نوع مقاله : علمی -پژوهشی
1 گروه زمینشناسی، دانشکده علوم، دانشگاه لرستان، خرم آباد، ایران
2 گروه زمینشناسی، دانشکده علوم، دانشگاه تربیت مدرس، تهران، ایران
3 پژوهشگاه علوم و فنون هستهای، سازمان انرژی اتمی، تهران، ایران
4 گروه معدن، دانشکده فنی و مهندسی، دانشگاه تهران، ایران
عنوان مقاله [English]
IntroductionThe 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.Materials and methodsThis 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.Results and discussionAfter 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, CePolymetallic elements: As,Sb, Ba, Cu, Pb, Zn, Mn, Fe, Se, SrRelated to acidic volcanism: Be, Mo, W, ZrRelated to basic magmatic activities: Co, Cr, Ni, VThe 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.ConclusionThe 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.