فهرست مطالب مهدی خراسانی پور

The objective of this study is to investigate the quality of water resources in Tahroud region in the northwest of Bam city, Kerman province through hydrogeochemical studies. For this purpose, 13 water samples, including 5 samples from the agricultural wells, 4 samples of Ghanats, 3 samples from springs and 1 sample of Tahroud river were sampled and analyzed in the laboratory using Inductively coupled plasma mass spectrometry (ICP-MS) method. Based on the hydrogeochemical analysis, the water resources of the studied area have dominant Na-Cl facies and are classified as saline waters. The average concentration of EC (6230 µS/cm), TDS (4050 mg/L) as well as of Clˉ (1391 mg/L), Na+ (9031 mg/L) and SO42- (771 mg/L) in the investigated water samples were remarkably higher than the normal or recommended values. The highest amount of these soluble ions were observed in the water samples collected from the playa section of the catchment basin, which was mainly covered by the Quaternary fine-grained deposits. In addition to the hot and dry climate and the high evaporation rate, the existence of Neogene formations containing gypsum and sodium salt under these sediments is another important factor that increase the solutes in underground water sources in this area. Among the investigated potentially toxic elements, the concentration of arsenic with natural origin and higher than the permissible limit of drinking water was observed in some water samples. The evaluation of the water quality of the region using the Schuler diagram also showed that these water sources have an unfavorable to unusable quality for drinking and even for agriculture in some cases.

The Tarz Pb-Zn deposit is one of the underground active mines in the Ravar-Kuhbanan area, located in the North of Kerman province. In this mine, mineralization was observed in two distinct sulfide and carbonate divisions within the dolomitic-limestone host rock units of the Middle Triassic succession (Shotori Formation). Field observations show that mineralization occurred mainly along the faults as veins or veinlets and in lesser extent as massive textures. Galena, sphalerite, pyrite and chalcopyrite are the most important primary sulfide minerals in the Tarz Pb-Zn deposit. Secondary minerals associated with the Pb-Zn deposits such as smithsonite, hemimorphite, cerussite and anglesite were also identified in some of the investigated samples. The average concentrations of Pb and Zn were 19 and 24% in the studied samples, respectively. Other elements such as Cd, Ag, S, Sb, Te, Se, As and Cu also showed significant enrichment in the investigated samples. Evaluation of the obtained results using multivariate statistical methods can reveal the possible relationships between mineralogical phases and geochemical analysis. For example, the correlation between Pb, Ag, Tl and Sb can be related with the galena mineralization or the geochemical relationship between As, Bi, Cu, P, Fe, Co, and S is related with the pyrite and chalcopyrite mineralization. Statistical relationships also showed that Zn has only a weak geochemical association with Se, U and Mo. The strong correlation of Ca and Mg is also due to the host-rock mineralogy, which is mainly composed of course and fine crystal dolomites at the margin and far distances of ore veins, respectively. Keywords: Mineralogy, Geochemistry, Tarz Pb-Zn deposit, Kuhbanan, North of Kerman  

Tarz Pb-Zn deposit is located at 30 km east of Kuhbanan and 5 km southwest of the Tarz village in the North of Kerman Province. From geological point of view, this mine is located on the southeastern margin of the Bahabad Pb-Zn belt, which is a part of Tabas-Poshte-e-Badam metallic belt of the Central Iran (Alavi 1991; Rajabi et al. 2013). In this area, there are a large number of Pb-Zn deposits that mostly occurs in the Triassic dolomite-limestone beds of the Shotori Formation. Major faults such as Kuhbanan and Behabad with NW-SE direction have been very effective role in the development of geology and mineralogy history of this region. However, The dominant trend of the faults in Tarz Pb-Zn deposit is about N40E, but field observations showed various faults and fractures in different directions, which demonstrate the active tectonic of this area. For example, one of the major mineralization parts of the mine was in a shearing zone produced by four major faults with NW-SE direction. Some authors such as Amiri et al. (2009) believe that based on the position of mineralized sections in the carbonate host rocks the Tarz Pb-Zn mine is classified as the Mississippi Valley Type (MVT) deposits. In the Tarz mine, mineralization is observed in two distinct sulfide and carbonate sections, which are located in the north and south of the mine, respectively. This study emphases on the texture, mineralogy and geochemistry of sulfide section of the Tarz Pb-Zn deposits in order to determine the elemental dispersion, and reconstruction of depositional history of Pb and Zn minerals.  

Fifty rock samples were collected from mineral veins and hosted-rock for mineralogical studies of sulfide section of the Tarz Pb-Zn mine. Ore mineralogy studies were done on the 30 polished-thin section and five polished-blocks by reflecting and polarizing microscope (OLYMPUS BH-2 model) at the Geology Department of Shahid Bahonar University of Kerman. Also, eight samples were selected for further mineralogical studies by X-ray diffraction (XRD) method in the Zarazma Laboratory, Tehran, Iran. After mineralogical studies, 10 samples were selected for major and trace elements analysis by the ICP-MS method in the Zarazma Laboratory. Geochemical data were used to (1) calculate enrichment factor; (2) identification of enriched elements; and (3) geochemical correlations of target elements. The spider diagrams of major and trace elements were plotted in order to determine their changes from ore veins to the surrounding hosted rocks. For drawing of spider diagrams, the data were normalized against the standard limestone.  

Mineralogy Mineralogical studies using ore microscopy and XRD showed that both primary and secondary minerals are present in the sulfide section of the Tarz deposit. The most important primary minerals were galena (about 60%), sphalerite (less than 40%), pyrite and chalcopyrite. These minerals were often found in the mineralized sections in the northern part of the mine, where mineralization occurs mainly as veins and veinlets, breccia and in lesser extent as pore-filling structures. The secondary minerals including smithsonite, hemimorphite, cerussite, anglesite and iron oxides also were identified in different parts of the mine. In addition to the mentioned minerals, dolomite and calcite were also observed as the main minerals of the hosted-rocks. The identified dolomites minerals can be classified into two groups including fine-crystalline and sudhedral, coarse crystalline or saddle dolomite. It seems that fine-crystalline dolomites have formed as primary minerals during the early time of diagenesis, while the coarse-crystalline dolomites have formed by hydrothermal fluids. Calcite in the hosted rocks was mainly in the form of microcrystalline or micrite type and it seems that this mineral is not affected by the Pb-Zn mineralization process.   Structure and texture The structures and textures of mineralization in the Tarz mine, were as veins and veinlets, massive, breccia, pore-filling and replacement types. These structures are mainly related to the active fault system of the region. Galena, sphalerite, pyrite and dolomite were the most important primary minerals in most of mineralized textures, however, secondary minerals such as smithsonite, hemimorphite and cerussite were also observe in pore-filling and replacement textures.  

According to the results obtained from normalized enrichment factor Pb, Cd, Zn, Ag, S, Sb, Te, Se, As and Cu have moderate to high enrichments in the investigated samples, respectively. Also, U, Tl, Bi, Mo, Co and Cr showed low enrichments in some samples. The geochemical relationships between enriched elements was well compatible with the mineralogical results. For example, identified sulfide minerals (galena, sphalerite, pyrite and chalcopyrite) have a great potential for replacing of several of enriched elements in their crystalline structures as impurities. The geochemical associations of most of the target elements in sulfide minerals can be considered as possible mechanisms for enrichment of these elements in the investigated samples. These geochemical association can be revealed using multivariate statistical methods. For examples, the following groups of geochemical associations were observed in the investigated samples:

1-     The correlation between Pb, Ag, Tl and Sb, which can be related with the galena mineralization; 2-     The correlation between P, Cu, Bi, As elements with Fe, Co and S can be related with the pyrite and chalcopyrite mineralization; 3-     The strong correlation between Ca and Mg is due to the mineralogy of the host-rock minerals; 4-     Zinc only showed a weak correlation with Mo, U and Se, which may be due to the alteration and weathering of its primary sulfide minerals mainly into the secondary carbonate minerals; The spider diagrams of major elements showed that except iron, other elements have the same values with standard limestone. Ore forming processes, especially the presence of sulfide minerals such as pyrite, chalcopyrite and even sphalerite are responsible for iron enrichment in the investigated samples. Contrasting to the most of major elements, trace elements, especially Pb, Cd, Zn, Ag, S, Sb, Te and Se, As and Cu, showed strong deviation from their values in the standard limestone. Concentration of these elements were decreased by increasing distance from ore veins to the host rock.   Possible mineralization model The Pb-Zn mineralization in the Tarz mine as well as other ore deposits in the Ravar-Bahbad region is often as veins and veinlets. A variety of lithological and structural factors control Pb-Zn mineralization in this region. According to Leach et al. (2005) diagenesis and tectonic processes have a fundamental role in the formation of MVT type Pb-Zn deposits. Field observation demonstrate that active tectonic and formation of a complex fault system have more important role than other factors in the formation of Tarz Pb-Zn deposit. Comparison of the obtained mineralogical and geochemical data in this study with the previous researches revealed that the Pb-Zn mineralization in Tarz area is more similar to the MVT type. Nevertheless, to determine the source of ore-bearing fluids and to draw up a comprehensive mineralization model, isotopic and structural data are required.

Accumulation of potentially toxic elements in agriculture soil is one of the main serious environmental concerns in the greenhouse cultivation. The environmental investigation of potentially toxic elements (V, Ag, Se, Ni, Pb, As, Cr, Co, Cd, Cu, Fe, Mo, Mn, Sn, Sb, Bi and Zn) in the greenhouse cultivated soils of the Bagher-Abad area, Jiroft is the main objective of this study. After preliminary field investigations, 20 soil samples were collected by mean of composite method. Collected samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) method at the Labwest laboratory, Perth, Australia. The results were discussed using statistical methods and environmental indices with respect to the natural background and worldwide concentrations of target elements. The data showed that only Zn, Cd, Mo, As and in some cases Sb have medium enrichment in the investigated soils. For some of the selected soils the bioavailability or solubility of target elements was determined using 0.005M DTPA leaching solution. Among the investigated elements Cd and Zn showed the maximum bioavailable fraction corresponding to the medium to high risk assessment codes. Antimony is the only trace element that showed poor enrichment (39.3 µg/L) in the irrigation water used for the target greenhouse soils.

Sediment environment has a special importance in the ecosystem, because it acts as a sink for the potentially toxic elements in the water/sediment environment and also in a special conditions can be a major source for the contaminant elements. The aim of this study is to assess the concentration and contamination potential of potentially toxic elements in the Zayaderoud sediments with a special emphasis on the role of the Isfahan metropolis. For this purpose, 23 sediment samples were collected from the Zayanderud River within the boundary of the Isfahan city. After preparation process, the total concentration of target elements was measured by ICP-OES method. Also, single extraction methods were applied to the samples using 0.43M acid acetic and 0.05M EDTA leaching solutions. Evaluation of the total concentration results using environmental pollution indices showed that the concentrations of Ag, As, Cu, Pb, Zn, and S were higher than the natural background values suggesting an anthropogenic source. The contamination potential was increased from upstream to the downstream, especially after treatment plant located south of the Isfahan. According to the PCA multivariate statistical method, elements with the same sources fall into the same groups, so that the elements with the anthropogenic source showed the same group with high correlation. Determination of the soluble fraction using single extraction methods showed that 50 percent of statistical population of Cu and S has mobility factor higher than 30 percent corresponded with the high risk potential. Also, 50 percent of statistical population of Pb, Mn, and Zn showed mobility factor between 10 to 30 corresponded with the medium risk of these elements.