48 research outputs found
Neogene ultrabasic volcanic rocks in central Urumieh-Dohktar Magmatic Arc (NW Iran): melilitites and nephelinites in subduction setting
No full textAbout 180 km SW Tehran (central-northern Iran) young (likely <1 Myr old) and small volume lava flows are emitted
from volcanic chains close to Nowbaran town. These volcanoes belong to the so-called Urumieh-Dokthar Magmatic
Arc (UDMA), running from NW to SE along the western margin of Iran. The volcanism of the UDMA is related to the
NE-ward Neotethys Ocean subduction beneath the Iranian plate since Early Cretaceous time, evolved into Arabia-Iran
continental collision during early Cenozoic. The lava flows consist of strongly ultrabasic magmas, represented by
melilitites and nephelinites. Clinopyroxene is the most abundant microphenocryst, followed by olivine, calcite and
biotite. Diopside is always twinned or shows normal zoning, and olivine is Mg-rich, with Fo content ~86. Primary
calcite largely occurs as large plagues (often including opaque minerals and diopside); Mg-rich (Mg# ~0.87) and Tirich
(TiO2 up to ~7.3 wt%) phlogopite-eastonite is also frequent. Cancrinite-sodalite group minerals are the main
groundmass foids, together with nepheline and minor Ti-magnetite.
The investigated rocks show anomalous mineral paragenesis and whole-rock chemical compositions compared to the
other Cenozoic volcanic rocks occurring in Iran. SiO2 content is extremely low (down to 36.0 wt%), with CaO reaching
contents as high as ~19.2 wt%, coupled with generally high MgO (~9.1-13.9 wt%). Alkalis range between ~2.2 and 6.2
wt%, with Na2O/K2O varying from ~0.9 to 8.5. Primitive mantle-normalized patterns show marked troughs at K, Rb
and Pb and enrichment in Nb and Ta, resembling typical HIMU-OIB compositions.
The presence of these compositions imply a carbonatitic component in the mantle source, which is uncommon in
subduction-related settings, and certainly unique within the entire Cenozoic volcanic rocks of UDMA. Experimental
petrology studies in the last decades have demonstrated that carbonated peridotite is able to produce melts characterized
by extremely low content of silica but high amount of CaO and MgO (e.g. Presnall and Gudfinnsson, 2005; Hammouda
and Keshav, 2015). It is therefore necessary to understand these peculiar rock compositions in order to constrain their
mantle source, the role of carbonates and their origin in a subduction-related setting
Quaternary Melanephelinites and Melilitites from Nowbaran (NW Urumieh-Dokhtar Magmatic Arc, Iran). Origin of ultrabasic-ultracalcic melts in a post-collisional setting
No full textThe small Quaternary volcanic district of Nowbaran (NW Iran) belongs to the Urumieh-Dokhtar Magmatic Arc, a ∼1800-km long NW–SE striking Cenozoic belt characterized by the irregular but abundant presence of subduction-related igneous products. Nowbaran rocks are characterized by absence of feldspars coupled with abundance of clinopyroxene and olivine plus nepheline, melilite and other rarer phases. All the rocks show extremely low SiO2 (35.4–41.4 wt%), very high CaO (13.1–18.3 wt%) and low Al2O3 (8.6–11.6 wt%), leading to ultracalcic compositions (i.e. CaO/Al2O3 > 1). Other less peculiar, but still noteworthy, characteristics are the high MgO (8.7–13.3 wt%) and Mg# (0.70–0.75), coupled with a variable alkali content with sodic affinity (Na2O = 1.8–5.4 wt%; K2O = 0.2–2.3 wt%) and variably high LOI (1.9–10.4 wt%; average 4.4 wt%). Measured isotopic ratios (87Sr/86Sr = 0.7052–0.7056; 143Nd/144Nd = 0.51263–0.51266; 206Pb/204Pb = 18.54–18.66; 207Pb/204Pb = 15.66–15.68; 208Pb/204Pb = 38.66–38.79) show small variations and plot within the literature field for the Cenozoic volcanic rocks of western Iran but tend to be displaced towards slightly higher 207Pb/204Pb. Primitive mantle-normalized multielemental patterns are intermediate between typical subduction-related melts and nephelinitic/melilititic melts emplaced in intraplate tectonic settings. The enrichment in Th, coupled with high Ba/Nb and La/Nb, troughs at Ti in primitive mantle-normalized patterns, radiogenic 87Sr/86Sr and positive Δ7/4 anomalies (from +15.2 to +17.0) are consistent with the presence of (old) recycled crustal lithologies in the sources.
The origin of Nowbaran magmas cannot be related to partial melting of C–H-free peridotitic mantle, nor to digestion of limestones and marls by ‘normal’ basaltic melts. Rather, we favour an origin from carbonated lithologies. Carbonated eclogite-derived melts or supercritical fluids, derived from a subducted slab, reacting with peridotite matrix, could have produced peritectic orthopyroxene- and garnet-rich metasomes at the expenses of mantle olivine and clinopyroxene. The residual melt compositions could evolve towards SiO2-undersaturated, CaO- and MgO-rich and Al2O3-poor alkaline melts. During their percolation upwards, these melts can partially freeze reacting chromatographically with portions of the upper mantle wedge, but can also mix with melts from shallower carbonated peridotite. The T–P equilibration estimates for Nowbaran magmas based on recent models on ultrabasic melt compositions are compatible with provenance from the lithosphere-asthenosphere boundary at average temperature (∼1200°C ± 50°C). Mixing of melts derived from subduction-modified mantle sources with liquids devoid of any subduction imprint, passively upwelling from slab break-off tears could generate magmas with compositions recorded in Nowbaran
A showcase of igneous processes in the Urumieh-Dokhtar Magmatic Arc: the Miocene-Quaternary collisional magmatism of the Bijar-Qorveh area, northwest Iran
No full textThe Cenozoic Arabia-Iran continental collision was associated with emplacement of a large variety of magmatic rock types. This aspect is particularly evident in the Bijar-Qorveh area of NW Iran, where Miocene andesitic to rhyolitic rocks and Quaternary basic alkaline rocks crop out. The Miocene intermediate to acid compositions show radiogenic Sr and Pb isotopic compositions (87Sr/86Sri 0.70531-0.71109, 206Pb/204Pb 18.71-19.01, 207Pb/204Pb 15.66-15.73, 208Pb/204Pb 38.76-39.14), coupled with unradiogenic Nd isotopic ratios (143Nd/144Ndi 0.51223-0.51265). These characteristics, together with primitive mantle-normalized multielemental patterns resembling “subduction-related” geochemical fingerprints, are considered ultimately derived from the Iranian plate mantle wedge, metasomatised during previous NE-directed Neothetyan Ocean subduction. The alkali-rich andesitic and dacitic rocks evidence both closed- and open-system differentiation, as typically observed for collisional settings in general. Both rock types display a high Sr/Y (37-100) and La/Yb (29-74) “adakitic” signature that it is interpreted here with plagioclase (± amphibole) accumulation or melting of local mafic crustal rocks. Open-system processes involve recycling of crustal cumulates for pyroxene-rich andesite and biotite-rich dacite varieties, and low-degree partial melting of the local crust for leuco-rhyolites.
A radical change occurred during the Quaternary, when SiO2-understaturated to SiO2-saturated poorly evolved rocks (basanites, tephrites, alkaline and subalkaline basalts) were emplaced. The complete change of mantle sources suggests a phase of local extensional tectonics related with WNW-ESE right-transcurrent faults. The major oxide, as well as incompatible trace element and Sr-Nd-Pb isotopic fingerprint of these younger rocks is more akin to that of intraplate magmas, but still bearing some evidences for a variable contribution from a “subduction-modified” mantle source. The NW-trend of increasing involvement of this subduction component, is indicative of the strong tectonic control on magmatism. Additional lithotypes indicate the presence of open-system differentiation and remelting processes in the youngest phase of magmatic activity
Albin volcanism in Marivan region: Indication of extension in the Sanandaj-Sirjan continental arc
No full textThe Marivan region located in the west of Kurdistan province, northwest of Iran and in the structural geological divisions of Iran (Stöcklin and Nabavi, 1973). The Mesozoic volcanic rocks are widespread in the Northern Sanandaj- Sirjan zone in comparison to the central and southern parts of this zone. The basic term of this volcanic belt with a calc-alkaline tendency is dominant where was formed in association with the Sanandaj-Sirjan arc magmatism in the Mesozoic which generated as a result of the subduction of the Neotethys oceanic crust under the active continental margin of Central Iran (Omrani et al., 2008; Azizi and Jahangiri, 2008; Moinevaziri et al., 2015).The studied area located in the Sanandaj Cretaceous volcanic belt (SVB) (Azizi and Moinevaziri, 2009), is characterized by the presence of basalts and andesite-basalts, often intruded shales, sandstones, and Cretaceous limestones. Rahimzadeh et al. (2021) investigated the North of Sanandaj-Sirjan magmatism in two basic and acidic phases and attributed their formation to a continental arc tectonic environment with extension. Also, the general age of the North Sanandaj-Sirjan zone magmatism varies from 110 to 130 million years (Barmian-Aptian). Ali et al. (2016) determined a bimodal model for the volcanic rocks of the Kata-rash region in Iraq Kurdistan (north of the study area), which originated 108 Ma (Albian) in an oceanic arc tectonic environment. The main purpose of the present paper is to study the petrology and geochemistry of the volcanic rocks of the area, in order to determine their tectonic setting.Regional GeologyThe The studied area is located in the north and east of Marivan city and is a part of the 1:100,000 geological map of Marivan (Sabzehi et al., 2009). Structurally, it is located in the northwestern part of Sanandaj-Sirjan zone. The rock units with Albian age, are a sequence of low metamorphosed volcanic-sedimentary rocks and consist of basaltic lavas, andesite-basalt, rhyodacite, pyroclastic, shale, calcareous shale, metamorphosed limestone, sandstone and minor amounts of conglomerate. A great volume of basic rocks is found in the north of Marivan while the acidic domes are seen in the east of the Marivan. The field relationships of volcano-sedimentary sequence indicates that the volcanic rocks erupted from deep to shallow marine environment (Rahimzadeh et al., 2021).Research methodEleven samples selected from the Marivan volcanic rocks for chemical analyses. The major elements were measured by ICP-OES method and trace and rare earth elements (REE) were measured by the ICP-MS method in the Canadian MS-Analyses laboratory.PetrographyCretaceous volcanic rocks with bimodal composition are often basic to slightly intermediate and acidic outcrops. The basic phase includes a large amount of basalt and a small amount of basaltic andesite and the acidic phase is composed of rhyolite and rhyodacite. Porphyritic and microlithic-glassy are the common textures in the rocks under study. The presence of zoned-plagioclases, quartz with embayed texture in rhyodacite, regrowth in crystals margin in both basic and acidic phases indicate the chemical imbalance of phenocrysts with melt in the magma forming these rocks.GeochemistryBased on the results of chemical analyses, the Marivan volcanic rocks are classified as the basic and acidic where the bimodality of rocks can be seen. The basic rocks show calk-alkaline with tholeiitic tendency whereas the acidic term display the calc-alkaline nature. The geochemical results in the spider diagrams show that the basic rocks of the region are enriched in LREE and LILE (K, Cs and relatively Ba and Rb), and depleted in HFSE (Nb, Ti, P) except U and Th.The acidic rocks are enriched in LILE (K, Cs, Rb, Th) except Sr and depletion of HFSE (P, Ti, Nb) except U and Zr. Nb and Ti depletion is one of the characteristic features of magmatic arcs. Also, these rocks have an LREE-enriched pattern in both the basic and acidic phases with a high LREE/HREE ratio and a specific negative Eu anomaly are found only in the acidic phase. The acidic rocks were originated from the lherzolitic spinel mantle with a 5 to 8% partial melting degree whereas the basic phase is generated from the lherzolitic spinel-garnet mantle with 10 to 22% partial melting degree.Tectonic settingThis volcanic complex is a part of the Sanandaj-Sirjan magmatic arc, which shows both subduction and extensional components. Extension in the continental arc happened relation to roll-back or slab collapse (Wei et al., 2017; Rahimzadeh et al., 2021). Rollback occurs as a result of its pressure, the subducting crust turns back and breaks, and extension occurs for a short period. So, in this geodynamic environment, bimodal volcanism can be happened where basic term show the tholeiitic affinity. It’s happened from continental arc position. In this tectonic setting environments, most of the volcanic rocks are basaltic rocks while in a typical continental arc such as the Andes arc and the Urumieh-Dokhtar abundant andesite rocks are widespread (Gill, 2010).ConclusionMarivan volcanic rocks are part of the northern Sanandaj-Sirjan zone continental arc, which is roll-back happened in the Albian and as a result occurred the local extension in the regional compression setting. Its signs include the presence of shales associated with volcanic rocks, the abundance of basalts over andesites, the tendency of calc-alkaline to tholeiitic nature in most of the basic rocks and as the several geodynamic diagrams display. However, the obvious evidence of subduction in the region can be seen as the depletion of Nb and Ti elements and enrichment of LILE and LREE compared to HFS elements
Pesteh-Set
No full textPesteh-Set, A Pistachio Dataset containing 6 videos and 423 labeled images.For more details refer to: https://github.com/mr7495/Pesteh-SetIf you find this dataset useful, cite it by:@misc{rahimzadeh2020introduction, title={Introduction of a new Dataset and Method for Detecting and Counting the Pistachios based on Deep Learning}, author={Mohammad Rahimzadeh and Abolfazl Attar}, year={2020}, eprint={2005.03990}, archivePrefix={arXiv}, primaryClass={cs.CV}}THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Pesteh-Set
No full textPesteh-Set, A Pistachio Dataset containing 6 videos and 423 labeled images.For more details refer to https://github.com/mr7495/Pesteh-SetCodes description is available at https://github.com/mr7495/Pistachio-Counting.If you find this dataset useful, cite it by:@misc{rahimzadeh2020introduction, title={Introduction of a new Dataset and Method for Detecting and Counting the Pistachios based on Deep Learning}, author={Mohammad Rahimzadeh and Abolfazl Attar}, year={2020}, eprint={2005.03990}, archivePrefix={arXiv}, primaryClass={cs.CV}}THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Pesteh-Set
No full textPesteh-Set, A Pistachio Dataset containing 6 videos and 423 labeled images.For more details refer to https://github.com/mr7495/Pesteh-SetCodes description is available at https://github.com/mr7495/Pistachio-Counting.If you find this dataset useful, cite it by:@misc{rahimzadeh2020introduction, title={Introduction of a new Dataset and Method for Detecting and Counting the Pistachios based on Deep Learning}, author={Mohammad Rahimzadeh and Abolfazl Attar}, year={2020}, eprint={2005.03990}, archivePrefix={arXiv}, primaryClass={cs.CV}}THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Characteristics of patients, by country.
No full text∧<p>Previously unpublished dataset.</p><p>*Contributed by author.</p>#<p>S. Rahimzadeh, F. Farzadfar F, and M. Ghaziani, unpublished data.</p
COVID-19 CT-Scans Dataset
No full textCOVID-CTset: A Large COVID-19 CT Scans dataset containing 63849 images from 377 patients
Some samples of the dataset are uploaded here.
For more details and using the Full dataset refer to https://github.com/mr7495/COVID-CTset
The shared links are available at the GitHub profile.
Please cite this dataset by:
@article {Rahimzadeh2020.06.08.20121541,
author = {Rahimzadeh, Mohammad and Attar, Abolfazl and Sakhaei, Seyed Mohammad},
title = {A Fully Automated Deep Learning-based Network For Detecting COVID-19 from a New And Large Lung CT Scan Dataset},
elocation-id = {2020.06.08.20121541},
year = {2020},
doi = {10.1101/2020.06.08.20121541},
publisher = {Cold Spring Harbor Laboratory Press},
URL = {https://www.medrxiv.org/content/early/2020/06/12/2020.06.08.20121541},
eprint = {https://www.medrxiv.org/content/early/2020/06/12/2020.06.08.20121541.full.pdf},
journal = {medRxiv}
Geochemical constraints on Eocene–Miocene geodynamic and magmatic evolution of the Varan-Naragh area, Urumieh-Dokhtar Magmatic Arc, Iran
No full textTwo different types of igneous rock formed during separate Cenozoic magmatic phases in the Varan-Naragh area in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran as a part of the Alpine-Himalayan system. The first phase comprises late Eocene – early Oligocene Naragh gabbroic rocks (Ns), and the second phase is characterized by the emplacement of both volcanic and plutonic rocks of the early Miocene. Both phases display moderate enrichment of large rare earth elements and depletion of high field strength elements coupled with negative Nb, Ti, and P anomalies, indicative of subduction-related magmatic events within an active continental margin. Initial values of 87Sr/86Sr and εNdT are 0.70684 and +0.15 and 0.70560–0.70654 and +2.55 to +3.49 for Ns and early Miocene intrusive and volcanic rocks, respectively. Comparisons of rare earth element patterns and mantle-like isotopic ratios suggest that Ns mafic and early Miocene magmatic rocks were derived from partial melting of a common subcontinental lithospheric mantle. Geochemical and isotopic ratios of Ns gabbroic rocks, in combination with the data related to other coeval and proximal mafic-intermediate intrusions (such as Nashalj), suggest enrichment of the lithospheric mantle by slab-derived fluids with a minor subducted sediment melt. The low εNdT of Ns gabbroic rocks can reflect involvement of slab-derived components. The geochemical similarity and the close spatial and temporal association of Varan intrusive and volcanic rocks suggest a common petrogenetic relationship. Geochemical, isotopic, and geochronological evidence from the region indicate three major phases of igneous activity in the Kashan magmatic segment of the central UDMA during late Eocene to Miocene, resulting in complex tectonic regime transition from compressional subduction to extensional post-collisional settings. Integrated with published studies, the new results support a model suggesting that subduction-related magmatic activity was still influencing the central UDMA in the early Miocene time and are also consistent with the notion of oblique and diachronous collision along the northeast margin of the Arabia plate.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
