مجله علوم دانشگاه تهران
سال سی و پنجم شماره 4 (زمستان 1388)

Kopet-Dagh sedimentary basin is located in the east northern of Iran and contains sediments of Jurassic to recent ages. One of the lithostratigraphic units in this basin is the Abderaz Formation. The formation is made up of calcareous shales, marly shales, chalky limestone. In order to syudy Palynology and Paleoenvironment of Abderaz formation in Hamam Ghaleh section samples. Some of the samples proved to be rich in dinoflagellates and some 85 species belonging to 52 genera were recorded. Age of Abderaz formation in Hamam Ghaleh section basis of Dinoflagellates is Late Turonian –Coniacian-Middle Santonian. Analysis palynofacies and index Dinoflagellates show that the formation was deposited in a shallow – open marine environment with variable energy conditions

The Jahrum Formation, at Kuh-e Gach, (Lar area) have been investigated in order to determine its biostratigraphy and palaeoecology. The Jahrum Formation with the total thickness of 404 m is conformably overlies the Sachun Formation and is overlain by Limestone of the Asmari Formation. Larger foraminifera are the main means for the biostratigraphic zonation of carbonate sediments. Based on study of foraminifera, four assemblages zone were identified. The distribution of the larger benthic foraminifera indicates that shallow marine carbonate sediments of the Jhrum Formation at the study area have been deposited during the Late Paleocene-Eocene. The restricted and hypersaline lagoon facies is characterized by various taxa of imperforate foraminifera. The shallow open marine with normal salinity is dominated by thin and flat Operculina. The most common skeletal components in limestones of the Jahrum Formation are large benthicforaminifera,whereas bryozoan,corallinacean algae, echinoid and gastropod components are less common.

The Paleozoic volcanic rocks in the Abyane - Soh area are predominantly basaltic in composition and occur as pillow lava, massive and occasionally as amygdaloid texture. Several sedimentary layers including sandstones and carbonate rocks exposed intermittently with theses greenish-black basalts characterized by calcic-plagioclase, olivine and clinopyroxene (augite). Geochemically, they are tholeiitic-alkaline in nature and are classified as transitional series. Furthermore, the high TiO2 content as well as the great thickness of volcanics and sedimentary interlayers suggest that these basaltic rocks likely generated in an extentional settinig related to the orogeny movements in central Iran during the Paleozoic period. The low amount of HREE in the basaltic rocks is compatible with the presence of lerzolitic garnet in the source area. On the basis of some spider and geochemical correlation diagrams.It is suggested that the studied volcanic rocks originated from a similar source.

Nowadays with significant increase in population and urban areas, development of infrastructures and roads as a basic issue for sustainable development is accelerating intensively. In fact, construction of retaining walls as an inseparable part of roads and bridges is increasing significantly. Comprehensive understanding of active and passive earth pressure plays major role in safe and economic designing of retaining walls. It has been tried to make a numerical model a cantilever retaining wall using PLAXIS software, which is more complicated and precise than classical methods. The results showed that distribution and magnitude of earth pressure as well as the point of application of resultant force differs with that of classical methods. This deviation is attributed to the flexibility of the retaining wall system and combinational mode of wall’s movement. Moreover, effect of cohesion on earth pressure in both active and passive conditions were examined and compared.

Rocks are natural materials which are used in a variety of engineering constructions, especially in buildings. Freeze-thaw is one of the most important environmental agents which causes change in the engineering properties, strength and durability span of rocks. In this study 14 samples of building stones with different origins were selected, then freeze-thaw test up to 30 cycles were performed and values the engineering properties of these rocks including Brazilian tensile strength, point load strength index and P-wave velocity, after every 5 cycles were determined. Results show that with increasing freeze-thaw cycles, the values of these properties have been decreased. Also, samples which had the effective porosity more than 1%, their Brazilin tensile strength, point load strength index and P-wave velocity have been more decreased.

In this investigation Dariyan Formation with the age of Lower Cretaceous (Aptian- Albian) were studied for microfacies analysis and diagenesis trend in the surface section at Kuh-e Siyah Anticline and subsurface section Sabzpushan well number 1. Based on petrographical studies 12 microfacies identified which are belonging to 5 facies belt, such as: intertidal, lagoon, shoal, shallow open marine and deep open marine. The observed facies patterns indicated a homoclinal carbonate ramp depositional environment. Important diagenetic processes were observed in Dariyan Formation including cementation, bioturbation, dissolution, physical and chemical compaction and replacement processes such as dolomitization and silicification. With the observations of transmitted and cathodoluminescence microscopes different generations of spary calcite cement were recognized that suggest diagenetic alteration of Dariyan Formation occured in a burial setting. Prosities in these sections are secondary, including vugy, fracture and channel types.

Volcanic ashes are pyroclastic materials that may convert to secoundary mineral associations through hydrothermal alteration. The most important factors for changes are chemistry and temperature of hydrothermal fluids which can normally form low temperature minerals such as zeolites. In the present study, phillipsite, hydroxy-sodalite and analcime are synthesized hydrothermally from volcanic ashes at alkaline conditions in the laboratory. In these experiments NaOH, KOH, NaCl and KCl solutions in 1.25-7.5 mol/lit concentrations were used as source of Na+, K+ and OH- ions and all of them performed at 150?C for 96h at hydrothermal conditions. The results show that philipsite forms by phase transition of volcanic ashes in presence of alkaline solutions from low to high concentrations of KOH solutions with or without extra salts such as NaCl whereas analcime is only synthesized in presence of NaOH solutions alone..

The ammonite biostratigraphy of the Upper Barremian- Lower Albian sequences (Sarcheshmeh and Sanganeh formations) in the Koppeh Dagh basin are studied. Based on assemblage faunas 12 biozones are suggested for the Upper Barremian to Lower Albian sequences. The Heteroceras spp. and Martelites securiformis zones are suggested for the Upper Barremian Sub-Stage. The Deshayesites oglanlensis, Deshayesites weissi, Deshayesites deshayesi and Dufrenoyia sp. zones are proposed for the Lower Aptian Sub-Stage. The Parahoplites spp. and Epicheloniceras subnodosocostatum zones are suggested for the Middle Aptian and the Acanthohoplites spp. and Hypacanthoplites uhligi zones for the Upper Aptian Sub-Stage. The Lower Albian biozones are Leymeriella tardefurcata and Douvilleiceras sp.

Dariyan formation of Aptian age is major the oil reservoirs in the South Pars field. Occurrence of the world’s great unconformity at the end of Aptian, has caused the formation is strongly influenced by the meteoric diagenesis processes and development of dissolution pores. The goal of reservoir characterization is to study Reservoirs properties such as porosity, permeability and water saturation. The porosity-permeability relationships in the framework of hydraulic flow units can be used to characterize heterogeneous reservoir rocks. A flow unit is defined as correlatable and mapple zones latterally and vertically within a reservoir which control fluid flow and is significantly different from those of other rocks. Each flow unit is characterized by a flow zone indicator (FZI).

Prediction of the Geologic Moment Rate is introduced as a new and cable tool to assess the tectonic activity and seismic potential of a given region. Here, we study the Central Albourz range as seismically active area. We estimate the geologic moment rate of the study area using geometric parameters of main faults exposed as the amount of fault length, fault dip, fault slip rate and seismogenic thickness. Despite of some data lack of faults, the geologic moment rate is estimate 1.2×1018 Nm/yr. This study suggest that despite large number of faults exits within the range, a significant amount of fault slip occurred along few large faults, Khazar, North Albourz, Mosha, Taleghan, North Tehran, Pishva and Varamin faults. Seismic potential is different between northern and southern parts of the Central Albouz. Apparently, the earlier reflects higher seismic potential

In this study thermal maturity of Pabdeh, Gurpi and Kazhdumi Formations in well numbers 112, 2, 33, 99 and 18 of Rag-e-Safid oilfield situated in Dezful Embayment were modeled using Rock-Eval and Vitrinite Reflectance data. Optimization of the model by %Ro and Tmax reveals that there is high geothermal gradient in well number 112 was due to Izeh-Hendijan fault, and also in well number 99, due to the presence of paleo-high (31°C/km and 26°C/km equivalent to 83 and 70 mW/m2 heat flow respectively). Other studied wells had a normal geothermal gradient (with mean of 23°C/km, equivalent to heat flow 63 mW/m2(. TOC data obtained from Rock-Eval analysis, demonstrates a high genetic potential for both Pabdeh and Gurpi Formations, while thermal modeling using Easy%Ro proves that; this rich formations have not entered oil window with respect to their thermal maturity.

Hydrocarbon resources form from several phyisco-chemical processes during geological time scale that end up to hydrocarbon generation, migration and accumulation. Basin modeling is a tool for simulation of these processes and it embraces complex calculations that are encoded in the modeling software. Advantages and results of such studies has caused frequent use of this method in oil industries and basin modeling software has improved accordingly. In this research a 2D model for one of the Zogros anticlines has been constructed using a 2D basin modeling software and available geological data. In the constructed model hydrodynamic processes, heat conductivity, hydrocarbon generation, migration and accumulation is simulated. Fluid saturation rate, temperature condition, hydrocarbon migration pathway is modeled in the studied cross section

The sediments of the Qom Formation in the north of Navab anticline located in southeast Kashan is composed of limestone, sandy limestone, argillaceous limestone, sandstone, conglomerate, marl and gypsiferous marl with 211 m thickness. The mentioned formation disconformably overlies the Lower Red Formation and underlies the Upper Red Formation. The collection and study of 101 hard and soft samples from the Qom Formation led to recognition of 53 genera and 99 species of benthonic foraminifera and 4 genera and 6 species of planktonic foraminifera, which 33 genera and 77 species are reported for at the first time. On the basis of stratigraphic range of faunal assemblage, the age of the Qom Formation in the studied section is Aquitanian to Burdigalian. Whereas based on previous studies, it is assumbed that at least part of the sediments must belong to Oligocene. On the other hand, Zhu et al. (2007).

Nord Anomaly deposit is an iron ore deposit in Bafq district. It contains 250 Mt iron ore with average grade of Fe=28 %. The host rocks of the mineralization in Nord Anomaly deposit are granitic and microgranitic rocks with probably Early Paleozoic age. Petrographic investigations reveal that sodic and calcic alterations are related to iron mineralization. Other alterations such as silisic, chloritic, epidotic and sericitic alterations are insignificant and post date the iron mineralization. Sodic and calcic alterations are characterized by formation of chessboard albite and actinolite –termolite respectively. Widespread sodic and calcic alterations are contemporaneous with the feldspar-magnetite and magnetite-amphibole ore respectively. Magnetite–amphibole ore is high grade and low tonage while magnetite–feldspar ore is low grade and high tonage. Geochemical studies show that alkaline cations (Na, K) concentration were increased and immobile elements (Fe, V, Ni) decreased during sodic alteration.

The Euch-Palang area located in the NE of the Kashmar city, is part of Central Iran structural Zone. Eocen volcanic and pyroclastics rocks with intermediate composition (andesite to latite) associated with are exposed in the area. Based on field, petrography and geochemistry, propylitic, quartz- phyllic (sericitic) and argillic- silicic alteration zones could be identified in this area. These zones show notable differences in REE behavior. The propylitic alteration zone contains mineral assemblage of chlorite, epidote, carbonate, sericite, apatite, iron oxides, titanite, zeolite, clay minerals and pyrite. It can be divided into two sub-zones of carbonate–chlorite and carbonate–epidote. In the carbonate–chlorite sub-zone, REE are commonly depleted, with the LREE relatively more depleted than the HREE.

One of the most important parameters in hydrocarbon reservoir evaluation is irreducible water saturation; commonly determined from capillary pressure or relative permeability experiments. Real reservoir rock samples are needed for doing these experiments. Usually such samples are hardly available and their preparation is expensive. In this study, estimation of irreducible water saturation has been done by combining capillary pressure data and hydraulic flow units. In this article the number of hydraulic flow units has been determined based on measured porosity and permeability on the samples of a carbonate reservoir.First by calculating reservoir quality index and pore to matrix ratio, flow zone indicator determined for each sample and then by histogram and sum square errors analyses the number of hydraulic flow units was clarified.

Golujeh Cu-Au deposit is located in 45 km north of Zanjan city. Structurally it is part of Tarom-Hashtjin polymetal province in Alborz-Azarbaijan Zone of Iran. Based on 1:100000 quadrangle map of Hashtjin, the oldest exposure belong to Carboniferous limestone followed by Jurassic siltstone and shale, Cretaceous recrystalized low metamorphosed (Laramid orogenic phase) limestone. The igneous rocks are mainly volcanic and subvolcanic rocks of Eocene-Oligocene age, composed of tuff, ignimbrite, rhyolite, trachy-andesite, porphyritic andesite and rhyodacite. Major alteration assemblage is propylitic, argillic, sericitic and silicic alteration formed next to mineralized veins. The mineralization occurred along four major veins with average 2.5ppm Au, 0.6-1.5% Cu, 10ppm Ag, 2-3% lead and 1-2% Zn in hypogene and supergene suites. Hypogene minerals include magnetite, specular hematite, chalcopyrite, bornite, galena and sphalerite in association with cerusite, chalcocite, malachite-azurite, dijenite covelite and hemimorphite as supergene minerals.

The Kopet-Dagh Basin is located in northeastern Iran and southern Turkmenistan. The Aitamir Formation (Albian-Cenomanian) is deposited in this basin. Based on four measured stratigraphic sections, depositional environments and relative sea level changes of the Aitamir Formation have been interpreted. Petrographic studies and field observations led to identification of carbonates and siliciclastic (mudstone and sandstone) lithofacies. Carbonate rocks are deposited in semi-restricted lagoon, lower shoreface and open marine sub-environments, while the siliciclastics are deposited in lagoon, bars, shoreface and open marine condition. Sequence stratigraphic analysis led to identification of two (Sheikh Section) and three depositional sequences (Sorkhozoo section) in the west and three (Gadganloo section) and four (Passkooh section) depositional sequences in the east parts of the study area. Comparison of interpreted sea-level curve of Albian-Cenomanian time in the Kopet-Dagh Basin with the global sea-level curve show some similarities and differences.