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

Radon concentrations has been measured in ground water in Anar with using of RAD7 apparatus at 33 wells. Measured radon concentrations are between 1.33 to 29.90 Bq/Lit. 40 percent of the wells have radon concentration more than 11 Bq/Lit. Most wells with high average radon concentrations located in Southwest part of the area on alluvial deposits composed of igneous clastics such as dacite and andesite whereas wells with lower radon concentrations occur in East and North-East of the area in sediments resulted from Flysch and carbonate rocks. Igneous clastic alluvium in Southwest part of the area generally have more ability to produce radon than sediments in East and North-East part of the area. On the other hand, measured radon concentrations in Anar groundwater decrease with increasing distance from Anar fault. These points can show the influence of type of sediment on radon gas release and the role of Anar fault and their related fractures on scape of radon gas in Anar ground water.

The Sahand volcano is located in the NW of Iran. Shand is a stratovolcano and is dominated by pyroclastic materials and lava flows of the Miocene-Quaternary. The last eruptions include subvolcanic and volcanic domes with dacitic to rhyolitic composition, which are studied in this paper as the young Sahand. These rocks indicate petrological features including sieve texture and zoning in plagioclases. Common features in the young subvolcanic and volcanic rocks of the Sahand are abundance of plagioclase and amphibole, enrichment of Ba, Rb and Sr and negative Nb and Y anomalies in primitive mantle normalized multi-element diagrams and enrichment of LREE compared to HREE in chondrite-normalized REE patterns. These characteristics and the location of the rocks studied in the Y-Sr/Y diagram implying an adakitic composition for these rocks. The young Sahand rocks are high SiO2 adakitic rocks. These rocks have been derived from partial melting of garnet-bearing crustal sources (thickened lower continental crust or oceanic crust) and underwent magmatic evolution during their ascent. The formation of studied rocks is related to the Arabian-Eurasia collision zone.

The peridotite rocks of Naein ophiolite compose about 70 percent of ophiolitic mélange of Naein. The rocks are mantle peridotites of an oceanic lithosphere that have been emplaced in Late Cretaceous to Early Tertiary time. Ophiolitic complex of the mantle section, includes harzburgite, dunite, lherzolite, wehrlite and pyroxenite. Harzburgites are very volouminous in comparison to the other peridotites. Serpentinized harzburgite have been listwaenitized in environments with favorable pH and Eh. Harzburgites, serpentinites and listwaenites contain spinel minerals. The spinels are most significant minerals with compositional variations. Spinel group minerals have also many applications in the industry. So that, the Cr and Al in these minerals can be indicators to determine the origin of the country rocks. Chrom-spinels composition are different in minerals crystallized in different environments, and crystallization environment and alterations are the most important factors influencing the composition of chrom-spinels. Mineralogical and geochemical variations of spinels during the process of the serpentintization and the following listwaenitization shows an increase in Cr2O3, Cr #, TiO2 and decrease in Fe3+ and the MgO, Mg # and Al2O3; demonstrating the spinel formation in different conditions of pressure and temperature.

Rock-Eval Pyrolysis and its results are commonly used for determination and interpretation of the characteristics of sedimentary basins. The aim of this study is to examine and compare hydrocarbon generation potential of Kazhdumi Formation by using Rock Eval analysis in 7 wells of the Azadegan oil field. For this purpose, geochemical investigation of Kazhdumi Formation as the potential source rocks was carried out with 22 core samples in the studied areas. Investigation of the variation S1+S2 and TOC parameters indicated that this formation is assessed as a good source rock for hydrocarbon generation in Azadegan oil field. Based on HI versus Tmax plot the kerogen of this formation is mainly a mixture of types II/III indicating the immaturity and no entry of samples into the oil window. Tmax examination also showed that this formation is not mature enough to generate hydrocarbon, and has not yet entered into the oil generation window.

178 samples of the stream sediments of southeast of Chadermalo in Yazd were analyzed for concentrations of Au, Ba, Cu, Mo, Pb, Sn, V, W, Zn, Fe2O3, MnO and TiO2. Pb, Sn, Zn, Fe2O3 and Cu showed anomalies in the sediment samples. Stepwise factor and cluster analyses and fractal models were used in identification of anomalies. The results showed that the anomalies in the north and south east of study area have been distributed in the Precambrian rocks including sandstone and slate. Zinc anomaly in the thick-bedded limestone has been located in the southwest of the study area. Copper anomaly in the west of the study area has been distributed in the sandstone.

The study area is located in 15km north of Torbate Heydariyeh and belongs to the Central Iran Structural Zone. This area has a variety of lithological composition. The main igneous rocks are diorites, with different mineralogies. These rocks consist of meta-diorites, sub-volcanic pyroxene diorites, pyroxene diorites and hornblende diorites. Petrographical studies show that these rocks usually include plagioclase, hornblende, pyroxene (augite) and chlorite. The main texture of these rocks is hypidiomorphic granular. Based on the geochemical studies, diorites show a tholeiite trend. The magmatic contamination processes have an significant role in the formation and evolution of these rocks. These studies also indicate that the rocks have formed in a volcanic arc setting.

Some pegmatites have been found in the Sanandaj-Sirjan Zone in a region located at 5 km south of Hamedan. These pegmatites contain sapphire, which is a precious mineral. In this study, the features and conditions of pegmatite formation have been presented as a key in exploration for this mineral. Based on the petrographic studies, these pegmatites are mica- sapphire bearing types and were not mentioned in previous studies of Alvand pegmatites. According to this study, there are genetic relationships between the igneous rocks of this region and pegmatites which have been formed as a result of differentiation of magmas with mafic composition. Tectonic discriminant diagrams indicate a syncollision tectonic environment for the rocks studied. The rocks are mainly peraluminous and S-type granites, in terms of the degree of aluminum saturation, which suggests the conditions of sapphire formation. Geochemical studies suggest that sapphire has been crystallized after microcline and before quartz. The existence of muscovite, zircon and tourmaline in pegmatites found in the south of Hamedan reflects the fact that these pegmatites are profound species which is a reason for the coarseness of formed sapphires. Also, the dark color of sapphire is due to the iron content in the pegmatites. In addition, Fe, Ti and Ga are also involved in the color of these gems. Gemological studies and sapphire processing tests indicate that a cut parallel to c-axis gives higher refractive index, luster intensity, color and specific gravity than a cut perpendicular to it which is especially useful in cutting these gems.