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Arousan -e- Kaboudan area, located about 115 km northeast of Nain (south of Choupanan), is part of Central Iran (Yazad block). The Eocene volcanic rocks of the area are composed of lavas and pyroclastic rocks. The lavas can be divided into acidic (rhyodacite) and relatively basic-basic (trachyandesite, mugearite and hawaiite) rocks. The textures of these rocks are trachytic, hyaloporphyritic and poikilitic. Plagioclase (albite to andesine), alkali feldspars (sanidine-Or: 65-86%), clinopyroxene (diopside to augite), mica (biotite to phlogopite), amphibole (magnesian hastingsitic hornblende to magnesian hastingsite) and chlorite (brunsvigite) from thaerochs were analyzed by electron microprobe. Geochemical evidence and mineralogical characteristics indicate that the acidic rocks are calc-alkaline and basic rocks have shoshonitic nature. The tectonic environment, in which these rocks were formed, is probably a volcanic arc related to subduction (in the continental margin of central Iranian micro – continental).

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Eocene volcanic rocks of north Anarak area are as scattered as masses. These rocks cross the Anarak schists and Ashin-Zavar ophiolites but had not metamorphosed them. Their outcrops follow the direction of within the area faults. Mineralogicaly, these rocks are limited in composition from Andesi-Basalt and Andesite to Dacite. These rocks have phenocrysts of amphibole and plagioclase in microcrystalline and microlitic matrix. The andesitic and andesibasaltic rocks in the study area have a lot of enclaves that contain many amphiboles.  Type of the amphiboles is Magnesiohastingsite. Similarity of composition of amphiboles and biotites in the volcanic rocks and their enclaves indicate that these volcanic rocks and their enclaves are possibly cogenesis. There are three types of feldspar in these rocks that are andesine-oligoclase, alkali feldspar and bytownite. Bytownite is found only in certain enclaves. Geothermometry studies on phenocrysts of plagioclase and amphibole, that are in equilibrium, indicate that crystallization temperature of these phenocrysts is 835°c to 925°c.

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The Tertiary volcanic rocks in the north and west of Birjand are dacite; andesite, basaltic andesite, trachyandesite and rhyolite.They belong to calc- alkaline from magmatic series. Mineralogcal, petrographcal and geochemical evidence show that they have formed in active continental margins. Most andesites and dacites are appeared as volcanic domes or subvolcanic dykes that injected older units contianing Late Cretaceous ophiolite melange and Late Cretaceous and Paleocene flysch. One of the most important characteristic of these rocks is the presence of enclaves with various compositions. These enclaves are xenolithic types including pelitic hornfels, amphibolitic, tonalitic gneiss and autolithic types with andesite (diorite) or dacite (tonalite) compositions. The xenoliths are fragments of older flysch and ophiolite melange units that fall to ascending magma and at least bearing two type metamorphism.The first type of metamorphism is dynamothermal that can be related to emplacement of ophiolite upon continental crust. Along with this metamorphism, flysch units change to slate, phyllite and micaschist; basic units change to amphibolite and acidic unit change to granitic geniss. Second type is contact metamorphism resulting from temperature of lava that caused these enclaves metamorphosed to medium or high grade.

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Eocene volcanic rocks in NE of Ordib, have a very good exposures near and along the Turkmeni-Ordib fault. These rocks, that are situated in the inner part of the Central Iran and margin of the Yazd block, comprise trachyte, trachy-andesite and basaltic trachy-andesite. Trachy-andesite is the pervasive rock unit. Rock forming minerals of these rocks are chloritized olivine, plagioclase, pyroxene, mica, amphibole, K-feldspar, quartz, ilmenite, magnetite and calcite. The most important mineralogical characteristics of the studied trachy-andesites are wide range of minerals in one rock sample, including two types of clinopyroxene, mica, plagioclase, sanidine, formation of reactionic clinopyroxene and calcite around the quartz, and oscillatory zoning of feldspars and amphiboles. Chemistry of clinopyroxenes and biotites with whole rock geochemical analyses, reveal that these rocks are similar to the continental volcanic arc rocks. Petrography and mineral chemistry demonstrate the magma mixing occurrence in formation of these rocks. 

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The tectonic settings for the Urumieh-Dokhtar volcanic-plutonic belt provided by different reaserchers including active continental margin rift and post collisional settings. Geochemical and tectonic studies indicate that this belt belongs to the active continental margin. Basaltic andesite, andesite, trachy andesite, trachy dacite and dacitic rocks in NE Naragh, of the Urumieh-Dokhtar magmatic arc, Eocene in age, show some affinities to the volcanic island arc, in terms of geochemistry of major and trace elements. In comparison with the island arcs (e.g. Marianna) and active continental margin (e.g. the Andes), these rocks demonstrate intermediate characteristics. Specific tectonic setting and low thickness of the lithosphere of Central Iran during subduction of the Neo-Tethyan oceanic crust, is the main reason that resulted in the NE Naragh volcanic rocks with geochemical similarities to the island arcs.

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Plio-Quaternary potassic to high potassic basaltic rocks are found in northern part of Uromieh-Dokhtar Magmatic Arc in NW Iran. The mineralogical composition of these rocks characterized with phenocrysts of Cpx, phlogopite, leucite and olivine in groundmass of plagioclase, sanidine, Cpx and biotite. Phlogopite phenocrysts display a euhedral platy form with reaction rims. Based on the International Mineralogical Association scheme, the phologopite compositions plot between siderophyllite and eastonite end members and show Fe/(Fe+Mg) ratios<0.33. Based on their TiO₂, MgO, MnO and Al^VI content, they are primary magmatic micas. The micas contain up to 5 wt% BaO and 8.62 wt% TiO₂ and indicate similarity in composition with barian titanian phlogopites from other potassic volcanic rocks in the world. As BaO, Al₂O₃ and TiO₂ increase, the SiO₂, FeO, MgO and K₂O decrease. In this regard, Different substitutions deduced from such variations, which is common to most magmatic barian micas are discussed. In comparison with other potassic and high potassic volcanic rocks, the studied phlogopites display similarity with phlogopites of Italian Roman type volcanic rocks.

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The Pliocene calc-alkaline volcanic rocks are exposed in two areas in southeast and northwest of Isfahan and consist of andesites and dacites. Based on geochemical data and multi- elements pattern, these rocks are medium to high calc-alkaline suite and they show LILE and LREE enriched normalized multi-element patterns, and negative Nb and Ti. Condrite-normalized REE patterns display a steep decrease from LREE to HREE without any Eu anomaly. They have higher SiO₂ and Sr content and Sr/Y and La/Yb ratios and low MgO, Mg#, Y and Yb contents than the normal calc-alkaline volcanic rocks. These volcanic rocks show adakite characteristics. These features are consistent with ratios obtained from orogenic related volcanic rocks. These rocks may have been produced by partial melting of thickened lower continental crust or slab probably transformed to eclogite or garnet -amphibolite. HREE and Y depleted pattern suggest the existence of garnet and amphibole as a residue in the source.

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The Surk ophiolitic mélange is located at the south west of central Iran and along the Naein-Dehshir-Baft ophiolitic belt. In petrological sequence, peridotites are nominated the undermost part of rock unit, and then gabbros and volcanic rocks are at the following ranks respectively. The predominant peridotitet of this ophiolitic mélange is harzburgite. Lherzolite that is the primitive mantle rock consists of olivine, orthopyroxene, clinopyroxene as major minerals and chromian spinel and amphibole (pargasite) as accessory mineral. Petrographical characteristics and mineral chemistry of these peridotites show the lithology evaluation from lherzolite to harzburgite and dunite ultimately. The average SiO₂ and Na₂O content of volcanic rocks in the ophiolitic melange are 70 and 5 weight percent respectively. Petrographical investigations and also classification of these volcanics based on major and trace elements and norm calculations show that these rocks are dacite. REE/chondrite normalized diagrams of these volcanic rocks show horizontal to positively sloping patterns, LREEs are lower than HREEs and their La/Yb ratio is lesser than 1; suggest tholeitic nature of their parent magma. Moreover, Hf/Zr, U and Pb contant of these rocks is higher than the content in the Primitive mantle but the Sr, Ti and Y contant is lower. These differences can be caused by melt migration of subducted oceanic lithosphere on mantle peridotites. By melt/rock reactions clinopyroxene dissolution, incongruent melting of orthopyroxene, formation of replacive olivines and SiO₂ increasing in ascending melt will occur. All these characteristics propose that the Surk ophiolitic mélange is a Harzburgite Ophiolitic Type (HOT) which is formed at the supra-subduction (back-arc basin) zone.

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The Paleogene volcanic rocks of Damash have a considerable outcrops in Alborz structural zone in Guilan Province. These volcanic rocks show a compositional range from olivine basalt, basaltic andesite, pyroxene andesite to andesite. The petrographical and geochemical studies indicate that the fractional crystallization of clinopyroxene and olivine play an important role in lithological varieties of the Damash volcanic rocks. The positive correlation of Hf and Nb v.s Zr, CaO/Al₂O₃ v.s MgO and Al₂O₃/CaO v.s SiO₂ are geochemical signatures of differentiation of clinopyroxene and olivine. The depletion in elements such as Nb, Ta, Zr, Hf, P, Ti and high ratios of Ba/Nb, La/Nb and Rb/Y, and low ratios of Zr/Nb and Y/Nb are geochemical evidences of crustal contamination of these volcanic rocks.The range of the incompatible elements and comparison with the crustal data range show that these volcanic rocks have a clear elemental equilibrium with continental crust and have been contaminated with it.

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The volcanic rocks of Silurian in Khosh yeylagh are located in eastern Alborz structural zone, east of Golestan Province. This volcanic mass is significantly affected by hydrothermal alteration.  Propylitic alteration is the most dominant alteration in this area. Based on field observation and X-Ray diffraction studies, four alteration zones of chlorite, epidote, albite and hematite are recognized in the study area. The results of XPMA show that chlorites present in rocks of this area as peninite, talc- chlorite and diabanite.  These minerals are formed in temperature ranging from 180 to 250 ⁰C. The average of pistasite amount in epidotes is 31.15 which shows that this mineral is magmatic type and is composed of saussuritized plagioclase.  Isocon diagrams show the high mobility of some immobile elements during alteration. In albite, alteration zone with an average isocon slope of 1.06 and 1.09 is the highest while in chlorite, alteration zone with an average isocon slope of 1 and 1.03 is the lowest mass transfer which can be observed during alteration. Also based on these diagrams, SiO₂ and P₂O₅ show depletion and L.O.I and Fe₂O₃ enrichment in all alteration zones. Chemical index of alteration (CIA) indicate that on epidote alteration zone 46.26% to 46.30%, albite alteration zone 47.86% to 51.49%, chlorite alteration zone 46.50% to 47.33% and hematite alteration zone 59.7% to 71.45% have gone under alteration.

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Eocene volcanic rocks in SW of Choupanan are exposed along the Choupanan fault as lava with andesite, trachyandesite to dacite composition and pyroclastic rocks. This area is a part of Central Iran (Yazd block). Andesite is the most predominant rock unit of the area and is composed of feldspars (andesine, oligoclase, and sanidine), amphibole (magnesio hastingsite, magnesian hastingsite, magnesio hornblende, and ferropargasite), mica (biotite and phlogopite), quartz, clinopyroxene (diopside, augite), garnet, opaque minerals (ilmenite, magnetite, titanomagnetite, and hematite), zircon, sphene and apatite. Minerals which are produced by alteration are calcite, chlorite (diabantite), and prehnite. SiO₂ content of these rocks ranges 55.1 to 61.1 wt% and LREEs exhibit an evident enrichment. These volcanic rocks present a transitional affinity (between calc-alkaline and shoshonitic) and geochemically are similar to the volcanic arc rocks. The field, petrography and geochemical studies reveal that the studied andesites are formed by same petrogenetic processes and affected by magma mixing and contamination during crystallization.

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The study area is located at 220 km southwest of Mashhad and 80 km south of Neyshabur and is situated between 58° 40' 30" to 58° 43' 30" E longitudes and 35° 47' 30" to 35° 52' 00" N latitudes. The study area is part of Sabzevar zone. The lithology of the area consists mainly of volcanic rocks with trachyte, trachy andesite, and basaltic trachy andesite composition and in some parts has been subjected to argillic, carbonate and propylitic alteratins. The dominent phenocrysts in these rocks are plagioclase, alkali feldespar, opacitized hornblende and pyroxene. The main texture in these rocks is porphyritic with fine and medium grain matrix. These rocks have calc-alkaline nature and show enrichment in LILE (except for Ba) and depletion of HFSE. The enrichment of LREEs relative to HREEs indicates that the parental magma formed in a subduction zone, which is well manifested by the volcanic rocks of Golcheshmeh area. Tectonic setting diagrams and geochemical properties of volcanic rocks of the study area suggest an active continental margin setting. The low ratios of (La/Yb)_N (5.3 to 9.3) and (Ce/Yb)_N (4.2 to 7) point to low degree partial melting at shallow depths and low garnet in the source magma. The source magma formed by 2 to 5% partial melting of a spinel-garnet lherzolite source (low garnet) accompanied by crustal contamination.

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The Upper Cretaceous volcanic and subvolcanic rocks from the Nageleh Sar, south of Mahmood Abad town in north Iran are dolerite, olivine basalt, trachyandesite and alkali trachyte. These units in an ordered stratification are set in a way that creates a syncline with WNW-ESE axial trend. The chemical data and discrimination diagrams represent medium alkaline bimodal series for the studied samples. REE and incompatible trace elements patterns indicate that they mostly originated from a mantle source similar to OIB with orthopyroxene, clinopyroxene, and olivine in terms of mineralogical content. Variation diagrams and patterns on spider diagrams imply that the parental magma evolved by dominant process of fractional crystallization. The diagrams of major and trace elements ratios clearly show that fractionated phases are often clinopyroxene, amphibole, iron, and titanium oxides. The generating magma of these rocks has been contaminated by crustal materials to some extent and emplaced in an intercontinental rift setting.

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Eocene volcanic and volcano- sedimentary rocks cover a large area in the Gardaneh Ahovan northeast of Semnan. These rocks comprise mainly of basalt, andesite, trachyandesite, rhyolite and dacite with hyalo porphyry, porphyry and glomeroporphyry textures. The basaltic rocks are composed of plagioclase and clinopyroxene phenocrysts. Sericite, kaolinite, calcite and chlorite also form the secondary minerals in these rocks. The size of the clinopyroxenes of these rocks range from fine to medium and their compositions include iron-magnesium-calcium type and plot in the diopside field. Medium-size clinopyroxenes show reverse zoning and compositional changes so the middle zone (btween core and rim) is depleted in Fe, Al and Ti whereas enriched in the Mg, Ca and Si. The determination diagrams of the magmatic series and tectonic environments, based on the chemical composition of clinopyroxenes, suggest that they are crystallized from alkaline to sub-alkaline magma, contianing 2-5% water and high oxygen fugacity. Thermo-barometery calculations also show that these clinopyroxenes were crystallized in pressures of ~1 kbar and temperatures of 1110-1230 °C.

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A sequence of Tertiary basic volcanic rocks is exposed in the east of Qazvin. The volcanic sequence is mainly composed of olivine-basalt to trachyandesite with porphyrictic, microlitic, and glassy textures. Clinopyroxene, plagioclase, amphibole, and iddingsitized olivine are the main phenocrysts. According to EPMA data plagioclase shows labradorite to bytownite composition and clinopyroxene is diopside. Geothermobarometry of clinopyroxene and amphibole represents the temperature of 1100 C to 1200 C and pressure of 1 to 5 kbar during crystallization of these minerals. According to the geochemical data, the sequence shows calc-alkaline affinity which is related to volcanic arc setting. In comparison to chondrite, they are enriched in LILEs and depleted in HFS elements. Also based on geotectonic diagrams, these rocks have been derived from a high potassium calc-alkaline to shoshonitic magma in an active continental margin setting. Ti and Nb negative anomalies and LILE enrichment support an enriched mantle in a supra-subduction zone as a source for magma. According to this study, the magma originated from a low grade 5 to 10 % partial melting from an enriched garnet-spinel lherzolitic mantle source at depth of 50-70 km and finally has risen to the surface via deep fractures and faults within an intra-arc extensional basin in Central Alborz zone during the Middle and Upper Eocene time.

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In the southeast of Nir, south of Yazd Povince, several acidic volcanoes  rocks are exposed and form the youngest volcanic rocks in this region with dacite-rhyodacite composition. These rocks are composed of plagioclase, hornblende, biotite and quartz phenocrysts with trachytic and hyallomicrolithic porphyry texture. Based on geochemical data, the magmatic affinity of these rocks is calc-alkaline with enrichment of LILE and depletion of HFSE. These characteristics with steep decrease pattern of rare earth elements and negative anomaly of HFSE, such as Nb, Ti and P, indicate the formation of magma in active continental margin. Higher levels of SiO₂, Sr, Sr/Y, and La/Yb with low levels of MgO, Yb, and Y, indicate high silica adakite affinity. It seems that the formation of parental magma of these rocks is consequence of the melting of garnet amphibolite or eclogite rocks of subducted metamorphosed Neotethys oceanic lithosphere in the Central Iran- Arabian plate collision zone during the Neogene time.

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Around The Karik village, east of Meiduk mine, Eocene volcanic rocks (andesitic basalt, andesite, dacite and rhyolite) and pyroclastic rocks (agglomerate and tuff) are exposed. These rocks are cut by several andesitic dikes. The major textures in the volcanic rocks are porphyritic and flow textures. The minerals such as plagioclase, alkali feldspar, quartz, pyroxene, amphibole, biotite and opaque are present as phenocrysts and fine grains. Sometimes, feldspar crystals (mainly plagioclase) are found as oriented microlites. In some cases, within the plagioclase phynocrysts disequilibrium textures such as sieve texture, corrosion and zoning are observed. Quartz crystals are corroded. Amphibole and biotite crystals are changed into Fe-Ti oxides on their rims. These textures are probably attributed to magma mixing, water vapor changes and decompression due to rapid ascent of magma. The Karik volcanic rocks are calc-alkaline and mainly metaluminous in nature. Primary mantle and chondrite normalized multielement diagrams for the study rocks are spiked and they have several peaks and troughs. In the diagrams, the depletion of the high field strength elements such as Nb, Ta, Ti and P is obvious which is characteristic of the subduction magmatism. The sharp positive anomaly of Pb might be attributed to crustal contamination. The chondrite normalized RRE pattern of the study rocks is relatively smooth with enrichment of LREEs relative to HREEs that is due to the high abundance of LREEs in the source or crustal contamination. According to the petrological and geochemical evidence, the Karik volcanic rocks are formed in an active continental margin setting due to the subduction of Neothetys oceanic lithosphere beneath the Central Iran micro–continent.

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The Kuh-e-Kalut-e-Ghandehari is located about 40 Km northwest of the Anarak (northeast of Isfahan). This area is a part of the Central Iran that is situated in west of the Yazd block; near to the Ashin ophiolite and drastic directional changes of the Great Kavir Fault. In the northwest of Anarak, the Ashin ophiolite is covered by the Cretaceous limestones, and crossed by the Eocene volcanic rocks. The Upper Eocene gabbro-diorite stock cross cuts the Eocene volcanic rocks. Andesites are the predominant unit of the Eocene volcanic rocks. They are grey to dark- grey in colour and have amphibolite xenolith. The main textures of these volcanic rocks are porphyritic, poikilitic, trachytic, sieved texture and glomeroporphyritic. The main phenocrystic minerals of andesites are plagioclase, amphibole and clinopyroxene situated in a matrix of the same minerals and sanidine, magnetite and apatite. Secondary minerals are formed as a result of the hydrothermal alteration and comprise zeolite, chlorite, epidot, sericite, kaolinite and calcite. Mineral chemistry indicates that plagioclases are andesine to labradorite (An= 30-52%), K-feldspars are sanidine (Or= 68-71%), amphiboles are calcic with pargasite composition (Mg#= 0.58-0.71), and clinopyroxenes are diopside (Mg#= 0.91-0.93) in composition. Whole rocks chemical analyses indicate that these andesite and trachy-andesite rocks have calc-alkaline property. The chondrite and primitive mantle-normalized REE and multi-element patterns show LREE and LILE enrichment and HFSE (Ti, Ta, Nb) depletion, which are characteristics of the subduction-related magmas. These data indicate that the primary magmas were genarated by medium degrees of partial melting of the lithospheric mantle spinel lherzolite. Subduction of the Central-East-Iranian Microcontinent (CEIM)-confining oceanic crusts (Naein and Ashin oceanic crusts) are possibly the reason of this volcanism. Geochemistry of these volcanic rocks are similar to the arc-related ones. 

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The Late Cretaceous basaltic magmatism in northern part of the Urumieh-Dokhtar Magmatic Arc (UDMA) includes subalkaline (transitional) basalts and basaltic andesites; which are formed in associated with various pyroclastic and sedimentary rocks. These rocks are charactrized by similar geochemical patterns including enrichment in light rare earth elements (LREEs), large ion lithophile elements (LILEs),  and depletion in high field strength elements (HFSEs; e.g., Nb, Ta, Ti). These geochemical evidence indicates magmatism related to volcanic arcs and subduction setting. In addition, the nearly flat heavy rare earth element (HREE) patterns are similar to that of the oceanic island basalt (OIB). These mafic magmatic rocks are characterized by a mantle dominated composition, evidenced by (⁸⁷Sr/⁸⁶Sr)i ratios of 0.70404–0.70414, and uniform positiveεNd(t) values of 1.00–4.14. The trace-element and isotopic modelling indicate that the studied basaltic rocks resulted from partial melting of metasomatized lithospheric mantle wedge at the garnet–spinel stability depth in transitional zone. The magmatism in the study area more likely occurred in an incipient volcanic arc setting due to asthenospheric upwelling in response to lithospheric extension during slab retreat 80 million years ago.

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The Hossein Abad area is located 120 km southeast of Zanjan. The volcanic rocks in this area belong to Eocene and younger a ges. Volcanic rocks include dacitic, trachyandesite and andesitic lavas, as well as tuff. Volcanic rocks have quartz, alkali feldspar, abundant plagioclase, pyroxene and amphibole. The alkali feldspar is Sanidine and plagioclases are oligoclase and andesine. The Porphyritic, microlithic porphyritic, glomeroporphyritic and poikilitic textures are predominant in these rocks. Examining the mineral chemistry of rocks in the study area shows that the clinopyroxenes are diopside and augite. Amphiboles in these rocks are magmatic and calcic with the chemical composition of pargasite. Based on magmatic diagrams, rocks in studied area are alkaline. According to the thermobarometric diagrams, these rocks have formed at temperature and pressure ranges of 700-750℃ and 5-6.5 kbar respectively. These values correspond to the depth of middle-lower crust. The rocks are formed in the active continental margin.