Mojgan Salehi Yazdi; Mansour Ghorbani; Nima Nezafati; Mansour Vossoughi Abedini
Abstract
Takab-Mahneshan's metallogenic area is essential in gold mineralization, and it is a part of the northern Urmia-Dokhtar magmatic belt. The northern Urmia-Dokhtar has two distinctive features. It contains the Precambrian basement, and the young Mio-Pliocene magmatism rocks overlie its Precambrian basement. ...
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Takab-Mahneshan's metallogenic area is essential in gold mineralization, and it is a part of the northern Urmia-Dokhtar magmatic belt. The northern Urmia-Dokhtar has two distinctive features. It contains the Precambrian basement, and the young Mio-Pliocene magmatism rocks overlie its Precambrian basement. Precambrian basement has two different compositions, oceanic and continental crusts (gneiss, granite, mica-schist, greenschist, amphibolite, serpentinite, marble). The Young rocks are composed of hyaloclastite, acidic tuff, andesitic-basaltic, acidic to intermediate intrusions (diorite, granite), limestone, and marl of Qom formation. We categorized the Young rocks into four phases based on their age and positions. The mutual effect of the basement and young magmatism --in the latest phase --creates hydrothermal solutions in the form of a heat engine. The heat engine has caused rotation and variety, increasing mineralization in the area. As a result, there are mines, deposits, gold indications, and some associated gold elements, including Tuzlar, Bayche Bagh, Baghcheh at Mahneshan area, Zarshuran, Agh-darreh, and Ay-Qalesi in Takab. The Tuzlar and Baghcheh deposits with gold mineralization are in a Silicic-argillic zone, including pyrite, gold-bearing silica, argillic and ferrous hydroxides minerals. The Ay-Qalesi polymetallic deposits often contain zinc and lead. The Zarshuran and Agh-darreh deposits are the gold types that the first one has a variety of mineralization of sulfides and sulfosalts. The second one has simple gold mineralization, and finally, the Bayche Bagh deposit with polymetallic type includes chalcopyrite, pyrite, rutile, arsenopyrite, sphalerite, bornite, smaltite, chloanthite, azurite, and malachite minerals.
Economic Geology
Kolsoum Fani Chenar; Mansour Ghorbani; Reza Kohansal; Jamshid Lotfian
Abstract
Ali abad chromites mines (north east of Forumad) are as a part of chromites assemblage dependent on ophiolite Sabzevar that are located in NW Sabzevar city. Chromitites deposits in these mines have been located as irregular lenses and layered or banded along with pods of dunite in depleted harzburgite. ...
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Ali abad chromites mines (north east of Forumad) are as a part of chromites assemblage dependent on ophiolite Sabzevar that are located in NW Sabzevar city. Chromitites deposits in these mines have been located as irregular lenses and layered or banded along with pods of dunite in depleted harzburgite. In attention to mineralogy observation, incongruent melting of orthopyroxenes and exsolution lamellae of clinopyroene in the orthopyroxenes, indicate that these rocks were originally formed at mantle pressures and temperatures conditions. Mineralography study on the textures and structures of Ali abad chromites indicate two types main textures that are primary and secondary. The primary textures and structures include massive and disseminated or separated grain. The milonitic, brecciated and tensional textures are from secondary types in chromites. On the basis of geochemical results the structural formula are calculated as the chromite minerals [(Mg,Fe2+)O (Cr,Al,Fe3+)2O3].These studies represent height percent Cr2O3 chromite mineral in disseminated texture than massive textures. Geochemical study on the chromitite area, site them in height Cr types and associated to podiform type that are originated from a parent melt with boninitic character resulting from high degree of partial melting of mantle peridotite in Supra Subduction Zone (SSZ).
Sedimentology
Somayeh Parham; Alireza Piryaei; Mansur Ghorbani; Seyyed Reza Moosavi Harami
Abstract
Late Cretaceous in Zagros encompasses regional tectonics and caused foreland basin to form in northeast of the Arabian Plate. Salt tectonics is also locally affected this area. One of the time periods that can better picture this tectono-sedimentary evolution is Maastrichtian. In order to investigate ...
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Late Cretaceous in Zagros encompasses regional tectonics and caused foreland basin to form in northeast of the Arabian Plate. Salt tectonics is also locally affected this area. One of the time periods that can better picture this tectono-sedimentary evolution is Maastrichtian. In order to investigate this evolution in the Maastrichtian time, a regional cross-section was made inthe Fars outcrops and wells. A sedimentological study and sequence stratigraphy have been accomplished along this transect. Maastrichtian deposits consist of the upper part of the Gurpi and the Tarbur formations in the studied transect. Based onsedimentological investigation, 14microfacies have been identified. This microfacies were deposited in 4microfacies belt including tidal flat, restricted and open lagoon, reef and open marine in a shelf carbonate platform. Based on sequence stratigraphic studies, 3 sedimentary sequences were identified in the studied interval. Correlation along the transect revealed that the Maastrichtian deposits occurred on the forebulge of Zagros foreland basin. It is also concluded that the fore-buldge shows a nearly smooth topography and thus accommodation space is homogeneous. Hence the thickness of the Maastrichtian deposits does not vary so much along this transect. Thickness anomaly in Namak-dehkuyeh occurs as a result of salt structure which decreased accommodation space.
Petrology
Elahe Namnabat; Mansour Ghorbani; Seyed hassan Tabatabaei
Abstract
The Youseflo pluton, a part of Ahar - Arasbaran magmatic belt, is located in south east of Ahar city in north east of East Azarbayejan province of Iran. The pluton is mainly composed of quartz monzonite, granodiorite and granite, however, the major investigated rock is granodioritic in composition. Quartz, ...
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The Youseflo pluton, a part of Ahar - Arasbaran magmatic belt, is located in south east of Ahar city in north east of East Azarbayejan province of Iran. The pluton is mainly composed of quartz monzonite, granodiorite and granite, however, the major investigated rock is granodioritic in composition. Quartz, Plagioclase, biotite, amphibole, K-feldspar, chlorite, zircon, sphene, apatite and opaque minerals are the minerals of these rocks. Biotites, as a significant ferromagnesian mineral in Youseflo pluton, are Mg- rich, Cl-poor where all are primary types. Considering Fe/(Fe+Mg) (from 0.36 to 0.43) and Al IV (average 2.32 apfu), minerals are classified as biotite between Annite- siderophyllit endmembers. The study of mineral chemistry of biotites demonstrates that the calculated pressure based on total Al content in biotites varies from 0.19 to 0.89 kb which is indicative of a shallow emplacement depth. Crystallization temperature of biotites based on Ti content and Ti/Fe+2 ratio suggests an average temperature of 735 oC.
E. Keshtkar; M. Ghorbani; J. Omrani
Abstract
In the north of Ziaran village, a Sill olivine gabbro to monzodiorite composition is injected into the Karaj tuffs. The dominate minerals composition of plutonic rock are Plagioclase, Alkali feldspar, Pyroxene, Olivine and Biotite. Plagioclase composition is varies, and it’s changed from Labradorite ...
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In the north of Ziaran village, a Sill olivine gabbro to monzodiorite composition is injected into the Karaj tuffs. The dominate minerals composition of plutonic rock are Plagioclase, Alkali feldspar, Pyroxene, Olivine and Biotite. Plagioclase composition is varies, and it’s changed from Labradorite to Bytownite. Alkali feldspar is in the Orthoclase range and Pyroxene is part of Diopside. Olivine composition change from Chrysolite to Hortonolite and most of the indicators are in the Hyalosiderite range. Biotite is one of the most prominent ferromagnesian mineral in the studied bodies. Compositionally, it is plotted between the field of annite and siderophylite. Most of these biotites are primary magmatic and some are plotted in the reequilibrated area. Based on the FeO*, MgO and Al2O3 binary and ternary diagrams, the studied biotites plot in the calc-alkaline orogenic field or crystallization temperature the have been calculated between 690º to 780 ºC. The chemical composition of the pyroxenes shows that these rocks have been crystallized in a subduction geological setting. The average crystallization temperature of clinopyroxenes is about 1215 °C. Furthermore, the calculated pressure for clinopyroxenes is less than 9 Kbars.
J. Rasouli; M. Gorbani
Abstract
Delfard area is located in the northwestern of Jiroft, formed the northwestern part of the Jabālbārez granitoid complex, in Uromiyeh- Dokhtar magmatic belt. The Jabālbārez granitoid complex has a wide range of rocks inclusive from diorite to alkali granite, which were formed by magmatic differentiation ...
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Delfard area is located in the northwestern of Jiroft, formed the northwestern part of the Jabālbārez granitoid complex, in Uromiyeh- Dokhtar magmatic belt. The Jabālbārez granitoid complex has a wide range of rocks inclusive from diorite to alkali granite, which were formed by magmatic differentiation process over the several course of consecutive pulses. Last pulses are masses of porphyry that showed evidence of copper mineralization. One of these intrusive bodies is Delfard. Copper mineralization in Delfard area is more important than other parts of Jabālbārez. Consequently, in the area, three porphyry masses showing the evidence of porphyry copper mineralization. Chalcopyrite, Pyrite, Malachite, Azurite and Magnetite are indicative minerals. Alteration zones in Delfard area are silicic, potassic, arjelic, phyllic, and propylitic that can be correlated with Lovell and Gilbert model. According to studies, Delfard has high potential for exploration and drilling. The average copper content in the ore is about 1800 ppm. Petrogenesis review of the mafic rocks in Delfard area shows that these rocks originated from a richer source than NMORB. In addition, the rocks of Delfard area are Flux melting pointer that happened in the subduction of oceanic crust under the adjacent crust. In other words, the sequence of calc-alkaline rocks of Delfard area attributed to compressional tectonic regime that intrusived and erupted along the Uromiyeh- Dokhtar zone with development and high volume in the form of magmatic horizons. Finally, petrogenesis of studied granite series is similar to the calc-alkaline granitoids, which was originated from basaltic magma mantle metasomatised by fluids from the subducted slab. Based on zircon U-Pb geochronology,the age of Delfard granitoid is 15/83±1/3 Ma. One can imagine that, magmatic differentiation process was completed in a short time and intrusive body was sequentially penetrated and placed in the earth's crust in a short time.
E. Keshtkar; M. Ghorbani; J. Omrani
Abstract
A gabbro to monzonite sill is injected into the Karaj tuffs at the north of Parachan village, North of Karaj.. The main minerals of these rocks are plagioclase, pyroxene, K feldspar, olivine and biotite. Clinopyroxene mineral chemistry studies carried out on the intrusive bodies, indicate two types of ...
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A gabbro to monzonite sill is injected into the Karaj tuffs at the north of Parachan village, North of Karaj.. The main minerals of these rocks are plagioclase, pyroxene, K feldspar, olivine and biotite. Clinopyroxene mineral chemistry studies carried out on the intrusive bodies, indicate two types of diopside and augite clinopyroxene composition. The chemical composition of the pyroxenes shows that these rocks have been crystallized in a subduction geological setting. The average crystallization temperature of clinopyroxenes is about 1120 to 1170 °C, and it seems that clinopyroxenes crystallized at lower temperature than orthopyroxenes. Plagioclase composition in these rocks is variable, changing from andesine to labradorite. K feldspars are in the orthoclase range and olivine are hyalosiderite. Biotite is one of the most prominent ferromagnesian minerals in the studied bodies. Compositionally, it is plotted between the fields of annite and siderophyllite. Most of these biotites are primary magmatic and some are plotted in the re-equilibrated filed. Petrological evidence represent that fractional crystallization from gabbro to monzonite had main role in genesis of these rocks. Enrichment in LILE) Ba, Rb and Th(and also depletion in HFSE (Nb and Ti) in Rare Earth Elements distribution pattern in spider diagrams, indicate features of subduction-related rocks. Also they are enriched in LREE rather than HREE, the characteristic which is usually observed in the rocks from subduction environments and active continental margins. Chemical and petrological studies, indicate role of fractional crystallization in the evolution of magma, although, minor amounts of assimilation and contamination of magma by crustal rocks occurred. This alkaline magma has been formed by low degree of partial melting of an enriched sub-continental lithospheric garnet-lherzolite mantle source.
L. Berahmand; M. Ghorbani; S. M. Pourmaàfi
Abstract
Dehaj-Meiduk area is located at North of Shahre-babak. There are nine porphyry intrusive bodies in this region, which include Meiduk, Parkam, Iejoo, Segino, Chah Firouzeh, Narkoh, Ayoub Ansar, Sara and Keder. Meiduk, Chah Firouzeh, Parkam, Iejoo and Segino are productive among them and Narkoh, Keder, ...
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Dehaj-Meiduk area is located at North of Shahre-babak. There are nine porphyry intrusive bodies in this region, which include Meiduk, Parkam, Iejoo, Segino, Chah Firouzeh, Narkoh, Ayoub Ansar, Sara and Keder. Meiduk, Chah Firouzeh, Parkam, Iejoo and Segino are productive among them and Narkoh, Keder, Ayoub Ansar and Sara are barren. These intrusive bodies are mostly composed of porphyry diorite, quartzdiorite and granodiorite. Geochemical studies indicate that the magma of these rocks has the peraluminous to metaluminous nature and magma series are calc-alkaline with high potassium and shoshsonitic nature. The geochemical variation diagrams of major oxides and minor elements, illustrate the continuous spectrum of rock compositions for the studied samples, which indicates high crystallization differentiation during magmatic processes. Field observations, petrographic and geochemical studies suggest that the rocks in the Dehaj-Meiduk area are I type. All available data demonstrate that these rocks are result of subduction of Neotethyan oceanic crust beneath the central Iran continental crust. Flat subduction happened in some parts of the study area and because of that, partial melting rate has been low and as a result adakitic rocks are produced. The adakitic rocks have formed intrusive bodies in Pliocene. Since magma is depleted in metallic elements by forming earlier stage productive plutons, the later rocks do not contain metallic elements and are barren.
R Kohansal; M Ghorbani; S.M Pourmafi; M Khalatbari Jafari; J Omrani
Abstract
The Forumad ophiolite pillow lavas crop out at west of Sabzevar and at the periphery of north central Iran microcontinent. These lavas include Upper Cretaceous pelagic limestone with microfossils and are classified in two Late Turonian- Santonian and Coniacian- Late Campanian groups. These basaltic ...
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The Forumad ophiolite pillow lavas crop out at west of Sabzevar and at the periphery of north central Iran microcontinent. These lavas include Upper Cretaceous pelagic limestone with microfossils and are classified in two Late Turonian- Santonian and Coniacian- Late Campanian groups. These basaltic pillow lavas have tubular and flattened forms, with external (vitrified), medial (variolite) and internal (intergranuler) parts. Each part has its own texture with mineral composition of clinopyroxene ± plagioclase ± olivine. The medial part is characterized by formation of skeletal crystals of olivine and lesser extend of plagioclase, indicating high nucleation rate. The nature of Late Turonian- Santonian lavas is tholeiitic and Coniacian- Late Campanian lavas are tholeiitic and calc-alkaline. Despite of enrichment in LILE, relative depletion of HFSE, different enrichment in LREE and various linear trends of HREE which suggest the formation of pillow lavas in the arc environment and the heterogeneous mantle with varying degrees of partial melting, but low ratios of Th/ Yb, La/ Nb, Ce/ Nb and Ce/ Th indicate that they are more inclined to intermediate between IAB and MORB environments. Unlike Late Turonian – Santonian lavas, high ratios of La/Yb, Nb/ Yb in Late Coniacian – Late Campanian lavas represent mantle fertility and decrease of Nb/ Ta ratios as well as relative increase of Th exhibit the effect of partial melting of subducted slab in genesis of these lavas. The depth of partial melting was 40 to 70 km in the spinel lherzolite stability zone. It seems that the formation of Forumad ophiolitic pillow lavas is accrued in a marginal basin to a back arc basin of a supra-subduction zone.
R Kohansal; M Ghorbani; S.M Pourmoafi; M Khalatbari Jafari; J Omrani; S Zolfaghari; S Soleimani
Abstract
Abstract The Forumadophiolitic rocks as a part of Iran marginal microcontinentophiolites have been situated in the western part of Sabzevarophiolite. Field study shows extrusive sequence in this area with Late Cretaceous in age. This sequence has included basaltic pillow lavas with radiolarian chert ...
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Abstract The Forumadophiolitic rocks as a part of Iran marginal microcontinentophiolites have been situated in the western part of Sabzevarophiolite. Field study shows extrusive sequence in this area with Late Cretaceous in age. This sequence has included basaltic pillow lavas with radiolarian chert related to Late Turonian-Santonian, in contrast to Coniacian- Late Campanian age, when this sequence has composed of basaltic pillow lavas in lower - middle part and various tuffs in upper part. Sheet flows, hyaloclasticbreccias and pelagic limestone are intercalations between lavas and tuffs.Abundantly, pillow lavas with phyric texture are most predominant feature contrast with sheet flows. Whereas enrichment of LILE and depletion of some HFSE (Nb, Ta) exhibit subduction environment (island arcs) for pillow lavas of Forumad, and different enrichment in LREE to HREE displays unhomogenous mantle in the generation of them; the presence of two magmatic nature in lavas (tholeiitic and calc-alkaline), their positions in tectonomagmatic diagrams and clear enrichment of Th element in Late Turonian –Santonian lavas which are generally exhibition of ophiolitic extrusive sequence in Forumad area have been generated in a supra-subduction environment and back-arc basin.
J Rasouli; M Ghorbani; V Ahadnejad
Abstract
Jebale-Barez granitoid complex is composed of intrusive bodyes included Mijan, Dareh hamzeh, Kerver and Hishin and is located In the southeastern province of Kerman on the lengths of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'.The petrologic composition ...
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Jebale-Barez granitoid complex is composed of intrusive bodyes included Mijan, Dareh hamzeh, Kerver and Hishin and is located In the southeastern province of Kerman on the lengths of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'.The petrologic composition in intrusive bodyes composed of granodiorite, quartzdiorite, granite and alkali-granite. The geochemical variation diagrams of major oxides, the continuous spectrum of rock compositions has been carried out which indicates the crystallization of magmatic differentiation and extensive appendices. The magma nature of these rocks is sub-alkaline-calc-alkaline, which in SiO2-K2O plot they fall into calc-alkaline series with high potassium. Field observations, petrographic and geochemical studies suggest that the rocks in this area have granitoides I type. Studying the geochemical diagrams of the rocks in the studied area indicates that these rocks have been formed in active continental margin tectononic setting. Most of the volcanic arc granites (VAG) are of "pre-collision" and "syn- collision" types. Three magmatic phases occurred in oligomiocene in this area. The first phase of magmatism in this area composed of the quartzdiorite and diorite that makes the main body of Jebale-Barez granitoid complex. Porphyry bodies will penetrate into the main body, after a short period of magmatic fractionation inside the nest of magma. Petrographic composition of the second phase is mainly diorite to tonalite. Oligo-Miocene magmatic final phase (Phase III) occurs in the region after a short time that the lithological composition of the granite to alkali granite. The third group of rocks in the study area from the main body mother came from magma fractionation. based on the location of Urmia-Dokhtar magmatic belt seems the rocks of this region there came to subducted oceanic crust Neotethyan beneath continental crust of central Iran.
H Alizadeh; M Aryan; M Lotfi; M Ghorashi; M Ghorbani
Abstract
The Dehaj-Sardoiyeh Belt, which is a part of the Urmia-Dokhtar Volcanic-Plutonic Zone, consists of several economic porphyry copper deposits. This area is located on the right lateral shear zone surrounded by the Rafsanjan fault in the north and the Shahr-e Babak fault in the south. In this research, ...
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The Dehaj-Sardoiyeh Belt, which is a part of the Urmia-Dokhtar Volcanic-Plutonic Zone, consists of several economic porphyry copper deposits. This area is located on the right lateral shear zone surrounded by the Rafsanjan fault in the north and the Shahr-e Babak fault in the south. In this research, spatial relationship among sixteen porphyry copper deposits, faults and fractures was studied. The results show a strong relationship between the Photo lineament factor and location of the porphyry copper deposits. The direction of lineament factor (d/D) was found to be highly correlated with the location of porphyry deposits. The results can be used in exploring preliminary porphyry deposits with regard to the geometry and mechanisms of the faults and fractures.
M.A Sajadi Nasab; M Vosoughi Abedini; M.H Emami; M Ghorbani
Abstract
The studied granitoidic intrusion with about 50 km2 area is located in the SW of Kelardasht, one of the regions in MazandaranProvince. It is one of the pluton masses of the Central Alborz structural zone. The mass has an age between 54±4 and 56±3 million years (late Paleocene to early Eocene) ...
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The studied granitoidic intrusion with about 50 km2 area is located in the SW of Kelardasht, one of the regions in MazandaranProvince. It is one of the pluton masses of the Central Alborz structural zone. The mass has an age between 54±4 and 56±3 million years (late Paleocene to early Eocene) and has intruded in the Mobarak and Shemshak formations. Petrologically it contains of two units of felsic (granite, qz-syenite, and qz-monzonite) and intermediate to mafic (monzonite to monzodiorite, diorite, and gabbro). The rocks of the first group especially granites and q-monzonites show many mineralogical and textural similarities and in which the evidences of magma mixing like rapakivi texture, poikilitic texture, acicular apatite, calcic plagioclase "spikes" in plagioclase, and micro granular mafic enclaves can be seen. These rocks have weak metaaluminous to peralumine nature (granite samples) and are richer in K2O+Na2O, K2O and the elements of Rb, Th, Hf than the second group. Due to the diagram related to REE, the rocks of this group have remarkable enrichment of LREE and related to the behavior of Y, Ba, Ce, and Zr in segregation process, they show the properties of low temperature I-type granites. In the second group, monzonite and monzodiorite rocks also show the evidences of alkaline metasomatism, associated with magma mixing textures including acicular apatite, septum biotites and anortite spikes in plagioclases. These rocks have meta alumine nature and show more richness in FeOT, MgO, CaO, bP2O5, TiO2, and the elements such as Sr, Ba, V, and Y than the first group; and also they show the properties of the high temperature I-type granites. Due to the geochemical evidences and the age of the mass, it can be categorized as post orogenic granite types, which have the properties between VAG and WPG. The isotopic investigation of 143Nd/144Nd revealed that only the granites of the region have can have enriched lithospheric source (negative εNd) and the other rocks have a depleted mantle source (positive). According to the petrographical and geochemical evidences, magma mixing has played an important role in magma evolution, and therefore, the crust melting model by mantle-derived magma is suggested for the magma generation of the area.
Behnaz Hosseini; M. Ghorbani; S. M. Pourmoafi; A. R. Ahmadi
Abstract
Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, ...
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Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, these rocks are divided into two groups of "augen geneiss " and "metagranitoid". During the course of previous studies, these two rock groups had been attributed to a magmatic phase in Mesozoic, which experienced different degrees of deformation. In this study we proceed to determine the age of these two granitoid rock groups based on U-Pb age dating method applied on Zircon minerals. As a result, the age of orthogneiss rocks is 514±24 million years old and they belong to Cambrian, whereas metagranitoid rocks are 173±9 million years old and attributed to Middle Jurassic. Based on geological and structural evidences, the magmatism occurred in Cambrian was related to tension tectonics in Late Precambrian to Early Paleozoic, while the magmatism in Middle Jurassic associated with dextral transpression tectonics in the studied area.
H. Gholamalian; M. R. Kebriaei zadeh; M. Ghorbani; S.M. Hosseini-Nezhad
Abstract
Investigation on brachiopods and conodonts of Mobarak Formation in Kalariz section confirms the age of Early Tournaisian to Middle Viséan. Some species as Bispathodus aculeatus aculeatus, Bi. stabilis, Spinocarinifera nigra and Shumardella sp.in the lowest part of section show the Early Tournaisisan ...
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Investigation on brachiopods and conodonts of Mobarak Formation in Kalariz section confirms the age of Early Tournaisian to Middle Viséan. Some species as Bispathodus aculeatus aculeatus, Bi. stabilis, Spinocarinifera nigra and Shumardella sp.in the lowest part of section show the Early Tournaisisan age, whereas the middle part is Middle to Late Tournaisian on the basis of the presence of Tomiproductus vaughani, Tomiopsis sp., Scabricosta sp., Polygnathus flabellus, P. rostratus, P. longiposticus, Clydagnathus cavusformis. Some faunas as Marginatia kinghirica and Buxtonia cf. praejuresanensis prove the Early to Middle Viséan for the upper part of section. Three domestic biozones are recognized on the basis of faunal distribution in the stratigraphic column. Biozone 1 (Early Tournaisian): this zone can be recognized by the association of these species: Spinocarinifera nigra, Rossirhynchus adamantinus, Shumardella sp., Cleiothyridina transversa, Bispathodus aculeatus aculeatus, Bi. stabilis, Polygnathus communis communis, P. inornatus. Biozone 2 (Middle to Late Tournaisian): Tomiproductus vaughani, Tomiproductus elegantulus, Tomiopsis sp., Scabricosta sp., Tylothyris planimedia, Syringothyris altaica, Leptagonia analoga, Leptagonia cf. regularis, Ripidomella michelini, Athyris hibernica, Spirifer missouriensis, Schelwienella sp., Leptagonia cf. regularis, Torynifer sp., Polygnathus flabellus, P. longiposticus, P. inornatus, P. aff. inornatus, P. rostratus, P. sp., P. communis communis, Bispathodus stabilis, Pseudopolygnathus primus, Clydagnathus cavusformis. Biozone 3 (Early to Middle Visean): this zone is identified by the presence of some index species as: Buxtonia cf. praejuresanensis, Megachonetes sp., Actinoconchus lamellosus, Orthotetes batesvillensis, Marginatia cf. kinghirica, Balakhoniasp. Mobarak Formation conformably overlies the Geirud Formation and disconformably underlies the Dorud Formation demonstrating Late Viséan to Gzelian hiatus as the result of Hercynian epeirogenesis.
S. M. Hashemi; M. Emami; M. Vossoughi Abedini; M. Pourmoafi; M. Ghorbani
Abstract
In southeastern Tabas there is a 400 square kilometer area of Quaternary basalts, which is geologically located in Lut zone. According to petrographic studies and EMPA analysis, the textures of these rocks are generally porphyric and some times aphyric. The phenocrysts of these basalts are generally ...
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In southeastern Tabas there is a 400 square kilometer area of Quaternary basalts, which is geologically located in Lut zone. According to petrographic studies and EMPA analysis, the textures of these rocks are generally porphyric and some times aphyric. The phenocrysts of these basalts are generally chrisolite, augite, and plagioclase (andesine to labradorite), which are embedded in a texture of plagioclase microlites and small blades of pyroxene. According to the diagrams of accumulative amount of alkaline against the amount of SiO2, the nature of the magma is alkaline to sub-alkaline. The reason for the sub-alkaline character of some of these rocks is that the alkaline magma has been contaminated with crust materials. One of the most important reasons for this is the reduction of niobium in rocks enriched with SiO2. The alkaline samples have normative nepheline and the sub-alkaline samples normative quartz. The studies of Nd and Sr isotopes have confirmed the crust contamination and also the source for early magma of basalts is the upper parts of mantle. Based on the field studies and tectono- magmatic diagrams, these basalts are of intercontinental type because of the activities of great fault of Nayband in Quaternary and separation in their cross point reaching the earth's surface.
S. Malecootyan; Sh. Hagh-Nazar; M. Ghorbani; M. H Emami
Abstract
Petrological,geochemical and isotropic evidence of crustal contamination of the Quaternary basic rocks of Ghorveh-Takab axis is presented in this paper. These rocks are olivine basalt and basalt and they are plotted in the field of alkaline suites in geochemical diagrams.
Some ...
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Petrological,geochemical and isotropic evidence of crustal contamination of the Quaternary basic rocks of Ghorveh-Takab axis is presented in this paper. These rocks are olivine basalt and basalt and they are plotted in the field of alkaline suites in geochemical diagrams.
Some evidence, such as the presence of gneissic xenoliths, quartz xenocrysts with reaction rims and biotite phenoblasts in the basic rocks of the study area and high amount of potassium and high values of ratios, high concentration of LREE in comparison with HREE, high values of ratios and low values of ratios all indicate the crustal contamination of basic magma during its ascent.