JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2007 | Volume:17 | Issue:65 (GEOLOGY ISSUE)|Papers Count:14

Mesgaran area granitoidic bodies has 5km2 expose, is located at West margin of East of Iran Ophiolite melange belt at Sistan suture zone. These granitoids consists of granodiorite, tonalite and aplitic granite dikes and main mafic mineral of them is biotite. Most plagioclases showing zoning textures, indicative of chemical equilibrium between magma and these zoned crystals.Existence of studied granitoidic bodies in active shear zone of Nehbandan fault system with north-south trend, caused deformation and appearance of orientation in micas of granitoidic rocks. Brokenness of most quartz crystals and undulatory extinction of them, recrystallization in quartz crystals, bending and strong curvature of cleavage surface of micas, fracture in plagioclases and appearance of deformational twins, are instances of deformation in studied rocks. Existence of chlorite and epidote-zoisite group minerals is demonstrative low grade metamorphism (green schist) in studied area. Geochemical study ofthe investigated samples shows ca1c-alkalineand metaluminous to peraluminous characteristics of these rocks. It seems that contamination of original magma by crustal materials is an effective process in generation of studied rocks. Most of the characteristics of studied rocks are comparable with I-type granitoids. Due to tectonic setting these granitoids are orogenic type and VAG.

The case study area is situated in south west of Kelardasht in south of Chalus city. The intrusion of granitoid, metamorphism and development of skam in the contact zone of igneous intrusions, prepareconditions for mineralization. Based on the existing evidences, the Akapol granodioritic body of Paleocene age intrudes into carbonate sedimentary rocks and is cross cut by Alam kuh granitic apophyses of Miocene age. The granitoides are divided into alkaline and sub-alkaline groups. The granodiorites which are derived from gabbrodiorite magma are set in calk alkaline suite and show I type magma generation. Whereas the granites, has potassic alkaline nature and are of A type characteristics. The geochemical parameters, elemental correlation, petrology and petrography indicate that tungsten mineralization depend on to granite rocks, but rare metals mineralizations such as Nb-Ta is related to gabbrodiorites and altered diorite.

Digital data and images gain from satellites are appropriate tools for geological studies specially in lithology and mineral exploration. In this research, to separation and detection of minerals and lithologic units, using ETM+ digital data from Landsat satellite, a region at 65 kilometers in the west of Isfahan and south of Tiran city was selected because of weak botanic cover and litological diversity. After initial processes in images, two multivariable statistical methods were used: Optimum Index Factor (OIF) and Crosta. OIF method, were used for selection of compositions contain most spectral information about minerals and rocks. Then, classification was applied to mentioned compositions and accuracy of different classifications in separation of Minerals and rocks were determined. Results of this method shows that because of existence of dense botanic cover in side of Zayandeh Rud river in region's image, using high OIF compositions, although leaded to satisfactory separation of botanic cover data class and water from rocks data class, but it was not effective in separation of minerals and rocks. Crosta method, based on principle components analysis using ETM+ 6bands, was done and components those contain information about minerals and rocks were specified. Results showed that this method reveals PC3 component of amphibole minerals in Green Stons and PC5 for clay minerals.

Darreh-Zerreshk and Ali-Abad are two relatively small porphyry copper deposits in Yazd Province in Central Iran. They are located within the central Iranian volcano-plutonic belt. The deposits are associated with igneous intrusions. The intrusions with Oligocene-Miocene age intruded to Eocene volcano-sedimentary and Cretaceous conglomerates and carbonate rocks. These granitoids, hosted Cu mineralization, were derived from I-type calc-alkaline magma, which are located in syncollisional volcanic arc environment. Biotites from granitoids of the Aliabad-Darreh Zereshk areas are green and brown types. Although, these tow types have different colors under microscope but their chemical compositions are not showing sharp differences. The ratios of 100 (Mg/ (Mg + Fe) vary between 17 and 22. Also, plotting of 100Fet / ( Fet + Mg ) ratio of the studied biotites on a stability diagram correspond to temperature about 600 t0750°C and confirming magmatic origin for these biotites. In addition, biotite composition can be used for discrimination of the granitoid magma. The chemical composition of studied biotites shows that the granitoids of the Aliabad-Darreh Zereshk areas are calc - alkaline I-type.

The research presented is based on the detection of groundwater flow system in Lagharak polje area, Kuhrang karstic environment. In this regard, Sinkholes, Linear features and Drainage pattern data are recognized to groundwater flow system indicators, which could be detection recharge, intermediate and discharge areas in karstic system, identified and extracted through the use of field checking, digital elevation modeling and digital image processing of data acquired by Landsat Satellite's TM & ETM+ sensors. The development of these features in study area, trinity zones of ground water flow system limited to the recharge and discharge areas.Landsat 5 & 7 Satellite's TM & ETM+ sensors spectral bands fusion and ETM+ sensor panchromatic bands can be used as an complementary step to spectral and spatial resolution of this sensors in visual and digital interpretation techniques which enables us to study and analyse groundwater flow system indicators in a shorter period of time.

Groups of the Nesen Formation (Upper Prmian) have been studied in Zal and pir-Esagh area to determine their facies, sedimentary environments and their sequences. The Nesen Formation (25 meters) consists of dark gray limestones have 8microfacies. These facies were deposited in open marine, barrier and lagoon subenvironments in a ramp carbonate platform.Sequence stratigraphyic analysis indicates the presence of two depositional sequences in the Nesen Formation. The lower boundary of the first sequence is a type 1 unconformity, but other boundaries are type 2 Unconformity.

Alluvial channels are sensitive in regard to changes of rivers and allocations of sedimentary load. A lot of the changes which occur in morphologic channel during the time, can be related to the mentioned changes. From the new view point of tectonic, growing faults and folds are to be counted as the most usual part of structures which effect the river's system.The size and length of the rupture increases by the replacement in fault's direction. In folds that are located above the blind faults, the folds are expected to grow in length and width side.By expanding faults plate, as that limbs come up related to local base level. It is often pointed to khorramabad Anticline as an instance of high Zagros' folds the Khorramabad River, in its route of 46 km, passes through the city's anticline. This anticline is located on a hanging wall-part of the blind faults of high Zagros (Berberian 1995).In this study, for avaluating the amount of activity of khorramabad anticline, some qualified indexes in direction of the khorramabad river were studied and measured.(e.g. guardian index of river's slope, sinusity of lengthwise profile and river's terraces). It was tried to find the appropriate estimation from the position of this anticline and also the part of high Zagros that located below that. It is called khorramabad fault (tavakoli and shabanian 2000), is account as a part of fault zone of high Zagros (Barbarian 1995). Regarding to the fact that Khorramabad fault is a part of a blind fault in Zaros zone it is very important of to prove its activity for using in evaluating the hazard seismic of this area and even city planning's. As a result, considering the agitations in the river system of khorramabad, is an efficient tool for the recognation of the activeness of khorramabad's anticline as well as it's original fault.

The Misho granitoid pluton is found in south-west of Marand city which is located in NW of Iran. This pluton is a S- type granitoid (Allahyari, 2001) and emplaced at Post- Cambrian to Pre-Permian time. This granitoid pluton has a main composition as Monzo-granite and in some location has a cataclastic and gneissic structure. Granular texture is main texture of these rocks. There is a high degree of alteration on the rocks of this region and some accessory minerals such as: sericite, kaolinite and chlorite are existed as a result of this alteration.This pluton formed during Hercynian orogeny by the partial melting of sedimentary and metamorphic crustal rocks.

Kuhbanan fault system, as one of the intercontinental faults of central Iran, is recognized by considerable seismogenic activities and modem morphotectonics evidences with a strike-slip (reverse component) motion. According to the geometric and kinematics data, Kuhbanan fault has been divided into 5 segments (S26, S27, S28, S29, S30) in Bahabad region. Measured geomorphic indices of ratio of valley-floor width to valley height (Vf) and morphology of the valley (V) manifest the maximum denudation rate for the S28segment. The mean calculated values of mountain-front sinuosity (Smf) and %facet parameters for different segments of the fault are 1.1 and 83.16, consequently. Regarding to these geomorphic indices, a denudation rate of about 2-4 mmyr-1 is suggested for this region.According to reconstruction of Kuhbanan fault since 360 ka, minimum horizontal cumulative displacement of 750 m and minimum slip rate of about 2-1.4±0.1mmyr-1 is inferred from well preserved geomorphology in the northern segment of the fault. Applying this horizontal cumulative displacement causes reconstruction of geomorphic markers such as drainages and shuttered ridges.

This research deals with the microbiostratigraphic analysis of the one outcrop section from the Asmari Formation in northeast of Behbahan, Khuzestan province. The sediments of the examined section comprise of limestone with 256.62 m thick. In Alamdar Section, the Asmari Formation conformably lies on the shales ofPabdeh Formation, and underlies the marls of the Gachsaran Formation. The study of 109 samples from the mentioned section led us to identify 36 genera and 56 species of benthonic foraminifera, one genus and species of planktonic foraminifera, 5 genera and species of the red algae, and two genera and species of bryozoa.On the basis of stratigraphic distribution of benthonic microfossils, the age of Alamdar Section is Oligocene (? Late Rupelian- Chattian) to Early Miocene (Aquitanian- Burdigalian).The microfossils assemblage in the examined section are comparable to the Borelis melo group- Meandropsina iranica Assemblage Zone, Miogypsinoides- Archaias- Valvulinid Assemblage Zone and Eulepidina- Nephrolepidina- Nummulites Assemblage Zone of Adams and Bourgeois (1967), and the biozones 56, 57, 59, 60 and 61 of Wynd (1965).

The area under investigation is located in the eastern part of the central Alborz, on the basis of the tectonics and the dominant focal mechanisms in this zone are reverse and thrusting.On the basis of the geological characteristic the area can be divided in 3 provinces. Seismic parameters for each province calculated.It is concluded that no.2 province is the most hazardous zone in this area and no. I and 3 provinces have mean and low seismic activity rates, respectively. In addition, a major E-W seismic trend recognized which is considers with the trend of the seismic sources of the Alborz.

The Bun Dasht anticline (with 70 km length and 10 km width) is a NW-SE trending anticline in the Interior Fars Sub-basin (Zagros simple folded belt). Asmari- labrum formations is cropping out in the core of this anticline in the area under investigation.We have investigated the elements of fold style and folding mechanism in the West and East part of the Bun Dasht anticline. Therefore, uplifting of the some parts and cropping out of Gurpi formation are due to development of two reverse faults (SW dipping) in the northeastern limb of the Bun Dasht anticline.

This study presents the results of a detailed structural analysis of the west-central Alborz with emphasis on the pattern of neotectonic stress field on the Manjil-Rudbar fault This part of the Alborz mountain is characterized by an abrupt change of structural trend from NW-SW to N-S in Talesh mountain. in order to determine th geometry and mechanism of faults around The Manjil-Rudbar-Earthqake-fault are fault planes and related striations in 28 stations measured. By inversion of these data, stress directions and associated tectonic regime for each station hsd been determined.Inferring principal stress direction (s1) from the geological indicators (inversion of the fault slip data) and the focal mechanisms (p-axis), a map of stress orientation around the Manjil-rudbar fault is proposed. The stress direction shows in vicinity of the fault an E-W directed stress that lies nearly parallel to the strike of itA way from the fault the stress direction becomes parallel to the regional stress direction namely NE-directed. Fault-parallel stress direction near the fault suggests an effect of the extremely high shear strength resulted from the N-S-directed convergent of the Iranian plate toward the rigid Caspian block. The tectonic regime deduced by version of fault slip data shows two distinct behaviors:in vicinity of the fault it shows a strike-slip regime, which  results from compressive regime away from it.