M Amighpey; B Vosooghi; M Motagh
Abstract
An earthquake with the magnitude of 5.9 ML shocked the Qeshm island located in the Persian Gulf on 27 November, 2005 at 13:53:22 local time. The earthquake occurred due to the reactivation of a NE-SW fault with a major reverse mechanism accompanied by a minor strike-slip component. Another earthquake ...
Read More
An earthquake with the magnitude of 5.9 ML shocked the Qeshm island located in the Persian Gulf on 27 November, 2005 at 13:53:22 local time. The earthquake occurred due to the reactivation of a NE-SW fault with a major reverse mechanism accompanied by a minor strike-slip component. Another earthquake of 5.5 MW occurred on the same day at ca. 20:00 local time. The interesting feature of this earthquake is that the calculated mechanism for its strongest aftershock, which occurred ca. 6 hours after the main-shock, was a strike-slip mechanism that is completely different from the pure reverse mechanism for the main-shock. This study uses inversion of InSAR observation of earth surface displacement field boundary values to solve parameters of these 2 earthquakes. The results show activation of southern part of the Qeshm fault caused by the first earthquake along 7 km of its length. This event induced the second earthquake by activation of another strike-slip fault which is parallel to the Gavarzin anticline. Estimated slip was 96 cm for the first earthquake and 9 cm for the second one. Based on the estimated parameters of the these 2 earthquakes, the maximum displacement induced by the first earthquake was 6.7 cm in west, 4.6 cm in south and 16.4 cm in vertical directions on the earth surface. The maximum displacement of the second earthquake in west, south and vertical directions were 1.3, 1.6 and 1.4 cm respectively.
Sh Fatahi; A.A Calagari; A Abedini
Abstract
Neyestanak bentonite deposit is located in northwest of Naeen, Isfehan province. This deposit is an alteration product of Oligocene tuff breccias. Mineralogical considerations of this deposit show that montmorillonite, kaolinite, and quartz are the principal minerals which are accompanied by lesser amounts ...
Read More
Neyestanak bentonite deposit is located in northwest of Naeen, Isfehan province. This deposit is an alteration product of Oligocene tuff breccias. Mineralogical considerations of this deposit show that montmorillonite, kaolinite, and quartz are the principal minerals which are accompanied by lesser amounts of anorthite, calcite, chlorite, illite, albite, dolomite, microcline, orthoclase, sanidine, and halite. Mineral chemistry investigations testify to the similarity of this deposit with Wyoming-type bentonite deposits. Geochemical studies reveal that bentonitization of tuff breccias at Neyestanak is accompanied by depletion of Ba, Co, Zn, Y, Ni, Sr, Au, Ca, Fe, Mg, Mn, P, Ti, and Na, enrichment of Si, Th, As, Hf, Nb, and U, and leaching-fixation of K, Pb, Cs, Rb, Zr, and Cu. Geochemical analyses make clear that variation of Eu and Ce anomalies in this deposit were controlled by the degree of alteration of feldspars and oxidation potential of the environment, respectively. By considering the results obtained from this study, it seems that factors such as differences in degree of alteration intensity of parent materials, physico-chemical conditions of the environment, adsorption, incorporation in crystal structure, access to complexing ligands, and differences in degree of resistance of the primary minerals against alteration played prominent role in mobilization, distribution, and concentration of elements in this deposit.
M Najafi; A Yassaghi; A Bahroudi
Abstract
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels ...
Read More
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels on structural style in the Central Zagros folded belt. Seismic interpretation indicates that the Miocene Gachsaran Formation forms a major median detachment level decoupling fold geometry in surface structures from Pre-Miocene units below it. In addition, the Infra-Cambrian Hormoz salt or equivalents decouple the folded sedimentary cover from basement. To evaluate the significance of multiple detachment levels, a scaled analogue model was set. Two layers of silicon putty, with thicknesses equal to 15% of total cover thickness, were placed at the base and in the middle of sedimentary cover. The rest of the sedimentary cover was simulated using dry loose sand. The result of modeling supports seismic interpretation of the Central Zagros proposing that thick middle detachment layer totally decouples structural style at surface from depth. However, the open synclines with long wavelength and low angle thrusting are developed at surficial levels, and duplex thrust systems are formed between two detachment levels. Therefore, the role of ductile detachment levels should be obtained before exploring deep hydrocarbon targets in the Zagros fold belt.
M.S Mirkamali; H.R Ramazi; M.R Bakhtiari; H Ramesh
Abstract
This study has focused on identifying fault systems in the HormuzStrait area using compilation of seismic attributes and artificial neural networks. Faults and fractures play an important role in creating areas of high porosity and permeability. In addition, they cut off the cap and reservoir rocks along ...
Read More
This study has focused on identifying fault systems in the HormuzStrait area using compilation of seismic attributes and artificial neural networks. Faults and fractures play an important role in creating areas of high porosity and permeability. In addition, they cut off the cap and reservoir rocks along fluid migration pathways. Intense tectonic activities and salt tectonics have resulted in complex structures in the Strait of Hormuz area. Therefore, precise identification of faults and fracture zones and their extensions has special importance in increasing petroleum production from traps. In order to identify the geometry and kinematics of faults in the Mishan and Aghajari Formations and in the units under the base-Guri unconformity in the HormuzStrait area (eastern part of the Persian Gulf), we have used structural imaging and visualization techniques of seismic interpretation. The structural imaging of the fault zones was obtained by this technique based on the integration of input attributes in an artificial neural network system and creating new attributes. First, a set of advanced attributes were introduced as input for the artificial neural network system to train and compile the calculated attributes on fault and non-fault interpreted points. As a powerful exploration tool, finally, the fault cube was obtained to precisely identify fault systems and better detect faults and fractures in quantitative modeling of the area. As a result of integrated attributes, the high correlation between the faults within the fault cube provides more accurate and reliable tracking of fault extensions. Therefore, three types of fault systems were identified in study area, which are thought to be results of the extensional and compressional tectonics of the Oman Orogeny, vertical tectonic movements of the Zagros Orogeny, and syn-sedimentary salt movements.
H Mardomi; B Oskooi
Abstract
During this project we tried to show high capability of the SIS scheme for 1D magnetotelluric (MT) sounding data inversion. The scheme transforms the nonlinear problem of estimating layer resistivities and thicknesses into a linear problem of estimating the coefficients of power series of the new response ...
Read More
During this project we tried to show high capability of the SIS scheme for 1D magnetotelluric (MT) sounding data inversion. The scheme transforms the nonlinear problem of estimating layer resistivities and thicknesses into a linear problem of estimating the coefficients of power series of the new response function. We have used this scheme for prospecting conductive structures in southeastern shore of the Caspian Sea. This area is located in the GolestanProvince in northeastern part of Iran at the border with Turkmenistan. Detecting conductive sediments in this area, which are supposed to bear iodine is economically of interest. We provided data from three MT sites and inverted the data by the SIS scheme. According to our results there is a conductive layer in the depths deeper than 600 m at all three sites. We have compared our results with the previous results, also compared the results with the geological witnesses, which accordingly existence of a conductive layer has been proved at about 700 m depth. This conductive layer is proposed to bear iodine in economic meanings.
S Ansari; F Yaminifard; M Tatar
Abstract
In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering ...
Read More
In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering southward-dipping nodal plane as the fault plane, are consistent with relatively low-angle thrusts. It also implies dominant compressionsl regime in the north of the Central Alborz. Focal mechanisms in 1990 Rudbar-Tarom Earthquake region show a combination of strike-slip mechanisms and a complex fault system in the middle of the Western Alborz. A major region of dominant strike-slip mechanisms is observed in the Talesh area, located in the west of the SouthCaspianBasin, and around the Masuleh, Sangavar and Bozqush faults. The only calculated focal mechanism close to the southern margin of the Western Alborz, considering the western part of the North Tehran fault as the fault nodal plane, implies leftـlateral motion in this area. In the south of the western AlborzMountains approaching the Central Iran, two calculated mechanisms indicate dominant reverse movement, similar to the 2002 Changoreh-Avaj Earthquake. Five focal solutions close to the Kushk-e Nosrat and Soltanieh Faults, considering these faults as the fault nodal planes, are consistent with right-lateral motion along them. Depth of the earthquakes in the studied region is in the range of 2 and 20 km, indicating the brittle upper crust in the region.
M.R Asghari; M Moktari; M Arian; M.R Vanaki
Abstract
This study has been done on “Ferdowsi” oil field, which is located on Persian Gulf. The geological studies show that the north slope of the field is situated along the Arabian shield in which its structure has been affected by the salt mass. The Fahliyan formation is the main reservoir in ...
Read More
This study has been done on “Ferdowsi” oil field, which is located on Persian Gulf. The geological studies show that the north slope of the field is situated along the Arabian shield in which its structure has been affected by the salt mass. The Fahliyan formation is the main reservoir in the field. In order to interpret seismic data, firstly by using sonic and density logs, synthetic wavelet was constructed and compared to pseudo 3D seismic data using software. Then, formation tops were picked, and time and depth maps were prepared. Acoustic Impedance pseudo 3D volumes were performed by preparing seismic inversion. It is to note that seismic attributes help greatly to estimate reservoir properties of target formation and it is useful in better identifying the reservoir and drilling wells with reduced cost impact. In addition, in this study, faults and stratigraphic features (such as channel) were recognized by seismic attributes that is important for development of the field.
Petrology
Mahsa Jamshidnia; manijeh Asadpour; Masoumeh Ahangari
Abstract
Qushchi gneisses in the north of Urmia city are a part of magmatic-metamorphic complex in NW of Sanandaj-Sirjan zone. Gneiss, with eldsparses and schist, form Precambrian basement of the area. These rocks contain lipidogranoblastic, augen, porphyroblastic and myrmekite textures, and composed of quartz+ ...
Read More
Qushchi gneisses in the north of Urmia city are a part of magmatic-metamorphic complex in NW of Sanandaj-Sirjan zone. Gneiss, with eldsparses and schist, form Precambrian basement of the area. These rocks contain lipidogranoblastic, augen, porphyroblastic and myrmekite textures, and composed of quartz+ alkaline eldspars (orthoclase and microcline perthites) + plagioclase+ biotite± pyroxene, muscovite± amphibole± epidote +zircon+ opaque. Field, petrography and geochemical evidences were used to know the genesis of igneous (ortho) or sedimentary (para) of these gneisses. All the evidences imply an igneous origin (ortho) for the studied gneisses. In fact, the protolith of these gneisses are porphyritic granite to monzonite rocks and has calcareous-alkaline and peraluminous nature. It can be inferred that the protolith of these rocks which formed in the late Neoproterozoic, belong to the calc-alkaline magmas in active continental margins or volcanic arcs (VAG). Further tectonic events have transformed them into gneisses.
Tectonics
Azizollah Tajvar; mohammadmahdi Khatib; mohammadhosein Zarrinkoub
Abstract
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on ...
Read More
The north Makran ophiolite mélange, is located on the northern part of Makran accretionary wedge, southeast of Iran. In this study, we investigate geometry and kinematic properties of structural elements, and analyze the deformation style of the north Makran ophiolite mélange. Based on the results, at least, two stages of deformation were identified in north Makran ophiolite mélange. The first stage, which was accompanied by the development of extension structures, led to the formation of sheeted dykes in crust sequence of oceanic lithosphere. By restoration of these dykes to pre-deformation states, we assigned a SSW-NNE extensional regime that illustrates initial geometry of north Makran ophiolite mélange formed. The second stage, which was formed because of convergence in a compressional or transpressional regime, has been characterized by the development of various types of thrust and strike-slip faults, thrusting of rock units on top of each other and their duplication, and folding of sediment rocks. WNW-ESE thrust faults with 20 to 40 degrees dip toward NNE have the most important influence on current features of the north Makran ophiolite mélange, they reflect the conditions and process that the oceanic basin closed and oceanic lithosphere emplaced.
Stratigraphy and Palaeontology
elahe zarei
Abstract
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of ...
Read More
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of pollen are identified (Middle Jurassic) and presence of some index dinoflagellate species led to the identification of three biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early to middle Callovian). Also, this Formation was divided into two biozone on the basis of Lenticulina varians-Ophtalmidium Assemblage zone and Globigerina bathoniana Taxon range zone. The close similarities of fauna assemblages of Dalichai Formation in this region (eastern Alborz ((dinoflagellate cyst, foraminifera, posidonia and radiolar) with assemblages recorded from different parts of Iran (such as central and eastern, western Alborz and Binalud and south of Iran) and other parts of world (northwest of Europe, and the northwestern Tethys and …) confirm the marine connection and faunal exchange between the mentioned basins during Middle Jurassic.
Economic Geology
Shiva Farangi; Zahra Alaminia; Mohammad Vahedi; Hamzeh Sadeghisorkhani
Abstract
The studied area is located in N-Sonqor and in the Sanandaj-Sirjan zone. Field relationships and petrographic evidence show that volcanic rocks of the north of Bashirabad comprise of trachydacite to trachyandesite (and altered basaltic trachyandesite) and in the south of this area, it consists of andesite ...
Read More
The studied area is located in N-Sonqor and in the Sanandaj-Sirjan zone. Field relationships and petrographic evidence show that volcanic rocks of the north of Bashirabad comprise of trachydacite to trachyandesite (and altered basaltic trachyandesite) and in the south of this area, it consists of andesite to trachyte. Their texture is mainly porphyry. Geochemical data {total abundance of (Na2O+K2O), enrichment of large lithophile ion elements and rare light earth elements) indicate that these rocks belong to the alkaline series. Spider diagrams show enrichment in LREE and depletion HREE, and parallel patterns in all volcanic samples confirm their common origin. According to modeling magmatic processes, fractional crystallization, assimilation and crustal contamination have played an important role in the magma forming the studied rocks. The discriminating diagrams the tectonic setting the Bashirabad volcanic rocks indicate their subduction-related volcanic arc that was formed in an active continental margin environment with local tensions.
Mohammad R. Ghassemi
Stratigraphy and Palaeontology
Kamyar Younesi; Anoshiravan Lotfali Kani; Hormoz Ghalavand
Abstract
A conformable passage between Sarvak and Surgah Formations in Lurestan sedimentary basin reveals the potential of studying the Turonian–Coniacian boundary within Surgah Formation. Two sections of the Surgah Formation at Posht-e-Jangal and Pasan anticlines situated on the southeast of the Lurestan ...
Read More
A conformable passage between Sarvak and Surgah Formations in Lurestan sedimentary basin reveals the potential of studying the Turonian–Coniacian boundary within Surgah Formation. Two sections of the Surgah Formation at Posht-e-Jangal and Pasan anticlines situated on the southeast of the Lurestan sedimentary basin have been studied on the basis calcareous nannofossils, and based on the observed distribution of nannoflora, the presence of CC12 to CC16 nannofossil biozones is documented which points to the latest Turonian to Coniacian age for the base of this Formation, while the top boundary is estimated approximately at earliest Santonian. Due to the absence of Micula staurophora, however, separation of CC13 and CC14 biozones is not possible and therefore, the Turonian–Coniacian boundary is placed somewhere within the said undivided interval. The FO of Calculites obscurus as the marker event for the top of CC16 biozone is not identified but on the basis of suspected LO of Lithastrinus septenarius as the marker event of the top of UC11 and onset of UC12, the record of early Santonian beds seems probable.
Economic Geology
Leila Amini; Mohammad Maanijou
Abstract
One of the common processes that lead to the formation and enrichment of precious metal deposits is boiling. The existence of a spatial relation between fluid boiling and deposition of precious metals is a valuable tool in exploration of epithermal deposits. Therefore, the investigating of the process ...
Read More
One of the common processes that lead to the formation and enrichment of precious metal deposits is boiling. The existence of a spatial relation between fluid boiling and deposition of precious metals is a valuable tool in exploration of epithermal deposits. Therefore, the investigating of the process occurrence in epithermal deposits will be able to predict the continuation of exploration trend. Chah-Morad epithermal gold deposit is located in 75 km northwest of Bazman in the Sistan and Baluchistan Province and in the Makran-Chagai Magmatic Arc southeast of Iran. The mineralization in the Chah-Morad deposit occurred in 3 stages and in quartz veins that exist between the altered argillic alteration zone and dacite and rhyodacite sub-volcanic rocks. Textural mineralogical and fluid inclusions studies indicate the occurrence of the boiling process in this deposit. The most important kinds of evidence for the occurrence of this process are: a) the presence of adularia, b) platy calcite texture, c) breccia, crustiform-colloform textures, d) different liquid-vapor ratios of fluid inclusions, e) the increase in the salinity of fluid inclusions with the decrease in homogenization temperatures, f) the coexistence of fluid inclusions with different salinities and g) co-existing liquid single-phase fluid inclusions with vapor single-phase fluid inclusions. Therefore, the existance of boiling is confirmed in the Chah-Morad deposit.
Stratigraphy and Palaeontology
Hamta Ranjbar; Abbas Ghaderi; Hossein Gholamalian; Vachik Hairapetian
Abstract
Middle Devonian to Lower Carboniferous siliciclastic-carbonate successions in Eastern Alborz are characterized by Khoshyeilagh Formation. It is underlain by the Devonian red siliciclastic sequences and is overlain by the Carboniferous Mobarak Formation, can be divided into three different members; lower ...
Read More
Middle Devonian to Lower Carboniferous siliciclastic-carbonate successions in Eastern Alborz are characterized by Khoshyeilagh Formation. It is underlain by the Devonian red siliciclastic sequences and is overlain by the Carboniferous Mobarak Formation, can be divided into three different members; lower carbonate, middle siliciclastic, and upper carbonate. The Khoshyeilagh Formation comprises various fossil groups of invertebrates, conodonts, palynomorphs and fish remains. In the present study, a collection of microscopic fish remains, obtained from the lower and upper carbonate members in Mighan, north of Shahrood, have been determined and described. This assemblage contains 14 different taxa of chondrichthyan fish including: Cladodoides cf. wildungensis, Ctenacanthiformis gen. et sp. indet, Dalmehodus turnerae, Deihim mansureae, Lissodus lusavorichi, Phoebodus aff. turnerae, Phoebodus fastigatus, Phoebodus gothicus gothicus, Phoebodus gothicus transistans, Roongodus phijani, Siberiodus mirabilis, Squatinactis glabrum, Stethacanthus resistens and Thrinacodus ferox. Some specimens of scales and teeth of actinopterygian and osteichthyan fishes are also present which all indicate a shallow environment of the continental shelf. The associated conodonts with this assemblage demonstrate the age of Frasnian (rhenana biozone) to early Tournaisian (duplicata biozone) for the whole succession.
Economic Geology
Mohammad Boomeri; Somayeh Naruyi; Mohammadreza Ghodsi
Abstract
The Chah Sorbi area is located in the Sistan suture zone. The geology in the Chah Sorbi, from old to young, are flysch type rocks, Zahedan granitoid, subvolcanic granodiorite porphyry, dioritic to granodioritic dikes and recent deposits. The Pb mineralization in the study area occurs as thin and short ...
Read More
The Chah Sorbi area is located in the Sistan suture zone. The geology in the Chah Sorbi, from old to young, are flysch type rocks, Zahedan granitoid, subvolcanic granodiorite porphyry, dioritic to granodioritic dikes and recent deposits. The Pb mineralization in the study area occurs as thin and short galena-bearing veins associated with pyrite, quartz, calcite, goethite and limonite. The host rocks are flysch and the subvolcanics that are undergone phyllic and argillic alteration. Propylitic alteration occurs in most dikes in the area and is characterized by chlorite, calcite and epidote. In northeast part of the area, the subvolcanic rocks were intruded by quartz stockworks and was strongly altered. The most intensive and extensive alteration with these rocks is phyllic alteration that is characterized by pyrite, quartz and sericite. Cu mineralization in the stock is characterized by presence of Cu-carbonate and –sulfides. Galena-bearing veins are probably epithermal type in the Chah Sorbi area that is situated in margin of a porphyry Cu system. Major and minor elements were measured in 7 least altered samples from intrusive rocks. The igneous rocks in the study area are metaluminous that are formed from a calc-alkaline magma in a continental margin volcanic arc setting.
Sedimentology
Mahdi Ghaderi; Mohsen Moayyed; Nasir Amel; Monire Mojarrad
Abstract
The Saray volcano is located on the East of the Urmia Lake. This extinct stratovolcano mainly consists of Leucitite lavas and related pyroclasts. Dykes with composition of Leucite phonolite, Lamprophyre, Trachyte and microsyenite intruded into leucitite. Field evidences indicate that minette and trachytic ...
Read More
The Saray volcano is located on the East of the Urmia Lake. This extinct stratovolcano mainly consists of Leucitite lavas and related pyroclasts. Dykes with composition of Leucite phonolite, Lamprophyre, Trachyte and microsyenite intruded into leucitite. Field evidences indicate that minette and trachytic dykes intruded into each other. A microsyenitic stock and dykes outcrops in the central valley of this volcano. The trachytic pyroclasts eruption is the last activity of the Saray volcano and probably caused the destruction of volcanoe’s caldera and formed its current shape. Leucitites maimly consist of leucite and clinopyroxene phonocrysts, minettes consist of biotite and clinopyroxene phenocrysts and trachytes consist of biotite, sanidine and clinopyroxene phenocrysts. The Saray magmatism has potassic to ultrapotassic nature and its geochemical features indicate that this magma should be originated from a micaceous garnet clinopyroxenite mantle. The coexistance of leucitite, lamprophyre and trachyte, could not be explained only by the function of fractional crystallization in leucitite magma. Sanidine is the most abundant feldspar in the Saray volcano. Sanidine megacrysts crystalize in a medium size magma chamber with continuing temperature cycling, so that the magma temperature remains close to the liquidus temperature of the K-feldspar for a long time.
Stratigraphy and Palaeontology
Fatemeh Vaez-Javadi; Mohammad Ali Ghanbarian
Abstract
Jurassic deposits are well spread in the north of Karim Abad village, north of Bahabad, central Iran. These deposits contain 41 species of palynomorphs, in which 15 spore species (12 genera), 15 pollen species (10 genera), and 10 species of dinocysts (3 genera) were identified. Vertical distribution ...
Read More
Jurassic deposits are well spread in the north of Karim Abad village, north of Bahabad, central Iran. These deposits contain 41 species of palynomorphs, in which 15 spore species (12 genera), 15 pollen species (10 genera), and 10 species of dinocysts (3 genera) were identified. Vertical distribution of miospores allows erection within the Hojedk Formation of one biozone–Klukisporites variegatus- Chasmatosporites apertus Interval zone based on the FOO and LOO of selected taxa. Moreover, vertical distribution of dinoflagellate cysts allows erection within this formation of one biozone- Nannoceratopsis triceras-Nannoceratopsis gracilis Assemblage zone. The relative abundance of dinoflagellate cysts, spore, and pollen is 86.21%, 7.2%, and 6.6%, respectively. Therefore, the relative abundance of dinoflagellate cysts was high and the marine environment was prominent in this area during Jurassic sedimentation. Based on relative abundance of miospores' parent plant fossils, ferns, cycads, and conifers are 37%, 31.5% and 11.82%, respectively, and related sporomorph ecogroups (SEGs) indicate that they occurred in different environments such as upland, wetter / drier lowland, river and coastal with temperate-sub-tropical and humid climate.
Enayatallah Haghfarshi; Peyman Rezaee; Seyed Reza Moosavi Harami; Mohammad Faridi
Abstract
Lignite Beds of Tabriz are among of the Neogene formations in the northwestern area of the Iran, which is spread in the eastern suburb of Tabriz. Its sedimentary facies includes facies groups of fine grains clastics, sandstones, limestones and facies of lignite, tuff and microfacies and petrofacies under ...
Read More
Lignite Beds of Tabriz are among of the Neogene formations in the northwestern area of the Iran, which is spread in the eastern suburb of Tabriz. Its sedimentary facies includes facies groups of fine grains clastics, sandstones, limestones and facies of lignite, tuff and microfacies and petrofacies under them. In this study, two stratigraphic sections of these sediments in the eastern part of Tabriz were studied and 171 samples and 42 thin sections were collected and studied. XRD analysis for mineralogy and SEM electron microscopy for 3-dimensional studies were used to identify microfossils. Identified fossils include the genera and species of gastropods, Pelecypods, ostracods, fish, diatoms, charophyte algae, and foraminifera. The studied fossil assemblages includes species from freshwater to euryhaline and marine. The identified sedimentary environments include the lake basin environment, the shallow coastal environment and the marshy lake environment. In the studied sedimentary strata, strong fossil evidence and sedimentological evidence of the marine environment are not observed, at least during its lifetime. Therefore, it is concluded that the marine taxis in these deposits remain and are adapted from a former marine environment.
Sedimentology
Elmira Shahkaram; Mohammad Hosein Adabi; Davood Jahani; Seyed Hamid Vaziri
Abstract
The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, ...
Read More
The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, the boundary of the Dalichai formation with the Lar formation is unclear. It is also very difficult to identify the primary carbonates mineralogy, due to the effects of diagenetic processes solely on the basis of petrographic studies. We studied a section of Sharaf mountain with a thickness of 1420m and 149 samples was studied. The study of the major and minor elements, the Oxygen and Carbon isotopes, and plotting of these values against each other represents that the Dalichai formation have had original aragonite mineralogy, and the nonmarine diagenesis have had the highest impact on them. Plotting the Sr/Ca ratio versus Mn value, shows that these carbonates are affected in a semi-closed to open diagenetic system. Using Sr, Sr/Na, Sr/Ca, Oxygen and Carbon isotopes, the boundary of this formation with the Lar Formation is recognized in thickness of 1200m. The diagenetic environment temperature for this section limestones is 32.9ºC.
Petrology
Mohsen Zadsaleh; Fariborz Masoudi; Hamed Pourkhorsandi; Karen Fontijn
Abstract
Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions ...
Read More
Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions and under different magmatic conditions. To investigate the crystallization trends in the Damavand magma chamber and its evolution over time, plagioclase internal textures in lava flows, pyroclastic flow and ash deposits were studied. Samples from six different lava flows and pyroclastic fall and density current deposits with different ages were collected. Plagioclase crystals with similar dimensions and sizes but with completely different textures, and plagioclases with different dimensions but similar textural characteristics were observed. Twenty-eight different texture types were observed in plagioclase crystals from lava flows, whereas only three texture types were distinguished in the pyroclastic deposits. A large population of plagioclase in pyroclastic deposits reveal the non-equilibrium crstallization in the Damavand magma chamber(s), while in lava flows, a series of plagioclase cumulates present both equilibrium and non-equilibrium crystallization conditions in the magmat chamber. Plagioclase crystals in the source magmas of lava flows have repeatedly remained in a non-equilibrium state without eruption, letting the crystals to overgrow. Changes in the rate of magma ascent, small- and large-scale convection cells in magma chambers, varying temperature and/or pressure, and different volumes of (non-)eruptible mush/melt, are some of the parameters that are revealed by our textural studies. In the period between about 7-450 ky ago, the magma chamber that led to the buildup of the young Damavand volcano, was in non-equilibrium conditions as demonstrated by individual crystals textures and chemistry. However, these conditions have not always led to volcanic eruptions.
Stratigraphy and Palaeontology
Hajar Mashayekh; Massih Afghah; Mahnaz Parvaneh- Nejad Shirazi
Abstract
In order to biostratigraphic studies of Gurpi Formation, a section was selected in the north-east of Noorabad city in Fars. Structurally, this section is located in the folded-thrust zone of Zagros and geographically in the Fars zone (coastal Fars). The Gurpi Formation is extended of 229 meters in thickness, ...
Read More
In order to biostratigraphic studies of Gurpi Formation, a section was selected in the north-east of Noorabad city in Fars. Structurally, this section is located in the folded-thrust zone of Zagros and geographically in the Fars zone (coastal Fars). The Gurpi Formation is extended of 229 meters in thickness, contains limestone, shale, marly limestone and argillaceous limestone. Its lower boundary with Sarvak Formation and its upper contact with Pabdeh Formation are discontinuous. The study conducted on foraminiferal biostratigraphy in this section led to the identification of 20 species belonging to 7 genera of planktonic foraminifera. Based on the stratigraphic distribution of the planktonic foraminifera, five biozones are determined which correspond with global biozonation. Described biozones are comprised of: 1-Globotruncanita elevata Partial range zone; 2-Globotruncana ventricosa Interval zone; 3-Radotruncana calcarata Total range zone; 4-Gansserina gansseri Interval zone; 5-Contusotruncana contusa, Contusotruncana walfischensis, Globotruncanita conica Assemblage zone. Based on these biozones, the age of Gurpi Formation is assigned to early Campanian to late Maastrichtian. The absence of the Marginotruncana and Dicarinella asymetrica in the lower part of the Gurpi Formation indicates of the Santonian-Campanian boundary and the determination of the early Early Campanian age for the base of this Formation.
Economic Geology
jahangir esmaeili; ahmad khakzad; mansor vosoghi abedini
Abstract
This area has been located in a scene ETM No. 164-37 and ASTER linear band prediction satellite image No. AST-L1A:002:ASTL1A 0108220733380109011021. Such measured images in different band combinations will be used for extracting of geological structures and types of alterations (iron oxide, Argillite ...
Read More
This area has been located in a scene ETM No. 164-37 and ASTER linear band prediction satellite image No. AST-L1A:002:ASTL1A 0108220733380109011021. Such measured images in different band combinations will be used for extracting of geological structures and types of alterations (iron oxide, Argillite and Carbonate) and for detecting different stones and minerals of the ground, a spectrum range of 1.5 to 2.5 μ is very important.This range includes short to average IR range covering six linear band predictions (SWTR bands). On the other side, to use spectral reflectance curves of such minerals in USGSENVI spectral library for spectral analysis, it is necessary to resample the curves to the spectral range of ASTER. Linear Band Prediction methods, LS-Fit, Matched Filtering and BandRATIO used of ASTER images for all Minerals and iron alterations and for iron oxides there were also used visual interpretations and ETM images were used in band combination of RGB:531. Considering the petrological and geological situation of studied area (Scale 1:25000 of Kamoo), the type of Alteration and its index minerals detailed as below; Alteration of iron (Gotit, Hematit and Jarosit and Limotit), alteration of Argilic (Kaolinite, Motmorilonit, Ilite and Haloysite) and carbonate (Calcite and Dolomite) have been considered. Alterations present in remote sensing studies are in conformity with field and results obtained fromtypes of analysis conducted.
Stratigraphy and Palaeontology
Nasrollah Abbassi; Majid Mirzaie Ataabadi; Mohammad Hasanpour
Abstract
A stratigraphic section from the upper part of Ziveh Formation (Middle Miocene) has been surveyed in north Ojagh Kandi village, northeast Kalibar, Azarbaijan province. Ziveh Formation overlayed by Tortonian sediments as an angular unconformity in the studied section and its lower boundary covered by ...
Read More
A stratigraphic section from the upper part of Ziveh Formation (Middle Miocene) has been surveyed in north Ojagh Kandi village, northeast Kalibar, Azarbaijan province. Ziveh Formation overlayed by Tortonian sediments as an angular unconformity in the studied section and its lower boundary covered by recent alluvium. A diverse body fossil assemblage includes molluscan, plants, and vertebrate collected from this section. Among them, abundant ichnofossils of bivalves on woodground, Teredolites longissimus discovered in a horizon. Occurrence of wooden substrate in this horizon shows first events of rising of the sea level, and its basal background is considerable for the lower boundary for TST. On the other hand, Teredolites bearing horizon indicates beginig of transgressive event in the sequence stratigraphic interpretation of the studied section.
Stratigraphy and Palaeontology
Ali Asaadi; Ali Imandoust; Mehdi Sarfi; Mehdi Ghane Ezabadi
Abstract
The Lower Cretaceous Fahliyan Formation is one of the main oil reservoirs in the Persian Gulf. In this study, for investigating facies characteristics, depositional environment, diagenetic features, sequence stratigraphy and describing factors controlling reservoir quality, the integration of the results ...
Read More
The Lower Cretaceous Fahliyan Formation is one of the main oil reservoirs in the Persian Gulf. In this study, for investigating facies characteristics, depositional environment, diagenetic features, sequence stratigraphy and describing factors controlling reservoir quality, the integration of the results from core description, petrographic studies, and petrophysical data was utilized. Nine main facies were recognized and grouped in four facies belts of lagoon, shoal, patch reef and shallow open marine, indicating deposition of the formation in a carbonate ramp platform. Various diagenetic processes that influenced facies, occurred in marine, meteoric, and burial diagenetic realms. Four main pore types have been identified in the reservoir that include interparticle, moldic, vuggy, and microporosity. From the sequence stratigraphy point of view, three third-order sequences which are correlatable within the Fahliyan Formation were identified. The development of grainstone and algal rudstone/floatstone in shoal/ patch reef sub-environment played an important role in developing the high reservoir. In view of their controls on reservoir quality and pore system, diagenetic features can be categorized into two classes: (1) diagenetic processes enhancing reservoir quality that include dissolution and fracturing, and (2) diagenetic processes reducing reservoir quality that include cementation and compaction.
