فهرست مطالب

Earth Sciences - Volume:7 Issue: 2, Oct 2015

Iranian Journal of Earth Sciences
Volume:7 Issue: 2, Oct 2015

  • تاریخ انتشار: 1394/11/10
  • تعداد عناوین: 7
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  • Shohreh Hassanpour*, Saeedeh Senemari Pages 89-105
    The Sorkheh deposit in northwestern Iran exhibits several readily visible general characteristics of sediment-hosted stratiform copper (SSC) mineralization. It consists of fine-grained disseminated base-metal sulfides within gray sandstones (gray beds, the basal whitish Miocene sandstone and shallow-water) that overlie a thick sequence of red beds (Miocene Upper Red Formation). The host gray beds are the basal sandstone and are intercalated with red bed sandstones, which are shown from textural studies to be carbonaceous and to have initially contained very fine-grained, disseminated, syndiagenetic pyrite. The sediment-hosted stratiform copper deposit of the Sorkheh area formed in a location where basinal fluids passed through a series of highly oxidized rocks and could obtained copper, which was then precipitated as the fluids encountered a reductant that destabilized the complexing ability of the fluid. According to the proposed model, the Sorkheh deposit appeared to have begun formation during diagenesis when mineralizing fluids became focused into constrained areas by stratigraphic and/or structural architecture. To form the Sorkheh sediment-hosted stratiform copper deposit, a number of major features must be present: abundant, highly oxidized metal source rocks, highly reduced strata in a position favoring interaction with significant amounts of fluid that previously passed through the oxidized strata package, and significant thicknesses of evaporates capping the reduced strata to serve as a hydrologic seal and a source of high-salinity (and possibly sulfur-rich) brines.
    Ore-stage sulfides are zoned vertically and obliquely through the mineralized zones, from cupriferous sulfides at low stratigraphic levels to copper-rich mineralization above, with unreplaced pyrite remaining within the upper Miocene. The zoned sulfides and their replacement textures, configuration of the mineralized zones, and the position of ore stage mineralization adjacent to a stratigraphically defined redox transition from red beds upward into graybeds indicate an overprint of copper (and accompanying ore-stage metals) on originally pyritic gray beds. The influx of ore-stage metals, presumably in an oxidized low-temperature brine, terminated with a silicification event that effectively sealed the host sandstones. Consequently, these observations and the overall genetic interpretation are consistent with the general deposit-scale genetic model for early diagenetic SSC mineralization. The regional geologic context is also consistent with its classification as a SSC deposit and is hosted by sediments that were formed in association with evaporates at a low latitude in a Sabkha environment. Source of Sorkheh deposition has been indicated as a sedimentary arid type. Sandstones of the Sorkheh area tectonic settings are obtained in a passive continental margin.
    Keywords: Sediment, hosted stratiform copper, Sorkheh, Azerbaijan, NW Iran
  • Balakrishna Gurugubelli *, Shamsh Pervez Pages 106-113
    Different approaches of source apportionment of dust fractions have been reported world-over. Predicting source categories within receptor chemical profiles using regression and factor analysis using PCA has been reported to evaluate possible source/routes of air pollution mass. The present study is focused on the application of all three approaches to investigate higher degrees of significance in source apportionment of indoor dust fallout in the Raipur city district, Raipur, India, which is located at 21°14’22.7” N latitude and 81°38’30.1” E longitudes. Modeled source categories obtained from regression and factor analysis (using PCA) has shown potential support in the selection of source profiles in CMB. About 65-78% agreement has been obtained between results of source signatures of dust fallout obtained from the three approaches. The application of the combined approach has been extended to respirable fine particulates measured indoors. Both fractions have shown a different dominance of selected source of emissions. Major approaches of source signatures has been investigated in combination with the hypothesis that prediction and modeled source profiles will support the selection and inclusion of field based source profiles in source apportionment of indoor dust fractions using CMB. A stratified random sampling plan using the longitudinal study design has been adopted for dust fallout source apportionment.
    Keywords: Source apportionment, CMB, Regression analysis, Indoor air
  • Jamal Tarrah*, Zahra Abedpour, Karl Strauss, Thomas Schimer, Kurt Mengel Pages 114-123
    Ten chromite ores from ophiolite complexes in SE Iran were analyzed mineralogically by XRD, chemically by XRF, and mineral chemistry by EPMA. The identified paragenesis of silicate minerals of chromite ores with the X-ray diffraction is pronounced differently. It consists of secondary phases formed as serpentine, Cr-containing chlorite (kaemmererite), chromic garnet (uarovite) with preserved partly primary minerals of peridotite parent rocks such as olivine and diopside. From the total chemical analysis by XRF results, a good correlation exists between the Cr2O3 and SiO2 content (as an index of the sum of the silicate minerals). This allows an easy decision for mine ability of chrome ores. In a relatively good correlation are also the Mg and Fe oxide contents. The mineral chemisty (EPMA analysis ) of spimel mineral provides valuable information about the the octahedral layer of the spinel,. The results of the microprobe analysis show a variation in the chemical composition of the spinel phase of a mixed crystal formation consisting of: chromite (Fe2ઽ), magnesiochromite (MgCr2O4), spinel (MgAl2O4), and hercynite (Fe2ɝ). This becomes even more complex by the mixed crystal relationship with picotite [(Mg, Fe2)(Cr,Al,Fe3)2O4], which contains Fe3 in the tetrahedral position. The chrome spinel vary inCr-numbers [100 ×(Cr / Cr Al) = 75-92] and Mg-numbers [100 * (Mg / Mg Fe2) = 38-57]. The partition of iron between Fe3 und Fe2 was made by assuming normal spinel structure, using the formula AB2O4. Correlations of microprobe analysis indicate that the mineral chemistry of the studied spinel is characterized mainly by the divalent elements of Mg and Fe2 in the A position and trivalent elements Cr and Al in the B position.
    Keywords: Ophiolite, Mineralogy, Chemical Composition, Microprobe, Spinel, SE Iran
  • Feridon Ghadimi * Pages 124-133
    In this study, water samples were collected from 10 thermal and non-thermal springs of Mahalat setting during four periods in 2011. The discharge rates of these springs vary from 2 l/s to 45 l/s and their temperature range from an average minimum of 18oC to maximum 47oC. Spring water is high in SO4-Cl and this is related to gypsum dissolution. Correlation coefficient, principal component analysis, and isotopic data of samples showed there was mixing of young and old water and meteoric water in springs. The quality of water for irrigation was assessed by parameters such as SAR, SSP, RSC, PI, MAR and Kelly’s index for major elements (SO42-, HCO3-, Cl-, Ca2, Na, Mg2 and K). All water quality indices have shown that the water is suitable for irrigation. The metal index of heavy metals (Hg, Zn, Co, As, B, Cu, Mn, Mo and Ni) was compared to the Standard Iranian Guideline values for irrigation and was also used to determine the contamination index. The calculated values have shown that almost all samples are above the threshold of warning and most of the water samples are contaminated.
    Keywords: Mahalat, chemical data, contamination, irrigation, thermal water
  • Keyvan Karami *, Peyman Afzal Pages 134-141
    The aim of this study was to identify various sulfidic mineralized zones in the Ghare-Tappeh Cu deposit (NW Iran) based on geo-electrical data including induced polarization (IP) and resistivity (RS) using the concentration-volume (C-V) and number-size (N-S) fractal models. The fractal models were used to separate high and moderate sulfidic zones from low sulfidic zones and barren wall rocks. Both the N-S and C-V fractal models confirm that there is a high sulfidic mineralized zone in the NW part of the studied area. Moreover, the application of multifractal modeling based on the geo-electrical data is considered to be a proper approach for delineation of various mineralized zones at depth for optimization of mineral exploration operations. Finally, the results can be useful for proposing grid drilling in a detailed exploration stage.
    Keywords: Multifractal modeling, concentration, volume (C, V) fractal model, number, size (N, S) fractal model, Sulfidic mineralized zones, IP, RS, Ghareh, Tappeh
  • Shayan Ghodratabadi *, Faranak Feizi Pages 142-152
    Water plays a vital role in the development of activities in an area. The surface water resources are inadequate to fulfill the water demand. Productivity through groundwater is quite high as compared to surface water, but groundwater resources have not yet been properly exploited. Keeping this view, the present study attempts to select and delineate various groundwater potential zones for the assessment of groundwater availability in Moalleman, using the remote sensing and GIS technique. Satellite images such as Landsat 8, Aster and SRTM DEM data have been used in the present study to prepare various thematic maps for the study area, such as geology, geomorphology, soil hydrological group, land use/land cover, and drainage maps. According to the relative contribution of each of these maps towards groundwater potential, the weight of each thematic map has been selected. Furthermore, within each thematic map ranking has been made for each of the features. All the thematic maps have been registered with one another through integrated step-by-step using the normalized aggregation method in GIS for computing groundwater potential index. Based on this final weight and ranking, the groundwater potential zones have been delineated. Thus from the present study it has been observed that an integrated approach involving remote sensing and GIS technique can be successfully used in identifying potential groundwater zones in the study area. Five categories of groundwater potential zones: excellent, very good, good, moderate and poor have been demarcated. Major portions of the study area have “good” or “moderate” prospects, while a few scattered areas have poor prospects. The excellent potential areas are mainly concentrated along the shore line. This groundwater potential information is useful to effectively identify suitable locations to extract water. Lastly, the final map has been overlaid with the map of springs and qanats for comparison and rolling as a checkpoint.
    Keywords: Groundwater Potential Map, GIS, Remote sensing, Weigh Overlay, Landsat8, Aster, STR DEM
  • Ali Amirkhani * Pages 153-163
    Three well - known source rocks of the Zagros basin and the Persian Gulf are Mesozoic in age.The Jurassic Sargelu, Albian Kazhdumi and Neocomian-Coniacian Garau formations have charged the Cretaceous reservoirs of this area. The northwest part of the Persian Gulf is strongly influenced by two major N-S trending paleohighs (Hendijan- Bahregansar-Regesafid-Izeh and Kharge- Mish) and surrounding plaeotroughs that play the most important role in the reservoir and source rock development. The most important reservoirs are the Cenomanian- Turonian Sarvak and Santonian Ilam formations which locally separated by a thin shaly unit of the Coniacion Laffan Formation. The reservoir facies are dominated by benthic and rudist debris on the paleohighs which laterally grading down to the basinal Cenomanian Ahmadi and Santonian Gurpi pelagic marls. In order to study the petroleum system of the northwest Persian Gulf, several 2D seismic lines and six wells were interpreted. Based on the interpreted seismic profiles the best locations for the reservoir facies could be within the pinch-out geometries around the plaeohighs which occasionally sealed by the baisn-type Campanian- Maastrichtian Gurpi marls at the top, Laffan shale at the middle and Albian Kazhdumi shale at the base as stratigraphic traps. A large hiatus exists between the top of the Cenomanian Sarvak Formation and Eocene Pabdeh Formation in the Tangue and Rage- Safid paleohighs, where these facies change could form stratigraphic traps. Toward the Nowrooz, Bahregansar Hendijan, structures, this hiatus is much shorter where Campanian- Maastrichtian Gurpi Formation directly has coverd the Sarvak Formation.
    Keywords: Petroleum System, Upper Cretaceous, Ilam, Sarvak Formations, Pinch–out, Stratigraphic trap