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دسترسی آزاد مقاله
1 - Biozonation, Paleobathymetry and paleoenvironmental study of the Gurpi Formation in southwestern Iran
Taghi Farmani Ebrahim Ghasemi-Nejad Bijan Beiranvand Saeed Maleki-PorazmianiPlanktonic foraminifera and major palynomorph groups (i.e. terrestrial, marine, and amorphous organic matter) of the Campanian-Selandian strata of the Gurpi Formation were studied to evaluate the changes in the Zagros paleobasin in southwestern Iran. Planktonic foramini چکیده کاملPlanktonic foraminifera and major palynomorph groups (i.e. terrestrial, marine, and amorphous organic matter) of the Campanian-Selandian strata of the Gurpi Formation were studied to evaluate the changes in the Zagros paleobasin in southwestern Iran. Planktonic foraminifera were categorized into four morphotypes according to their paleodepth, extending from Morphotype 1, comprising surface generalists, to Morphotype 4, comprising deep-water aphotic heterotrophic species. The relative amount of species belonging to Morphotype 4 is noticeable in the Campanian-Maastrichtian. It shows that the depth of the basin was generally greater than 200 m in the Late Cretaceous. Two major sea-level regressional phases could be recognized during the formation deposition. The first one occurred near the middle of the Maastrichtian in the Contusotruncana contusa Biozone, during which the relative abundance of terrestrial palynomorphs increased prominently, and the species belonging to Morphotype 4 became notably rare. This regression correlates well with the eustatic curves, suggesting that it was controlled by global factors. Also, the species belonging to Morphotype 4 disappeared in the Danian, the relative abundance of terrestrial palynomorphs increased, and the relative abundance of planktonic foraminifera (P%) decreased prominently. However, this regression does not correlate with the eustatic curves and indicates that local tectonic events should be considered. The palynofacies study of the strata shows that during the Campanian-Maastrichtian, the strata were deposited in a deep suboxic-anoxic setting (Palynofacies IX), whereas the Danian strata were deposited in a shallow-shelf setting (Palynofacies VI). The studies show that during the Selandian, the depth of the basin increased again. پرونده مقاله -
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2 - Study of A-type granite from the South of Lake Urmia, Sanandaj-Sirjan Zone: implications for the Neotethys opening in Iran
Nasser Ashrafi Mehrdad Pourmohsen Morovvat FaridazadThe magmatic evidence of the Neotethys opening in Iran, such as the Late Paleozoic A-type granitoids, was mainly discovered along the Sanandaj-Sirjan Zone and parallel to the Neotethys suture. Therefore, they may provide important clues about the geodynamic evolution of چکیده کاملThe magmatic evidence of the Neotethys opening in Iran, such as the Late Paleozoic A-type granitoids, was mainly discovered along the Sanandaj-Sirjan Zone and parallel to the Neotethys suture. Therefore, they may provide important clues about the geodynamic evolution of the Sanandaj-Sirjan Zone. The South of Lake Urmia (SLU) granite is situated near the Khalifan A-type pluton (315±2 Ma) with a cover of the Permian sediments. The rock-forming minerals of the SLU granite consist of quartz, alkali-feldspars (K-rich and microperthitic), sodic plagioclases, biotite (Fe-rich), zircon, apatite, and Fe-Ti oxides. The chemical composition of the SLU granite is characterized by high FeOt/MgO and (Na2O+K2O)/CaO ratios, which are typical features of A-type granites. Furthermore, the studied rocks exhibit the chemical characters of the A1 subgroup of A-type granites with peraluminous and K2O-rich affinities. On the multi-element spider plot, the SLU granite shows distinct negative Ba, Sr, P, and Ti anomalies and positive Pb anomalies. Moreover, the Chondrite-normalized rare earth elements (REE) patterns display slope downwards from LREE to HREE, with flattening at the HREE end and distinct negative Eu anomalies. The ratios of trace elements provide evidence for the contribution of the OIB-like mafic melts with crustal interactions to generate the granitic magmas of the SLU pluton. The compositional and stratigraphic features of the SLU granite are also consistent with an extensional setting during the Late Paleozoic in Iran. Therefore, the genesis of the SLU granite can be attributed to the syn-rift magmatism of the Cimmerian terranes. A comprehensive review of the Late Paleozoic rocks occurrence shows that they mainly are emerged in the northeast margin of the Sanandaj-Sirjan Zone and around the structural depressions such as Lake Urmia (so-called Tertiary fore-arc or Mesozoic back-arc). پرونده مقاله -
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3 - First report of the SardinellaSardinites (Heckel, 1850) in the Kond formation in the Saran area, Central Alborz in Iran
Saeedeh Senemari Leila Fazli Alireza CheginiInvestigating the fossil-bearing horizons of the Kond Formation in the Saran area resulted in the identification of Sardinellasardinites (Heckel 1850) belonging to the family of Clupeidae Bonaparte (1831) for the first time the east of Tehran province. Furthermore, bios چکیده کاملInvestigating the fossil-bearing horizons of the Kond Formation in the Saran area resulted in the identification of Sardinellasardinites (Heckel 1850) belonging to the family of Clupeidae Bonaparte (1831) for the first time the east of Tehran province. Furthermore, biostratigraphic analyses based on the presence of benthic and planktonic foraminifera in this area demonstrate that the sedimentary sequence including strata of conglomerate, tuff, shale, gypsum, limestone, and marl with a thickness of 376 m in the Saran area belongs to the Priabonian, which is discontinuously located on Middle Eocene green tuffaceousshales. In the present study, 18 species belonging to 9 genera from the benthic foraminifera were identified. In the late Middle Eocene, the performance of the orogenic Pyrenean phase led to the rising of the sedimentary strata and subsequent retreat of the sea and then the sea re-advanced during the Priabonian stage. The presence of a conglomerate at the base of the formation reveals the next activity of the tectonic phase. In this study, the rock unit of the Lower Red Formation belonging to the Oligo-Miocene is located on the deposits of the Kond Formation. پرونده مقاله -
دسترسی آزاد مقاله
4 - Mesozoic paleogeography and facies distribution in the Northern Mediterranean Tethys from Western Carpathians view
J. MichalÌkWest Carpathian Mesozoic paleogeographic development indicates the effect of a left lateral shift of the Alpine- Carpathian microcontinent along the European shelf since the Early Jurassic. The evolution during Late Triassic/Early Jurassic was controlled by convergence چکیده کاملWest Carpathian Mesozoic paleogeographic development indicates the effect of a left lateral shift of the Alpine- Carpathian microcontinent along the European shelf since the Early Jurassic. The evolution during Late Triassic/Early Jurassic was controlled by convergence along the border of the Meliata Ocean and by contemporaneous divergence along the Middle Atlantic/Penninic rift. During Mid-Cretaceous, the convergence between Africa and Paleoeurope started, which finally resulted in collision of Alpine-West Carpathian microcontinent with the Paleoeuropean margin and in the formation of the Alpine Orogen. پرونده مقاله -
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5 - Petrological and geodynamical constraints of Chaldoran basaltic rocks, NW of Iran: evidence from geochemical characteristics
Farhad Moharami Issa Azadi Mirsaleh Mirmohamadi Javad Mehdipour Ghazi Mohammad RahgoshayChaldoran area in NW of Iran has Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks show continental volcanic a چکیده کاملChaldoran area in NW of Iran has Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks show continental volcanic arc natures and Eocene lava flow shows OIB-like nature. During the Mesozoic,the Chaldoran region was situated in the active continental margin of the Iranian plate due to Neotetyhan subduction beneath the SSZ (Sanandaj-Sirjan Zone). As the Neo-Tethyan subduction regime changed, a rift in the Chaldoranareagenerated, which caused a continental back arc basin during the Upper Cretaceous. Along with spreading basin in the oceanic ridge, in the surface of new formed oceanic crust, some oceanic island were active and formed volcanoclastic rocks in the Chaldoran Oceanic crust. They were result of ascending continental arc nature plumes that formed in the sub-oceanic crust and up on Neo-Tethys subducted slab in the mantle wedge. After of finishing of spreading this basin in early time of Paleocene, sedimentation followed up to the Middle Eocene. In the Upper Eocene, alkaline and OIB-like volcanism was active in the Chaldoranareadue to breaking off the Neo-Tethyan subducted slab in the sub-oceanic crust of Chaldoran area and developed an asthenosphric window. پرونده مقاله -
دسترسی آزاد مقاله
6 - بررسی پتروگرافی و ژئوشیمی گرانیت دهنو
اسماعیل درویشیتوده گرانیتی دهنو در شرق روستای دهنو و جنوب شهرستان خمین و درون کمربند دگرگونی سنندج - سیرجان واقـع شـده اسـت.ترکیب سنگ شناسی ایـن تـوده در محـدوده گرانودیوریـت، کوارتزدیوریـت)تونالیـت(، مونزوگرانیـت و لویکوگرانیـت مـی باشـد.کوارتز، آلکالی فلدسپار، پلاژیوکلاز، بیوتیت، ه چکیده کاملتوده گرانیتی دهنو در شرق روستای دهنو و جنوب شهرستان خمین و درون کمربند دگرگونی سنندج - سیرجان واقـع شـده اسـت.ترکیب سنگ شناسی ایـن تـوده در محـدوده گرانودیوریـت، کوارتزدیوریـت)تونالیـت(، مونزوگرانیـت و لویکوگرانیـت مـی باشـد.کوارتز، آلکالی فلدسپار، پلاژیوکلاز، بیوتیت، هورنبلند، مسکوویت، تورمالین، زیرکن، آندالوزیت و آپاتیت ازجمله کانی هـای اصـلیو فرعی موجود در سنگ های این توده مـی باشـند. ایـن تـوده، میزبـان آنکلاوهـای میکروگرانـولار مافیـک و رگـه هـای سیلیسـیتورمالین دار و دایک های آپلیتی متعدد و به ندرت دلریتی می باشد. مطالعـات کـانی شناسـی و ژئوشـیمیایی بـر پرآلـومین و کالـکآلکالن بودن و منشاء دوگانه حاصل اختلاط ماگمای جبه ای )حاصل ذوب بخشی پوسته اقیانوسی نئوتتیس به زیـر خـرد قـاره ایـرانمرکزی( و مذاب آناتکسی )حاصل ذوب بخشی رسوبات پوسته قاره ای( سنگ های این توده دلالت دارند و غنی شدگی سنگ هـایگرانیتی منطقه از عناصر LILEنظیر Rb,K,Csو تهی شدگی از عناصر HFSEبه ویژه Ti,Nbو Pبـا الگـوی گرانیـت هـایمرتبط با فرورانش همخوانی دارد همچنـین از لحـاظ محـیط تکتـونیکی جـزء گرانیتوئیـدهای قـوس ولکـانیکی) (VAGمحسـوبمی شود پرونده مقاله
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