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The study area is located in northeastern Iran (south of Mashhad). Paleo-Tethys Ocean opened during Silurian time and subduction under Turan plate was started in Late Devonian. By Late Triassic (225 Ma) there was no Paleo-Tethys left on an Iranian transect, therefore Turan plate obducted over Iran Plate. Two stages of low grade regional metamorphism are exposed, that are related to Hercynian (Late Paleozoic) and Cimmerian (Jurassic) orogenies. The Paleo-Tethys remnants (meta-ophiolite and meta-flysch) were intruded by Sangbast monzogranite. Chemically, monzogranite is moderately peraluminous S-type granitoid. It has low values of magnetic susceptibility [(5 to 11) × 10^-5 SI] therefore it is classified as belonging to the ilmenite-series of reduced type granitoids. Monzogranite is characterized by strong light rare earth element (LREE) enrichment and less low heavy REE (HREE). All samples have very small negative Eu anomalies (Eu/Eu* = 0.62 to 0.88). Total REE content of monzogranite is between 212-481 ppm. The result of U-Pb zircon age dating of monzogranite is 201.3 ± 3.6 Ma (Upper Triassic, Rhaetian time). The initial ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios for monzogranite is (0.706776 and 0.512219) when recalculated to an age of 201 Ma, consistent with the new radiometric. The initial ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios for slate is (0.720613 and 0.511601) respectively when recalculated to an age of 201 Ma, consistent with the new radiometric results. Initial εNd isotope values for monzogranite is -3.13 and the slate is -15.19. Based on radiogenic isotopic data and REE monzogranite magma originated either from lower continental crust which was very different from slate or it is originated from mantle and contaminated in continental crust during ascending.

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Palygorskite is a widely distributed clay mineral that is commonly found in soils and sediments of arid regions, particularly in the Middle East. This study aimed to determine the distribution of palygorskite in major parent materials of soils developed on central Iranian Tertiary sediments. Based on field observations and geologic maps, 12 geological formations with Tertiary age were sampled and analyzed for mineralogical composition using x-ray diffraction (XRD) and transmission and scanning electron microscopy (TEM and SEM). Results showed that sediments of Miocene and Pliocene ages had the highest amount of palygorskite in the study area. In contrast, no trace of palygorskite was found in samples of Paleocene, Eocene and Oligocene ages. Smectites were highly associated with palygorskite. Stability diagrams for smectite-palygorskite system in Tertiary sediments of diff            erent ages showed that geochemical conditions were not conductive for pakygorskite formation during the Late Oligocene. Occurrence of palygorskite in the Tertiary sediments of Central Iran suggests that the most possible source of this mineral in soils of the study area, and probably those of other areas with similar conditions, is the inheritance from parent materials. It seems that the geochemical conditions of the Tethys Sea became gradually suitable for palygorskite formation in the Tertiary sediments of central Iran. Today's arid environment prevailing in central, eastern and southern Iran has led to the stability of palygorskite in soils developed on Tertiary sediments.

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 Shanderman eclogites are exposed at the west of Shanderman town, Talesh Mountains, in north Iran. Protoliths in these rocks has basaltic composition. Geochemical studies indicate that most of the samples have tholeiitic feature. Mg^# versus Cr and Ni show that they experienced olivine and clinopyroxene fractionation. Spider diagram shows more fractionation of olivine compared to clinopyroxene. The trace element versus major oxides diagrams show that major oxides had no significant (except Na and to some extent Fe) variation during alteration and subsequent metamorphism. Based on ∑REE, eclogite of the Shanderman can be divided into two groups. First group shows ∑REE= 31.1 ppm and (La/Lu)_N=0.6. Second group have ∑REE= 139.2 ppm and (La/Lu)_N=2.3. Chondrite REE normalized patterns show that they are comparable with N-MORB and E-MORB. These patterns (N-E MORB) indicate that either Shanderman eclogite protolith magma source was not homogenous or it experienced different melting degrees, changing from LSS (slow spreading ridge) to FSS (fast spreading ridge).

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In northwest of Marand northern part of Urumieh Dokhtar Magmatic Arc (UDMA) a set of volcanic rocks crop out with composition of andesite, dacite, and sodic, potassic and ultrapotassic alkaline basalts with Upper Miocene until Plio-Quaternary in age. This paper report the andesitic and dacitic lavas erupted within pyroclastic rocks. These rocks have porphyritic texture and consist of plagioclase, hornblende, pyroxene and a minor biotite phonocrysts. Based on geochemical study, these rocks have SiO₂ in rang of 57.5-65.2, high Al₂O₃ (14.5-16.2) and Sr (557-1185), high Sr/Y (30.7-84.46), La/Yb (13.27-67.36) ratios, and low Y (11.2-20.2) that show adakitic characteristic for the parent magmas. On the base of geochemical characters, these rocks are high- SiO₂ adakites which is considered to represent subducted basaltic slab-melts that have reacted with peridotite during ascent through mantle wedge. Also these samples are enriched in LILEs and LREEs and are depleted in some HFSEs like Ta, Nb, and Ti. Intensive fractionated pattern of REEs and low quantities of HREEs and Y may prove existence of garnet or amphibole in the residua of melt. High Sr and negative anomalies of Ta, Nb, and Ti may be resulted from lack of plagioclase and having iron and titanium oxides in the residua phase. Breaking of oceanic slab during subduction and melting of this slab product adakitic magmatism in NW of Marand. High Mg^#, Cr, and Ni in rocks indicate metasomatism of melt with mantle wedge. High Ba, Rb, and K₂O contents of studied rocks indicate assimilation of magma with crust during rising of magma.

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Toye-Darvar granitoidic pluton is located in southwest of Damghan, in the southern flanke of eastern Alborz structural zone. Despite of its uniform appearance in the field, this pluton is composed of a rock with a wide range of composition including of diorite, monzodiorite, monzonite, quartzmonzonite and granodiorite with monzonite-quartzmonzonite prevalence. Based on the field observations, this pluton intruded in the Bayandor, Soltaniyeh, Zagoon and Laloon formations with the Late Precambrian-Cambrian age and not found in Jirood Formation, in opposite of pervious reports, then its age isn’t Late Devonian. Absence of contact metamorphism indicates the fluid deficence and relatively dry nature of magma, smal size of pluton and diapiric ascent of the magma in a cold solid state in shallow depths of the crust. Existence of Fe-Mn oxide-hydroxides, fluorite, barite, zinc and lead viens in the country rocks, prevalence of hypersolvous-subsolvous reaction fine grain granular textures (perthitic, myrmekitic, graphic and granophyric), alkaline nature of magma, LILE and incompatible elements enrichment, high contents of HFSE in comparision to the other granitoids, low CaO and MgO contents, high FeO_t/MgO ratio (prevalence of iron rich mineralogy), high Ga/Al ratio and plotting the samples in the A-type granitoid fields in geochemical discriminat diagrams, all suggest that this pluton is A₁ sub-type granitoids (related to intraplate rifting magmatism). Different evidences indicate a close relationships between Toye-Darvar granitoidic pluton and Lower Paleozoic rifting magmatism (Ordovician-Silurian time) in the Gondwanian uniform platform of Iran in relation to initiation of the opening of the paleotethys ocean that reported from different localities in Iran, particularly in Alborz and Central Iran, and the other adjacent countries.

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The Bayazeh ophiolite, with Paleozoic age, is located in the eastern margin of the Yazd Block (Central Iran). This ophiolite consists of serpentinized peridotites, metagabbro, ultrabasic metamorphosed dikes, metapicrite, serpentinite and metalistvenite. Rock forming minerals of the metapicrites in the Bayazeh ophiolite are olivine (completely altered to serpentine), clinopyroxene (diopside, augite), phlogopite, apatite, opaque (ilmenite, magnetite), amphibole (tremolite, actinolite, and tremolitic hornblende), chlorite (clinochlor, penninite) and prehnite. Main textures in these rocks are granular and poikiloblastic. Chemical composition of clinopyroxenes indicates that crystallization of clinopyroxenes has occurred during ascending of the magma. Geochemical analysis of the Bayazeh metapicrites conclude high values of MgO (25.8 to 28 wt %) and low values of SiO₂ (37.5 to 39.4 wt. %) that reveal their ultramafic nature. Presence of phlogopite as a primary hydrous mineral together with geochemical criteria of the studied rocks, reveal amphibole presence in the source rock of the Bayazeh metapicrites. Amount of REEs, enrichment from HFSEs and LREEs associated with high value of Mg# and Ni in these metapicrites indicate metasomatic enrichment of a mantle source. Metasomatic enrichment of this mantle source could be affected by fluids related to the Paleo-Tethys subduction. Geochemical characteristic of metapicrites in the Bayazeh ophiolite show that these rocks generated from 40% of partial melting of a metasomatized asthenospheric spinel lherzolite.

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Outcrops of the Upper Ordovician igneous rocks, as basaltic lava and microgabbroic dyke and sill, present within the Abarsej and Ghelli formations in north and southwest of Shahrood. These rocks have basaltic, trachybasaltic and basaltic trachyandesitic composition with alkaline nature. Their parallel patterns on the primitive mantle and chondrite normalized spider diagrams indicate the common source of these rocks and the role of fractional crystallization in their generation. These rocks plot on the field of alkali basalts related to intracontinental rift on various discrimination tectonic setting diagrams. This tectonic setting corresponds to paleogeography of the Alborz during early Paleozoic (occurrence of Turan intracontinental Paleotethys rift) in Ordovician- Silurian times. Geochemical investigations indicate the magma forming of these basaltic rocks generated from 14-16% partial melting of an enriched garnet peridotitic astenospheric mantle source in 100-110 km depths. This magma has not contaminated by continental crust during ascending to the earth surface.

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HP/LT metabasite rocks can preserve some evidences of tectonic and geochemical processes of a subduction zone. Sabzevar Ophiolite and metabasites which are located at the north of Central Iranian Microcontinent Block (CIM) have preserved such evidences. The metabasites are fossil oceanic crust of Neotethys-related basin. Metabasites are composed of glaucophane schist, amphibolite and greenschist. Major and trace element contents of the rocks indicate that blueschist and amphibolite protoliths were MORB basalts. Rare earth elements show presence of two MORB types, N- and E-MORB. ΣREE is 132-246 (ppm) and 617-744 (ppm) for the N- MORB and E-MORB basalts, respectively.  La/Yb ratio is ranging from 0.43-0.79 for N-MORB and 8.7 and 1.1 for E-MORB. The Mg^# ranges are between 0.24-0.27, 0.23-0.24, 0.42 and 0.38 for glaucophane schist, garnet amphibolite, amphibolite and chlorite schist, respectively, which indicates a weak fractional crystallization in the original magma. High pressure rocks were formed due to northward subduction of Neotethys-branch of Sabzevar basin between CIM and Eurasia since Upper Cretaceous to Eocene. 

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Dioritic plutons and pinkish alkali-feldspar granitic dikes of Kalateh area (northwest of Khur city) intruded in Neoproterozoic basemental of Jandagh- Arousan complex. Field observations, petrography and geochemical studies indicate that these intrusive rocks have I-type nature and belong to medium-high K calc-alkaline granitiods and also have genetically relationship with each other. Their parental magmas produced by partial melting of metasomatized mantle wedge which was located above the subducted Neotethyan oceanic slab. The mentioned magmas generated in an intracontinental back arc extensional setting in relation to the subduction of oceanic Neotethys slab. U-Pb dating results on separated zircon from dioritic and alkali-feldspar granitic rocks indicated 213.9 ± 1.6 to 221.16 ± 1.6 Ma interval age (corresponding to Late Triassic). These igneous rocks are indications of magmatic manifestations of Early Cimmerian Orogeny.

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One of the most prominent cases of the study of alteration processes and their effect on geochemistry is the ophiolite investigation. The Marivan-Palangan ophiolite (MPO) complex is a part of the Neotethyan ophiolites, which situated in the Kurdistan Province, western Iran. The studied samples reveal the occurrence of the secondary minerals such as epidote group, chlorite, zeolites, and less calcite and iron hydroxides in the form of veins, vesicles and fractures infilling, and replacement phases. The element concentration variation versus Loss on ignition (LOI), normalization of the samples as to fresh sample in the study area and standard sample, and immobile element modeling indicate that element contents changes vary depending on the degree of alteration so that the concentration of Large-Ion Lithophile Elements (LILE) such as Rb, Cs, K, Ba, and Na shown a significant increase. CaO and FeO oxides are relatively depleted. Light Rare Earth Elements (LREE) display slight enrichment, while Middle Rare Earth Elements (MREE) and Heavy Rare Earth Elements (HREE) are almost constant. Therefore, in evaluation of the geochemical characteristics of extrusive section of the MPO complex, the effect of alteration on the changes in the concentration of elements, in particular LILEs, CaO, FeO and also LREEs should be considered.

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The Esmaeilabad granitic body with the Late Triassic age is situated in the central part of the Posht-e-Badam block (Central- East Iranian Microcontinent), in the northeastern of the Yazd Province. This granitic body cross cut the metamorphic rocks of the Posht-e-Badam complex and covered by the Cretaceous limestone. Rock forming minerals of the studied granites are K-feldspar (orthoclase), plagioclase (andesine, oligoclase), quartz, amphibole (magnesio-hornblende), biotite, apatite, titanite and zircon. According to the mineral chemistry analyses, amphiboles represent the igneous nature. Biotites are rich in Magnesium. Chemical characteristics of biotites indicate that they are primary biotites which are generated by calc-alkaline magma. Chemical composition of the amphiboles and biotites in the Esmaeilabad granites suggest that they belong to the I-type granites and generate in an environment with high fO₂. Geothermobarometry estimations yield temperatures between 550 to 700 ^oC and pressures in the range of 2 to 3.8 kbar. Based on the geological position and age of the studied rocks, generation of this granitic body can be related to the subduction and closure of the Paleo-Tethys Ocean in the western part of the Central- East Iranian Microcontinent, which can be the reason for granitic plutonism in this area.

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Tarazoj-Soushab tectonic window is located between Tarazoj and Soushab villages at the upper corner of the northeast of 1:100,000 Hashjin sheet. This area is a part of the West Alborz Tertiary magmatic belt. Mafic igneous rocks include basaltic pillow lava and gabbro bodies and felsic igneous rocks include granite and trachytic flows. The main minerals of the gabbroic and basaltic rocks are plagioclase, olivine and clinopyroxene and the main minerals of the granitic rocks include plagioclase, orthoclase and quartz, and the trachyte consists mainly of potassium feldspar. Gabbroic and basaltic rocks show calc-alkaline nature and granitic and trachytic rocks have shoshonitic nature. Examination of chondrite and primitive-mantle normalized spider diagrams in basalts and gabbros indicates enrichment of LREEs relative to HREEs. The LILE and LREE enrichment and HREE depletion in the pattern may indicate low melting rate, high fugacity of CO₂/H₂O in the magma formation environment or high depth of generation of basaltic and gabbroic magma. Examination of chondrite and ORG-normalized spider diagrams in granites and trachytes indicate enrichment of light rare earth elements (LREE) and incompatible elements relative to heavy rare earth elements (HREE). These patterns show a marked depletion of Eu (especially in granites). Gabbroic and basaltic rocks are located in an oceanic environment with E-MORB basalts tendency and the granites and trachites associated with this assemblage belong to anorogenic granitoids (A-type) and subgroup A₁. These features indicate that the studied outcrops in the Tarazoj-Soushab tectonic window belong to the rift-related magmatism and opening of the Paleo-Tethys ocean (Paleo-Tethys II) in the northwest of Iran.

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The mineralogical composition and geothermobarometry of the peridotites from the Marivan-Kamyaran ophiolitic complex, as a part of the Neo-Tethyian ophiolites in the Zagros Mountains, western Iran, are investigated. The studied samples are belonged to mantle and crustal peridotite types. Results of electron probe microanalysis in peridotites indicate that olivine is forsterite (Fo₈₇-Fo₉₂), clinopyroxene is augite-diopside (En_48-56Fs_3-6Wo_39-49) and orthopyroxene is enstatite (En_90-91). Cr-number (Cr#) and Al-number (Al#) in spinels of the mantle peridotites are 33-59 and 41-67, respectively. The same values in spinels of the crustal peridotites are 67-98 and 2-32, respectively. Geothermobarometry calculations for the mantle peridotites show average temperature of ~1104°C and average pressure of ~14 kbar. The crustal peridotites are formed at ~900 °C and ~7 kbar. Two distinct mineral chemistry of the mantle peridotites indicate existence of two types of mantle peridotites in the area, suggesting the possibility of the influence of melt-rock interaction on the chemical composition of the mantle peridotites in the area.

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Many mafic dykes, with the Early Paleozoic age, have intruded into Zarigan granitoid pluton and its host sedimentary units in the northeast of Bafq city. Petrographycal studies show these dykes are alkaline gabbro to monzogabbro with medium to fine grain intergranular to granular textures. Major minerals include clinopyroxene, amphibole and plagioclase and minor minerals are a few amounts of biotite, olivine, alkali feldspar, and nepheline. Amphiboles are calcic and belong to kaersutite-potasic kaersutite type. Geothermo-barometry calculations, based on amphibole mineral, show the prevailing pressure and temperature of kaersutites crystallization at 6.3-8.2 Kbar and 1040-1140 °C. According to geochemical composition, kaersutites are in the range of alkaline amphiboles, so that they are derived from mantle and are related to intercontinental extensional tectonic environment. Based on these evidences, minerals have been crystallized from the magmas originated from asthenospheric upwelling during Paleo-Tethys early rifting and associated with Posht-e-Badam block basement tension faults function.

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The Dumak ophiolitic mélange in the Baluchistan region is one of the ophiolitic mélanges that contains all of the components of a complete ophiolite, located in the middle parts of the western margin of the Eastern Iranian range. Field studies indicate the presence of a large volume of pillow lavas in different parts of the Dumak mélange. The outcrop of sheeted dikes associated with the Dumak mélange is limited to the Shuru region. These dikes present below the pillow lava and Cretaceous pelagic sediments. Compositionaly, most of pillow lavas and sheeted dikes are basalt. Variations in SiO2 to FeOt/MgO in the pillow lavas and sheeted dikes indicates a tholeiitic trend for their productive magma. The pattern of REE elements and amounts of (La/Sm)_N in these rocks are similar to E-MORB. The study of pillow lavas and sheeted dykes of Dumak ophiolitic mélange shows that the MORB ophiolitic body in Dumak has been gradually and continuously evolved in a supra-subduction zone environment and beginning of intra-oceanic subduction. Considering structural evidence of the region, after adding the Dumak ophiolite to the Lut block, during the continuation of tectonic movements related to orocline bending, a new mélange has formed with the presence of Eocene carbonate blocks.