جستجوی مقالات مرتبط با کلیدواژه « uranium » در نشریات گروه « زمین شناسی »

Geochemical composition and uranium occurrences in Tahlab aquifer, southeastern Iran, were studied in order to understand the source of U and geochemical processes controlling chemistry of Tahlab aquifer. Also the contamination and health risk assessment of uranium for drinking purposes in 16 sampling wells were investigated. Sulfate, Cl, K and EC for all water samples reveal higher concentrations than the drinking water standard values. Piper diagram of major ions indicated that the water is mostly Na-SO4-Cl type with sulfate and sodium as the dominant anion and cation respectively. The hydrogochemical signature of the investigated groundwater samples suggests that they are mostly affected by a hydrothermal source related to deep circulation waters from Taftan volcano. The results of saturation index (SI) show that the Tahlab aquifer groundwater samples are oversaturated with respect to quartz, chalcedony, hematite, uraninite (68.75% of samples), caffinite (43.75) and U4O9 (31.25%). Principal component analysis (PCA) results and high positive factor loading of U, V, HCO3 and Si revealed that the geogenic activities were major source of uranium in Tahlab aquifer and suggests that the U concentration is controlled by Si-bearing minerals. The results of hazard quotient (HQ) for adults were higher than one in the 81.25% of the groundwater samples, indicating that groundwater of this area may not be safe for drinking purposes. Health risk assessment shows that the consumption of uranium contaminated groundwater poses an emerging health threat to the populations in the study area, and hence needs regular monitoring and management measures.

Unlike similar sedimentary conditions in the Lower Cretaceous, the Upper Cretaceous sediments of Iran do not have the same facies features. Therefore, in this study, we try to study the sedimentary environment and microfacies. By using data and geochemical methods of Upper Cretaceous sediments, valuable information about the environment and conditions of formation and primary mineralogy of Upper Cretaceous sediments of Dombak-kuh are achieved.

In Dombak-kuh section, sampling has been done based on lithological and facies changes in the perpendicular direction towards the layers and at distances of less than 0.5 m to more than 2.5 m. These sections were stained with red alizarin solution and potassium ferrocyanide to distinguish calcite mineralogy from dolomite as well as iron content and the amount of iron in it by Dickson method (Dickson, 1965). The classification and naming of rocks is based on Dunham's method (Dunham, 1962). In sample naming, an attempt has been made to include all major allocations in sample naming in order of frequency. The percentage of abundance was obtained by comparing with Baccelle and Bosellini (1965) comparison tables. The known facies have been compared with the Flugel (2010) facies belt. In presenting the sedimentary model, the terms used in Burchett and Wright (1992) have been used.

Petrographic studies of this sections revealed 11 microfacies, with 2 microfacies from tidal flat, 1 microfacies from lagoon, 1 microfacies from shoal and 7 microfacies from open marine. All of them belonged to carbonate ramp and are mentioned hereforth: 1. Dolomicrites – Dolomicrosparaite 2. Intraclast Grainstone3.Bioclact Wackestone4. Bioclast Pelloidal Grainston 5. Oligosteginids Packstone6.Nezzazatinella, Dictyoconella Wackestone-Packston 7. Lenticulina/Marginotruncana/ Oligosteginids Wackestone-Packstone 8. Heterohelix /Globotruncana/Macroglobigerielloides Wackestone 9. Oligosteginids/ Macroglobigerielloides / Heterohelix Packstone 10. Heterohelix /Globotruncana/Marginotruncana packstone 11. Globotruncana/ Heterohelix  /Macroglobigerielloides Wackestone-packstone.
 The characteristics of these deposits indicate that the sedimentary environment was a ramp (hemocline). The absence of calcite turbidite deposits, fall structures, and large reef and oncoid and piezoidal dams confirm the carbonate ramp environment. The results of elemental analysis and plotting of these values against each other indicate that the Upper Cretaceous sediment limestones had primary aragonite mineralogy. The plotting of Mn values against Sr / Ca indicates a semi-closed to open diagenetic environment with a high water/rock ratio.

According to the studies carried out in the Dombak-kuh region, the Upper Cretaceous sediments (Cenomanian-Campanian) have a thickness of 327.7 m, the lower boundary of which is the Tizkuh Formation and is of a steep type, and its upper boundary is a fault which cuts through. Cenomanian sediments, which are 54.26 m thick, start with a progressive conglomerate, and then thoronine sediments, which are 22.85 m thick, first with thick-layered limestone and then with chert limestone, and then with Oligosthenic limestones change the facies and settle on it. Kenyasin sediments with a thickness of 19.85 m with a combination of oligoesterated limestones followed by Santonin sediments with a thickness of 182.80 m and then Campanian sediments with a thickness of 48.5 m form the Upper Cretaceous stratigraphic sequence. . In these sediments, 11 micro-facies were identified, which include tidal zone with 2 micro-losses, lagoon with 1 micro-loss, a dam with 1 micro-loss and open sea with 7 micro-losses. The characteristics of these deposits indicate that the sedimentary environment was a ramp (hemocline). The absence of calcite turbidite deposits, fall structures, and large reef and oncoid and piezoidal dams confirm the carbonate ramp environment. The results of elemental analysis and mapping of these values together indicate that the Upper Cretaceous sediments in this section have an aragonite primary compound, which is placed in a semi-closed to semi-open diagenetic region with a high proportion of water to rock (W/R).

The Seh Qaleh agates, located at 120 km NW Birjand, are parts of Central Iranian (Lut block) (Aghanabati, 2004) with geographic coordinates of 58˚ 00′ to 58˚ 30′ longitudes and 33˚ 00′ to 34˚ 00′ latitudes. The host rocks of the agates are Eocene-Oligocene tuff, andesite and basalt. Silica mineralization in the area has occurred inside the volcanic units in the form of filling cavity and fractures. Here, the agates have very attractive textures such as concentric, flow and dogtooth textures that are accompanied with jasper, amethyst, opal, calcite and gypsum.Although Seh Qaleh agates are attractive and delightful, with high economical values, there is no scientific research about them. Therefore, their petrography, geochemistry and Raman spectroscopic characteristics are reported in the present paper for the first time.

More than 400 samples of agates have been collected for this research study and five of these samples were in yellow, white, green, red and black colors. Moreover, four of these rocks were selected for major and trace elements analysis by XRF and ICP-MS. The samples were powdered in Tehran University by a tungsten carbide mill and analyzed in the Zarazma Company (Mashhad). XRD analyses and Raman spectroscopic studies on the agate of the Seh Qaleh area were done in Damghan and Shahrood University of Technology, respectively.

Petrography and Raman spectroscopy:

The combination of different analytical techniques such as polarizing microscope, XRD and Raman spectroscopy provided information about the distribution of silica phases in the Seh Qaleh agates. Polarizing microscopy was used here to distinguish between the chalcedony and quartzine fibrous varieties. Moganite has similar optical properties with chalcedony, whose presence in agate is difficult to reveal. Thus, Raman studies were used to investigate these structural disparities. Raman spectroscopic studies showed that moganite and chalcedony can be distinguished based on their different spectral characteristics (Fig. 4, B, C). The use of a focused laser beam (diameter 1 μm) enabled us to analyze the variations in phase composition in the μm-range.The measurement of Seh Qaleh agates by Raman spectroscopy provided an overview of the quantitative distribution of moganite in the studied samples, in which the fibrous chalcedonies contain more moganite in comparison with nodule chalcedonies (Fig. 4, B, C). The presence and spatial distribution of different silica phases in the Seh Qaleh agates is a result of the primary crystallization processes such as temperature and chemistry conditions (Götze, 2011). Moreover, the presence of moganite and calcite in the Seh Qaleh, confirmed by petrography and XRD studies suggest that the agates had formed in an arid, alkaline environment.

Geochemistry of the agates:

Major and trace elements can be incorporated into the agates by substitution of Si by Al, Fe, Na, and Ca and as inclusions or fluid inclusions. The substitution of these elements are limited due to the small number of ions that have similar ionic radii and valence and can substitute for Si4+ in the crystal structure. The Seh Qaleh agates have 95.78 to 98.9 wt.% SiO2 with minor amounts of Al2O3 (0.01-0.34 wt.%), Fe2O3 (0.01-1.07 wt.%), Na2O (0.11-0.15 wt.%), and CaO (0.01-0.4 wt.%), supplied from alteration of the volcanic host rocks.The high concentrations of U in some of the agates of the study area (especially ~ 38 ppm in the red one) are surprising and propose the operation of specific processes for mobilization, transport and deposition. These processes caused concentrations of U in quartz and chalcedony that can exceed the concentration of U in the Seh -Qaleh volcanic rocks (Table 1).Zielinski (1979) observed a parallel accumulation of Si and U and investigated the mobility of U during the alteration of volcanic rocks. Based on the theory that the transport of chemical compounds is mainly realized by diffusion processes in aqueous fluids (e.g. Si as monomeric silicic acid Si(OH)4), Porter and Weber (1971) inferred for the uranyl ion a complex with monomeric silica UO2SiO(OH)3+. In addition, the presence of calcite, as associated mineral with silica polymorphs and the concentration of Na, K and Ca elements in agates, indicate that volatile chloride compounds might play a role in the alteration of volcanic rocks as well as the mobilization and transport of SiO2 and other chemical compounds (Götze et al. 2012).

The study area is located at east of Bam city and southeast of Kerman province. This area is located at 45 km from the Bam-Zahedan Road. From the main asphalt road of Bam - Zahedan it has 15 km of dirt and car accessible road. It is part of the NW-SE trending volcanic belt east of Bam.

This study aims to geochemically investigate the behavioral pattern of hydrothermal mineralization elements in the region in order to determine local and regional uranium enrichment at 1: 5000 scale. For this purpose 616 lithogeochemical samples were collected and analyzed. The study area is located southwest of Allahabad 1: 250000 Map. The Eocene outcrops are divided into two classes of pyroclastic and lava based on 1: 5000 scale studies. These deposits are cut by numerous dykes with an approximate northwest-southeast trend. These basaltic-diabase dykes can actually be attributed to the Eocene. The most important statistical parameters used in interpretation of area data are mean, median, mode, variance, standard deviation, coefficient of variation, skewness and kurtosis which were calculated for all data.

After normalizing and eliminating outlier values data, the data were analyzed using Pearson correlation matrix method to identify the correlation coefficients of the elements that accordingly, the highest correlation of uranium was observed with Be, Cd, Co, Cu, Mn, Mo, Na, Ni, Sc, Se, Tl, V, Y, Zn, Zr, Ga, Ge, and Hf. It indicates the paragenetic relationship of these elements with each other.Based on data clustering, four groups of chemical elements can be of particular interest due to their strong association with uranium, which include:Rare earth elements: Y, La, Ce Polymetallic elements: As,Sb, Ba, Cu, Pb, Zn, Mn, Fe, Se, Sr Related to acidic volcanism: Be, Mo, W, Zr Related to basic magmatic activities: Co, Cr, Ni, V The pattern of uranium paragenesis element groups in this diagram is roughly consistent with previous studies in the field of uranium volcanogenic deposits. Based on factor analysis, an 8-factor model with 78.6% variance was obtained for 43 elements. The second factor with a variance coverage of about 12.5% contains As, Mo, Sb elements with high factor loadings and Ag, Be, Ce, La, Pb, Tl, U, W, Y elements with average factor loadings. This factor is related to uranium mineralization in the region. Based on the results of the statistical analysis and interpretation of the geochemical map of the uranium element, the enrichment limit for this element is considered to be 5.67 ppm and background and threshold values were 2.39 ppm and 4.3 ppm, respectively.

The impact of hydrothermal solutions is strongly observed on the volcanics of the area, resulting in geochemical imbalances. Mo in the region forms large lithogeochemical haloes that are highly consistent with U elemental haloes and are generally concentrated at high U concentrations. Due to the Mo mineralization in the deeper regions, probability of U mineralization also exists in the deeper parts of the region and it is anticipated that subsurface studies will show significant results in terms of the occurrence of U compounds. Much of the southern half of the region, except for abnormal areas, is consistent with fault trends and concentrated along fault lines. There is widespread argillic alteration in the Eocene units of the region, with enrichment of the REEs, especially associated with lanthanum. Increasing the intensity of alteration and increasing joints and fractures allow the fluid to move, thereby increasing the fluid / rock ratio and facilitating migration of anomalies. The trend of uranium anomalies is often consistent with the cerium, yttrium, and lanthanum anomalies, and is usually in the margins of the basic dykes which indicates the convection of these elements from a mineralized fluid. This indicates the mobility of rare earth elements during alteration processes and their concentration by geochemical dams, including basic dykes. By comparing the obtained paragenesis for the uranium element in the region and the geochemical pattern observed with different types of known uranium deposits in the world, the most likely option for the type of mineralization in the region, is volcanogene uranium type.

The Urmia-Naqadeh-Mahabad basin is a part of the south and west Urmia Lake drainage basin that covers some parts of East-and-West Azerbaijan and northern Kurdistan. This study is the integration of geological, hydrological, remote sensing, geochemical and airborne geophysical data classifying promising areas that are related to sandstone type uranium (U) mineralization in Iran. Based on positive factors such as favorable source, host rocks and suitable hydrological pattern, this basin is a favorable basin in Iran. According to the characteristics of lithology, tectonic, sedimentary environment, geotectonics and etc. the basin could be classified into favorable, promising and possible subbasins for mineralization of U sandstone type.
Material and Geological data show that this region is a part of the Sanandaj-Sirjan zone and consists of Precambrian metamorphic rocks which are covered by younger sedimentary and volcano-sedimentary rocks that are influenced by different metamorphic phases. More than 7597 stream sediment samples from the area have been analyzed for Se¡V¡ Mo¡ As¡Cu¡ Ag¡ Zn¡ Co¡ Ni¡ Pb¡ Ti¡ Th¡ Zr¡ P and Sn. The basin is divided into 11 individual sub-basins. Radiometric data of the basin have been acquisitioned during 1976-1978 by an Australian-German- French Company with line separation of 500 meters and 120 meters of nominal terrain clearance.
Remote sensing data reveals that the western subbasin is suitable for sandstone type uranium mineralization. Based on geochemical evidences, the Au, Zn, Sn, As and Pb elements were enriched. Geophysical investigation reveals that the Eastern basin includes high amounts of U and low amounts of Th. Hydrogeological study demonstrates that the trend of groundwater is from the west to the east.
Geochemical data revealed that we can divide the basin into 11 subbasins which are characterized as follows: 1. Ghara Aghaj (126 Km2), North to south trend is situated at the northern part of the basin. At this basin Ni, Co, Cu and V are reported but it is not related to mineralization.
2. Ghoma – Bezrgah (36 Km2). The East to the West trend is situated at the western part of the basin. At this basin Pb, As, Sn, Zn and Au are reported which can be related to skarn mineralization.
3. Piram – Shilan (342 Km2). At this basin Pb, Zn, As and Mo are reported which contain source rocks of uranium mineralization but there is no evidence of host rock and mineralization.
4. Pirestan1 (28 Km2). According to geological data a granitic body which can be the source of uranium mineralization and cretaceous volcanic rock outcropped. The fault system is weak by the north to the south trend. The anomalies of Pb, Mo, As and Sn are reported but there is no evidence of mineralization.
5. Kooh-e sabz poosh (34 Km2). Based on geological data half of the area is covered by granodioritic body which can be the source of uranium mineralization. The fault system has two trends (NE-SW and N-S). The anomalies of V, As, Mo and Co are reported but there is no evidence of mineralization.
6. Pirestan2 ((83 Km2). According to geological data a granitic and granodioritic body can be the source of uranium mineralization. The anomalies of Mo, Sn, Co, As and Zn are reported but there is no evidence of mineralization.
7. Chahar Taq (36 Km2). The fault system has the NE to SW trend and trusted mechanism. The anomalies of Zn, Ni and Au are reported but there is no evidence of mineralization.
8. Zaveh Kooh (111 Km2). The rock units have the NW to SE trend according to the Sanadaj-Sirjan trend. The anomalies of Pb, As, Sn, Mo, Ti, Cu, Ni and Au are reported but there is no evidence of uranium mineralization but there is some evidence of orogenic gold mineralization.
9. Saqqez-Baneh (465 Km2). The rock units have the NW to SE trend according to the Sanadaj-Sirjan trend. The anomalies of Co, Ti, Cu, Zn, Pb, Ni, Mo, Sn, Ag, Au and As are reported but there is no evidence of uranium mineralization and the same as the 8th subbasin there are known deposits of orogenic gold mineralization.
10. Charkeh (104 Km2). The rock units have the NW to SE trend. The anomalies of Zn, Mo, Sn, V, Ni, Au, As and Pb are reported but there is no evidence of mineralization.
11. Sheikh Ebrahim (38 Km2). The anomalies of Mo, Au, As and Pb are reported.
The integration of the different layers shows that the prospecting area is suitable for future exploration of blind deposits.
Geophysical data was processed and revealed those areas which have data. They can be classified into 5 different classes based on U and Th concentrations.
The Hydrogeological data consist of EC, pH, Eh, DO and salinity. And the temperature was measured at the field by Sension 156 multimeter and was sent for ICP-MS analysis to the AMDEL and Applied Geological Research Center (Karaj) laboratories. Two samples were obtained from each well by Widel et al.’s (1998) method. One sample was analyzed for Ca2¡ Mg2¡ Na¡ K¡ CO32-¡ HCO3-¡ SO42-and Cl- and the other samples were analyzed for major and trace elements. At each basin charge, the discharge and the trend of underground water were defined.
The results revealed that this basin contains alkaline magmatic rocks such as alkaline rhyolite and tuff which are situated in reduced shale and continental volcanic clastic rocks and can be the source of uranium at the study area. Besides these rocks, tuffaceous sandstone, metamorphose sandstone and young alluvial by the reduction condition can be the suitable hosts for mineralization.
Based on geological, geochemical, hydrogeological and geophysical data, the western basin is suitable for sandstone type uranium deposit and also there is some evidence of mineralization.

The occurrence of uranium anomalies associated with secondary Cu mineralization (malachite) at some parts of the Razgah metaluminous -peralkaline stock situated at the northeast of Sarab caused it to be a priority of Atomic Energy Organization of Iran (AEOI) to inspect the intrusion for likely uranium mineralization. Hence the current study, which is supervised by AEOI, was carried out to investigate the U mineralization potential of the stock by applying the mineralogical, petrological and geochemical studies. A fractionation trend is inferred from variations in rock compositions stretching from nepheline-bearing monzodiorite to nepheline monzosyenite, pseudoleucite monzosyenite andnepheline syenite. Consideration of geochemical features of fresh rocks of the stock and its associated dikes with emphasis on geochemical behavior of U and REEs during magmatic fractionation revealed that apatite has played a prominent role in controlling concentrations of REEs, U, and Th, in addition to zircon, which played a considerable role in accommodating HREEs, U, Th and HFSEs (Ti, Ta, Nb, Hf, Zr) in more differentiated rocks.Nepheline syenite rocks of peralkaline composition,s which are considered to be the most differentiated have low contents of HFSEs, U (up to 21 ppm), Th (up to 56 ppm) and REEs compared to average nepheline syenites but are relatively more enriched in these elements than less differentiated rocks of the stock. Most of the rocks possess negative Eu anomalies (Eu/Eu*≤1) and differentiated nepheline syenites have strong negative Eu anomalies. Abundance of ilmenite and magnetite and lack of amphibole in rocks suggests the parental magma had a reducing nature and meagre contents of volatile components, which along with metaluminous character and prepondarence of apatite in rocks have rendered the magma incapable of enriching U. Minor amounts of hydrothermal fluids released from some parts of the stock led to leaching of U from hosting minerals (apatite and zircon) and resulted in weak hypogene mineralization of U and Cu. Later supergene leaching process affected the weak primary mineralization and upgraded U tenors concurrent with formation of secondary Cu carbonate minerals. Due to thin and limited extention of these enrichment sites, they are not economically viable for uranium extraction; consequently, this area does not suggest for semi-detailed and detailed exploration program for uranium by AEOI.

The original mineralogy of carbonate- evaporite series of Kangan and Dalan formations in central Persian Gulf area has been determined in this study. Uranium and strontium elemental concentrations were determined in the samples of two wells using inductively coupled plasma tool. The concentrations of these two elements show the same variations in the studied formations. Comparison of these elements with uranium wire line data showed the same trend. As both uranium and strontium preferentially enrich in aragonite other than calcite, they can be used for determination of the original mineralogy of carbonate deposits. The results showed that in the end-Permian time, there was an aragonite sea stage that was favorable of life for carbonate secreting organisms. After that, an equilibrium condition was dominated with simultaneous precipitation of aragonite and calcite. At the end-Permian time just below the Permian-Triassic boundary, there was an acidic condition that was hostile to life. Comparing this period with other sections withcomplete end-Permian record showed that there is a gap in these sediments. Using carbon- hydrogen- uranium and oxygen system, anoxic conditions determined at the later stage. These results show that combination of acidic and anoxic conditions made a serious problem for life at the end-Permian time in central Persian Gulf area at the time of deposition.

The purpose of this paper is to analyze geological samples (water) using cartridge in order to pre- concentration of these samples. In this paper, the study of Uranium ion imprinted polymer (IIP) synthesis is addressed. The Uranium ion complex in (CH3Coo)2 Uo2. 2H2O is considered as the initial nucleus of polymer. This complex is formed by di vinyl phosphonic acid (VIP) ligand. Then, ethylene glycol dimethacrylate (EGDMA) is used as cross linker and azobis isobutyronitril (AIBN) acting as initiator in polymerization is applied for the final synthesis of polymer. The synthesis of these polymers is performed by covalent interactions. The complex of non- imprinted polymer (NIP) is also synthesized under above- mentioned condition but without the presence of Uranium ion and ligand. IIP was obtained can be used as a high absorbent for solid phase extraction (IIP-SPE). In addition, the study of condition andtests such as pH effect on absorption, permeability factor, acid concentration and volume which is required for elution is conducted in order to test the column efficiency. The experimental evidences indicate that the maximum absorption of Uranium ion is in pH= 7. In addition, 1M nitric acid solution with 5 ml volume has the highest elution rate. The rate of uranium permeation was measured above 200 mm. The results were obtained by ICP-MS as reference and ICP-OES to promote the analytical reading and reduce the detection limit. These results indicate very high absorption of IIP for Uranium ions. It must be noted that this process was successfully applied for pre-concentration of geological samples, inparticular water samples and led to the promotion of results from analyzing all metallic ions such as uranium ion in geological samples (water) by ICP-OES and analytical optimization with lower detection limit by ICP-MS.

Uranium becomes soluble and mobile under oxidizing conditions in aqueous environment, and presence of complexing agents with uranium increase this mobility. Existence of such conditions in groundwaters of Ayrakan and Cheshmeh Shotori areas has led to oxidation, solubility and mobility of uranium minerals. Hydrogeochemical study of uranium in the study areas reveals the presence of bicarbonate ion, as the complexing agent with uranium (UO2 (CO3)22-) and icreasing factor of uranium mobility in groundwaters. Calculating the uranium mineral’s saturation index also indicates the super saturation of water samples in pitchblende. The positive saturation index of pitchblende expresses the proper water flow rate to steady-state equilibrium with probable uranium mineralization in depth and indicates that the permeability of groundwaters by porous flow has provided the enough time for their contact with hidden uranium mineralization (uranium ore deposit). As a result of this contact and because of the presence of carbonate complexes, solubility and mobility of uranium has increased. Hydrogeochemical studies, high activity of water and soil samples and all the above evidences indicate the possibility of existence of hidden uranium mineralization in depth and the distance between Ayrakan and the Cheshmeh Shotori areas.