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Introduction Granitoids are the main rock units in the continental crust. Study of granitoids reveals significant information on tectonic mantle and upper crust. Many researchers have investigated petrogenesis and origin of granitoids (e.g., Chappell and White, 2001; Barbarin, 1999; Frost et al., 2001). For example, Chappell and White (1992), Pitcher (1993) and Chappell et al., (1998) have divided granites into two major groups of: (1) I-type granites (high-temperature or Cordellerian granitoids, including low-K granitoid to high-Ca tonalite, without inherited zircons) formed by partial melting of mafic rocks at >1000 ℃ in mantle or subduction zones of continental margins, and (2) S-type (low-temperature or Caledonian granitoids with inherited zircons) granites formed by partial melting of felsic crust at ~700-800 ℃. Northeast of Iran is a key location for studying the Cimmerian Orogeny, which is related to the Late Triassic collision between it and Eurasia, and the closure of the Paleo-Tethys (Samadi et al., 2014). Mesozoic Mashhad granitoids have cropped out along with the Paleo-Tethys suture zone. Distinct granitoid suites, i.e., monzogranite, granodiorite, tonalite, and diorite occur in Mount Khalaj located in the south of Mashhad. It comprises of monzogranite and granodiorite. However, monzogranite is the most abundant. To study the plutonic events during the Turan and Central Iran collision, the origin and tectonic setting of monzogranite of Mount Khalaj are investigated in this study based on whole rock geochemical data. Materials and methods This research study is based on field studies and petrography. Fresh thin sections samples were selected for geochemical analysis. Whole rock composition was measured on pressed powder tablets by X-ray fluorescence (XRF) using a Philips PW 1480 wavelength dispersive spectrometer with a Rh-anode X-ray tube and a 3 MeV electron beam Van de Graaff Accelerator, at the center for Geological Survey of Iran. The trace element data of a sample was measured at the Activation Laboratories, Ontario, Canada (ActLabs). Samples were digested by lithium metaborate/tetraborate fusion and analyzed with a Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP/MS. GCDkit 4.1 and CorelDraw software packages were used for plotting diagrams and calculation of saturation temperatures. Results The Khalaj granitoid is mineralogically composed of quartz, potassic feldspar, plagioclase, mica, and accessory minerals of zircon and apatite. Geochemically, it is an unaltered acidic intrusion with ~72-73 wt.% SiO2. It is a granitoid (monzogranite) based on various classification diagrams (e.g., Cox et al., 1979; etc.). It shows the peraluminous nature (A/CNK~ 1.08-1.24) with negative Eu anomaly of ~0.62-0.73 (Eu/Eu*

Introduction Study of the petrology of the ophiolites as the relics of ancient oceanic lithosphere, is a powerful tool to reconstruct Earth’s history. Mantle peridotites have mostly undergone alteration and serpentinization to some extent. Thus, the relics of metamorphic signatures from the upper mantle and crustal processes from most of the peridotites have been ruined. Several recent papers deal with the mantle peridotites of Nain Ophiolite (e.g. Ghazi et al., 2010). However, no scientific work has been carried out on the metamorphosed mantle peridotites. The study area of the Darreh Deh that is located in the east of the Nain Ophiolite, is composed of huge massifs of metamorphosed mantle peridotites (i.e. lherzolite, clinopyroxene-bearing harzburgite, and harzburgite, and small volumes of dunite), characterized by darker color, higher topographic relief, smaller number of basic intrusives, lower serpentinization degree, and amphibolite-facies metamorphism. In this study, the petrography and mineralogy of metamorphosed peridotites in the Darreh Deh has been considered based on geochemical data. Geological Setting The Mesozoic ophiolitic mélange of Nain is located in the west of CEIM, along the Nain-Baft fault. As a part of a metamorphosed oceanic crust, it is mainly composed of harzburgite, lherzolite, dunite and their serpentinized varieties, chromitite, pyroxenite, gabbro, diabasic dike, spilitized pillow lava, plagiogranite, amphibolite, metaperidotites, schist, skarn, marble, rodingite, metachert and listwaenite (Shirdashtzadeh et al., 2010, 2014a, 2014b). Geochemical investigations indicate a suprasubduction zone in the eastern branch of the Neo-Tethys Ocean (Ghasemi and Talbot, 2006; Shirdashtzadeh et al., 2010, 2014a, 2014b). Materials and Methods Chemical analyses of mineral compositions were carried out using a JEOL JXA8800R wavelength-dispersive electron probe micro-analyzer (accelerating voltage of 15 kV and a beam current of 15 nA) at the Centre for Cooperative Research of the Kanazawa University (Kanazawa, Japan). The Micro-Raman spectroscopy (a HORIBA Jobin Yvon, LabRAM HR800 system equipped with a 532 nm Nd:YAG laser of Showa Optronics co., Ltd, J100GS-16, and an optical microscope of Olympus, BX41, Kanazawa University) were used in determination of serpentine minerals. Results The lherzolite is primarily composed olivine, orthopyroxene, clinopyroxene and Cr-spinel, but secondary hydrous and non-hydrous Mg-silicate minerals have been formed during the further serpentinization and metamorphism. Lherzolite is including of olivine (~70 Vol%, forsterite-rich), orthopyroxene (~15-20 Vol%, enstatite – bronzite), clinopyroxene (5-7 Vol%, diopside - augite), and vermicular brown Cr-spinel (60-70 Vol%, chrysolite), orthopyroxene (~30 Vol%, bronzite), a small amount of clinopyroxene, and subhedral dark brown Cr-spinel, talc, tremolite, magnetite, and chlorite. Dunites are composed exclusively of olivine, minor amounts of subhedral, dark brown Cr-spinel, serpentine, metamorphic tremolite, talc and chlorite. The rocks show secondary textures of mesh, poikiloblastic, nematoblastic and jack-straw textures, but original granublastic and porphyroclastic textures are well preserved. Pyroxenes show kink bands, warped cleavages, and undulatory extinction related to metamorphic condition of upper mantle. Petrographical features indicate that a metamorphism at amphibolite facies occurred after serpentinization and chloritization of the Darreh Deh peridotites. Chrysotile cut the primary phases of olivine and pyroxene, but not the metamorphic phases of olivine neoblasts, tremolite, talc and chlorite. Some chlorite crosscut the serpentine veins, and some are in the rim of Cr-spinel and clinopyroxenes. They are mostly replaced by tremolite. Metamorphic olivines have recrystallized as fine-grained neoblasts with lower CaO content (in comparison with the primary and replacive olivines), because they have been formed at the expense of Ca-free mineral of serpentine. Tremolite were produced after chrysotile, talc, and chlorite, wherever enough Ca2+ ions were released from the associated olivine and/or orthopyroxene by serpentinization. Discussion Petrographical and geochemical studies indicate a greenschist-facies stage (serpentinization and chloritization) followed and overprinted by amphibolite-facies metamorphism. The regional metamorphism is verified by the formation of antigorite after lizardite and chrysotile, metamorphic olivine neoblasts after serpentines, chlorite after Cr-spinel, talc after olivine and orthopyroxene, and tremolite after pyroxene, talc, serpentine, and chlorite. The metamorphism imprints on harzburgite and dunite indicate that metamorphism has occurred after melt-rock reactions. Acknowledgment The authors appreciate Prof. Shoji Arai for providing geochemical facilities. References Ghasemi, A. and Talbot, C.J., 2006. A new tectonic scenario for the Sanandaj-Sirjan Zone (Iran). Journal of Asian Earth Science, 26(6): 683-693. Ghazi, J.M., Moazzen, M., Rahgoshay, M. and Shafaii Moghadam, H., 2010. Mineral chemical composition and geodynamic significance of peridotites from Nain ophiolite, Central Iran. Journal of Geodynamics, 49(5): 261-270. Shirdashtzadeh, N., Torabi, G. and Arai, S., 2010. Metamorphism and metasomatism in the Jurassic of Nain ophiolitic mélange, Central Iran. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen, 255(3): 255–275. Shirdashtzadeh, N., Torabi, G., Meisel, T., Arai, S., Bokhari, S.N.H., Samadi, R. and Gazel, E., 2014a. Origin and evolution of metamorphosed mantle peridotites of Darreh Deh (Nain Ophiolite, Central Iran): Implications for the Eastern Neo-Tethys evolution. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen, 273(1): 89–120. Shirdashtzadeh, N., Torabi, G. and Samadi, R., 2014b. Geochemistry of pillow lavas and their clinopyroxene: ophiolitic mélanges of Nain and Ashin (Northeast of Isfahan Province). Journal of Economic Geology, 6(1): 49-70. (in Persian with English abstract)

The Nain and Ashin ophiolites are located in northeastern Isfahan province, in western Central-East Iranian Microplate. Pillow lavas are one of the most significant Cretaceous rock units. The lower partial melting degree in mantle peridotites of Ashin ophiolite, and the derived melt by melting their clinopyroxene caused a more basic (basalt) and enriched nature for the Ashin pillow lavas, whereas higher partial melting degree and consequently incongruent melting of orthopyroxene and increment of silica in the ascending melt, together with aqueous fluids led to formation of more acidic (andesite – basaltic andesite) and depleted melts (in trace elements) in Nain ophiolite. The REE content of Nain samples have IAT chemical affinity, but the samples from Ashin show MORB characteristics. Based on petrograhic observations, lower Eu/Eu* of clinopyroxene phenocrystals of Ashin, calculated Kd of clinopyroxene together with HREE enrichment in the melt in equilibrium with clinopyroxene (especially in Ashin when compared with Nain), the plagioclase crystallization was primer and higher in comparison with clinopyroxene, especially in Ashin compared with Nain. The melt in equilibrium with clinopyroxene in Ashin was similar to MORB composition, whereas it is similar to IAT in Nain. Thus, despite the proximity of these two ophiolitic series and some field and petrographic similarities, pillow lavas from them are different from each other in both primary melt composition and the processes of differentiation and the tectonic setting.