan metamorphic-plutonic band. In SE-Qorveh, parts of granitic intrusive and dykes are emplaced in a shear zone after they formed. Based on differences rate of strain and progressing of mylonitization, Shear band of granite show varied treatment such as protomylointe and mylonite (50 Cm to up to 100 M). Often, mylonitic foliation in granitic mylonite has NW-SE strike toward NE plunging and also some of them show folding. Plunging of lineations is low-medium toward NE plunging. Shear sense indicators (e.g. foliation, lineation, C & S shear bands, mica fish and mantled prophyroclstes) in this shear zone show revers slip with right lateral component movement. Microstructural evidence are such as smokey extinction, sub grain, new grain, polycrystalline bands, SGR, BLG, GBM in quartz, shear fracturing, flame perthite, myrmekite, emplaced microcline, rounding and pressure shadow in plagioclase.  All of these evidence show structural changes occurred in up to 300 to 570 C.

Dogan area with surficial Copper-oxide mineralization located at the northeast of Iran, where the northeastern edge of Toroud-Chah Shirin volcano-magmatic belt hosts the numerous Copper-oxide deposits. The Dogan area lies at 18 Km north of the ENE-WSW striking active left-lateral and basement Toroud fault zone in which dominantly deformed by brittle structures. The original field-based structural measurements in the study area that characterized structural anatomy of the Dogan which show the main faults have E-W, NW-SE and NE-SW orientation. We also identified right- lateral E-W striking south Dogan fault zone with longer than 15 km length and NE-SW striking north Dogan reverse fault. Paleo-stress inversion analysis has performed on all the measured faults that yield horizontal NW-SE directed maximum compression direction (sigma 1) for faulting in Dogan area. Furthermore, integration of field-based data and remotely sensed data reveled that Copper-oxide mineralization and associated alterations are tightly aligned along the E-W and rather the N-S to NW-SE fault zones. To identify the role of the faults in Copper-oxide mineralization at Dogan area, our results suggest that major deep faults, dense fracture zones, and fault intersection zones provide weak and low-pressure zones for concentrating the Cu-containing fluids that are high potential places for copper-oxide mineralization.