Petrology
Behnaz Bakhtiari; Nahid Shabanian-Broujeni; Alireza Davoudian-Dehkordi; Hossein Azizi
Abstract
The Muteh–Golpayegan Metamorphic Complex is located within the center of the Sanandaj-Sirjan Metamorphic Zone. The strain parameter measurements by the strain ellipsoid including strain ratio in the XZ principal plane, strain ellipsoid (RXZ), strain ellipsoid shape (K), and strain intensity (D) ...
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The Muteh–Golpayegan Metamorphic Complex is located within the center of the Sanandaj-Sirjan Metamorphic Zone. The strain parameter measurements by the strain ellipsoid including strain ratio in the XZ principal plane, strain ellipsoid (RXZ), strain ellipsoid shape (K), and strain intensity (D) exhibit prolate shape for the amphibole mineral for the deformed amphibolitic rocks in the Muteh–Golpayegan Metamorphic Complex. Several kinematic shear sense indicators consist of the asymmetric fold, kink fold, boudin, S/C fabrics, oblique grain shape, and mineral fishes show a dextral shear sense. The quantitative kinematic analyses highlight that Wk varies between 0.6 and 0.93, implying a general shear flow with 42% < simple shear <74% and 26% < pure shear <58%.
Petrology
Farzaneh Valinasab Zarnagh; Mohsen Moayyed; Ahmad Jahangiri; Hossein Azizi
Abstract
There are discontinuous outcrops of volcanic rocks in the West Azarbaijan province and in the north of Maku city. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. Mineral chemistry studies show that clinopyroxenes in the studied rocks are diopside. These ...
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There are discontinuous outcrops of volcanic rocks in the West Azarbaijan province and in the north of Maku city. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. Mineral chemistry studies show that clinopyroxenes in the studied rocks are diopside. These pyroxenes have a high magnesium number (0.87 to 0.99). Magma series and tectonic determination diagrams show that the basaltic rocks that make up the studied clinopyroxenes have an alkaline nature and were formed in a whitin plate environment. According to geothermobarometry studies, clinopyroxenes were formed at temperature 1100 - 1250 ° C and pressure of 3 - 9 Kbar. The depth for generation of magma was at about 22 kilometers.
Petrology
Mohsen Moayyed; Farzaneh ValinasabZarnagh; Ahmad Jahangiri; Hosein Azizi
Abstract
there are Discontinuous outcrops of volcanic rocks in the northern regions of Maku. The volcanic rocks were metamorphosed in the green schist facies. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. The lava of this unit covers the Cambrian and equivalent ...
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there are Discontinuous outcrops of volcanic rocks in the northern regions of Maku. The volcanic rocks were metamorphosed in the green schist facies. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. The lava of this unit covers the Cambrian and equivalent of Lashkarak rock units and is progressively covered by Devonian dolomitic units. The geochemical data of metabasic and metarhyolite rocks signify transitional to alkaline nature of the primary magma and they have a negative gradient of REE and LREE / HREE ratio of those rocks are high and enriched inHFS elements. Metarhyolite rocks are similar to the rift setting rhyolites (A1-Type). Geochemical data indicate that the studied rocks are due to fractional crystallization of basic magma with crustal contamination, and in particular, the studied rocks have a genetic relationship and originate from a commen magma. The magma of the studied rocks generated by 3-10 percent partial melting of an enriched garnet peridotitic mantle source in an intra-continental extensional rift setting. This tectonic setting is concordant with the known extensional rift setting governed on other parts of Iran during the early Paleozoic, primary stages of generation and development of the Paleotethys.
Petrology
Zahra Alaminia; Zahra Rahmati; Hossein Azizi
Abstract
The Dorojin granitoid at the northeastern Isfahan is located in the central Urumieh-Dokhtar zone and within the volcano-sedimentary complex. The Dorojin iron deposit is the one of the several ore deposits that Dorojin granitoid body is caused in its surrounding rocks. According to microscopic evidences, ...
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The Dorojin granitoid at the northeastern Isfahan is located in the central Urumieh-Dokhtar zone and within the volcano-sedimentary complex. The Dorojin iron deposit is the one of the several ore deposits that Dorojin granitoid body is caused in its surrounding rocks. According to microscopic evidences, mineral assemblage of wollastonite, garnet, pyroxene (diopside), amphibole, epidote, feldspar, calcite and quartz, Dorojin deposit attributed to the class of calcic skarns that occur during two stages progressive and regressive. Based on electron microprobe analysis, some garnets are andradite (An92-97Gr1-5) in core and andradite-grossular (An53-66Gr30-41Sp2-4) in rim. In the beginning, andradite fluid inclusions with temperature range from 369˚ to 444˚C and salinity range from 11.22 to 12.96 wt.% NaCl eqv., originate from magmatic fluids, while with change in the acidity condition of environment and the opening of system, grandite, epidote and calcite fluids with a temperature between 221˚ and 305˚C and salinity between 0.4 and 10.11 wt.% NaCl eqv., are dominated by mixing and dilution of early magmatic fluids with meteorite waters. Sr isotopic ratio of garnet vary between 0.70760 and 0.70805, suggesting that prominent role of the magmatic fluids for the formation of andraditic garnet.
Petrology
Mahin Hashemi; Nahid Shabanian; Alireza Davoudian; Hossein Azizi
Abstract
Estimation of temperature- pressure deformation path for metamorphic rocks experiencing a complex deformation history commonly rely on the relationship between successive metamorphic assemblages and different microstructures that remain. However, by changing the temperature-pressure conditions, metamorphic ...
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Estimation of temperature- pressure deformation path for metamorphic rocks experiencing a complex deformation history commonly rely on the relationship between successive metamorphic assemblages and different microstructures that remain. However, by changing the temperature-pressure conditions, metamorphic minerals with a microstructure, which are specific to those conditions, can be chemically re-equilibrate. Mylonitic paragneisses around the lake of Zayandehrood Dam, have range low-grade to medium-grade mylonites. According to petrographic and microstructural studies, we define at least three stages of metamorphism and deformation. The first stage metamorphism (the earliest recognizable metamorphic stage) took place during eclogite facies conditions. At this stage, high pressure minerals such as rutile, phengite, garnet and alkali-feldspar formed that enclosed in garnet or feldspar, and or located in matrix. These hosted garnets and feldspars based on the evidence of petrography formed at the amphibolite facies condition. Eventually a retrograde metamorphism took place in the lower green schist facies condition, That's evidence includes the sericitization of some feldspars, the chloritization of some biotite, and the formation of cholorite and quartz in and around some garnets. contemporaneous whit these retrograde processes, there is evidence of a relatively high temperature to low temperature deformation microstructure. The combination of evidences of metamorphism and deformation results is that these rocks have risen from relatively high depths, which during the rising stages undergone the various metamorphism condition, and many deformations have affected on this collection.
Afsaneh Badr; Nahid Shabanian; Alireza Davoudian; Hossein Azizi
Abstract
The North Shahrekord Metamorphic Complex (NSMC) in the center of Sanandaj-Sirjan Zone includes metagranite bodies, which has been intruded in some metamorphic rocks, especially schists. The NSMC metagranites display metamorphic and distinctive ductile deformation characteristics. These rocks are composed ...
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The North Shahrekord Metamorphic Complex (NSMC) in the center of Sanandaj-Sirjan Zone includes metagranite bodies, which has been intruded in some metamorphic rocks, especially schists. The NSMC metagranites display metamorphic and distinctive ductile deformation characteristics. These rocks are composed of quartz, alkali feldspar, plagioclase, biotite, amphibole, epidote, garnet, zircon, allanite, titanite, apatite and magnetite. Ages of the NSMC metagranites by zircon U–Pb shows the age of 523.92 [+ 5.03 – 5.73] Ma, and the whole rock Rb–Sr isotopes represents the age of 504 ± 47. The ages of NSMC metagranites (middle Cambrian) are younger than the Late Neoproterozoic - Lower Cambrian granitoids of the Sanandaj-Sirjan Zone, the NSMC metagranites are formed in the post-collisional setting, while the older granitoids are mostly related to volcanic arc. According to the morphology and shape of zircon crystals in NSMC metagranites, most of zircons are placed on S19 and S15 areas in morphology classification of zircon crystals, therefore, the granite magma of the area has hybrid (crust and mantle) origin. The crystallization temperature of metagranites, according to zircon morphology studies, is 750 to 850 °C, based on Zircon saturation calculation method, is 753.2 to 828.5 °C, and based on the graphical method (results of total rock chemical analyses), is 760 to 830 °C.
H. Azizi; A. Akbarpour
Abstract
Volcanic rocks with mainly andesite composition and lenzoid form outcropped in the Eocene sedimentary host rocks in the east of Sanandaj. Field studies confirm that they are intercalation with the sedimentary host rocks. In thin section, those have porphyritic, glomoroporphyric microlithic and microlithic ...
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Volcanic rocks with mainly andesite composition and lenzoid form outcropped in the Eocene sedimentary host rocks in the east of Sanandaj. Field studies confirm that they are intercalation with the sedimentary host rocks. In thin section, those have porphyritic, glomoroporphyric microlithic and microlithic porphyric textures. Some texture evidences such as glassy inclusion in the center of plagioclase phenocrysts, displacement of plagioclase and mafic phenocrysts with mafic hydrate minerals imply amalgamation of volcanic activity with soft sediments in shallow water; also cracking of plagioclase phenocrysts confirms this subject. Geochemical study shows that these rocks are enriched in incompatible elements such as U, Th, Pb and depleted in Nb, and Ti elements compared with chondrites, primitive mantle and NMORB. If crustal contamination can be responsible for these changes, but as usual these anomalies imply the primary magma generated above the subduction zone. This volcanic rock may have a unique origin the same as Urumieh-Dokhtar volcanic belt.
