GEOCHEMISTRY
Year:2015 | Volume:3 | Issue:4|Papers Count:7

Ghassemabad area is located in 40km southwest of the Neyshabour, and is considered as a part of the Sabzevar structural zone. The composition of the Eocene volcanic rocks, are tracyandesite to dacite and composition of the Oligo-Miocene plutonic rocks is varied from alkali feldspar granite to gabrodiorite. Based on the geochemical diagrams, they show calc-alkaline and meta-aluminous nature belonging to I-type granitoids. Based on the geochemical studies, tectonic setting of the Ghasemabad dahaneh intrusion is comparable to the volcanic arc granitoids (VAG). These bodies have been created in volcanic arc of subduction continental margins. On the basis of the geochemical data and field relations, they have been resulted from the contribution of melts from oceanic subducted crust and its above mantle wedge. Genereted magma underwent fractional crystallization and assimilation and contamination with the upper crust.

The Dalan Upper Member is one of the most important gas reservoirs in the Zagros basin and Persian Gulf. This research is focused on the analogy of diagenetic processes affecting on this member in the surface section of this member in Surmeh Mountain section and a subsurface section in the Persian Gulf. The paragenetic sequences and diagenetic history of surface and subsurface sections are compared to each other and the effect of diagenesis on the geochemistry of dolomites has been investigated. This investigation revealed that the Dalan Upper Member has different diagenetic history in these two sections. Petrographic evidences revealed that subsurface section was affected by marine diagenetic processes. Some parts like oolitic shoal subareally was exposed and affected by meteoric environ ment and then placed into burial environment. Evidences of marine diagenesis have been identified in surface samples. Stylolites, saddle dolomite, fracturing, coarse spary calcite cement and silicification indicate that this member was affected by burial diagenetic processes. Then as a result of uplifting, Dalan upper member exposed in meteoric environment. Study and analogous of major elements of these dolomites in surface and subsurface sample revealed remarkable impact of meteoric diagenesis. The surface sample shows higher content of Na and Sr because of low partition coefficient of these elements and low concentration in meteoric water. Since concentration of Fe and Mn in meteoric water is high and their partition coefficients are higher than 1 (e.g.>15 for Mn), the diagenetic products have higher content of these elements.

Kalut-e-Chapedony is a part of the Eocene Chapedony metamorphic core complex, which is located in western part of the Posht-e-Badam block. This complex consists of migmatite, gneiss, amphibolite, marble, micaschist and various types of granitoid. In the northern part of the Kalut-e-Chapedony, a granitic rock unit which evidently presents the mylonitization evidences, crosscuts the other rocks. The main minerals of this granite are plagioclase, orthoclase, quartz, garnet and fibrolitic sillimanite. The accessory minerals are muscovite, zircon, apatite, biotite and spinel. In spite of mylonitization of this granite and formation of fibrolitic sillimanite, the primitive igneous granular and poikilitic textures are preserved. Sillimanite fibrolites are formed at the expense of orthoclase and plagioclase. Chemical analyses of minerals indicate that plagioclases are albite (An9Ab87Or4), garnets show (Alm78Sps12Prp9) composition and orthoclases are as (Or84Ab16). The field evidences (association of this granite with migmatite and other rock units of Chapedony metamorphic core complex), petrography characteristics (high values of orthoclase, presence of garnet and muscovite, as well as formation of fibrolitic sillimanite) and mineral chemistry of garnets (enriched in spessartine) indicate that the magma which produced these granites should be formed by melting of pre-existing sedimentary rocks and presents the S-type characteristics. These granites have suffered the mylonitization in 400oC at subsolidus condition and consequently the fibrolitic sillimanites were formd.

Jaldehbakhan area, located at southeast of East-Azarbaidjan, forms a part of the Tarom-Gaharadagh metalogenic province. The regional geochemical explorations led to the discovery of anomalous areas for variety of elements. The Control on geochemical anomalies was implemented by studies of heavy minerals of stream sediments and mineralized samples. The most important identified heavy minerals includes magnetite, hematite, limonite, martite, micaceous hematite, pyrite, oxidized pyrite, galena, native copper, gold, malachite, cuprite, zircon, apatite, rutile, ilmenite, sphene, pyroxene, amphibole, garnet, and epidote. The identified metallic heavy minerals are intimately associated with veinlet and epithermal mineralization. Analysis of some collected litho-geochemical samples from zone of anomalies show notable grade for elements such as Au, Ag, As, Ba, Bi, Ce, Co, Cu, Mo, Ni, Sb, V, and Zn. Combination of obtained data from chemical analyses, heavy mineral studies, petrographic examinations of mineralized samples, and field relations led to identification of zone of anomalies corresponding with main valley in the study area. Superposition of final anomaly map with fault density map of Jaldehbakhan area indicates that faults played a crucial role in creation of these anomalies. The overall obtained results from geochemical considerations show that the identified anomalies principally belong to elements such as Au, Ag, Ba, Co, Cu, Sb, and Zn that can be used as important tracer for exploration of epithermal gold and silver as well as polymetallic Au-Ag-Cu-Pb-Zn deposits.

Kan Gohar reaction skarn is located at Sanandaj- Sirjan zone and is a part of Tutak complex. Based on the field observations and petrographical studies, the deposit included granite-gneiss, micaschist, carbonate rock, and skarn, and Three zones, garnetit skarn, amphibole and epidote skarn are classifications. Geochemically the intrusion is S-type, peraluminus and the nature of magma is calc-alkaline. Which located in the volcanic arc geological setting. Tutak intrusion is S-type; therefore it could not be related to the mineralization and skarnification. On the based of XRD results garnet (ugrandites-pyralspites), calcite, hematite, magnetite, and dannemorite, magnesiohornblende are the main minerals. Rare earth elements pattern in garnets shows two different patterns, can be indicator of presence of ugrandites and pyralspites garnets in the Kan Gohar skarn. Ugrandites garnets (grossular-andradite), enrichment in LREE and depleted in HREE. Whereas, pyralspites garnets enrichment of HREE, and depletion of LREE. Based on geochemical studies the Kan Gohar skarn were formed at T<500oC, fO2~ 10-21 and XCO2<0.2 bar.

The study area is a part of Kermanshah ophiolite in High Zagros Zone in western Iran. The High Zagros Zone (or Crushed Zone) units, are consist the Cretaceous-Triassic sedimentary rocks and Kermanshah ophiolite. The Kermanshah ophiolite complex which is part of Zagros orogenic system is a highly altered, and in the north of Lorestan province manganese ores occur within radiolarite consisting pyrolusite and braunite mineral. The chemical composition of the manganese ores in the study area shows that Mn mineralization was produced by hydrothermal process related to submarine volcanism in the Neotethyan ocean.

Sarkoobeh Gabbroic bodies are located in 16-18 Km of the North of Khomein city, as a part of Markazi province. The gabbroic rocks have intruded in to Cretaceous limestones and they are attributed to a probably Eocene age. The study area is a part of Sanandaj-Sirjan Zone. Mineralogical and geochemical studies show the main composition of bodies is gabbro. The main minerals are plagioclase, diopside, and opaque. They display ophitic to sub-ophitic textures petrographically. Based on geochemical data classification of major and trace elements, the rocks have SiO2 from 43.89 to 50.91 wt. % and mostly plot in gabbro field with alkali nature and some of the samples show calcite sub alkaline nature, because of assimilation of limestone rocks. The chondrite-normalized pattern from the rocks shows the enrichment of LREE than HREE, also they display small positive anomaly of Eu due to crystallization of plagioclase. The enrichment of Nb and Ti in the MORB and Primitive Mantel normalized patterns clear that original magma of the rocks have the affinity of intra-plate magmatism. Also, the spider diagrams show LILE enrichment and HFSE depletion. Geochemical studies of trace and rare earth elements suggest that magma source of gabbro is garnet-spinel lherzolite from asthenosphric mantle.