GEOSCIENCES
Year:2007 | Volume:17 | Issue:65|Papers Count:17

In this research a Decision Support System (DSS) has been used to support decision makers for policy making regarding the landslides which typically take place around villages. Definite software was utilized to design a model which includes three strategies: landslide stabilization, village relocation, and risk acceptance. The model introduces the optimal strategy considering four effects (i.e., cost, reduction of fatalities, peoples and local manger point of views). To determine the cost of stabilization, in the first step the stabilization method should be selected. This is also is performed using the other DSS system. In the next step, the cost of stabilization is computed. The cost for the other alternatives is also assessed. The other effects are evaluated for the other alternatives. The user can select the optimal method for a certain landslide after completing the designed questionnaires regarding engineering geological characteristics, reduction of fatalities, people and local manger point of views. The Barikan landslide in Taleghan region was studied using the model. The stabilization method was selected as the most appropriate strategy for the landslide. The selected alternative is in a good agreement with those presented as the results of site investigation.

According to historical maps of Iran, changing the course of Sepidrud from Dastak to Kiyashahr has occurred in a very recent time. Although migration of meandering streams over the delta plain is a natural phenomenon and oscillations of Caspian Sea might have affected the course of Sepidrud River, the deflection of Sepidrud between Astaneh and Koochesfahan is probably related to activity of concealed structures within the delta deposits. This research uses calculation of morphotectonic indexes to study effects of active range boundary within range faults in study area on drainage pattern and river streams.

The first studied Abtalkh Formation with Campanian – Maastrichtian age is well exposed in Kopeh Dagh area (Mozduran section). This formation conformably underlain carbonates of Abderaz Formation and overlain by Neyzar sandeston Formation, both formations have a gradual contact.The second studied formation so called Echinid marl formation of Santonian –Late Campanian age is exposed in Baharestan section, Central Iran, Esfehan area.Based on 100 studied samples, there are litological and paleontological similarities between Abtalkh and Echinid marl formations. These evidences support strongly paleoecological and environmental similarities.This ascertainment shows the close relation between the Kopeh Dagh and Central Iran basins.The fossil evidences found in both sections are as follow:Globotruncana ventricosa (White), Globotruncanita elevata (Brotzen)Globotruncana arca (Cushman), Globotruncanita stuartiformis (Dalbiez)Globotruncana bulloides Volger, Globotruncana lapparenti BrotzenGlobotruncanita calcarata (Cushman), Globotruncana linneiana (d' Orbigny)

Nannofossils are suitable for biostratigraphical studied since they are aboundant, planktonic, rapidly evolving and largly cosmopolitan, especially in Late Cretaceous.According to this, due to the lack of any precise Paleontological study, the nannofossil of Neyzar Formation has been investigated in type locality. This formation consists of thick- bedded glauconitic sandstone, shale and a sandy limestone bed in the upper part. The Neyzar Formation conformably overlies the Abtalkh Formation and is itself conformably overlained by the Kalat formation.  As a result of this study, for the first time, 22 genera and 42 species of nannofossils have been identified. Based on these obtained nannofossils, the section is Late Maasrichtian in age, corresponding to CC25- CC26 (Sissingh, 1977) (equivalent to CC25c-CC26a-b, Perch- Nielsen, 1985).

Coherency attribute is one of the proper tools in interpretation of structural discontinuities and stratigraphy features in 3-D seismic data. Coherency measurements in three dimensions discuss trace-to-trace similarity and therefore represent interpretable changes in these cases. The similar traces are mapped with high coherence coefficients while anomalies and discontinuities have low coherence coefficients. Coherency attribute shows evaluation criterion of lateral changes in the seismic response, caused by variation in structure, stratigraphy, lithology, porosity and the presence of hydrocarbon. Output of this attribute is a coherence cube which illustrates structural discontinuities and stratigraphy features with higher resolution. In this paper, the application of two conventional coherency attributes based on eigenstructure and crosscorrelation for detection of faults in 3-D synthetic seismic data and actual seismic data is presented.Considering the experimental results, this method has an appropriate response to low SNR for 3-D synthetic models and 3-D actual data. In addition, the comparison of eigenstructure -based coherency attribute method with crosscorrelation-based coherency attribute method indicates the former has higher resolution for detection faults than the latter.

An investigation on beneficiation of Lakhshak antimony ore was carried out using flotation methods. The grade of antimony in representative sample was 17.23%. The most important minerals were stibnite, quartz and pyrite and the degree of liberation of stibnite was found to be 700 micrometer. The raw material was divided into three size fractions and beneficiation of fine size fraction (-210+38 m) was floated. The grade of mentioned fraction was 20.50%. Taguchi method was used in flotation tests and optimum conditions were determined as follows: CuSO4 (1700g/t) as an activator, potassium etyle xanthate (900 g/t) as a collector, MIBC as a frother, pulp density 22% and grain size -150+38 m. All the experiments were carried out at pH=6.8. As a result the grade and recovery of antimony was obtained 38% (Sb) and 91% respectively.

The 31 March, 2006 earthquake with Mw=6.1 destroyed villages in the Darb-e-Astaneh (Silakhor) region of the Lurestan province. The epicenteral area of this earthquake lies near the Main Recent Fault (MRF) and its right lateral mechanism indicates that it belongs to this fault zone. The main shock was followed by relatively large number of aftershocks. In this research, the aftershock sequence of this earthquake has been studied by measuring quantitative indices of coefficient of variations (CV), the exponent of the power spectral density function, and the generalized multifractal dimensions. The results reveal the presence of fractal structure in the temporal and spatial distribution of aftershock sequence. The multifractal behavior of the aftershock sequence indicates the clustering of the earthquake activity and the degree of the heterogeneity in the seismotectonic and geodynamic processes in the focal region. The results show that the multifractal dimensions of the aftershock sequence decreases and the multifractal dimensions of aftershock epicenters increases with time. It seems that these changes in the multifractal dimensions are related to the activity of secondary and sympathetic faults and changes in the tectonic stress regime of the region. The results also indicate that the multifractal method rather than monofractal approaches is a powerful tool for quantitative analysis of aftershock process's clustering behavior.

Chah-Calap W (Cu-Zn) deposit is located in Lut Block. It is a part of Central Iran Paleozoic platform which has been subjected to late Cimmerian orogenic movements. Chah-Calap ore- bearing volcano-sedimentary sequence of upper Triassic-Jurassic age was metamorphosed to green schist-lower amphibolite facies. This sequence includes siliceous meta-pellite, lower meta-felsic tuff, meta-limestone with meta-chert interlayers, (main mineralized horizon occurred at the base of it) alternation of micritic and sparitic limestone, upper meta-felsic tuff and mylonitic rhyolite. In meta-limestone, 3 facies were recognized, in which the mineralization corresponds only to meta-chert bearing facies. No intrusive body outcrops in the study area. Two NW-SE and NE-SW trending fault systems can be observed in Chah-Calap mining region.The stratiform mineralization with layering and lenticular geometry has 2 kilometer length. Based on these investigations, six mineralized horizons can be distinguished in Chah-Calap volcano-sedimentary rocks: siliceous meta-pellite (ore horizon I), lower meta-felsic tuff (ore horizon II), calc-silicate layers, bands and lenses occurring at the contact between meta-limestone and lower meta-felsic tuff (ore horizon III), at the middle of meta-limestone layer (ore horizon IV) and at the upper contact between meta-limestone and upper meta-felsic tuff (ore horizon V) and mylonitic rhyolite host rocks (ore horizon VI). Main mineralized horizon in Chah-Calap occurred at the base of meta-cherty limestone, at lower contact between meta-carbonate and lower meta-felsic tuff. Regionally metamorphosed chert-bearing parts of meta-limestone, forming calc-silicate horizon, composed mainly of sparitic calcite, tremolite, actinolite, diopside, hedenbergite and grassular-rich garnet. Ore assemblage includes: scheelite, chalcopyrite, sphalerite, pyrite, arsenopyrite, pyrrhotite, covelite, bornite, chalcocite, azurite/malachite and iron-oxide/hydroxides having massive, disseminated, laminated, breccia like and open space filling textures. Tungsten mineralization in Chah-Calap is considered to be of distal syn-sedimentary-syn-diagenetic type with exhalative origin. Diagenetic processes lead to primary concentration of mineralization which later experienced remobilization and re-concentration during regional metamorphism.

Magnetic and electrostatic properties of minerals are the important characterizations used in mineral processing technology for concentration of minerals. Mineralogy and degree of liberation of the ore with a uranium average content of 1540 ppm, has been studied by XRD and microscopic methods. Major minerals such as alkali feldspar (Orthoclase), plagioclase (Albite), biotite, chlorite, carbonate and minor minerals such as sphene, zircon, actinolite, tremolite, pitchblende and betafite have been identified in this ore. Additionally, the degree of liberation of orthoclase, albite, biotite and uranium minerals was determined 320, 290, 190 and 110 microns respectively.  Based on the results of mineralogy and degree of liberation studies, magnetic and electrostatic tests have been performed on fractions: -420+250, -250+125 and -125+74 microns. High intensity magnetic tests in two ways, wet and dry separations were done by HIMS separator and plate separator. Analyses of magnetic test results showed that the separation has low recovery. Recovery for dry and wet methods was 45.03 and 26.99% respectively. Analyses of electrostatic test results showed that the maximum recovery of these tests is 51.36% uranium and in this state 27.63% uranium in 42.02 weight percent of feed is rejected. Generally, the recovery of these separations was low, so these methods are not suitable for concentration of this ore.

Sangan Iron ore deposit is located 300 km southeast of Mashhad (Eastern Iran). Based on the high grade, low P- content and big ore reserve, Sangan is an important Iron mine in Iran. It is a magnetite skarn and can be classified as iron-oxide type deposit. Based on the surface exposure, the western magnetite skarn (A´), a Ca-rich type skarn, was formed at the contact of intrusive. Eastward, the skarn gradually becomes distal and Mg-type. The A´ magnetite skarn contains andradite, magnetite, K-rich amphibole, hedenbergite and calcite. Magnetite skarn in A, B, and C- south contain magnetite, repidolite, ferro-actinolite, siderite and minor pyrite. Baghak and C- north magnetite skarn comprise Mg-rich- magnetite, phlogopite, chinochlore, talc, dolomite, forsterite, dolomite, pyrite ± chalcopyrite ± arsenopyrite ±  pyrrhotite. High S-content is found mainly in Baghak and C-north deposits. In this research, the igneous source rock is found in A´ deposit and identified as ultra-potassic type (K2O> %9). Sarnowsar granite which used to be the source rock for Iron, contains less than %5 K2O, therefore it cannot be the source. The K2O content of Sarnowsar granite increases near the magnetite skarn due to alteration. The Fe-ore bearing solution moved along the contact between Sarnowsar granite and the limestone. Sarnowsar granite was altered and skarn formed in the limestone.The source rock is quartz biotite-hornblende alkali syenite to quartz hornblende syenite porphyry. The younger intrusive rocks are biotite granite, biotite-hornblende quartz monzonite porphyry and quartz syenite porphyry. Potassium within the ore bearing solution controlled the mineralogy of skarn. Contact skarn in A´ magnetite deposit comprises K-rich amphibole and distal skarn (Baghak and C-north) contains phlogopite.Comparison of trace elements from source rocks with Sarnowsar granite indicates that the Nb, Zr, Zn and Rb contents are high in the former rocks and Cu and Sr ones are higher in the latter rock. Furthermore, comparison of some trace elements from source rocks with younger intrusive rocks indicate that Cr, Ni, Zr, Ce, Cu, Sr, and La contents are higher in younger intrusive and Rb content is higher in source rocks.

The Lakhshak granitoid pluton which is located at 10 km northwest of Zahedan, has intruded into the Eocene flysch sediments with an elliptical shape and NW-SE direction. This pluton after emplacement has been cut by numerous dykes with NE-SW trend. These dykes comprised about 20-30% of the Pluton with various compositions, ranging from granodiorite to monzodiorite in composition.The Lakhshak plutonic rocks are mainly metaluminous, calc-alkaline and belong to I type granites based on the P2O5 and Th content versus SiO2. Regarding TiO2 content these rocks resemble the continental margin granites. The MgO, Na2O, Ni, Cr content as well as Mg# and depletion in Y, these plutonic rocks are similar to the adakite, a rock type produced by partial melting of young oceanic crust. The low Ba/La content of the studied samples may suggest that subducted slab suffered dehydration prior to partial melting.These rocks are enriched in LIL, LREE; however, they are depleted in HREE and Y. In addition, they show negative anomalies of Nb, Ta, P and Ti, and positive anomaly of Pb. The negative anomalies of Nb and Ta may indicate the effect of mantle wedge metasomatism by oceanic crust. The positive anomaly of Pb may demonstrate continental crust assimilation by magma associated with mantle metasomatism.It seems that Lakshak pluton has been formed by subduction of Sistan young oceanic crust under the Afghan Block. Moreover, the low content of HREE and Y besides a decreased ratio of Yb versus SiO2, Y<15.13, Yb<1.2 and existence of amphibolite enxenoliths in these rocks may suggest partial melting of amphibolites. The latter is formed during the oceanic crust subduction in depth more than 35 km.

The Kopet Dagh basin was formed during and after the collision of Turan plate with Iran plate before late Carnian (about 225 m.y. ago). It is located in the northeast of Iran and has a WNW to ESE trend. Neyzar Formation is composed of siliciclastic sediments and sandy shale and sandy limestone. This unit is widespread in the east and northeast parts of the basin. To determine the stratigraphy, microfossils, microfacies and depositional environment of Neyzar Formation, three stratigraphic sections were selected and measurement and detailed sampling carried out on each of them. These sections from east to west are as fallows:1) Tang-e Neyzar (Neyzar gorge) section 2) Tang-e Chahchaheh section3) Jalil abad sectionIn the previous studies, the base and top boundaries of Neyzar Formation with Abtalkh and Kalat Formations were reported conformable and transitional (Afshar Harb, 1373). However, according to present investigations in eastern regions, lower boundary of Neyzar Formation with Abtalkh Formation in sections 1 and 2 are disconformable (as a Paleosol). This boundary in the section 3 is conformable and transitional. The upper boundary of Neyzar Formation with Kalat Formation in 1, 2 and 3 sections are disconformable (as a paleosoil).Two types of facies were identified based on micropaleontologic and petrographic studies: 1) Siliciclastic facies, 2) Carbonate facies. Based on microfacies studies it seems that the siliciclastic parts of Neyzar Formation was deposited in a lagoonal-barrier island environments and the carbonaceous parts in a shallow carbonate platform (ramp type).In most of the published reports and articles Neyzar Formation was introduced as low fossil bearing unit with no index–fossil. The age of this formation was determined only by the basis of its stratigraphical situation, but in the present investigation, in addition, 41 genera and 30 species of microfossils have been identified for the first time from index fossils such as:Orbitoides apiculata, Orbitoides tissoti, Lepidorbitoides sp., Siderolites calcitrapoides, Pseudosiderolites vidali, Abathomphalus mayaroensis.These fossil assemblages suggest the Maastrichtian, especially Late Maastrichtian age for Neyzar Formation.

The Kopet Dagh Basin of northeast Iran formed in the Neotethys Ocean after the closure of Paleotethys in the south of Turan plate. A thick sequence of Jurassic to Miocene sediments has been deposited in this basin without any major break. The siliciclastic Kashafrud Formation (Middle Jurassic), overlying unconformably on Triassic rocks and ultrabasic rocks comprises nearly 2 km of turbidite and fluvio-deltaic facies, consists of sandstone, shale and conglomerate. Trace-fossil assemblages are presented in some units with different environments. The most important ichnofossils in this formation are Skolithos, Palaeophycus tabularizes,Belerhaphe, Thalassinoides suevicus, Psilonichnus , Planololites beverleyensis, Rhizocoralium jenese, Scolicia, Conichnus, Lophactenium, Palaeophycus striatus,Taenidium. It is interpreted, based on identified ichnofossils, the Kashafrud Formation may have been deposited in fluvio-deltaic and deep water (turbidity conditions) environment. We hope that these data can help in a better understanding of palaeogeography and tectonic setting of the region during Middle Jurassic.

study several 2D and 3D math models have been tested in order to correct slant range SAR data geometrically. Some of these models consider the imaging geometry at the time of imaging while the others relate the ground space to the image one by mathematical polynomials. The images used here are 3 ENVISAT ones of Bam area. In order to extract the 3D GCPs, a topographic map with a scale of 1:25000 and SRTM DEM were used. The 2D math models used in this study include Global polynomial, Point wise, Piece wise and Projective while the 3D models are DLT and Rigorous SAR model. Since the images used in this study were originally ordered for interferometry studies, their baseline is so small that the precision of 3D coordinates extraction is not satisfactory enough. However, the results of 2D models are much better.