JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2008 | Volume:18 | Issue:69 (GEOLOGY ISSUE)|Papers Count:16

Litostratigraphic studies of 15 stratigraphic sections of the Mishan Formation from Fars Group in cenetral part of Dezful embayment show that the thickness of sediments increases toward east and southeast of the examined area .The maximum thickness is 590 m at well no. 39 in Parsi oil field, and the minimum with 300 m is related to well no. 222 in Maroun oil field. The Mishan Formation in the studied area, conformably overlies Gachsaran Formation and Underlies Aghajari Formation.

Eqhlid Shear Zone (ESZ) located on 230 Km north of Shiraz City and 45 Km southeast Eqhlid City. This area is part of the Sanandaj-Sirjan paired metamorphic zone, which have been affected by brittle-ductile and ductile deformation. Metamorphic rocks of this area are mainly composed slates, phyllite, metasandstone, crystalline limestone, metadolomite, metavolcanics, and mylonite.In Eqhlid area, several thrust and duplexes are present with NW-striking and NEdipping. The main thrust in area is ESZ. The shear zone and associated thrust and folds are portion of the Main Zagros Thrust orogenic belt and they are parallel with this belt. Observation en-echelon, folded boudinage and asymmetrical folds in mesoscopic scale indicate dextral shear sense of the ESZ.Microscopic studies of the S-type and C-type shear band cleavages and mantled prophyroclasts confirm dextral shear sense. These microstructure formed in greenschist facies conditions.The current studies of kinematics and geometry of thrust and strike-slip faults and shear zone plus micro-structures such as S-C fabrics and asymmetrical folds display dextral oblique transpression of the Afro-Arabian convergence.

The Kopet Dagh sedimentary basin is situated in the north-east of Iran and the south of Turkmenistan. In order to inspect the Abtalkh Formation in Koppeh-Dagh basin, it’s type section has studied by consideration stratigraphy properties. Most lithology of Abtalkh Formation in study area consists of gray marls. Ordinates Abtalkh Formation base is at type section 600 33’10” length eastern and 36010’56” width north In this study 26 planktonic species of 11 genus have identified and presented. On the basis of identified planktonic foraminifera, age of Abtalkh Formation has determined from Early Campanian to Late Maastrichtian.

The Copper-Gold deposit of Masjid Daghi area is located in the East Azarbaijan Province in north-west Iran (Jolfa mapsheet 1:100000) The outcropping rocks are andesite, trachyandesite and quartz mostly resulting from Tertiary volcanic and volcano- sedimentary activities which have affected the region and intersected by Late Eocene intrusives. Mineralography, XRD and SEM studies have shown the variations in mineralization of the area. The main agent of mineralization in the area under study is intrusion of a quartz- monzonitic pluton in felsic volcanic rocks and Tertiary sedimentary units.Mineral graphic studies have shown that the mineralization in the area is copper sulfide type in the form of veins, veinlets and stock work. The economic minerals present are: native gold occurring in siliceous veins and within the sulfides (chalcopyrite); and copper sulfides including chalcopyrite and chalco-pyrrhoyite. Pyrite is the principal sulfide present in the area occurring in the form of disseminations, cavity filling and colloform textures. The amount of pyrite, chalcopyrite and chalco-pyrrhoyite increases with depth. Supergene alteration has produced secondary minerals like digenite, covellite, bornite, and malachite. Alteration types present in the area are potassic, phyllic, argillic and propylitic. Furthermore, selective sercitic, sericitic-chloritic and alunitic alterations are seen around the mineralized veins.The results from studies indicate the presence of some types of alterations suchas potassic, phillic, argillic and propylitic in regional scale and silicious alteration near mineralized veins. In the margins of the veins, there are sericitic, chloritic and alunitic alterations. The alteration development and the achieved results indicate the probable existence Presence of porphyry copper ore and alteration in the vicinity of mineralized veins imply epithermal gold ore.

The complex of plutonic igneous rocks of the Ghorveh outcropped in the south of the Ghorveh city. This complex is part of the plutonic igneous belt of Mesozoic–Tertiary in the north of the Sanandaj-Sirjan zone. Igneous plutonic rocks in the south of Ghorveh can be divided into Gabbros, Diorites, Granites and Syenites. Felsic and Mafic plutonic rocks in the four districts of Shanevareh, Kangareh, Khers sareh and Ghalay Lan that the located in the Ghorveh region indicate evidence of magma mingling. Evidence of magma mingling in the four districts include mafic micro granular enclaves with rounded, discoidal, elongated, lenticular and tabular shapes and also syn-plutonic (co-mingling) or composite dykes. Shape and size of these enclaves display coeval flow and partial mingling between felsic magma (granite) and mafic magma (gabbros-diorite). Some of micro granular enclaves with pillowlike structure have crenulated like margins. Morphological features are results of influence of mafic magma in state of small to large globules into felsic magma. Another enclave in granite body can be observed such as surmicaceous, xenoliths, cumulate and double (polygenic). Morphological features of mingling heterogeneous structures such as MMEs with different shapes and sizes into the plutonic bodies that have granitic composition are result of magma mingling processes. Can be mention to heterogeneous distribution of enclaves in interaction zones to low mobility between two end-members.

The area under investigation is Consist of the Zagros Mountain belt and its southern coastal margin. The dominant focal mechanisms in this zone are reverse and thrusting too. In this research, investigation area has divided to 14 provinces by difference in geological characteristics and then, their seismicity parameters have estimated.Therefore, the provinces that have highest seismic activity rate and seismic potential are introduced. In addition, the six main siesmogenic trend with N-S trending are distinguished that one of them (Qatar-Kazerun fault system) has accompanied by surface ruptures.

The Nayband Formation in Central Iran, has a very a very good extension with different sedimentary environments. By Systematic study of the Nayband Formation in the type section at North of Nayband village and 11 other sections in Central IRAN (ALI ABAD, PARVADEH, KOH-E-TIZI, BOLBOLO-E-IEH, MARAVAND, BAGHAR ABAD-EMAHALLAT, SALLAKH, CHASHMEH SOUR, MOUR-CHEH-KHORT & CHAL SEFIDE KASHAN )10 sedimentary environments has been proposed.The lower contacts of the Nayband Formation is usually on the Shotori Formation, with a disconformities in between and The upper contact gradually changes to Shemshak Formation, and in some areas the differentiation between the Two Formations is very difficult, So they are collectively called Shemshak group.The Cimmerian orogenesis activities and uplifting of different basin parts, has made the sedimentary environments of the Nayband Formation very versatile, which consist of: Gelkan member is mainly in on stormy environment ( Sedimentary environment 2), Hoze-e-Shiekh member is mainly in a lowenergy environment (S.E.1), Bidestan member is mainly composed of abundant deltoid channels (S.E.4), Hoze-e-Khan member is mainly composed of reefal sedimentations (S.E.8) and Ghadir member is formed in laons.

Eocene felsic to basic shoshonitic lavas are located in the Uromia-Dokhtoar structural zone. These association rocks are Absarokite, shoshonite, banakite and toscanite. Petrology and geochemistery evidence indicate that the lavas were formed by fractionation of alkali basalt magma combined with assimilation of continental crust. Eruption of alkali basalt correlates with a Postcollisional arc.

Fluorite ore deposits of Savadkoh region distributed as a chain belt which has 30 km wide and 100km length. this belt extended from Deraseleh in the west to Era in the eastern part of the study area. Except of Emaft, the host rock of the rest deposits are situated in Elika formation, but Emaft lies in Tizkoh formation. Three galena and four barite samples were selected to isotopic analysis in Tasmania University of Australia. The results show that all heavy sulfur in barite are generated from Rayleigh isotopic fractionation system in middle Triassic sediment environment and effected from Palan evaporated formation. Since the d34S value of barite is 48/4 per 1000 different from galena,so bacteria are considered as the main factor to generate H2S (sulfur of galena) which is a bacterial reduction of sulfate. However, other mechanisms may caused to generate sulfur to form of galena such as termochemical organic reduction of sulfate, sulfate reduction by ferrous iron and decomposition of organic matter at elevated temperature. The d34S value of barite in ore deposits in the Savadkoh region is nearly similar to the fluorite ore in southern Appalachian area, especially Sweet Water and New Prospect. The d34S value of galena in the study area is the same as galena in Illinois-Kentucky and Southpennine.

Around Soleymanieh village in the NE of Sabzevar, there are a numerous gabbros and microgabbros dykes that have interruped Sabzevar's ophiolites. Most of these dykes turn from black to green, white, yellow and reddish. The surrounding ophiolites have highly altered to serpentine, too.The petrographic studies of discoloured dykes show that, olivine, clino- pyroxenes, orthopyroxenes and calcic plagioclases, (high energy level minerals) have been converted to: wolastonite, prehnite, chlorite, epidote, hydrogrossular, pectolite, and xenotlite (low energy level minerals).Furthermore: XRD, thermic analysis and micropropic studies confirme the mineralization studies and rodingite reactions recognized by polarized microscope. Assemblages minerals and textures show that this complex is a rodingite association. Generally, rodingite mechanism start with serpentinization of olivine and pyroxenes in harzburgites and lherzolites and release of Ca+2 from their structures. These Ca+2 cations can not be accommodated in serpentine crystal structure, therefore, they are concentrated in the fluid associated with serpentinization. Oversaturated fluids of calcium, and with low amount of CO2, under suitable condition, (presence of reactional rocks like gabbros) react with above meantioened rocks and form calcium rich minerals. These fluids will react with basic roch minerals especialy Plagioclasis and creat a host of roddingites minerals (Xenotlite, grossular, Pectolite and others). In Some cases, somme minerals, such as pectolite and xenotlite are replaced in the form of veins within rodingites.

Asmari anticline (with 30 km length and 10 km width) is a NW-SE anticline in the Dezful Embayment sub-basin of Zagros. Fars Group is cropping out in the cores of more anticlines in the area under investigation. But, abnormally cropping out of the Pabdeh and Asmari formations in the core of Asmari anticline, caused that anticline had been Analyzed. Because, there is a unique outcrop of Asmari formation in the Dezful Embayment. We have investigated the elements of fold style and folding mechanism (Fault Bend Fold, Mode I) in the Asmari anticline. Therefore, uplifting and cropping out of Pabdeh formation are due to ramping a blind thrust in the core of Asmari anticline.

North east–south west trending Darioun plain is a train that is located in the simply folded Zagros belt. The trends of its geological structures are parallel to general trend of Zagros.The sedimentary succession is composed of several rock units. The oldest belonging to Precambrian (Hormoz Formation) and the youngest one belonging to Pleistocene (Bakhtiary Formation). Uncemented alluvial deposits cover older rock units.The faults of study area mostly have many surface traces and they have been covered by alluvial or fluvial deposits.One of the most important geological structures is Qale Ghachi or Izadkhast saltdome which outcropps in the east of study area. It has been affected by basement faults, in south east of Zagros. It occurrs in the same direction as that Sarvestan salt dome.This salt dome has caused to propagate salinity in groundwater westwardly. So it has destructive effect on fresh groundwater source.The Bamo fault which has caused Dariun plain has coused to propaget salinity in groundwater of northern part of the plain.

Different outcrops of granitic rocks in the Gosheh- Nelkhast area, NE of Borujerd, have been studied in order to investigate the magmatic evolution and related events. Three granitoid bodies were intruded into sedimentary and metamorphic rocks of Precamberian, Triassic and Jurassic ages in Senandaj-Sirjan metamorphic belt of Iran. Optical observations and XRF analyses show that the majority of the plutonic rocks are granites and granodiorites. Considering the geochemical diagrams and textural evidences such as micro perthite, granophyre and micrographic textures, maximum temperature at which granitoids were formed is estimated in the range of 700 to 850oC and maximum H2O pressure is estimated about 5 Kbar. The Granitoides are calc-alkaline and metaluminous types. All plutons have both I-type and S-type characteristics, although some evidences, such as low normative corundum, indicate an I-type characteristic for the Gosheh granites. From the tectonic setting point of view, the granitoid bodies are of the collisional type and they formed as syn-tectonic to post-tectonic intrusions.