GEOSCIENCES
Year:2008 | Volume:17 | Issue:66|Papers Count:13

The studied area is located at the middle structural zone of Sanandaj-Sirjanin Malayer Esfahan axis. Lower Cretaceous sequence disconformably overlay the Triassic-Jurassic sequences. The sediments have been folded during Middle Cimerian (Bajocian-Batonian) and Laramian (Upper Cretaceous) orogenic phases. The carbonate sequences are the host rock of Pb and Zn mineralization in Robat area.The true thickness of the sequence in south and north slopes of Aregijeh Mountain are 256m and 230m respectively and in the south slope of BarAftab Mountain is 408 m. Major and trace elements such as Ca, Mg, Sr, Na, Fe, Mn, Sr/Na, Sr/Mn, Sr/Ca and d8O and d13C isotope values in carbonates are used for recognition of original mineralogy. Trace elements and oxygen and carbon isotopes indicate a mixed calcite-aragonite original mineralogy.Petrographic and geochemical studies indicate that carbonates affected mostly by meteoric diagenesis in an open system. Paleotemperature calculation, based on lightest oxygen value, indicates that the diagenetic temperature was about 75oc.The genetic types of ore deposits in Robat area is a kind of diagenetic-epigenetic forms, controlled by hydrothermal fluids at low temperature, similar to the Mississippi Valley Type deposits (MVT). The model of ore formation is illustrated below: The passage of meteoric waters through fractures and faults removed Pb, Zn and Mg from shale layers and precipitated the elements in the limestone rocks. The shale layers above the limestone sequences played as a feeder trap for lead and zinc deposits. Siliceous (jasperoid) and dolomitic alteration are the main alterations in the area.

Safakhaneh batholith, situated at 47 km southwest of Shahin Dezh, northwest of Iran, is located in the central Iran structural zone intersecting the Cretaceous rocks. The absolute age of the batholith, determined for the first time by K- Ar method, has been calculated 69.535 Ma. Showing upper Cretaceous- Paleocene epoch and Laramide tectonic orogeny. Geochemical investigations of the batholith show that the major part of the batholith is of mantle magma, in which magmatic changes of the crystalline differentiation and contaminations have occurred. The crystalline differentiation has caused the formation of different rock types of quartz monzonite, quartz monzodiorite, tonalite, granodiorite and monzogranite respectively. Primary magma of the rocks is of calc – alkaline and generally metaluminous. The specifications of batholith rocks can be compared with the I – Type Caledonian granites. From the tectonic point of view, the specifications of the batholith can be comparable with the volcanic arc granitoids (VAG).

Yarim-ghayeh cave is located in the border of Iran and Turkey and is hosted by the Oliogocene-Miocene limestone body. It’s in and outside rough topography implies that the cave is very young and in fact in the beginning stage of its formation. Overall volume is 9600 m3 with 631 m2 dry area and 4700 m3 occupied by water with 4 to 6 meters in depth. Structurally, the cave has been formed by a fault system cause a sinkhole form on the top of the cave approximately of 10000 m2. Its water is clean and clear with pH of 7.36 and its fluorine is only 1.7ppm compared to 4.5ppm in Maku area.Yarimghayeh playa with an area of 5 m2 is in the close eastern part of the cave with permanent water flow. Elevation of the water surface of playa is 1414m which is 2 m higher than the water surface of the cave (1412 m). 500 m3 water is daily pumped out without any change in water level. Since there is no any other water flowing to the cave, therefore, the playa is supplying the cave water system. The ecosystem of the cave and playa are tight together and any change in one will affect the other. To protect its water quality from contamination, access to this small scale cave must be restricted except for scientific research.

The amount of total organic carbon (TOC) is one of the most important parameter in evaluating hydrocarbon source rock. This parameter is not only used for hydrocarbon geochemical studies but also plays an important role in evaluating the extension of hydrocarbon source rock. As the increase in TOC may indicate the presence of source rock, the depletion of TOC reveals no extension of source rock in a certain depth. Therefore the need for a powerful tool in this aspect is essential. One of the linear methods for solving such problem is artificial neural network, a biologically inspired computing method which has an ability to learn; self adjusted and are trained, capable of classification, image processing and different problem analysis, with an attempt to estimate.This paper presents the features and framework for application of neural network in estimating TOC for hydrocarbon source rock in Binak oil field, Bushehr province, using well log data.The results of this study reveal that Multi-Layer Perception (MLP) is the optimum network which was used for TOC estimation. MLP topology was a hidden layer with 6 nodes, back propagation momentum learning algorithm and tangent activation function. After training is completed, the estimated error calculated as 0.0013, and then the network performance was tested upon training and testing data. Ultimately the predicted TOC values were compared with the actual one which showed reliable network performance (R=0.9956). Finally the sensitivity analysis was attempted on effective parameters and based on neutron porosity parameter (NPHI) found to be as the most sensitive, and the sonic travel time (DT), the least sensitive parameters in estimating TOC.

The Tarom Sofia copper ore zone includes several oxidized copper ore deposits, the most famous being Cheeseh, Aghdarreh and Yarnaghan deposits. In view of the diversity of reserves and productivity of ore deposits in the area, two production capacities ( high: 2000 tpd and low: 90 tpd) , two leaching processes and two methods of recovery were considered to compare the economics of cementation vs. solvent extraction for recovering copper from leach solutions of these ores. Taking all the three parameters (production capacity, leaching processes and methods of recovery) into consideration eight alternatives was evaluated. Capital costs were estimated by employing order of magnitude calculations while operating costs were estimated by scaling up lab- scale costs. Economic comparison was made by the NPV method.The results showed that the NPV of the high capacity model was higher than the low capacity model while vat leaching has a lower NPV than agitation leaching. Similarly it was shown that cementation for the low capacity model has a higher NPV than solvent extraction while for the high capacity model the order is reversed. Hence it is concluded that for capacities less than or equal to 90 tpd cementation is the economically preferable method for recovering copper from leach solutions but for capacities greater than or equal to 2000 tpd solvent extraction is the better option.

Locating the critical slip surface and the associated minimum factor of safety are two complementary parts in a slope stability analysis. A large number of computer programs exist to solve slope stability problems. Most of these programs, however, have used inefficient and unreliable search procedures to locate the global minimum factor of safety. This paper presents an efficient and reliable method to determine the global minimum factor of safety coupled with a modified version of the Monte Carlo technique. Examples are presented to illustrate the reliability of the proposed method.

Rocks are natural materials used in a variety of coastal protection structures, especially in rubble mound breakwaters. Engineering properties of rocks, such as durability and resistance to degradation factors of the marine environments are important properties which construction material of marine structures should behave. Rock durability is a function of rock properties and condition of environment in which the rock will be used. Regarding the economical importance of constructed coastal ports and facilities in coast lines of south Iran, it is necessary to evaluate the engineering properties of rocky construction materials in such structures from durability and degradation point of view. In this study, by investigating and sampling the used rock material in 27 constructed rubble mound breakwaters along the 1000 km south Iran's coastlines, from Amery Port in western part to Pasabandar Port in 85 km east Chabahar, and regarding the observations that collected in field visual investigations and engineering tests of durability examination, the experimental relationship between physical, mechanical and durability parameter of studied rocks have been concluded and consequently criterion to select the suitable rock of three groups of rocks limestone, igneous rock and bioclastic sedimentary rock (lomashell) have been presented individually.

The Pleistocene sediments in the east of Iran belong mostly to extinct herbivores of Order Pressiodactyle and Arssiodactyle. The tooth remains of Equidae from Pressiodactyle, bones and tooth remains of domestic and wild herbivores such as Rhinoceros that some of which are extinct today have been found. The existence of Rhinoceros teeth in the study area, Maragheh sediments, Linxin basin in China and other areas indicate that after the extinction of fauna in Maragheh, a similar fauna was formed and the climate in the Late Cenozoic in Mediterranean basin, Western and Central Eurasia were warm and humid.

Almabolagh region is located in northwestern part of the Sanandaj-Sirjan zone of Zagros orogen in western Iran. This area islocated 15km to the west of Hamadan. Three rock units consisting of volcani-sediments (Almabolagh sequence) at the lower part, carbonate (Chenarsheikh sequence) in the middle, and slate (Hamadan slate) at the upper part are identified. These rocks that are metamorphosed at green schist facies have been exposed in a dome structure. Four stages of deformation (D1, ..., D4) areidentified in the tectonites. D1 structures include first generation folds and related axial planar schistosity. D2 structures are recognized by tight to isoclinal, recumbent shallowly plunging folds, with horizontal to sub-horizontal axial plane schistosity which is the predominant foliation in this area. The mechanism of folding in this stage is flexural shearing and passive flow. D3 structures are identified by the third generation foliation that is weakly developed parallel to the axial surface of related upright, open to gentle folds. The third generation folds were produced by flexural slip mechanism. A dome structure generated by intrusion of magmatic batholiths in this region and structural elements of the main deformation stages (D2) were rotated.

Zahedan granitoidic pluton (750 km2) with general NW-SE elongation is located in the middle part of the Zahedan-Saravan anitoidic belt. It includes granites, granodiorites and diorites and it is also cut by numerous of andesitic to dacitic dikes. The gionalmetamorphic rocks of the area, with the age of Eocene, have been intruded by this pluton. In this research, emplacement echanism of the northern part of Zahedan pluton has been studied with the aid of anisotropy of magnetic susceptibility (AMS) method. The results show that granitic rocks of the Zahedan pluton belong to paramagnetic granites (500mSI) while diorites Idgranodiorites belong to ferromagnetic granites (500mSI). The magnetic lineations and foliations of the pluton mainly have low dip or sub-horizontal In contrast, dioritic rocks which cover a small area, have magnetic lineations and foliations with high dip (sub-vertical). Therefore, dioritic rocks are considered as the feeder zone or the ascent location of the magma for this part of the Zahedan granitoidic pluten. Very low dip magnetic lineations and foliations suggest that Zahedan granitoidic pluton has been emplaced as sill. The activity of a very low dip simple shear movement has an impartment role in preparing a suitable space fir emplacement of this granitodic pluton.

Karaj-Chaloos Road is always considered as the most hazardous road due to rockfalls and landslide events. The road, located in the Central Alborz Mountains, is a vital route connecting Tehran and the southern part of Alborz to the northern part and the resort areas along the Caspian Sea. The aim of this paper is to study and evaluate the potential of rock falls and landslides along the middle part of the route. The study area has a very complicated geological and geomorphological condition and many deep cuts were made along the road to provide a safe passage through the mountains. Since most of the slope instabilities along the road are of rockfall type, cone-fall theory proposed by Evans and Hungr (1993) was used to analyze and predict the rockfalls along the route. The results show that the potential of rock fall is directly related to morphology and higher for steeper slopes. Rock type and the geological structures of the slopes also influence the rockfall potential in the study area.

Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, various limiting factors such as spatial and temporal decorrelation, atmospheric effects and thermal noise of the radar sensor introduce different types of noise into the interferograms, which makes the phase unwrapping too difficult to obtain the accurate results. In this study, an algorithm for noise suppression is presented based on wavelet transform in the complex domain. The high-frequency data due to the phase jumps is not appeared in the complex domain. Therefore, the wavelet coefficients obtained in the complex domain include mostly the noise. The wavelet coefficients of the noisy interferogram are then filtered using the threshold computed from the related wavelet band. In comparison with the other noise reduction methods such as multi-look processing and those based on Fourier transform in small windows, the proposed algorithm can reduce the noise while keeping the spatial resolution without the need for windowing the interferogram. Quantitative and qualitative evaluations of the results obtained by the new method applied on the simulated and real noisy data show high performance of the wavelet transform in noise reduction.

Kuh- Shah granitoidic pluton is located in the NE part of 1:100000 geological map of Baft. Lithological composition of this plutonincludes Alkali- feldspar granite, granite, granodiorite, quartzdiorite, diorite and gabbro. This pluton has been intruded in volcaniclastics of Eocene age. On the variation diagrams the trends of major and trace elements of studied samples indicate the continuity of lithological compositional range of this pluton and they have been from differentiation of a basic (basaltic) magma. From the genetic classification point of view the studied granitoidic pluton is from I type granite and it belongs to magnetite series. Based on the geochemical features Kuh-Shah granitoidic pluton is metaluminous with high and medium potassic calcalkaline nature. High amounts of LILE and low amount of HFSE on the spider diagrams show that the parental magma of these rockshave been enriched from trace elements and incompatible elements. Based on the tectonic setting discrimination diagrams, this pluton is belong to VAG type and therefore it has been resulted from subduction of neotethys oceanic crust beneath the central Iran continental crust.