GEOSCIENCES
Year:2011 | Volume:20 | Issue:80|Papers Count:26

A thick succession of Middle–Late Jurassic rocks in the western part of Binalud Range has been studied. This succession consists mainly of limestone, marly limestone and marl. The thickness of the succession in the study section (Baghi, north of Neyshabour) is 709 meters and is subdivided into 4 members. The lower boundary with the underlying dark shale and upper boundary with the overlying buff limestone are inconspicuous and transitional. Ammonites are the most important and abundant macrofossils in this section.43 genera and 76 species have been identified among them 8 species are reported for the first time from Iran. Based on the ammonite fauna, Early Bathonian to Kimmeridjian ages are purposed for these rocks. The fauna show close relationship to Sub- Mediterranean province and there is a great similarity between ammonite fauna of the investigated area with Kopet–Dagh and Alborz Range.

In this article, we try to study deserts of Iran on the basis of geological specifications with the help of 1: 100000, 1: 250000 scaled maps of G.S.I and N.I.O.C using Geographical Information System (GIS) methodology. Then quaternary and evaporate formations in every study province were recognized. Saline and evaporatic formations were determined as “primary deserts”. With overlaying drainage network on the basic map of Quaternary formations, the secondary deserts were recognized. Both of these processes (The primary and secondary deserts) have formed provincial deserts. After recognition of the provincial deserts in the country map by utilization of the coordinate system of Iran’s map georeferences and control check point all desert units were set up on the whole country map. Results showed that 12.6% (208041 km2) of Iran is known as deserts formed by evaporate formations.

In order to studying salinity and biostratigraphy in Central Alborz basin, two sections Jorband and Ziarat-kola are sampled and studied Planktonic foraminifera and Echinoids fossil. Studying of foraminifera In Ziarat-Kola section determining three biozone by planktonic foraminifera. 1: Racemiguembelina fructicosa Interval zone, 2: Pseudoguembelina hariaensis Interval zone, 3: Pseudoguembelina palpebra Interval zone.That showing late maastrichtian. As well, at Jorband section assigning three biozone by Planktonic foraminifera 1: Contusotruncana contusa Interval zone, 2: Planoglobulina brazoensis Partial range zone, 3- Racemiguembelina fructicosa Interval zone. That showing maastrichtian.Likewise, in order to determining Paleosalinity select two sections at Jorband and Ziarat-Kola. Main object assigning Paleosalinity confirm sensitiveRugoglobigerina to changes of salinity. At former section used from excessive changes of Echinocorys and in later one used from ratio of kinds Foraminifera tests (Porcelaneous, Agglutinate and Hyaline). In middle parts of Ziarat-Kola section, percentage of porcelaneous tests was more than basal and upper ones. In middle parts of Jorband section salinity was less than basal and upper ones that examined by abundancy of the genus of Echinocorys. Physiological changes of body in this echinoderm also justify salinity changes throughout Jorband section.According toWhitenella is ancestor of Rugoglobigerina and also sensitive to salinity, it is possible that Rugoglobigerina shows characteristic of its ancestor that justify by studying of salinity changes in two section of Central Alborz.

This paper present a new method for evaluating relative active tectonics based on morphometric indices useful in evaluating morphology and topography. Indices used include: Bifurcation ratio (BR), Basin Relief (Bh), Drainage Density (DD), Ruggedness number (Rn), Stream frequency (Fu), Form Factor (FF), Shape Factor (Ll), Sinuosity (Sl) and Elongation ratio (Re) of drainage basin. Results from the analysis are accumulated and expressed as an index of relative active tectonics, which we divide to from relatively low to highest tectonic activity. The study area in the central Zagros fold – thrust belt of the south western Iran is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than river system or mountain front. The study area has variable rates of active tectonics resulting from the collision between the continental Arabian plate and the so–called Iranian block belonging to Eurasia that has produced linear NW–SE anticline forms and thrusts. We test the hypothesis that areas of known, relatively high rates of active tectonics are associated with indicative value index of relative active tectonics.

The Khoy ophiolite complex in northwest Iran hosts several podiform chromitite bodies. The chromitite deposits of Aland area in this ophiolite have lenticular, tabular and irregular vein shapes and emplaced in depleted mantle hurzburgite. Chromitites have different textures including disseminated, massive, nodular, banded and cataclastic textures. The ore bodies are surrounded by dunitic envelopes of variable thickness.Mineral chemistry of chromite grains indicate that they are recognized by #Cr[Cr/ (Cr+Al)] values range between 0.66 and 0.88, #Mg [Mg/ (Mg +Fe+2)] values range between 0.42 and 0.66. Cr2O3, Al2O3 and MgO values range between 45.89 and 54.95%, 8.53-17.18% and 8.38-14.29% respectively. There is a negative correlation among #Cr and #Mg of chromites, typical of podiform chromitites. The composition of chromites including #Cr, #Mg, their contents of Cr2O3, Al2O3, Fe2O3, MgO and TiO2 and also correlation coefficients between different components of them have conformity with total composition of podiform chromitites. Compositions of chromites in Aland area correspond to Cr-rich chromites with #Cr>0.6 and Al2O3<25%. Their lower content of TiO2 accompanied with their compositional location in TiO2 vs. Cr/ (Cr+Al) and TiO2 vs. Al2O3 diagrams may reflect the crystallization of chromites from boninitic magmas in supra-subduction geotectonic setting. The bulk rock analyses of chromitites indicate that their Cr2O3 values have widespread range, 19-51.6 wt %. Compositional variations in their Cr2O3, Al2O3, Fe2O3, SiO2 and MgO components are reflections of their textural characteristics.

Soil erosion is one of the improper natural phenomenons. Soil erosion effects on soil degradation. To study and estimate sediment yield, there are several methods. Rainfall simulator is one of them. At this research, in first step, the work units' map is prepared by overlying lithology, erosion and dip maps with together. At each work unit, 51 soil samples obtained in 17 stations. Volume of runoff and weight of sediment of each rainfall simulator test measured. The rainfall simulator was two kinds; one has rain surface 84 cm × 120 cm and the other one 25cm×25cm. Every two kinds are adjustable in various dip degrees. The results in Hiv watershed showed that the highest producted runoff occurred in limestone and dolomite lithology with surface and rill erosion types at general dip more than 40 % and highest amount sediment yield is happened in sandstone lithology with surface and rill erosion types at general dip more than 40 %. With attention to the results and generalization of them to soil lose amount of Hiv watershed, for one rainfall event with 19mm/h intensity at 30 minutes duration, the total soil lose of the watershed, 1057.74 ton is estimated.

The shear and compressional wave velocities (Vs and Vp, respectively) have many applications in petrophysical, geophysical and geomechanical studies. Vp is very easily obtained from sonic logs that are available in most of oil and gas wells, but some wells (especially old wells) may not have Vs data. In this study Vs was predicted from porosity well log data (neutron, density and sonic) using fuzzy logic and neuro-fuzzy techniques. For this purpose a total of 3910 data points from Sarvak carbonate reservoir which have Vs and porosity log data were utilized.These data were divided into two parts, one part included 2046 data points used for constructing models and the other part included 1864 data points used for testing models. The results show that fuzzy logic and neuro-fuzzy techniques were useful methods for prediction of Vs in this carbonate oil reservoir.

Geometry and kinematics analyses of structures developed along one of the transverse fault zone (Izeh) in the Zagros fold-thrust belt has been presented to document the origin and to present the effect of this fault zone on the belt structures. Surface deformation of Izeh fault zone on the cover sediments are including changes on the Zagros major structures trends and development of minor structures (such as minor folds and faults) that are overprinted on the belt major structures. Detaeled structural mapping showed the precense of three major restraining zones between the mapped subsurface en-echelon faults along the Izeh fault zone in the Zagros fold-thrust belt. Analysis of isopach maps, facies variation of formations together with interpretation of seismic reflection profiles showed that these subsurfase faults are younger orders of the Izeh fault zone reactivation as a basement fault. Oblique convergence of the Arabian Plate toward the Central Iran is in favor for the reactivation of the fault zone and formation of surface deformations along it. Based on earthquake data this reactivation is continuing until the present time.The result of this study can be used for interpretation of deformation on the sedimentary cover along the similar transvers fault zone in the Zagros fold-thrust belt.

In this paper, the evidences of Quaternary deformation in the west of Shahrood, in an area starting from Deh-Molla valley and extending to Tazareh valley in the southern domain of eastern Alborz have been studied. The studied area is bounded on the North and South by two main faults that trends east- west and dips to north. In the field inspection, the evidences of Quaternary activity like cutting and displacing of Quaternary sediments in some localities such as Deh-Molla and Tazareh valleys have been observed. This study showed that the indications of Quaternary activity are present in the whole of the region; but the North fault with a dominantly left lateral strike slip mechanism that is the eastern continuation of Astaneh fault, has a main role in Quaternary deformation. The left lateral strike slip movement on South fault is finished to east where it connects to a normal transfer fault. This latter transfer fault trends north- south and dips to east.

Masjed Soleyman reservoir is located in Zagros Mountain of western Iran, which is one of the most seismically active zones of the Alpe-Himalaya belt. So, it seems to be necessary to carry out widespread studies, especially on the impact of this reservoir with 177 m height and 261 million m3 capacity on occurrence of induced seismicity in the surrounding region. During impounding of the reservoir regards to national and international catalogues such as International Institute of Earthquake Engineering and Seismology (IIEES) and EHB catalog, an incensement in seismic rate is observed in the Masjed Soleyman region, and 90 days after completing the impounding, an earthquake with magnitude Mw=5.6 is occurred in the close vicinity of the Masjed Soleyman reservoir. In order to better understanding of the impact of this reservoir on seismic activity, a local seismic network of 5 seismological stations was installed in the area on June 2006. Seismic events recorded during a period of 15 month were used in this study. The largest recorded earthquakes during the monitoring of Masjed Soleyman reservoir have magnitudes of ML=3.9 and ML=3.6. Statistical methods such as correlation of the water level changes with variation of the regional seismicity, the foreshocks and aftershocks pattern and decay rate of aftershocks reveal the existing of induced seismicity in the Masjed Soleyman region. In absence of a local network before 2002 September, 25 earthquake (Mw=5.6), our observations indicate this earthquake is truly the first and largest induced earthquake that have been occurred and recognized in Iran.

Hydrocarbon fluid extraction from high compactable and low permeable reservoirs resulted in gradual surface deformation that causes significant costs due to overburden failures. However, surveying benchmarks make it possible to compare the repeated leveling measurements at the specific locations, then it is necessary to introduce an effective method that is more real time and cost-effective. Differential SAR interferometry (DInSAR) is a new technology in which satellite images are used for field surface displacement monitoring. In this method, the high resolution images derived from Radar measurements are used for surface deformation rates assessment to improve the management and mitigation of traditional production costs. In this study, surface displacements caused by fluid withdrawal in Aghajari oil field are presented using Radar observations as the InSAR data reveal both subsidence and uplift signals for each production and observation wells distributed over the site. A number of production site inspections in a time series of interferograms reveal that the surface deformation signals developed due to extraction in several months as well as different subsidence or uplift rates and deformation styles occur locally depending on the geological conditions and excavation rates.

Jajarm bauxite mine as a largest known bauxite ore reserves with more than twenty million tons of diasporic bauxite, located in the north of Khorasan province, Iran. This bauxite mine cannot provide the suitable feed for at least twenty tears. Therefore, the possibility of using other bauxite deposits such as Shah-Bolaghi bauxite mine in Tehran province and Sorkh-cheshmeh mine in the north of Khorasan province was investigated. These studies were carried out based on the dissolution and sedimentation velocity of red mud. The results show that using these deposits separately is not applicable, because of low dissolution and/or low sedimentation velocity of red mud. The other parameters such as dissolution temperature, the amount of lime and Na2Oc must be carefully controlled to have the better results. Accordingly, a mixture of 50-50 Jajarm and Shah-Bolaghi bauxite ore has had the better performance with higher dissolution efficiency and also the lesser alumina amount in red mud.

Takht-e-Solayman zone is highly rich from the viewpoint of diverse morphological units. This morphological diversity is mostly caused by climatic factors and lithological characteristics, erosion, weathering processes and tectonic movements. Geomorphologic characteristics of Takht-e-Solayman zone are influenced by internal and external morphodynamic factors. As a geomorphologic-environmental achievement, this research has been dealt with the investigation of external factors. The available morphologic indicationsin the study area are divided into 3 general groups including morphodynamic, morphotectonic and morphogentic units and then presentedin the form of a geomorphologic map.For this purpose, several new information layers of the zone are preparedin GIS environment using basic maps and field investigations and finally the landforms evaluated using ASTER and ETM+satellite images.

The Talle-Pahlevani anorogenic magmatism with Leuco-quartz diorite and anorthosite compositions injected into the southwest of the Qori metamorphic complex, which extends in southwest of the Sanandaj-Sirjan zone, at c.170 Ma. As a result of this process, the metapelite host rock from the complex was metamorphosed and broken down. Fragments (xenoliths) of the host rock, which are primarily regional metamorphic kyanite schists, fell into the magma. These xenoliths underwent a high grade contact metamorphism due to H2O-free magma with high-initial temperature. The partial melting of the metapelitic xenoliths (schists) occurred because they were saturation or super-saturation in H2O, and as such, some of these xenoliths became weak, because of partial melting, and scattered throughout initial magma of the batholith, and contaminated it due to convective flows in the batolith.

Acid rain is one of problems due to air pollution. In areas with polluted atmosphere, SO4 and NO3 are among most important contaminator, which constitutes sulfuric and nitric acids solutions, as a result of combining with hydrogen ions. Also, these solutions are among important agents in building stones dissolution and deterioration. Regarding the involved acid and its pH, these solutions have different effects on stones.In this research, we selected 14 building stones samples of different origins. Then, in order to investigate their dissolution and deterioration and, also comparing sulfuric and nitric acids dissolving effect, we performed Durability Test up to 15 cycles, and calculated Durability Index on mentioned solutions-with pH=1.5, 3, and 5, and also fresh water with pH=7.3. The results show that the samples with non-carbonate composition are resistant against those acids, while the carbonate ones are not. Furthermore, comparing results of Durability Index indicates that sulfuric acid has 0.06 to 0.93% greater dissolving effect than nitric acid. In addition to, a decrease in both acids pH, leads to a greater dissolution of carbonate samples. Finally, according to obtained results, we recommended the most suitable stones for exterior façade of buildings.

Coastal region are influenced by land and sea. Geomorphologic coast features are related to sea level change, regional river regime, erosion processes, sedimentation, climate change, geological outcrops and weathering and tectonics. Tom bolo, lagoon and barrier are geomorphologic coast features that can be seen in Bir coast of Iran. Therefore, recognizing the producing mechanism and their changes, leads supervisors to have better management, and do their best for civil and improving planning in coast area. In this research in addition to field studies and sampling, aerial photos 1.40000 (1993), topographic maps 1.20000, high resolution images (ETM and IRS) 1998, 2005, 2008 were used. It is concluded that the area is tectonically active, sedimentation; erosion processes, river regime and sea level change are caused to the Tom bolo, Lagoon and Barrier in Bir coast. Surveying the forms, sediment shows an obvious computation between marine currents as constructive process of Tom bolo, lagoon and barrier, and rivers as destructive process in Bir coast.

Today, the best coordinates of stations on the ground are obtained by using Global Navigation Satellite Systems (GNSS) such as Global Positioning System (GPS). There are many error sources affecting the GNSS observations that limit the required accuracies. But differential positioning methods, like double difference, are big helps to us to achieve an accuracy of millimeter. Differential operation of GNSS is based on placing a reference station with a GNSS receiver at a known location. One of such errors is the coordinate error of reference station and its propagation on unknown stations. In fact the coordinates of a reference station should be known in a reference system coordinate, such as WGS84 used in GPS, which we usually assume is exactly known. In practice, the position of the reference station in the reference system coordinate may not be exactly known due to different reasons. Therefore, in this study, the effect of the reference station position errors on various ranges from ~4 km to ~90 km, in static mode and using double difference carrier phase, is investigated. The results show this effect could be of the order of a few ppms depending on error magnitude of reference position and the range of baseline.

A Permian residual horizon is located in ~30 km northeast of Malekan, which was developed as stratiform layer in Ruteh carbonate rocks.Mineralogically, this horizon includes minerals such as boehmite, diaspore, hematite, kaolinite, rutile, anatase, montmorillonite, muscovite, calcite, and chlorite. Calculations of normative values of minerals in a selective profile show that this horizon consists of five distinct lithological facies which are, from bottom to the top, (1) kaolinitic ferrite, (2) ferritic kaolin, (3) ferritic bauxite, (4) kaolin, and (5) bauxitic kaolin. Based on obtained data, it seems that the distribution of REEs in the studied profile was principally controlled by factors such as (1) Eh variations of the environment due to decomposition of organic matters, (2) the pH increase of weathering solutions by carbonate bedrocks, (3) scavenging and fixation processes, and (4) fluctuations of underground waters table. Further geochemical evidence indicates that the concentration of LREEs were occurred by muscovite, Mn-oxides, and secondary phosphates (e.g., monazite, gorceixite, rhabdophane) and that of HREEs by rutile, anatase, and zircon in the studied profile.

Ground water, cavities, and isolate buried structures embedded at shallow depths are well detectable by resistivity and GPR methods because of distinct contrast in their electric and electromagnetic properties in comparison with their surrounding media. In this research work, 3 different profiles on such targets have been chosen, and their responses have been investigated. Using both resistivity and GPR methods together, it has also been possible to investigate capabilities and limitations of the methods in practice. The results obtained from this research work indicate that the GPR method, in addition to its speed and simplicity in data acquisition, is very successful in detection of interfaces or boundaries between different media in which electromagnetic properties at the boundaries change rapidly. The resistivity surveys, which have been carried out using Wenner array in this study, indicate low resistivity of the media under investigation. The low resistivity of the subsurface media caused the depth of penetration of the GPR method to be low, and as a result, made it impossible to investigate the targets buried at depths greater than 2 meters. Unlike the GPR method, the resistivity method has not been very successful in detection of multiple targets with high resistivity contrasts. Lower resolution of the resistivity method in comparison with GPR method has caused this problem. In this study, considerable information has been obtained by selecting two different processing algorithms and applying them on a series of raw GPR dataset.The obtained information from the resistivities of the subsurface structures as a result of the resistivity surveys has made it possible to choose and apply these processing algorithms. This research work well indicates that high conductive areas in resistivity sections coincide with the areas in the GPR sections having intensive attenuation. This characteristic can be used well in the interpretation of the GPR sections. Finally the resistivity method can be introduced as a suitable supplementary geophysical method to the GPR method.

Biotite-muscovite leucogranite and associated pegmatite intruded meta-ophiolite and meta-flysch (the remnants of Paleo-Tethys) during collision of Turan plate with Iran plate. Four types of pegmatite dykes, crosscutting biotite muscovite leucogranite, are identified. The results of U-Pb zircon age of Khajeh Mourad biotite muscovite leucogranite is 205.9±4.1 Ma (Late Triassic, Rhaetian). Chemically, biotite muscovite leucogranite and aplite granite are peraluminous S-type pluton. Magnetic susceptibility of biotite muscovite leucogranite and aplite granite are between than 0-5×10-5 and the ratio of ferric to ferrous ratio (<0.35), therefore they are classified as belonging to the ilmenite-series (reduced type). The total REE content of biotite muscovite leucogranite is between TREE=130-176 and aplite is very low Total REE=50.79. They have small negative Eu anomalies (Eu/Eu*=0.52 to 0.76). The initial87Sr/86Sr and (143Nd/144Nd) i was recalculated to an age of 205 Ma. Initial 87Sr/86Sr ratios for B-M leucogranite and aplite are 0.708161-0.709853. The (143Nd/144Nd) i isotope composition for B-M leucogranite 0.512214, aplite dykes 0.512024. Initial ε Nd isotope values for B-M leucogranite -6.48 and aplite dykes is -6.83. These values could be considered as representative of continental crust-derived magmas. The ratios of Rb/Sr=1-1.3 and CaO/Na2O≈0.3 of biotite-muscovite leucogranite indicate that the source rock had a composition between meta-pelite and meta-psammite.

Behavior of sands under static and dynamic cyclic and monotonous loadings is the most common problem of Geotechnitiens. This paper presents results of cyclic loading on loose and dense silica and carbonate sands using a modified direct shear box. The laboratory shear box was modified so that the lower part of the box was composed of a metal plate with sand grains glued at its surface. Various test parameters such as sand type, sand density, interface conditions, number and form of cyclic loading were studied to explore behavior of soil-soil and soil-structure under naturally occurring loading conditions. Results showed that the two sand types tested demonstrate contraction behavior at the beginning but dilation performance later on. Shear and normal forces decreased during the tests; the decline was larger for carbonate sand than for the silica one. The reduction of shear and normal force increased with decreasing density of sand. This reduction behavior of forces in tests with zero displacement under cyclic loading is similar to the liquefaction phenomena and these results might be applied to evaluate liquefaction problem.

There are always limitations for appropriate borrow materials in common engineering activities which results in wide usage of mixed soils with larger particles up to boulders. Using these types of materials need correct knowledge of their behavior. For example, shear strength characteristics of mixed soils are usually required for stability analysis of slopes, landslides and earth dams. However, there are limitations in experimental studies on soil mixtures due to the small size of testing specimens. In the present study, a regular set of large scale direct shear tests performed to investigate gravel particles shape and size effects on shear strength characteristics of fine sands. The tests conducted using direct shear apparatus with 300 mm×300 mm shear box. Poor graded fine sand was used as the base material and mixed with zero, 20, 40 and 60 percent of angular and rounded gravel grains with maximum size of 12.5 and 25.4 mm as oversized particles. All tests performed on dry samples in drained condition. Samples prepared in three different relative densities of 35, 60 and 85 percent and tested using three surcharge pressures of 150, 300 and 450 kPa. According to the results, shape and size of oversized particles strongly affect direct shear strength characteristics of sand-gravel mixtures. Mixtures with angular and larger gravel grains show more shear strength and dilation compared to mixtures contain rounded and smaller oversized particles. Enhancement of gravel content, surcharge pressure or relative density increases the effects of oversized particle on shear behavior of mixture.