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Balazard prospecting area is located in eastern Iran, about 120 km south-west of Nehbandan in the Central part of Lut Block. This area consists of exposed Eocene volcanic rocks, intruded by several diorite and monzodiorite dykes and stocks. These intrusive rocks display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase, clinopyroxene and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, quartz, and opaque minerals. The assessment of geochemical properties of the major elements showed that these granitoids are metaluminous and of high-K calc-alkaline variety. The patterns of trace elements are identical, denoting enrichments in the light REE (LREE) to heavy REE (HREE). Moreover, LILE enrichment relative to HFSE and Nb, Ti, and P show negative anomalies. The Eu/Eu* ratios range from 0.96 to 0.76, which means that the plagioclase is a slag remnant in the origin of magma. The (87Sr/86Sr)i values of the assessed intrusive rocks range from 0.706 to 0.707, assuming an Oligocene age, while the εNdi values are between -1.9 to -3.2. These results manifest that the magmas were contaminated by continental crust. The contamination has probably occurred over the ascent of magma to crustal levels, and geochemical data verifies the preposition that the investigated intrusions were intruded in a volcanic belt resting on a subduction zone. Early magmas were created through the melting of mantle wedge peridotite, occasioning magma differentiation through crystal fractionation and crust contamination as they ascended to crustal levels. Introduction Balazard prospecting area is located 120 km of the south-west of Nehbandan in South Khorasan Province, Iran. The area is part of the volcanic-plutonic belt known as Lut Block, which owns an elongated shape stretched north-southwardly. Nehbandan Fault forms the eastern boundary of Lut Block. This is while it has been bordered by the Great Kavir Fault in the north, and by Nayband Fault in the west. The southern part of the block is likely defined by South Jazmourian Fault. Karimpour et al. (2012) argue that ~65% of the rocks cropped out in Lut Block are volcanic and plutonic. The magmatic activity of Lut Block initiated over the Middle Jurassic, particularly between 165-162 million years ago, which was associated with the intrusion of Shah-Kuh batholith (Esmaeily et al., 2005). This activity reached its highest level over the Tertiary period, particularly over the Middle Eocene (Arjmandzadeh & Santos, 2014). Over half of Lut Block is overlain by volcanic and subvolcanic rocks of Tertiary. These rocks show a thickness of up to 2000 m. They have been developed as a result of subduction before the collision between the Arabian and Asian plates (Berberian & King, 1981). There is a perceptible potential for a variety of mineralization in Eastern Iran and particularly in Lut Block, which is due to its past tectonism as a subduction zone that led to extensive magmatic activity. The Middle Eocene to the Early Oligocene (30-39 million years ago) is perceptible, particularly, in respect of magmatism and mineralization (Karimpour et al., 2012). Karimpour et al. (2012) believe that a great deal of the magmatism and mineralization events in eastern Iran have occurred over the Tertiary. However, mineralization associated with Cretaceous magmatism has also been identified, such as Sn-Cu mineralization observed in Cretaceous monzonitic rocks in Kalateh Ahani (Karimpour et al., 2012). Here we present new geochemical data (elemental and isotopic) from shallow intrusive rocks, with the aim of providing a more detailed understanding of the petrogenetic processes and geodynamic evolution of Lut Block. Material and methods A total of six samples from unaltered intrusive rocks at Balazard prospecting area and representing the main lithologies were grabbed to chemically analyze major and trace elements through petrographic assessment. Major and trace elements were determined using fused disks and a Philips PW 1410 spectrometer through wavelength-dispersive X-ray fluorescence (XRF) spectrometry. The chemical analysis was undertaken at Amethyst Laboratory in Mashhad, Iran. Inductively Coupled Plasma-mass Spectrometry (ICP-MS) was applied to analyze four of the samples for trace elements at Acme Laboratories in Vancouver (Canada). The samples were tested by a lithium metaborate/tetraborate fusion and total digestion with nitric acid prior to analysis. Four whole-rock samples of Balazard granitoid rocks were analyzed for their Sr and Nd isotopic compositions at the University of Aveiro's Laboratory of Isotope Geology in Portugal. The ground samples were treated with a HF/HNO3 solution in Teflon Parr acid digestion bombs, which were heated at 200°C for three days. The ultimate solution was evaporated and the samples were then dissolved in HCl (6.2 N) in acid digestion bombs and dried again. The elements were purified before being analyzed by means of a two-stage conventional ion chromatography technique: a) Sr and REE elements were separated in an ion exchange column by AG8 50W Bio-Rad cation exchange resin; b) Nd was purified from other lanthanides by means of columns with Ln Resin (ElChrom Technologies) cation exchange resin. All reagents that were applied to prepare the samples were sub-boiling distilled, and the water was produced using a Milli-Q Element (Millipore) apparatus. Sr was loaded onto a single Ta filament with H3PO4, while Nd was loaded onto a Ta outer side filament with HCl in a triple filament arrangement. The 87Sr/86Sr and 143Nd/144Nd isotopic ratios were determined using a Multi-Collector Thermal Ionization Mass Spectrometer (TIMS) VG Sector 54, with data acquired in dynamic mode and peak measurements at 1-2 V for 88Sr and 0.5-1.0 V for 144Nd. The Sr and Nd isotopic ratios were corrected for mass fractionation relative to 88Sr/86Sr = 0.1194 and 146Nd/144Nd = 0.7219. While the investigation was in progress, the SRM-987 standard yielded an average 87Sr/86Sr value of 0.710266 ± 14 (conf. lim 95%, N = 13) and a 143Nd/144Nd value of 0.5121019 ± 75 (conf. lim 95%, N = 12) in comparison to the JNdi-1 standard. Result and discussion Balazard intrusive rocks consist of diorite, quartz diorite, and quartz monzodiorite, and exhibit characteristics typical of high-K calc-alkaline rocks from a volcanic arc setting. The primitive mantle-normalized trace element spider diagrams display significant enrichment in LILE, including Rb, Sr, Ba, Zr, Cs, and Th, and depletion in some HFSE, such as P, Nb, and Y. Chondrite-normalized plots exhibit LREE enrichment and a significant La/Yb fractionation. Balazard granitoid rocks have (87Sr/86Sr)i values that vary between 0.7064 and 0.7066. In terms of isotopic compositions, Balazard granitoid rocks have εNdi between -1.9 and -3.2. The geochemical data are commensurate with the settlement of the investigated intrusions in a magmatic belt above a subduction zone suggesting contamination through being exposed to the continental crust during magma ascent to crustal levels. Balazard granitoid rocks display a range of (87Sr/86Sr)i values between 0.7064 and 0.7066. Additionally, the isotopic compositions of the rocks show εNdi values ranging from -1.9 to -3.2. These geochemical characteristics suggest that the investigated intrusions were emplaced in a magmatic belt above a subduction zone and were subsequently contaminated during magma ascent to continental crust.

Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization. These rocks are divided into syenite porphyry and granodiorite porphyry based on their geochemical characteristics. They are I type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Comparing the mineralization potential of the subvolcanic rocks of this area based on the use of the graph of SiO2 against K2O, MgO, Na2O+K2O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid. The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios also confirms the presence of meteoric water in the formation of the skarn zone. The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu* had acidic and oxidant conditions and high temperature, and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered the pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone. Introduction Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization (Amini and Khannazer, 2000(. This study found that at least four subvolcanic intrusion rocks are present in this region: Granodiorite porphyry, biotite syenite porphyry, quartz syenite porphyry, and quartz diorite to monzodiorite porphyry. These are divided into syenite porphyry and granodiorite porphyry based on the geochemical characteristics. Material and methods About 90 samples were collected for laboratory investigations of petrogenesis studies. Moreover, 25 samples were selected to be analyzed using the XRF and ICP-MS methods. Laboratory studies were carried out in Ferdowsi University of Mashhad and samples were analyzed in Acme and Zarazma laboratories. Results Subvolcanic rocks are I-type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Moreover, some samples have been placed at the border of syn-collision due to high Rb, which is the result of high potassium. Enrichment of LILE elements such as K, Cs, Ba, Rb and incompatible elements that behave similar to them like Th compared to HFSE elements is observed in all samples compared to the primitive mantle. Enrichment of LILE relative to HFSE indicates magma related to subduction zones. The Sr element shows opposite behavior compared to the LILE elements. This issue can be justified by the high amount of CaO in magnetite ore (from 0.3% to more than 3.5%), because the two elements are similar in terms of chemical properties. Comparing the mineralization potential of the subvolcanic rocks of this area using the graph of SiO2 against K2O, MgO, Na2O+K2O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn Meinert, 1995(. For igneous rocks, it was confirmed that the amount of Rb increases during the fractionation and crystallization processes (Meinert, 1995 (. Granitoids with potential for iron skarn have lower Rb (39 ppm). This amount is 103 ppm for copper skarn and 69 ppm for gold skarn. The amount of Rb content for all granitoids of Shotorsang area is 80 ppm. Considering the connection of these granitoids with iron skarn in this area, the high Rb content can be justified by crustal contamination of these rocks (Martin-Izard et al., 2000). Moreover, it can be mixing of a mafic magma with a felsic magma at a shallow depth. The amounts of V and Ni in iron skarn deposits are the highest; that is, 152 and 35 ppm, respectively. Ni and V for Shotorsang syenite porphyry group are 16 and 82, respectively and for Shotorsang granodiorite porphyry are 20 and 48, respectively. These values are lower than the global average of iron skarn. In general, the high amount of Rb and the low amount of Ni and V confirm the hypothesis that the magma has been fractionated and contaminated with crust. If the amount of Rb as well as the amount of Ni and V increase, the mixing of a magma derived from the mantle or a mafic magma with a highly fractionated magma would seem to be a more acceptable hypothesis (Meinert, 1995). Therefore, according to what was stated about the tectonic setting and the cases mentioned above, as well as the process of changes in the spider diagram of the rare earth elements of the studied area, it can be expected that the fluid forming the iron skarn of this region has undergone magmatic fractionation and been contaminated with crust. (La/Yb)n, (La/Sm)n and (Gd/Yb)n ratios were used to evaluate the separation degree between REEs. (La/Yb)n determines the degree of separation between LREE and HREE (Aubert et al., 2001; Yusoff et al., 2013), while the other two ratios are used to determine the degree of separation between LREE and MREE, and between MREE and HREE, respectively (Yusoff et al., 2013). These ratios vary for (La/Yb)n from 1.12 to 1.69, for (La/Sm)n from 6.7 to 40.72, and for (Gd/Yb)n from 0.89 to 4.22. As it is known, during the skarnization process, the highest degree of separation has occurred between LREE and HREE (up to about 70 times) and the lowest degree of separation has also occurred between MREE and HREE. The highest value of these ratios is in the mineralization zone, which indicates that the highest amount of separation of REE elements has taken place in this zone. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid. Discussion The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios confirms the presence of meteoric water in the formation of the skarn zone (Kato, 1999). The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu*, had acidic and oxidant conditions and high temperature and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered in pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions (Meinert, 1995) with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone. Acknowledgements The authors are grateful for the cooperation of the employees of the Shotorsang iron ore mine, especially Mr. Qotbi.

Balazard prospecting area is located in eastern Iran, about 120 km southwest of Nehbandan in the Central part of Lut Block. This area consists of exposed Eocene volcanic rocks, intruded by several diorite and monzodiorite dykes and stocks. These intrusive rocks display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase, clinopyroxene and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, quartz, and opaque minerals. The assessment of geochemical properties of the major elements showed that these granitoids are metaluminous and of high-K calc-alkaline variety. The patterns of trace elements are identical, denoting enrichments in the light REE (LREE) to heavy REE (HREE). Moreover, LILE enrichment relative to HFSE and Nb, Ti, and P show negative anomalies. The Eu/Eu* ratios range from 0.96 to 0.76, which means that the plagioclase is a slag remnant in the origin of magma. The (87Sr/86Sr)i values of the assessed intrusive rocks range from 0.706 to 0.707, assuming an Oligocene age, while the εNdi values are between - 1.9 to -3.2. These results manifest that the magmas were contaminated by continental crust. The contamination has probably occurred over the ascent of magma to crustal levels, and geochemical data verifies the preposition that the investigated intrusions were intruded in a volcanic belt resting on a subduction zone. Early magmas were created through the melting of mantle wedge peridotite, occasioning magma differentiation through crystal fractionation and crust contamination as they ascended to crustal levels. [ABSTRACT FROM AUTHOR]

Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization. These rocks are divided into syenite porphyry and granodiorite porphyry based on their geochemical characteristics. They are I type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Comparing the mineralization potential of the subvolcanic rocks of this area based on the use of the graph of SiO2 against K2O, MgO, Na2O+K2O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid. The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios also confirms the presence of meteoric water in the formation of the skarn zone. The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu* had acidic and oxidant conditions and high temperature, and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered the pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone. [ABSTRACT FROM AUTHOR]

Introduction The magmatic evolution of the Urumieh-Dokhtar arc is related to the Neo-Tethys subduction and the continental collision between the Arabian and Eurasian plates, which has led to the creation of diverse and different magmatism along different parts of this belt (Shahabpour, 2005; Agard et al., 2011; Richards, 2015; Karimpour et al., 2021). Volcanic rocks, with various lithological compositions located in the central part of the Urumieh-Dokhtar belt, are part of the extensive Eocene activity, Knowing the nature of basicintermediate volcanic rocks northwest of Nain requires more detailed investigations. For this purpose, the exploration areas of Chakad, Safafoulad, and Mehrando, located northwest of Nain, were selected for further investigations. The main goal of the present paper is to understand the origin and the tectonic of the volcanic rocks of this part of the Urumieh-Dokhtar magmatic belt using their petrography and geochemical characteristics. [ABSTRACT FROM AUTHOR]

The Lakeh-Siah region is situated in the Central Iran Zone (CIZ), 40 km northeast of Bafq city in the Yazd province. The rocks of the study area belonging to the lower Cambrian; including rhyolite, andesite and pyroclastic surge with porphyry to glomeroporphyric textures. The intrusive igneous rocks occur as stock and dyke and have monzonitic and dioritic composition with intergranular and granular textures. Based on geochemical studies, the rocks under study are calc-alkaline, metaluminous to peraluminous nature. The study apatite shows LREE- enrichment relative to HREE, this is a remarkable feature of the Kiruna- type iron deposits. Also, the enrichment of LILE (such as Rb, Ba, La, U, K and Th) and depletion of HFSE (such as Nb, Ta, Zr and Y) in the host rock, is known as a characteristic of the magmatism in the subduction zones. Based on the concentration of rare and trace elements, the volcanic and to the magmatic arc setting. The overall evidences demonstrate that the primary intrusive rocks belong magma of the rocks have been generated from partial melting of oceanic crust, during the closure of the Proto-Tethys Ocean. Iron oxide- phosphorus magma derived from magmatic differentiation of primary mafic magmas and ascended to higher levels through faults and fractures. Oxygen and hydrogen isotopic study of quartz along with magnetite ore in this deposit and calculation the fluid equilibrium with it shows that the ore- bearing fluid has a magmatic origin.

The rocks of the Robaie area located in the Torud-Chahshirin belt and south of Damghan, includes the Eocene andesite and trachyandesite rocks in which subvolcanic igneous rocks as stoke and dyke with diorite, monzonite and monzodiorite porphyry composition are intruded. The main textures of volcanic rocks are porphyritic characterized by plagioclase, hornblende and biotite phenocrysts as well as apatite and zircon as minor minerals. The rocks studied are mainly of shoshonitic nature and only one sample is considered as high-K calc-alkaline. Several line of evidence including LILE and LREE enrichment, HREE and HFSE depletion, high Th/Yb with negative anomalies of Ti, Nb and the position of the samples on the tectonic discrimination diagrams indicate that the volcanic rocks in discussion were emplaced into the subduction zone related to an active continental margin setting. The initial 87Sr/86Sr, 143Nd/144Nd ratios and (εNd)i value of andesite are 0.704445, 0.512691 and 2.29, respectively. All of these evidences confirm that the studied volcanic rocks were generated from partial melting of the mantle wedge above the subduction zone. Petrographic observations along with geochemistry of rare earth and trace elements suggest that the calc-alkaline affinity of the rocks studied and their parent magma from a subducted-related environment as well as crustal assimilation and fractional crystallization

The magmatic activities in north Qazvin, as a part of the Western Alborz zone, contain a sequences of volcanic lavas associated with pyroclastic rocks with Eocene age. According to petrographical investigations, volcanic lavas are basalt, basaltic andesite, pyroxene andesite, trachy-andesite, dacite and rhyolite. The texture of these rocks is more porphyritic with fine-grained groundmass including plagioclase, clinopyroxene, quartz, alkali feldspar, amphibole and biotite minerals. On the basis of geochemical features, all samples show high-K calc-alkaline to shoshonitic affinities. Also, these rocks are enriched in LREE and LILE, and depleted in HFSE characteristic of calc-alkaline series in subduction-related environment. Petrogenesis indicate that the mafic lavas have been derived from 5 to 10 % partial melting of enriched garnet lherzolite mantle source. Qazvin volcanic lavas have moderate Nb/Yb and Ta/Yb ratios indicative of an enriched mantle source compositions (e.g., E-MORB). Furthermore, these lavas have high values of Th, U and Pb consistent with slab-related sediments and/or crustal contamination in their mantle source.

The rocks of the Robaie area located in the Torud-Chahshirin belt and south of Damghan, includes the Eocene andesite and trachyandesite rocks in which subvolcanic igneous rocks as stoke and dyke with diorite, monzonite and monzodiorite porphyry composition are intruded. The main textures of volcanic rocks are porphyritic characterized by plagioclase, hornblende and biotite phenocrysts as well as apatite and zircon as minor minerals. The rocks studied are mainly of shoshonitic nature and only one sample is considered as high-K calc-alkaline. Several line of evidence including LILE and LREE enrichment, HREE and HFSE depletion, high Th/Yb with negative anomalies of Ti, Nb and the position of the samples on the tectonic discrimination diagrams indicate that the volcanic rocks in discussion were emplaced into the subduction zone related to an active continental margin setting. The initial 87Sr/86Sr, 143Nd/144Nd ratios and (εNd)i value of andesite are 0.704445, 0.512691 and 2.29, respectively. All of these evidences confirm that the studied volcanic rocks were generated from partial melting of the mantle wedge above the subduction zone. Petrographic observations along with geochemistry of rare earth and trace elements suggest that the calc-alkaline affinity of the rocks studied and their parent magma from a subducted-related environment as well as crustal assimilation and fractional crystallization. [ABSTRACT FROM AUTHOR]

The Sadrabad iron deposit is located 28 km west of Sadrabad village (west of Yazd) at the Urumieh-Dokhtar magmatic arc. The Upper Triassic-lower Jurassic sedimentary rocks (dolomitic limestone, sandstone, shale and marl), the Cenozoic granite to dioritic intrusive bodies and the Quaternary unconsolidated deposits outcrop in the study area. The intrusive bodies are of I-type calc-alkaline series formed in syn-collision to post collision settings of continental margin subduction zone. The later quartz monzodiorite intrusions played a significant role in iron mineralization. The location of mineralization controlled by NW-SE and NE-SW fault systems. Olivine, clinopyroxene, garnet, tremolite-actinolite, epidote, serpentine, talc, phlogopite, calcite, dolomite, brucite and hydromagnesite are the main skarn minerals. The ore bodies consist mainly of magnetite with minor pyrite, chalcopyrite and pyrhotite which occur as massive, vein-veinlets, brecciate and disseminated magnetite. Skarn formation occurs in two prograde and retrograde stages. Olivine, clinopyroxene and garnet formed in prograde and the remaining minerals in retrograde stages. The temperature and salinity of fluid inclusions in quartz veins associated with serpentine (in retrograde stage) range from 217 to 280˚c and 8 to 16 (wt %) NaCl respectively, indicating the mixing of magmatic and meteoric water in retrograde stage. The Mg-bearing silicates such as serpentine, phlogopite, diopside and talc in the Sadrabad skarn, point to the mineralization of magnesian type.

Khur area is located in east of Iran and northwest of Birjand. The area comprises outcrops of Eocene to Oligocene volcanics with basaltic andesite to rhyolite composition, which were intruded by subvolcanic and intrusive bodies of granodiorite to gabbro. In the present work, petrogenesis of volcanic units in Cheshmeh Khuri and Shekasteh Sabz areas was studied, which are located in Khur area and these volcanics have most widespread in them. Rhyolite, dacite, andesite, trachyandesite and basaltic andesite units in Cheshmeh Khuri and trachyandesite unit in Shekasteh Sabz were identified. The main textures of these units are porphyritic, hialoporphyritic and microlitic and plagioclase, pyroxene, K-feldspar, hornblende, biotite and quartz are the main minerals. Volcanic units of Cheshmeh Khuri have characteristic of high-K Calc-alkaline. Enrichment of LREE relative to HREE and LILE to HFSE are important evidences that magma was formed in a magmatic belt of a subduction zone. Based on the initial 87Sr/86Sr of andesite and dacite, their magma has originated from partial melting of an enriched mantle and contaminated with the crust through its differentiation. Trachyandesites of Shekaste Sabz have characteristic of shoshonitic nature. These units are characterized by high FeOt/FeOt+MgO, K2O/Na2O and Zr>360 ppm, Y>39 ppm, and Ce> 100 ppm. Also, they are enrichment in REE particularly in LREE, depletion of Eu, strong enrichment in HFSE, and depletion in Ba and Sr. Therefore, trachyandesites of Shekaste Sabz belong to post collision volcanics.

Introduction Hornblende-bearing gabbroic rocks are quite common in subduction-related magmatic suites and considered to represent magmatic differentiation process in arc magmas (Heliker, 1995; Hickey-Vargas et al., 1995; Mandal and Ray, 2012). The presence of hornblende as an important mineral phase in gabbroic rocks of subduction zone has been considered either as an early crystallizing mineral from water-bearing mafic magmas (Beard and Borgia 1989; Mandal and Ray, 2012) or as a product of reaction of early crystallized minerals (olivine, pyroxene and plagioclase) and water-rich evolved melt/aqueous fluid (Costa et al., 2002; Mandal and Ray, 2012). The careful study of petrology and geochemistry of hornblende-bearing gabbroic rocks from Chahak area, of Neoproterozoic age, can provide important information about their petrogenesis. Because of the special characteristics of Chahak hornblende gabbros according to their age and their situation in the main structural units of Iran, their study can present critical keys for the knowledge of geological history of Iran specially central Iran zone. Material and Methods This study carried out in two parts including field and laboratory works. Sampling and structural studies were carried out during field work. Geological map for the study area was also prepared. 65 thin and polished thin sections for petrographical purpose were studied. Major oxides, rare earth elements and trace elements were analyzed for 4 samples (92P-1, 92P-3, B1and B6) from hornblende gabbros on the basis of 4AB1 method using ICP-MS of ACME Laboratory from Canada. In addition, major oxides of three hornblende gabbro samples (89P-62, 89P-59 and 89P-46) were used from Partovifar (Partovifar, 2012). Results and discussion Fariman metamorphic terrains, of Proterozoic age, consist of metamorphosed sedimentary and igneous (plutonic and volcanic) rocks. Hornblende gabbros of the study area include plagioclase, hornblende, biotite pyroxene and olivine as major minerals and apatite, ilmenite and magnetite as minor minerals. In many examples, hornblende and biotite can be seen as corona textures around plagioclase, pyroxene and olivine, while plagioclase, pyroxene and olivine show obviously corrosion features. This can be considered to be formed by the reaction of early formed crystals with aqueous fluid/evolved melt. In some cases, amphiboles show rhythmic overgrowths. The rhythmic amphibole overgrowths represent deep-seated crystallization in a volatile-rich magma under conditions of high but varying gas pressure. In the study area, the most dominant texture of the hornblende gabbros is hypidiomorphic granular, but intergranular and porphyric textures are common too. Based on geochemical data from major and minor elements, studied rocks belong to tholeiite series with meta–aluminous nature. The geochemical behavior of main elements of the studied rocks reveals the normal trend of differentiation in their magma. Chondrite-normalized REE diagram of hornblende gabbros indicates an obvious enrichment of LREE in compare with HREE. MORB-normalized spider diagrams indicate variable enrichment in LILE and depletion in high field strength elements (HFSE). Primitive mantle-normalized spider diagram show negative anomaly for Nb and Zr. Gabbros from southeast of Fariman have an island arc tholeiite nature and based on trace element diagrams, they formed as a result of 3 to 10% partial melting of a garnet lherzolite source. The mineralogy, texture and geochemistry of the studied rocks show striking similarities with gabbroic rocks of subduction zone developed in supra subduction zone of arc-marginal basin setting. Acknowledgments The Research Foundation of Ferdowsi University of Mashhad, Iran, supported this study (Project 28035.2). I thank the university authorities for funding. Reference Beard, J.S., and Borgia, A., 1989. Temporal variation of mineralogy and petrology in cognate gabbroic enclaves at Arenal volcano, Costa Rica. Contributions to Mineralogy and Petrology, 103(1): 110–122. Costa, F., Dungan, M.A., and Singer, B.S., 2002. Hornblende- and phlogopite-bearing gabbroic xenoliths from Volc´an San Pedro (36◦S), Chilean Andes: Evidence for melt and fluid migration and reactions in subduction-related plutons. Journal of Petrology, 43(3): 219–241. Heliker, C., 1995. Inclusions in Mount St. Helens dacite erupted from 1980 through 1983. Journal of Volcanology and Geothermal Research, 66(1-4): 115–135. Hickey-Vargas, R., Abdollahi, M.J., Parada, M.A., Lopez-Escobar, L. and Frey, F.A., 1995. Crustal xenoliths from Calbuco volcano, Andean southern volcanic zone: Implications for crustal composition and magma-crust interaction. Contributions to Mineralogy and Petrology, 119(4): 331–344. Mandal, A., Ray, A., Debnath, M. and Paul, S.B., 2012. Geochemistry of hornblende gabbro and associated dolerite dyke of Paharpur, Puruliya, West Bengal: Implication for petrogenetic process and tectonic setting. Journal of Earth System Science, 121(3): 793–812. Partovifar, F., 2012. Petrology and geochemistry studies of granitic rocks from Chahak village, Kariz-Now area, southeast of Fariman, Iran. Unpublished M.Sc. thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 145 pp. (in Persian)

The Sadrabad iron deposit is located 28 km west of Sadrabad village (west of Yazd) at the Urumieh-Dokhtar magmatic arc. The Upper Triassic-lower Jurassic sedimentary rocks (dolomitic limestone, sandstone, shale and marl), the Cenozoic granite to dioritic intrusive bodies and the Quaternary unconsolidated deposits outcrop in the study area. The intrusive bodies are of I-type calc-alkaline series formed in syn-collision to post collision settings of continental margin subduction zone. The later quartz monzodiorite intrusions played a significant role in iron mineralization. The location of mineralization controlled by NW-SE and NE-SW fault systems. Olivine, clinopyroxene, garnet, tremolite-actinolite, epidote, serpentine, talc, phlogopite, calcite, dolomite, brucite and hydromagnesite are the main skarn minerals. The ore bodies consist mainly of magnetite with minor pyrite, chalcopyrite and pyrhotite which occur as massive, vein-veinlets, brecciate and disseminated magnetite. Skarn formation occurs in two prograde and retrograde stages. Olivine, clinopyroxene and garnet formed in prograde and the remaining minerals in retrograde stages. The temperature and salinity of fluid inclusions in quartz veins associated with serpentine (in retrograde stage) range from 217 to 280˚c and 8 to 16 (wt %) NaCl respectively, indicating the mixing of magmatic and meteoric water in retrograde stage. The Mg-bearing silicates such as serpentine, phlogopite, diopside and talc in the Sadrabad skarn, point to the mineralization of magnesian type. [ABSTRACT FROM AUTHOR]

Khur area is located in east of Iran and northwest of Birjand. The area comprises outcrops of Eocene to Oligocene volcanics with basaltic andesite to rhyolite composition, which were intruded by subvolcanic and intrusive bodies of granodiorite to gabbro. In the present work, petrogenesis of volcanic units in Cheshmeh Khuri and Shekasteh Sabz areas was studied, which are located in Khur area and these volcanics have most widespread in them. Rhyolite, dacite, andesite, trachyandesite and basaltic andesite units in Cheshmeh Khuri and trachyandesite unit in Shekasteh Sabz were identified. The main textures of these units are porphyritic, hialoporphyritic and microlitic and plagioclase, pyroxene, K-feldspar, hornblende, biotite and quartz are the main minerals. Volcanic units of Cheshmeh Khuri have characteristic of high-K Calc-alkaline. Enrichment of LREE relative to HREE and LILE to HFSE are important evidences that magma was formed in a magmatic belt of a subduction zone. Based on the initial 87Sr/86Sr of andesite and dacite, their magma has originated from partial melting of an enriched mantle and contaminated with the crust through its differentiation. Trachyandesites of Shekaste Sabz have characteristic of shoshonitic nature. These units are characterized by high FeOt/FeOt+MgO, K2O/Na2O and Zr>360 ppm, Y>39 ppm, and Ce> 100 ppm. Also, they are enrichment in REE particularly in LREE, depletion of Eu, strong enrichment in HFSE, and depletion in Ba and Sr. Therefore, trachyandesites of Shekaste Sabz belong to post collision volcanics. [ABSTRACT FROM AUTHOR]

Volcanic and volcaniclastic rocks with Cenozoic age are widespread at Bozghush Mountain, south of Sarab, northwest of Iran. The composition of the studied rocks is trachybasalts, trachyandesites and megaporphyritic andesites with probable middle Eocene age(?). The main texture of these rocks is porphyritic. Plagioclase, clino-pyroxene and sanidine are the main minerals in these volcanic rocks. All volcanic sequences show similar trace element and REE patterns, with troughs in Nb, Zr, strong enrichments in Rb, Ba, Th, La and depletions in Ti, Yb, Y, relative to N-MORB, indicating a subduction-metasomatized lithospheric mantle as their melt source. On the basis of Sm/La versus Th/La diagram and Ba/Nb (>49) and Ba/Ta (>900) ratios, the influence of slab-derived sediments and fluids on the genesis of these rocks is obvious. It seems that the lithospheric mantle source beneath the Bozghush Mountain was metasomatized by subducted NeoTethys oceanic lithosphere derived fluids and subsequent slab break, delamination of the mantle lithosphere and tectonic extension due to the roll-back of the subducting Tethyan lithosphere which gave rise to decompression melting of the subduction-metasomatized lithospheric mantle and the generation of the studied rocks at Bozghush Mountain. [ABSTRACT FROM AUTHOR]

The Mahoor area is located, about 135 km south-west of Nehbandan in the center of Lut Block. The area comprises outcrops of Eocene volcanic and pyroclastic (Eocene) that were intruded by several intrusive rocks consist mainly of diorite as dykes and stocks. Chemical classification shows that plutonic rocks are gabbro-diorite, diorite, monzodiorite and tonalite. These granitoids are high-K calc-alkaline series and they are metaaluminous. Magnetite suitability (1485x10-5 SI) mineralogical and geochemical features show that they belong to magnetite granitoid series (I type). Enrichment in LREE rather than HREE and enrichment in LILE rather than HFSE, and typical anomalies of Nb, Ta and Ti are important evidences that show the intrusions were formed in a mamgmatic belt of subduction zone. Eu element show negative anomaly and Eu/Eu* ratios are from 0.65 to 0.88. Negative anomaly of Eu is due to presence of plagioclase in magma source. Geochemical studies show that Mahoor granitoids are co-genetic and they formed in subduction zone and belong to calc-alkaline volcanic arc setting in active continental margins. Mineralization is present as disseminated and hydrothermal vein related to monzonite and diorite porphyry. [ABSTRACT FROM AUTHOR]