نشریه علوم زمین
پیاپی 84 (تابستان 1391)

Metamorphic rocks of Dehnow area mainly consist of gray to black fine-grained schists. Garnet schists are closer to the tonalitic body than the garnet chloritoid schists. There is a thin layer of staurolite and andalusite bearing hornfels between these schists and the Dehnow tonalitic body. Garnet schists and garnet chloritoid schists of Dehnow area are mineralogically comprised of quartz, biotite, muscovite, garnet, chlorite, chloritoid, tourmaline and ilmenite. Geothermobarometry results indicate that hornfels (550oC, 4.3 kbar) and garnet chloritoid schist (486-497oC) have formed in lower equilibrium condition in comparison with garnet schist (569oC, 5.3 kbar).

In this research, the role of various existing tectonic plate and faulting motions in the middle-east region has been investigated on the geodetic data and its purpose is to estimate the contribution of these motions in the GPS velocity field of campaign global geodynamic network in the region of Iran using fracture mechanics concepts and dislocation modeling. For modeling the faulting data in the Middle-East region were decomposed to various categories by considering the tectonics of the region and were included in the model and the induced velocity field due to them were modeled and compared with GPS velocity field. Obtained results show that the contribution of Arabian plate in observational GPS velocity field is more than the contribution of Anatolian plateau faultings and inside faultings of Iran create an internal north-south compression component and a counterclockwise rotation component in the modeled velocity field. According to modeling results about 30% of GPS velocity field components are produced by Iranian inside faults, 60% by Arabian plate and 10% by Anatolian plate.

Vertebrate fossil fauna of Late Miocene age in Maragheh contains various mammals preserved in pyroclastic deposits of southern Sahand volcano. This study has been conducted on Gazella capricornis (a perfect skull). Since no other sample with such a good perfectness was found before at other localities (previous ones were isolated horns or tooth rows), it can be proposed as a complemental to the samples type. Gazella capricornis was found not only in Maragheh but also in Samos and Pikermi (Greece), Akkaşdaği (Turkey), Bulgaria, … (east of Europe and west of Asia); which indicates similarities in Late Miocene-Early Pliocene fossil fauna, paleogeography, relative ages, sediments and paleoecology between these regions.

The study of planktonic foraminifera of the Gurpi Formation at Kuh-e Khane Kat (east of Shiraz) led me to find standard biozones Early Santonian to Middle Campaninan. Four biozones were determined: biozones I (Dicarinella asymetrica zone) and II (Rosita fornicata zone) belong to Early and Late Santonian. Biozones III (Globotruncanita stuartiformis zone) and IV (Globotruncana ventricosa zone) represent the Early and Middle Campaninan. Due to a decrease in water depth in Kuh-e Khane Kat, Globotruncanita calcarata zone and other Maastrichtian plagic biozones were not recognized. In this section, Gurpi Formation is 220.5 meters thick and contains shale and argillaceous limestone. Its underlying and overlying formations are Sarvak and Tarbur.

During the Carboniferous time, Iran was a part of the northern margin of Gondwana. Carboniferous deposits of Iran are characterized by continental to shallow marine deposits. The studied section (Simeh- Kooh) is located in 5 Km Northwest of Damghan city in the east Alborz region. The lower Carboniferous Mobarak Formation consists of variable thickness of limestones interbeded with shale beds. The thickness of this section is about 115 m. The Mobarak Formation overlay the upper Devonian Jeirud Formation with a transitional contact and is unconformably underlain by lower Permian mixed siliciclastic-carbonate succession of Dorud Formation. This research is focused on the conodonts and facies. Conodont elements consist of 13 genus and 19 species. 5 Biozones is identified including, costatus zone (Latest Famennian), Sandbergi-L. crenulata zone, isostaticha-U. crenulata zone (Middle Tournaisian), typicus-anchoralis-latus zone (Late Tournaisian) and G. bilineatus zone (Middle-Late Visean) correspond to global zonation. The Tournaisian succession consist of alternation of organic matter rich shales and dark thin-bedded limestones is supposed to have deposited in a deep marine environment with a low oxygen condition. The paleontological and facies characteristics of Devonian-Carboniferous transition definitely show a rapid sea level rise and flooding event in this time in Eastern Alborz which corresponds with the Hangenberg Bioevent known in other parts of the world.

Bouin– Miandasht Intrusive body is located in South- West of Golpayegan quadrangle and Sanandaj- Sirjan Zone. This Intrusion is composed of a compositional range including: porphyroid granite (monzogranite- syenogranite), granodiorite and gabbro – diorite. Variation diagrams of major and trace elements show a trend of continuous compositive spectrum and affinity in granite to granodiorite and noncontinuous spectrum and lack of affinity between gobbro- diorite with the former group. All samples are metaluminous and slightly peraluminous, and rich in K contents. On the basis of geochemical data, these rocks are I- type granites characterized by depletion in Ta, Nb, P, Ti and enrichment in Cs, K, Sr, Rb, Ba that are obvious in the multi-element spider diagrams. The enrichment in LILEs and depletion in HFSEs reveal I- type metalominous volcanic arc granitoid (VAG).Satellite images and geological evidences show that there are 2 main fault systems in Golpayegan region with two trends of NW-SE and NE- SW.

Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, these rocks are divided into two groups of "augen geneiss " and "metagranitoid". During the course of previous studies, these two rock groups had been attributed to a magmatic phase in Mesozoic, which experienced different degrees of deformation. In this study we proceed to determine the age of these two granitoid rock groups based on U-Pb age dating method applied on Zircon minerals. As a result, the age of orthogneiss rocks is 514±24 million years old and they belong to Cambrian, as metagranitoid rocks are 173±9 million years old and attributed to Middle Jurassic. Based on geological and structural evidences, the magmatism occurred in Cambrian was related to tension tectonics in Late Precambrian to Early Paleozoic, while the magmatism in Middle Jurassic associated with dextral transpression tectonics in the studied area.

Lithology Prediction is a fundamental stage in petroleum engineering and formation evaluation. This research is a type of artificial neural network modeling in order to use well bore logs in lithology prediction in a South Pars hydrocarbon reservoir. Here, two networks with three-layer back propagation (BP) method and Levenberg-Marquwardt algorithm have been used for lithology estimation. The network in the first stage, utilized gamma-ray, neutron, density and photoelectric effect (PEF) logs as inputs. On the other hand, the data of sonic log has been also added to the inputs and the results of the two stages have been compared in the second network. Considering the excessive coring expenses, this method can be used as a milestone in decreasing the coring expenses. In this paper, the following procedure is considered first, data four wells in South Pars field has been used. Second, the network has been trained in one of the reservoir wells (well C) in which core analysis data was available. Third, in another well (well D) which its data does not affect the training process, it has been tested. Forth, after approching to the desired level of confidence in network efficiency, it has been utilized to estimate the lithology in the two other wells (wells A and B). lithologies investigated interval consist of: Dolostone, Limestone, Dolomitic Limestone, Limy Dolostone, Anhydrite, Shale, Shaly Limestone and Shaly Dolostone. In the first case, the mean square error (MSE) for well A was 0.081 and for well B was 0.094. In the second case, the sonic log was added to other input, MSE has become 0.051 in well A and 0.063 in well B. Comparing two cases, it was revealed that the model accuracy has been improved significantly in the second case and sonic log data caused the estimated lithology become closer to the real case.

Siahkal area (15 km southwest of Lahijan), is located in SE of Rasht 1:100000 geological map. According to the geochemical samples, collected in the coverage of this map, concentration of some elements like Mn, Co, Ni and Pb, have been detected to be higher than normal values, creating a series of symptoms and environmental pollution. For example, they can result in some malformations in plants decreasing the root and stem diameter, shortening, or a change in the color of leaf and stem of plants and trees. Environmental pollution may give rise to diseases in human beings such as sensitivity of respiratory problems, and even cancer. According to the Siahkal 1:50000 map, in some regions such as: Paeen gavaber, Jeer gavaber, up and down Zarkooti, some elements like Mn, Co, Ni and Pb, show high concentrations than the standard values.

One of the most basic problems in the exploration and extraction of the ornamental stone quarries is the recognition and modeling of the discontinuties. Generally, in the most of the ornamental stone quarries, analysis of the discontinuties is not considered. This study is concerning to the discontinuities analysis in the saeedi ornamental stones quarries (NE Kerman). The Saeedi ornamental stones quarries are located in the Cretaceous limestone. Geological study shows a development of disconitinuties due to effect of two fault systems. Normal faults have dominated features and cause an intensive fracturing in the Saeedi ornamental stones quarries. In order to modeling of disconitinuties, characteristics of discontinuities(e.g. orientation, spacing, persistence,…) were identified in two scan lines, and with use of 3DEC software, block diagram of disconitinuties was prepared for each of face. Block diagrams were contoured for two stages. 1) without effect of face, 2) with effect of face. Comparison of two block diagrams showd an intensive fracturing in rocks due to incorrected position of face. It is concluded that most of face have an incorrected position and must be recontoured and by displacement and change in dimension of face, crushing of rocks will reduce and some of face could returned to extraction cycle.

Zoning is an important practice in earth sciences. In zonation, the study area is divided into separate parts and by compiling the results of these parts, a unique model is obtained. In this study, clustering methods are applied for zoning of Semilan dam site. Optimal number of clusters are measured based on geotechnical parameters (lugeon, RQD), the importance of various dam structures and lithology indicators. By ranking of 7 clustering validity indexes, the optimum number of clusters found to be 4. In this paper, clustering was performed by faults locations and self-organizing neural network. In the former case, the study area was divided into four zones based on faults. This two dimensional zoning is independed of the third dimension (depth) and each sample belonged to a cluster. In the later case, a self-organizing map (SOM), which is a kind of neural network capable of clustering, was used. The SOM input data consists of, three dimensional parameters (X,Y,Z), geotechnical parameters (lugeon, RQD) and finally indicators of importance of various dam structures and lithology. Then, 7 input parameters were normalized between 0 to 1 and entered the network for training.The output data were allocated to four zones (clusters). For RQD spatial distribution realization, variography and anisotropy parameters for all four zones were calculated for both cases, Based on the main principal of clustering method which is maximum difference between clusters and maximum similarity between members of each cluster, performance and validation of two cases of clustering, RQD data were defined. Clustering quality index defined as sum of mean differences between two clusters divided by sum of standard deviation of clusters. Maximizing of this index is optimal solution. This study showed that clustering by SOM gives more accurate results than clustering by faults.

The goal of this study is to use petrographic and other sedimentary features to interpret depositional environment of Faraghan Formation (Lower Permian) in one of the wells in Golshan Field. Golshan Gas Field is located at about 180 km South East of Bushehr between South Pars and North Pars and Ferdowsi Fields. In this study, 130 thin sections of cuttings have been studied, and 8 petrofacies and 3 microfacies and 2 hybrid arenite fasies were identified in the well. Textural maturity of sediments, such as well- sorted and rounded quartz grains, show that the Faraghan Formation was deposited in coastal and shallow marine environments. The identified Facies has been deposited in sabkha, estuarine, foreshore, shoreface and offshore subenvironments.

The studied area is located in southern part of the Torghabeh quadrangle, 90 km SE of Mashad city. The rocks of the investigated area are alkaline basalt and trachy andesite. The major minerals are plagioclase and pyroxene, minor amounts of olivine. The accessory minerals are rutile, titanite and apatite. The major texture is hiyalomicroporphyry. The nature of magma by various diagrams show that the generated magms are alkaline.The linear trends between Rb/Sr, K/Nb, in the rocks of the study area can show mixing of two sources mantle astenosphere and lithosphere. Also positive anomaly of Pb and enrichment in LREE, in the studied samples may indicate crustal contamination. The low SiO2, high Mg and also negative Nb anomaly suggest strong role of crustal contamination in the petrogenesis of the studied rocks. The tectonic environment studies shows that these rocks are within plate basalts. Regarding the presence of coral fossil in the associated carbonate rocks and sand stone facies which belong to Devonian age it can be concluded that volcanic rocks of the study area are produed as a Caledonian eruption and shallow depth environment.

Various atmospheric correction algorithms were performed on ASTER L1B VNIR SWIR datasets, and the results were compared with calibrated AST-07 dataset to introduce the best method. Neyriz ophiolite was chosen as a test area for this purpose. ASTER VNIR SWIR datasets were calibrated to apparent reflectance using two techniques: 1-Absolute atmospheric correction methods including ATCOR-2 (Atmospheric correction), ATCOR-3 (Atmospheric and Topographic correction); 2- Relative atmospheric correction methods that included IARR (Internal Average Relative Reflectance), FF (Flat Field), EL (Empirical Line), LR (Log Residuals), DOS (Dark Object Subtraction), AR (Apparent Reflectance) and COS (t). Results were evaluated by principal components analysis (Image-based algorithm) and spectral angle mapping (spectrum-based algorithm). Field spectra were used as end-members and confusion matrix was used for comparing the results of spectral angle mapping. Results of calibrated images showed that applied methods could be ranked in descending order according to the achieved accuracy of enhancing rock units as ATCOR-3, AST-07، IARR، LR, SWIR data set (L1B) and other methods had low accuracy for enhancing rock units.

Black shales of the abandoned antimony mine of Aq-Darreh Bala Village in northwest of Takab city, northwest Iran, contain high concentrations of toxic elements, especially As (4403–11883 ppm), Sb (405–1022 ppm) and Hg (30–58 ppm). Enrichment factor calculations revealed that some trace elements including As, Sb, Hg, Zn, U, Sr, Ni, V, Co, Cu, Mo, Ni, and Zr have been depleted, while, Pb, Th, Ga, Rb, and Ta are enriched during weathering. Mass balance calculation results show the highest release percents (% loss) belongs to Cd, Zn, U, Sr, Ni, V, Cu, As, Mo, Tl, Zr, Hg and Sb respectively. The highest weight amount of released elements belongs to As, Sb, Sr, Zn, Ni, V, Zr, Cu, U, and Hg respectively. As a result, it can be concluded that the black shale outcrops in the Aq-Darreh Bala abandoned antimony mine area have a main role as a geogenic source in environmental contamination of downstream environments.

Determination of different facies is one of the important and basic tasks of geological engineering characterization of reservoir rocks well logs and core data. Our objective is to identify and determine different facies of the South Pars Field using RBF and PNN neural networks in order to perform static and dynamic simulation. These networks are utilized to identify facies of the South Pars Field for the first time in Iran. In this study, we use different parameters of mentioned networks such as ‘spread’ and ‘goal numbers’ to improve networks operation. In this regards, the optimum values of these two parameters were 0.01-10 and 0.02-0.04 respectively. The results show that the RBF and PNN neural networks are robust means to determine and model the facies of the South Pars Field in Iran.

The outcrop of northern part of North Eshtehard Thrust has been ed for study of structural evolution and geological processes. The study area includes folding structures with different scales regional to outcrop which belong to fault related folding category. Analysis of joints in the region among upper red formation strata shows two main sets which are usually tensional (j1 & j2). These joints are visible in sandstone units of upper red formation and most of them are filled with gypsum. It is obvious that the j1 joints are younger than j2. j1 and j2 joints are related to folding processes. The local stress field which could be measured the joint study is σ1=337/75, σ2=189/13 and σ3=077/03 and corresponds with the given paleostress direction for southern part of central Alborz.

Kahang exploration area located in Esfahan state and 10 Km of the east of Zefreh town that is located on Uromieh-Dokhtar volcanoplotonic belt. Primary results showed that it has good potential for resources of Copper (Cu) and Molybdenum (Mo). Kahang region is an alteration and breccia zone. Generally, more than

The North Tehran Fault with a length of about 110 km in North of Tehran and soutern of central Alborz with W-E trend (N25˚E) and dipping (30˚NE) is located in western of Mosha Fault.The branch of Chitgar such as Milad and Vardavard Fault in the form of propagation fault is increased toward south. Previous morphotectonical investigation along the North Tehran Fault show that shear of quaternary sedimentation and pressure mechanism with left-lateral component. Determination of seismic parameter and seismic action that result of this fault movement, need to doing paleoseismological investigation. In this text with using stratigraphy correlation method, estimated of subsidence rate is 0.16 mm/yr and logging with ratio and ortho photography method, 3-6 event is determined with 6.4-7.4 magnitude and recurrence time is 3650 yr at Chitgar trench.

Two stratigraphic sections of Kazhdumi Formation were ed form Sivand (165m.) and Kuh-e-khanekat (108m.) Areas for Pelecypoda avd Echinoides study. Recognized taxones of Bivalvia and Echinoides are following as: Neithea striatocostata, Exogyra undata, Isocardia aff. neglecta, Astarte sp., Opis sp., Leptosolen sp.,Trigonia crenulifera, Exogyra flabellata, Salenidia boulei, Pliotoxaster cf. lyonsi, Epiaster whitei, Inoceramus sp. Assemblage- zones of the mentioned taxones and comparison of them with accompanied zones (foraminifers), age of studied sediments is Albian to Early Cenomanian.

Received: 2010 June 15 Accepted: 2011 February 08 AbstractThe extrusive sequence of Kermanshah ophiolite complex are exposed in Tamark and Gashor area, in east of Kermanshah and Harsin, in west of Iran. These lavas are located along the Main Zagros Reverse Fault, which marks the ophiolitic suture zone between the Zagros belt and the Sanandaj-Sirjan zone. These rocks with pillow structures are nominated in Tamark area as basalt to basaltic andesite and in Gashor area as basalt to basaltic trachy-andesite. According to classifications for magmatic series Tamark’s pillows are belong to subalkali series and Gashor’s pillows are belong to alkaline series. In classifications of tectono magmatic patterns, Tamark and Gashor’s basalts respectively are plotted in E-MORB and WPB. These rocks in both of pillows enriched LILE, LREE and some HFSE and the enriched mantel is the source of the primitive magma. They represent the Neo-Tethyan oceanic lithosphere originally existing between the Arabian and Eurasian continental margins.

Dahaneh Qaleh exploration prospect is located about 300 km southwest of Mashhad and 50 km northwest of Bardeskan. The exploration prospect is also a part of Taknar massive sulfide mineralization zone and lithology of the area consists of chlorite sericite schist, biotite sericite schist and sericite schist with metamorphosed basic and intermediate igneous rocks in the type range meta-gabbro diorite to meta-diorite that they belong to Taknar Formation.Taknar Formation was intrusived by low grade metamorphosed intermediate subvolcanic intrusive rocks with porphyry texture in the type range of meta-hornblende-quartz monzonite porphyry, meta-hornblende-quartz monzodiorite porphyry, meta-hornblende monzodiorite porphyry, meta-quartz monzonite porphyry and meta-hornblende-quartz monzosyenite porphyry. All of the geological unites are affected by moderate to severe alteration and sulfide minerals including pyrite, were transformed to secondary iron oxides due to oxidation. Before the field investigation, ETM and ASTER sensors data were processed with "color composition of band ratios", "standard and ive principal component analysis" methods and finally "spectral angle mapping" as a successful method for more accurate separation of altered minerals that introduced Hematitic, Chloritic, Epidotic, Sericitic and Silicification alteration zones in the study area. Accuracy of the processes were proved by the following field, petrography and mineralography studies.

Bafq-Baghin fault system has formed by 8 fault segments. On this fault system has not recorded any historical seismic data. Instrumentally earthquakes are located in low depth and their magnitude is small to medium. Morphometric parameters and the presence of fault scarp along the fault segments indicate their activeness. Recent earthquake epicenters of the region (2005-2009) have northeast-southwest trend are located at the intersection of southeast of the Bafq-Baghin fault system. Field investigations and satellite images of region show that the concentration trend of recent earthquake epicenters is located on the cross fault trend that introduced as Rafsanjan-Zarand fault. This fault is one of the X faults in the region that has formed by movement of shear zone.