Tectonomagmatic setting of the Siahbaz A-type granitoids and mafic intrusions (Northwest of Khoy

The Siahbaz granite-gabbro-appinite outcrops from the Northwest Khoy is related to one of the complex of the Late Ordovician-Early Permian. The complex is located on the north Sanandaj-Sirjan Zone. Synchronous activities of the mafic and felsic melts indicate that hydrous mafic melts during or after injection to the crust have been able to mingle with felsic magmas produced from the base of the crust. Fractional crystallization in the magma chambers of the hydrous mafic melts caused to form appinite mafic rocks c. 25 to 60 modal percent of hornblende and gabbros. The felsic melts could form A-type granitic rocks. The mineralogical observations along with geochemical and tectonical studies show that subduction of the Paleo-Tethys under an island arc (Siahbaz) in the Northwest Iran were produced all rock types at the Late Ordovician-Early Permian. The hydrous mafic melts were produced in the mantle wedge because of the presence of subduction fluids and then transferred to the base of the island arc, formed the A-type felsic liquids as a result of the partial melting of the base. Convection in the mantle wedge in the supra subduction zone, led to the formation of an extensional setting in the region (the extensional region in the active margin); hence, the conditions for the formation of A-type felsic melts were provided

Geochemical and tectonic significance of the Arbat alkali gabbro-monzonite-syenite intrusions, Urumieh-Dokhtar Magmatic Arc, Iran

The Oligocene Arbat alkali intrusions of the Eastern Miandoab are located in the northwestern part of Iran and belong to the Urumieh-Dokhtar Magmatic Arc (UDMA). The intrusions show a ring structure with gabbro-monzogabbro-monzodiorite (mafic units) on the edges, with monzonite-monzosyenite-syenite (felsic units) gradually going towards the central parts. The textures in different rock types are cumulate, granular and laminated. The high values of (La/Sm)n and (La/Yb)n, contents of K, Rb and Cs (positive anomalies normalized on the basis of the primitive mantle), low concentrations of Hf, Nb, Zr and Ta (negative anomalies), and the changes in Th/Nb, Th/Ta, La/Nb and Ce/Pb ratios along with the geochemical and tectonic setting evidence exhibit a subduction-modified mantle origin for the formation of these rocks. Accordingly, the intrusions were formed between the Central Iran and the Arabian plates as a result of the partial melting of a mantle wedge at a syn-collision or post-collision arc-related environment. Our data suggested that, after the end of the oblique Neotethys subduction and during/after the continental collision, the break-off or rollback of the Neotethys slab beneath western Iran, in the Oligocene, might have occurred. Such a process led to the change in the geothermal gradient of the mantle wedge because of the subduction fluids, transtension, pressure reduction along the SE-trending lateral depth strike-slip fault zones in the upper part of the mantle wedge, decompression partial melting at the mantle, and the resulting formation of a mafic potassium-rich melt. The mafic magma was injected into crustal magma chambers; probably, the fractional crystaliization and partial contamination occurred with crustal components, forming the intermediate and felsic rocks in the intrusions. Geochemical evidence related to the variations in the ratios of Th/Yb, Ta/Yb, Rb/Y, and Nb/Y and Harker variation diagrams along with the spider diagrams confirmed fractional crystallization and partial FC (fractional crystallization) and AFC (assimilation and fractional crystallization) in the intrusions

Geochemical characteristics and conditions of formation of the Chah-Bazargan peraluminous granitic patches, ShahrBabak, Iran

Xenoliths of garnet-biotite-kyanite schist from the Qori metamorphic complex (southern part of the Sanandaj-Sirjan zone, northeast Neyriz, Zagros orogen in Iran) in the 173.0±1.6 Ma Chah-Bazargan leuco-quartz diorite intrusion were studied. This intrusion caused these schist xenoliths to be metamorphosed to the pyroxene hornfels facies (approximately 4.5±1.0 kbar and 760±35 °C), converting them to diatexite migmatite as a result of partial melting of the xenoliths. These melts are granites in composition. Melt volumes of 20 to 30 vol. % were calculated for small patches of the peraluminous granites. It is possible that anatectic melting affected only the leucosome, such that melting was more than 20 to 30 vol. %. It is possible that a large amount of melt was not extracted due to balanced in situ crystallization, the adhesion force between melt and crystal (restite), and high viscosity of the leucosome. The Chah-Bazargan peraluminous granites are depleted in trace elements such as REEs, HFSE (Ti, Zr, Ta, Nb, Th, U, Hf, Y), Ba, Pb, and Sr. These elements are largely insensitive to source enrichment, but sensitive to the amounts of main and accessory minerals. These elements were hosted by minerals such as garnet, biotite, muscovite, K-feldspar, plagioclase, ilmenite, apatite, monazite, and zircon in the source (diatexitic migmatitic xenoliths)

Zoning and contamination rate of magnesium and heavy metals of iron, zinc and copper in the north and northwest aquifer of Khoy (Zourabad) based on GIS and determining the contaminated source

Introduction Heavy metals are the most toxic pollutants in aquatic ecosystems. This contamination can result from the release of heavy metal elements during alteration and weathering of ultramafic and mafic rocks (ophiolite zones). Among the important metals and pollutants in the ophiolite; chromium, cobalt, nickel, iron, magnesium, manganese, zinc and copper could be noted. Basically, a mass of serpentine consists of serpentine, amphibole, talc, chlorite, magnetite, and the remainder of olivine, pyroxene and spinel (Kil et al., 2010). In such areas, the prevailing cold climate, during the serpentinization, chloritization and epidotiization, the activity of the solvent, such as chloride, fluoride, carbonates, sulfide, sulfosalt would be able to import the elements such as magnesium and iron, copper and zinc into the soil and groundwater. The study area is located in northwestern Iran. This area is located in the northwest of the city of Khoy. Because of the proximity to the north and northwest Khoy plains with ophiolite rocks, the soil of this region could possibly show the potential of contamination with heavy metals. Due to the toxicity and disease of unauthorized grades of these elements in groundwater in the study area, this study is focused on the more contaminated groundwater of the areas. Materials and methods In this study, over a period of 5 days, sampling from 42 water sources, including fountains, aqueducts, wells, piezometers and wells in operation, was performed. The container was washed with acid and then rinsed 3 times with the water sample. The pH and temperature of the water in the samples was measured in the field. Then to each of the samples was taken from 2 to 5 ml of concentrated nitric acid (This causes that the metal elements would not adsorbed or precipitated by these particles) and pH of the samples was measured with litmus paper to reach level 2. This was done to ensure the consolidation of the water samples. Analysis of samples carried out in the chemistry laboratory of the University of Urmia. All water sampling procedures were performed based on standard protocols (SMEWW, 2010). The maximum concentration of heavy metal contamination of drinking water with EPA, WHO and national standards were compared. In this study, the chemical analysis of heavy metals, were used by graphite furnace atomic absorption spectrometry (at ppb) for the elements Cu, Mg, Fe and Zn. Concentration of the heavy metals in acidified water samples (pH value of 2), using a flame atomic absorption spectrophotometer were analyzed. Discussion There are enormous amounts of Fe and magnesium in groundwater from the north and northwest Khoy plain, and the amount of Cu and zinc are in the normal range in water resources. The source of iron and magnesium in the groundwater of the study area is ultramafic and mafic rocks of the Khoy ophiolite complex. Weathering of ultramafic and mafic igneous rocks such as peridotite, olivine basalt, gabbro and pillow lava and then soil formation, high concentrations of the elements Mg and Fe were transferred to soil. Ferromagnesian olivine is formed Mg2+ and Fe2+ ions and tetrahedral silicon. If sufficient amount of Mg2+ and Fe3+ ions combine with silicon and oxygen, silicon into the soil, forms silicic acid (H4SiO4), or magnesium or iron smectite (clay minerals) (Alexander et al., 2007). Several types of pyroxene are more stable than olivine. Orthopyroxene during weathering decompose into talc and smectite. Magnesite (MgCO3) is present in some serpentine soils. With respect to the empirical relationship (Kierczak et al., 2007) and based on temperature and rainfall, the study area with a drought index of 12.48 places in the category of semi-arid-cold climate between 10 and 19.9. Temperature changes in the condition cause weathering and leaching of serpentine soils, and subsequently can remove large amounts of magnesium. Weathering and leaching serpentine soils, releases immediately magnesium and its concentration in soil decreases. As a result, the concentration of the element in the water increases. Results Based on the charts and maps of iron, magnesium, zinc and copper contaminations, it is found that the concentrations of Fe and Mg in the north and northwest Khoy plain are higher than the permissible limit for drinking water. In some parts of the sample, the concentrations of Cu and Zn are exceeded WHO. However, based on EPA standard, the amount of copper is less than the limit. On the basis of three criteria: EPA, WHO and national standards, except for the village Ghez Ghaleh, zinc concentration is below the standard. According to the geological map of Khoy, the Khoy ophiolite complex containing mafic rocks and ultramafic is a source of iron and magnesium in groundwater. Acknowledgements Editor of the Journal of Economic Geology, Professor Mohammad Hassan Karimpour and reviewers of this article are acknowledged for their unwavering assistance. Also, the authors thank Deputy of Research of the University of Urmia for the support required for this study. References Alexander, E.B., Coleman, R.G., Keeler-Wolf, T. and Harrison, S., 2007. Serpentine Geoecology of Western North America, Geology, Soils, and Vegetation. Oxford University Press, London, United Kingdom, 512 pp. Kierczak, J., Neel, C., Bril, H. and Puziewicz, J., 2007. Effect of mineralogy and pedoclimatic variations on Ni and Cr distribution in serpentine soils under temperate climate. Geoderma, 142(2): 165–177. Kil, Y., Lee, S.H., Park, M.H. and Wendlandt, R.F., 2010. Nature of serpentinization of ultramafic rocks from Hero Fracture Zone, Antarctic: Constraints from stable isotopes. Marine Geology, 274(1): 43–49. SMEWW, 2010. Standard Methods for the Examination of Water and Wastewater (SMEWW). American Public Health Association (20th Edition), New York, 2671 pp. <br