GEOSCIENCES
Year:2007 | Volume:16 | Issue:63|Papers Count:23

Petrofabric, structural and geochemical study of the ultramafic tectonites in the Khoy ophiolitic complex suggest that these tectonites including low-temperature NW-SE shear zones cut the high-temperature to medium-temperature NE-SW mantle flow direction. Microstructures in these tectonites, record a fabric transition from oblate porphyroclastic and oblong porphyroclastic textures (related to the high- and medium-T deformations in mantle sections) to mylonitic textures (with low-T deformation in the shear zones). The study of olivine LPO patterns in high- and medium-T deformation samples of mantle shows slip on the (010) [100] high-temperature-low stress and (Okl) [100] moderate-temperature systems (up to 1000o)while olivine LPO patterns in the low-T deformation samples within the shear zones indicate gliding along (001) [100] low temperature slip system (800-900o). Spinels in these peridotites show high variations in Cr number (10 to 90) and Mg number (50 to 90). Cpxs rich in Cr suggest a low degree of partial melting in these peridotites. The very variable composition of the spinels may be the result of partial melting process and recrystallization of these minerals in the mantle lithosphere during the detachment phase and the development of the shear zones.

The purpose of this study is to determine the genesis of the manganese occurrences around the Hashtroud city, with special regard to Idahlu-Jokandy region. In this region Mn mineralization is sparse and rather extensive. Mineralization has originated from hot springs and precipitated on the earth surface. The mineralization is mainly massive and vein form. Due to the presence of hot springs and their traces in the study area, it can be concluded that Fe and Mn components were in the hot springs as solution and precipitated on the earth surface or penetrated into existing fractures and faults of the region by the hot springs and consequently caused the mineralization. The main Mn minerals are pyrolusite and psylomelane accompanied by gypsum, travertine, barite and jasper.

The Kazhdomi and Sarvak Formations (Bangestan Group) are mainly composed of carbonate rocks. In order to study facies, depositional environments and sequence stratigrphy of these formations in the northwest of Fars Province, 4 stratigraphic sections including Namak Kangan, Khartang, Khormonj (Coastal Fars) and Shah neshin (Sub-coastal Fars) have been studied. Carbonate rocks of the Kazhdomi and Sarvak Formations have been deposited in tidal flat (A), lagoon (B), barrier (C) and open marine (D) facies belts. The sandstone facies of the Kazhdomi Formation (Sandstone tongues equivalent to Burgan Sandstone) are quartzarenite, which were probably deposited in a beach environment. Facies analysis and comparison with Modern and ancient environments indicate that the Kazhdomi and Sarvak Formations were deposited in a ramp platform.Sequence stratigraphy of the Bangestan Group in the study area indicate that the Kazhdomi Formation (except for Namak Kangan,which consists of one depositional sequence) include two depositional sequences (sequences 1 and 2) of early to late Albian age. The Sarvak Formation consists of one depositional sequence in Namak Kangan (sequence 3) and four sequences I (sequences 3 to 6) of late Albian to Turonian age in other sections.The lower contact of sequence 1, t he lower contact of sequence 2 in Namak Kangan and the lower and upper contacts of sequence 6 are type 1 unconformity (SB 1) but the contact of other sequences are type 2 unconformity (SB2).

Tabriz fault, oriented NW to SE, on its NW continuation that includes Mishow northern fault, is a right- lateral strike-slip fault and one of the most seismically active zones in Azerbaijan of Iran. Studies on different parts of this fault indicate that there are numerous geomorphologic features due to tectonic activities along it. Sag ponds are one of the features that in spite of their importance from geologic, geomorphologic and tectonic point of view have not been studied in this area. Therefore, this paper attempts to study several sag ponds along Tabriz and northern Mishow faults including Bostan-Abad Ghouri-ghol, Payam, Aralan, and Mishow Ghouri-ghol dry sag ponds. An introduction to sag ponds as a geomorphic effect of the strike-slip faults to recognition of active faults is the main goal of the paper. All of these sag ponds are bounded by stike-slip and normal faults, subjects for previous investigations, field observations and geomorphic indices such as offset and deflected drainage and displaced terraces and alluvial fans. Obtained results from sag ponds and infilling of these basins by young Quaternary deposits indicate that Tabriz and northern Mishow faults are active faults, capable of generating relatively strong earthquakes in the future.

In this research, two stratigraphic sections were chosen from the late Paleocene to early Miocene (Jahrum and Asmari Formations).These sections includes Sadra and Dodaj plus 645 meters of late Paleocene to early Miocene scdiments. For this investigation360 thin sections were prepared and 12 samples analysed by XRF. We studied Biotope that includes biozone. These index biozones and percentage of elements that appears in biotope are identified. Principally index foraminifers, identified in the studied sections, are listed below: Miscellanea sp. Kathina sp., Fallotella alavensis Mangin, Opertorbitionlitessp. Alveolina sp. Lituonella ruberti Stache, Rhapydionina urensis Sirel, Orbitolites complanatus Lamark, somalina Stefaninii Silvestri, Dictyoconus sp. Coskinolina liburnica Atache., Nummulites fabianii Prever, Silvestriella tetraedra Gumbel., Nummulites fichteli Michelotti, Austrotrillina howchini Schlumberger, Meandropsina anahensis Henson. Regarding the frequency, type of wall and biotope percentage ratio of each foraminiferal biozone, there are different biotopes that indicate change in the trend of paleoecologic conditions of the late Paleocene to Oligocene sediments.

Bibi Maryam: granitoid body with 5 km2 exposure area is located in the east Iranian ophiolite melange belt in Sistan Suture zone. This intrusive body consists of tonalite- quartzdiorite and granodiorite. The main mafic minerals are hornblende and biotite in quartzdiorite-tonalite. Existence of microdioritic enclave in tonalite and its absence in granodiorites is one of the Main characteristics of the body. Perthitic and granophyric textures in granodiorites represent low water vapor pressure and Relatively fast crystallization, respectively.Geochemical study of rock samples shows that the body is calc-alkaline and metaluminous to peraluminous. Trace element Patterns in spider diagrams represent a trough for Nb and enrichment for K, Rb, Ba and Th that indicate contamination by Crustal materials. Although Bibi Maryam intrusive body cuts the ultramafic rocks, it lacks petrographic and geochemical Characteristics of oceanic plagiogranites. The geochemistry of the body is comparable with I-type granitoids and based on Tectonic setting it can be classified as orogenic and VAG type.

In this paper, iron removal studies on high iron diasporic bauxite by thermochemical treatment was investigated for the first time. For this purpose, bauxite samples were calcined in temperatures between 600 and 1100oC and then leached with hydrochloric acid. Obtained results revealed, in spite of gradual decrease in both iron and aluminum extaction with rising calcinations temperature, iron extraction to aluminum extraction is selective at calcination temperature above 900°C. Leaching studies of calcined sample at 900°C proved that leaching temperature is the most important parameter for iron dissolution in Acid and rising leaching temperatures from 20 to 95oCincreases iron extraction over 70%. The other optimum parameters are: leaching time l20 minutes, acid concentration 50% VIV, grinding size of 210 mm, pulp density of 15% solid by weight. As a Result of optimizing parameters, 96.5% of bauxite iron content removed successfully with 88.5% aluminum recovery and solid Residue iron content, i.e., the obtained concentrate, decreased from 27.02 to 1.59%.

Geirud formation deposits of Kalariz in the Eastern Alborz start with a relatively thick sequence of sandstone, shale, and red, white and brown colored siltstone changing into yellow dolomitic layers, fossiliferous limestone and shaly or marly limestone. This formation lies over Mila formation with a disconformity and covered transitionally by limestones of Mobarak formation. In the above mentioned sequence, numerous and various conodonts and brachiopods were identified. Based on the distribution of brachiopoda, two assemblage zones and based on the conodonts, four assemblage zones were recognized with Famennian and Strunian age. The first brachiopoda biozone, equivalent to the first and second conodont biozones, belongs to Early Famennian age (older than late crepida zone and romboidea to late trachytera zone) and the second Brachiopoda biozone which is equivalent to conodont biozone of number three and four has the late Famennian age (postera to late expansa zone and Praesulcata zone). Paleontological and stratigraphical evidence indicates that Frasnian sediments are absent in the study area.

Drilling is one of the most expensive stages of open pit mining and has more complexity. In drilling process many Parameters influence simultaneously, where studying each parameter requires recognition of the effects of the characteristics of the rock mass and its material. In this paper, the main aim was directed to investigate the joints dipping among the structural parameters of the rock mass. In the course of study, geometrical condition of penetration and transition of drill bit from joint surface were analyzed and different conditions of dips considered mathematically. This was followed by physical modeling of each of the geometrical conditions and penetration rate of cross bit measured by using rotary drilling system. Based on the numerical results obtained from experiments, mathematical equation between angles of joint dip with respect to drilling prolongation and penetration rates was presented. Furthermore, in conformity with the presented equation, by decreasing relative angle of joints dip, penetration rate of drill bit in jointed rock masses decreases linearly.

Bisotun inscription located on the mid-way of Hamedan- Kermanshah road (40 km to Kermanshah city), is carved on Limestone cliffs exposed in the area. Dissolution of the inscription caused serious damage to the most important heritage of the country. The area comprises massive gray limestones of the Lower Cretaceous as a part of high Zagros thrust belt. Accordingly, the limestones are extensively tectonized and two main joint sets are developed in the area. Joint study was Performed in an area of one km around the inscription. Thereby, it is revealed that these joint sets had impact on the dissolution of limestones. Limestone beds containing inscription are composed of mud stone to bioclastic algal wackestones. Original mineralogy of these algal bioclasts was aragonite. A few foraminifers and pellet also occur in some samples. Extensive jointing and unstable original mineralogy of limestone components lead to the dissolution of limestones in a meteoric condition. Evidences such as moldic, vuggy, canal, and cavern porosity suggest a meteoric diagenetic environment. Vugs up to centimeter Scale in the field observations are evidences of karstification in the area. Jointing and dip direction of the bedding plane cut Across the middle part of the inscription; conduct the corrosive rainfall precipitation toward the inscription surface. Consequently dissolution pit and holes were developed on it. Apparently the only practical way for remediation is to keep the inscription surface away from these corrosive waters. Considering the dip direction of the bedding plane, jointing on limestones and karstification in the area, it is recommended to drain the waters from bedding plane through a canal in a considerable distance from the inscription surface.

Various stratigraphical sections of the Permian rocks in the northwest of Iran (Azerbaijan) shows that this sequence consists Of Doroud, Ruteh, and Nesen formations in the southern flanks and Doroud, Surmaq, Julfa and Ali-Bashi formations in Zal And illanlu sections. The analysis and study of forminifera assemblages in the carbonate sequence of the area and the comparison of these Microfossils with other parts of Iran and neighboring countries indicate that the age of carbonate units is Kubergandian to Dorashamian in Zal and ilIanlu areas and Kubergandian to Djulfian in others sections. Throughout the Azerbaijan, Lower Permian shows a great hiatus.Field investigation, rock and microfacies studies show many progressive and regressive phases in the Permian sequence of Azerbaaijn.

The Lateshur Watershed is a part of Central Iranian drainage basin located northeast of the city of Pakdasht in northeastern Tehran Province. This watershed has an elongate form and its surface area is more than 22.2 square kilometer. It is a part of central Alborz zone and geologically is composed of Neogen red beds units, Hezardareh Formation and Quaternary alluviums.Geomorphologic studies show that this watershed is within an anticline and surrounded by Dahaneh Mountains in the south and Gara-aghaj Mountains in the north respectively. Structural and lithological variability have a very important role in the formation of this watershed; therefore, the watershed has the same trend as structures (NW-SE). Based on this study, the Lateshur River has a braided pattern with gravelly bed. Sedimentological studies along rivers in Lateshur basin show that three basic factor (sudden changes in slope gradient, floods events and distributaries) are the main reasons for changes in texture of bed load sediments within the channel as well as the break in sedimentary links. Lithofacies identified in this watershed include gravelly (Gmm, Gmg, Gcm, Gt), sandy (Sp, Sm, St, Sh) and muddy (Fl, Fr). Based on lithofacies, Boundary surface and current direction architecture elements identified in main river of Lateshur basins include: (1) Gravel bars and Bed forms [Element GB], (2) Lateral Accretion deposits [Element LA], (3) Sandy bed forms [Element SB] and (4) Fine grain classtic deposits [Element FF]. Also, based an lithofacies and architectural elements, Facies models have been purposed for the Lateshur river from upstream toward downstream as fallows: Shallow gravel braided river, Gravel wandering river, Gravel bed meandering river, Sandy meandering rive and Fining grain meandering river.

Strong motion records from the 2002 Barn Earthquake are used to investigate the shape of attenuation function in several Frequencies ranging between 0.8 to 18 Hz Amplitude spectra of the records are inverted to find source scaling factor and Attenuation parameters using Singular Value Decomposition method (SVD). After correcting the obtained attenuation Functions for geometrical spreading effect, the values of Qb follow the frequency dependent relation, Qb=95¦10 which Is in good agreement with similar results in other tectonically active regions in the world and could be served as a basic input Parameter for r future seismic hazard studies in the region of barn.

Maharlou lake located in southwest of Iran is an intra-continental sedimentary basin. Its area is about 280 km: extended with an average water depth of 1.5 m during wet seasons. The water level in the lake is controlled by several factors such as Runoff volume from Maharlou catchment underground water seepage, and direct rainfall over the lake and also evaporation. Generally, hydrochemical analysis of water resources showed that the water types are mainly bicarbonates and sulfates due to Geology of the surrounding areas. Hydrochemical investigation has been carried out for a time period between 1975 and 2002 usingpreviously published analyses together with new collected water samples. 230 samples were collected during summer 200I. Summer 2002 and spring 2005. Results show a change in the brine type through time: with an Mg-SO4-CI type in 1970 toan Mg-CI-SO4 type in 2001 and currently Na-Mg-CI brine type, in recent time, which is comparable with Great Salt Lake in USA. Due to changes in diluted water compositions from HCO3³ (Ca+Mg) to HCO3« (Ca+Mg), the path of brine on the Eugster and Hardie flow diagram changes from row III to the path It, indicating that the bicarbonate water comes into the lake From a fault occurring in the lake floor.

The Masjeddaghi area is a part of Alborz-Azarbaijan Zone and located in the Jolfa 1:100000 geological map sheet. The Oldest rock units cropped out widely in the south and northeast of the area belong to the Eocene flysch-type sediments. The Other outcrops consist mainly of volcanic rock complex of andesites and trachyanuesites affected by quartz monzonite Intrusion and caused alteration of phyllic and carbonate phyllic type. The mineralization in volcanic complex is also Accompanied by quartz and barite veins. The study of alterated zone around veins shows sericite, silicified, prophillitic, Chloritic and alunite (jarosite) alterations. Investigation of alteration zones around mineralized veins shows epithermal gold ore in which alunitic alteration (jarocite) is the most important characteristics. The result of the study on alteration and extension of altered zones in the whole study area give rise to the probability of porphyry type copper deposit (potassic. phyllic. argillic and prophylitic alteration zone).

Kal-e Kafi granitoid complex is a part of Central Iranian structural zone called Yazd block. This complex is composed of a Wide spectrum of plutonic rocks ranging from gabbro to alkalike granite with age range of Upper Eocene-Lower Oligocene. Potassic granitoid shows geochemical and mineralogical characteristics distinct from other plutonic rocks in the complex. The Potassic granitoids are peralkaline and ferroan while other plutonic rocks in the complex are alkaline to calc-alkaline and magnesian. With respect to REE abundances and patterns, the potassic rocks of the complex are different from other Kal-e Kafi granitoids. Low REE abundances of the potassic granitoids indicate that the rocks could not be related to other plutonic bodies through magmatic differentiation. This would probably demonstrate that different petrogenetic processes were involved in petrogenesis of the potassic granitoids. The potassic granitoids are likely to be the consequence of crustal partial melting.

Petrofacies analyses of Asmari Formation carried out on thin sections, obtained from oil wells of number 11, 85 and 89 in Ahvaz oil field, show 5 carbonate-evaporate microfacies associations (related to a carbonate ramp) and 2 siliciclastic petrofacies. Point counting data plotted on Qt93.34 F4.10 Lt2.59 Qm86.75 F4.10 L9.15 diagrams imply the cratonic and recycled orogen tectonic provenance. Furthermore, these results and the other petrographic evidences indicate a source rock with sedimentary and low to medium degree metamorphic composition for Ahvaz sandstone. Combining the obtained results with global sea level changes, variation in sediment supply and regional and local tectonic evolution, assisted us to recognize 6 evolutionary stages for Samara basin. In fact, Asmari Formation deposited in a carbonate-evaporate ramp with different amount of sediment influx through the time.

Mineralogy of clay deposits named Gel-E-Sarshour, mainly mined in Central Province, Tafresh area, has been studied. This material is mined from Oligocene Lower Red Formation in wells up to 30 m depth. Clay layers have different thicknesses from 1 cm to 2 m in different parts. It comes in olive green and has a soapy touch. The clay will change to paste if mixed with water and used mainly as shampoo as well as treatment for some of the skin diseases. Grain size analysis has shown that 92.3% of the material is <2m. XRD, lR and chemical analysis have established that the main constituents of <2m fractions of Gel-E Sarshour are: 91 % high layer charge, dioctahedral mixed-layered illite/smectite and 9% kaolinite.