JOURNAL OF SCIENCE (KHARAZMI UNIVERSITY)
Year:2008 | Volume:8 | Issue:3|Papers Count:14

The Javaherdasht basalts have considerable outcrops in the north part of Alborz mountains in the east of Guilan province. The petrographical, geochemical and isotopical evidence is indicative of the contamination of the basalts with continental crust. The petrographical evidence such as corosion gulf and crenated margins in pyroxene phenocrysts and chemical composition difference between clinopyroxene phenocrysts margins with matrix clinopyroxenes suggest of crustal contamination and nonequilibrium due to the change of matrix composition as compared with pre-existed phenocrysts in rock. The depletion in elements such as Zr, Nb, TiOz, PzOs and enrichment of LIL elements, high ratios of Pb/Nd and Ba/Nd, low content of Zr/Nb, Y/Nb, Ce/Pb, positive correlation between SiO2 and 87Sr/86Sr and positive correlation between MgO and ENd are geochemical and isotopical evidences of crustal contamination of these basalts. Our studies show that these basalts have a clear elemental equilibrium with lower and middle crust rocks and that they have been contaminated with them

Volcanic rocks of NW Marand Ageing Plio-Quatemar consist of andesite, Basaltic andesite, leucite tephrite, leucite basanite and tephrite. High concentration of K2O and MgO and also the ratio of K2O/Na2O indicate that volcanic rocks of this area could be classified as potassic and ultra-potassic, whereas they are shoshonite from magmatic series point of view. The study of minor elements shows that the rocks of the area are rich in of LILE and depleted of HFSE, indicating that lehrzolitic-gamet metasomatised mantle part of the lithosphere and high fugasity ratio of CO2/H2O play a crucial rule on the genesis of these rocks. Also contamination of part of the responsible magma with crustal material resulted in the change of magma chemical compotion from alkaline to sub-alkaline.

Malayer granitoid rocks, as a part of Sanandaj-Sirjan plutonism, are located at latitude 34°00'-34°18' and longitude 48°30'-48°52'. Tectono-magmatic investigation on the history of Sanandaj-Sirjan Zone attributed the formation of these plutonic rocks to convergence of Iranian and Arabian plates in conjunction with subduction of Neo-Tethys in the western part of Sanandaj-Sirjan Zone. Geochemical studies of Major and Trace elements on Malayer granitic rocks reveal that these granitic plutons are formed in a compressive environment, such as active continental margin in the convergent zone of oceanic crust and continental plate at the magmatic arc of continental margin. High ratio of LILEs/HFSEs and negative anomaly of Sr, Nb, Ba and Ta confirm the relation of these granitoids to subduction zone. These, also point out the role of shallow continental crust in formation and evolution of granitoidic magma. Broad range of mineral composition in petrographical observations and large variations in field studies, high-K calc-alkaline affinity and assessment of trends observed in AFM, K2O-SiO2, FeO-MgO diagrams versus those of plutons of known tectonic setting accentuate the similarities between Malayer granitic rocks and Andian type Magmatic Arc of Active Continental Margins and as a result highlights the role of upper mantle mafic magmas and tectonic movement in formation of their parental magma.

The area under study is located in central Iran and 235 kilometers of south west of Tehran is a part of Qom quadrangle. Volcanic sequences, which constitute the most major parts of the outcrops in the region mainly, have seen in north eastern and east of Ashian. These volcanic rocks are included of andesite basalt, andesite, trachy andesite, dacite, rhyodacite and rhyolite that are emplaced during Eocene (middle Lutetian to late Lutetian) along the Oromieh-Dokhtar volcanic belt that divided to six members from E1 to E6 in Tafresh and Ashtian area. Plutonic rocks related to Oligo-Miocene. There are not any rocks older than Triassic in area under study. Volcanic rocks both pyroclastics and laves have covered the most of area and could be seen in the continental and marine so we can see ignimbrite and tuffs. Acid eruptions are more than basic in this area. Mineralogically, these rocks have plagioclase, alkali feldespar, quartz, clinopyroxene, amphibole, biotite and a lesser amount olivine. Plagioclases have zomng structure and amphibole crystals have opacite rimmed. This phenomenon shows that magma responsible for rocks had a high temperature. Geochemically, petrographically and petrologically studies based on major and trace elements and differentiation index versus SiO2 indicate that changes in the volcanic processes at the area are the result of magmatic crystallization and differentiation magmatic rocks magma of area under study is calc-alkaline and they belong to subduction. Using of petrological and tectonic setting diagrams indicate that these Eocene magmatic rocks are compared to calc-alkaline series of subduction orogenic andesitic belts. The rare and trace element patterns of thes rocks have investigated and the examples of anomalies are related to Sr and Nb. Also the study of trend show that the calc-alkaline magma has formed in the upper mantle. Similarities between volcanic and plutonic rocks in ashtian area show that these rocks may be having the same origin.

Jahagh anticline in south of Kashan is host to the Silurian volcanic rocks at the base of Niure formation (with sandstone lithology). This area is located in the western edge of Central Iran zone. The volcanic rocks under study involved basalt until trachy basalt and contain Plagioclase. These rocks belong to alkali basalt to sub-alkali basalt field on the geochemical diagrams. The investigations of rare earth elements indicate garnet presence in the source with low partial melting degree. High Ti and Zr content in these rocks show that the magmatic series is alkalinetransitional. The geotectonic setting is intracontinental rift that follow the extension phases after Caledonian orogeny and creatie the deep faults in Iran cratonic crust. In all probability, Isfahan fault activation that is one of the old and basal faults in this area cause the eruption and volcanism at Silurian in this part of Iran.

In this study, trace determination of benzene, toluene, ethyl benzene and xylenes isomers (BTEX) in aqueous samples was carried out by static headspace-gas chromatography-mass spectrometry. Important parameters of extraction by headspace such as extraction temperature, extraction time, sample volume and salt concentration were optimized. Under optimal conditions (extraction temperature: 70oC, salt concentration: 4M, extraction time: 20 min and sample volume: 10mL) and using selected ion monitoring (SIM) mode of mass spectrometer, detection limits of BTEX were found to be in the range of 1.0-2.2mg/L.

The data gathered from implemented investigations provides enormous information yet if not organized properly, they would not yeild useful and credible results. GIS cannot only organize the mineral potential-related information, but also integrate different datasets and produce quickly and precisely-required mineral potential maps. It also supports the spatial decisionmaking process. Here, we have used GIS to produce the mineral potential map of Sonajil porphyrtic copper prospect to determine sufficient drilling localities. The utilized layers include rock type, alteration, mineralization indicators, anomaly zone of Chargeability and Apparent resistivity, anomaly of Copper, Molybdenum and gold. After information preparation, Factor maps were weighted and integrated in the inference network and mineral potential map was prepared. Using Fuzzy logic operators in inference network can eliminate defects in other models and provide more flexible integration of factor maps. With respect to prepared mineral potential map, most probable mineral potential zones of porphyrtic copper are located in two north-east and south-west parts of studied area. Eventually, the degree of correlation between mineral potential maps and those operated exploration boreholes have been estimated for two different classes, 90.91% and 83.33%. Regarding to the resulted mineral potential map, some new promising drilling localities have been suggested. Comparison of the high potential points indicated by our mineral potential maps with those previous drilled boreholes reveals about 85% miscorrelation. In other words, if the present proposed methodology had been performed before drilling operation, about 600,000$ could have been saved in this stage.