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  • 1.
    El-ghali, Mohamed Ali Kalefa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Tajori, Karima
    Mansurbeg, Howri
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    The influence of transgression and regression on the spatial and temporal distribution of diagenetic kaolin in the Upper Ordovician paralic glaciogenic sandstones within sequence stratigraphic framework, the Murzuq Basin, S W Libya2006In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 89, no 1-3, p. 87-91Article in journal (Refereed)
    Abstract [en]

    Reservoir quality prediction can be considerably improved with an integrated approach between sequence stratigraphy and diagenesis. Here, we demonstrate that the occurrence of low-porosity sandstones (pseudomatrix-rich, i.e. matrix formed by mechanical compaction and squeezing of soft clasts in intergranular pores) deposited in shallow marine settings can be predicted in a sequence stratigraphic framework. These sandstones occur as lags bounding parasequences and, thus may form baffles and barriers for vertical fluid flow, and reservoir compartments between two sandstone bodies of adjacent parasequences. The prediction of their occurrence and precise spatial distribution is, therefore, very useful for production of shallow marine reservoirs.

  • 2.
    Gleisner, M.
    et al.
    Stockholm Univ, Dept Geol & Geochem.
    Herbert, Roger
    Stockholm Univ, Dept Geol & Geochem.
    Sulfide mineral oxidation in freshly processed tailings: batch experiments2002In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 76, no 3, p. 139-153Article in journal (Refereed)
    Abstract [en]

    This work focuses on sulfide mineral oxidation rates under oxic conditions in freshly processed pyrite-rich tailings from the ore concentrator in Boliden, northern Sweden. Freshly processed tailings are chemically treated in the plant to kill bacteria and to obtain increased metal yields, resulting in a high pH level of 10-12 in the process water. Different oxidation experiments (abiotic oxidation in untreated tailings, acid abiotic oxidation and acid microbial oxidation), containing the Boliden tailings, were performed at room temperature with dissolved oxygen (0.21 atm O-2) for 3 months. The different pyrite oxidation rates given from the study were 2.4 x 10(-10) mol m(-2) s(-1) for the microbial, 5.9 x 10(-11) mol m(-2) s(-1) for the acidic abiotic and 3.6 x 10(-11) mol m(-2) s(-1) for the untreated experiments. Because of the potential precipitation of gypsum in the batch solutions, these oxidation rates are considered minimum values. The release rates for copper and zinc from chalcopyrite and sphalerite in the acid experiments were also investigated. These rates were normalized to the metal concentration in the tailings, and then compared to the release rate for iron from pyrite. These normalized results indicated that metal release decreased in the order Cu>Zn>Fe, demonstrating that pyrite is more resistant to oxidation than sphalerite and chalcopyrite. Pyrite was also more resistant to acidic dissolution than to microbial dissolution, while a significant fraction of sphalerite and chalcopyrite dissolved in the acid abiotic solutions.

  • 3.
    Herbert, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Seasonal variations in the composition of mine drainage-contaminated groundwater in Dalarna, Sweden2006In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 90, no 3, p. 197-214Article in journal (Refereed)
    Abstract [en]

    Groundwater down-gradient from a mine rock dump in Dalarna, Sweden was sampled from the onset of snowmelt runoff (April) until October in order to investigate seasonal variations in groundwater composition. The results demonstrate that considerable variation in solute concentration (Al, Cu, Fe, SO42-, Zn) and acidity occurs in groundwater; the greatest change in solute concentrations occurs during the melting of the snow cover, when sulfide oxidation products are flushed from the rock dump. During this period, groundwater flow is concentrated near the soil surface with an estimated velocity of 1 m/day. Groundwater acidity varied by a factor of four closest to the rock dump during the sampling period, but these variations were attenuated with distance from the rock dump. Over a distance of 145 in, groundwater pH increases from 2.5 to 4.0 and acidity decreases from 3-13 to 0.8-1.1 meq/L, which is the combined effect of ferric iron precipitation and aluminosilicate weathering. As a result of flushing from the upper soil horizons, peaks in total organic carbon and ammonium concentrations in groundwater are observed at the end of snowmelt. In soils impacted by acidic surface runoff, the sequential extraction of C horizon soils indicates the accumulation of Cu in well-crystallized iron oxyhydroxides in the upper C horizon, while Cu, Fe, Ni and Zn accumulate in a well-crystallized iron oxyhydroxide hardpan that has formed 2.5m below the ground surface. Surface complexation modeling demonstrates that SO42- and Cu adsorb to the abundant iron oxyhydroxides at pH < 4, while Zn adsorption in this pH range is minimal.

  • 4. Ladenberger, Anna
    et al.
    Demetriades, Alecos
    Reimann, Clemens
    Birke, Manfred
    Sadeghi, Martiya
    Uhlback, Jo
    Andersson, Madelen
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    GEMAS: Indium in agricultural and grazing land soil of Europe - Its source and geochemical distribution patterns2015In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 154, p. 61-80Article in journal (Refereed)
    Abstract [en]

    Indium is a very rare element, which is usually not reported in geochemical data sets. It is classified as a critical metal, with important applications in the electronics industry, especially in the production of solar panels and liquid-crystal displays (LCDs). Over 4000 samples of agricultural and grazing land soil have been collected for the "Geochemical Mapping of Agricultural and Grazing Land Soil of Europe" (GEMAS) project, carried out by the EuroGeoSurveys Geochemistry Expert Group. Indium concentrations in soil have been analysed using aqua regia extraction followed by ICP-MS, Median values of In for both land use types are nearly identical, 0.0176 mg/kg for agricultural soil and 0.0177 mg/kg for grazing land soil. The spatial distribution patterns of In in European soil are mainly controlled by geology and the presence of Zn and Sn mineralisation. The preference of In to accumulate in the fine-grained fraction of soil with high clay content dominates the major anomaly patterns on the geochemical maps. In the Mediterranean region, secondary In enrichment is visible in karst areas. A notable feature of the In spatial distribution is the large difference between northern and southern Europe, with median values of 0.012 and 0.021 mg In/kg, respectively, suggesting that, in addition to lithology, weathering and climate are important factors influencing In soil enrichment over time.

  • 5.
    Morad, S.
    et al.
    Department of Petroleum Geosciences, The Petroleum Institute, Abu Dhabi, United Arab Emirates.
    Al-Aasm, I.S.
    Department of Petroleum Geosciences, The Petroleum Institute, Abu Dhabi, United Arab Emira.
    Sirat, M.
    Schlumberger Oilfield Middle East and Asia, Abu Dhabi, United Arab Emirates.
    Vein calcite in Cretaceous carbonate reservoirs of Abu Dhabi: Record of fluid flow2010In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 106, no 1-3, p. 156-170Article in journal (Refereed)
    Abstract [en]

    Petrographic, geochemical analyses (major, trace and rare-earth elements and C, O- and Sr-isotopes), and fluid-inclusion microthermometry study of vein calcites in primarily Cretaceous reservoir carbonate rocks in oilfields from Abu Dhabi, UAE, helped to unravel the formation conditions and origin of diagenetic fluids.

    The vein calcites have diverse crystal shapes (equant blocky, bladed and fibrous) and sizes (up to 3 cm across) and display complex cross-cutting relationships. These calcites display a wide range of stable carbon (δ13CV-PDB = − 11.1‰ to + 9.6‰) and oxygen (δ18OV-PDB = − 12.7‰ to − 2.3‰) isotopic compositions, indicating formation under diverse geological conditions. The oxygen isotopic composition suggests that the precipitation of vein calcites occurred at temperatures of ca. 30–100 °C assuming that the fluids had δ18OV-SMOW values of marine pore waters which evolved to basinal brines (i.e. − 1.2‰ and + 2‰, respectively). These inferred temperatures corroborate the fluid-inclusion microthermometry, which revealed a predominantly single, whole liquid phase that suggests entrapment temperature less than ca. 50 °C. A few two-phase fluid inclusions in equant and bladed calcite indicate precipitation at ca. 68–100 °C and salinity of ca. 3.9–10.1 wt.% equivalent NaCl).

    The carbon isotopic signatures suggest derivation of dissolved carbon from the host marine carbonates and, less commonly, from the degradation of organic matter by methanogenic and sulfate-reducing bacteria. The diverse sources of carbon coupled with the inferred wide range of precipitation temperatures presumably account for the lack of correlation between the carbon and oxygen isotopes. The derivation of dissolved carbon mainly from the host rocks is in good agreement with the marine Sr isotopic ratios of these calcites (87Sr/86Sr = 0.70744 to 0.70766). Rare-earth element patterns suggest significant fluid interaction with upper continental crustal rocks as evidenced by negative Eu anomalies and LREE-enriched patterns.

  • 6.
    Weihed, Pär
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Luleå tekniska universitet.
    Lithogeochemistry, metal and alteration zoning in the Proterozoic Tallberg porphyry-type deposit, northern Sweden1991In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 42, no 2-3, p. 301-325Article in journal (Refereed)
    Abstract [en]

    The Tallberg porphyry-type deposit is situated in the Early Proterozoic, syntectonic Jörn Granitoid Complex (JGC). The occurrence shows similarities with Phanerozoic porphyry type deposits: (a) low grade (0.27% Cu) and large tonnage, 44 × 106 metric tonnes, (b) stockwork as well as disseminated sulphides, (c) hydrothermal propylitic and phyllic alterations, (d) sulphides spatially associated to tectonic lineaments, and (e) genetically related to granitoid porphyry stocks. Lithogeochemical investigations indicate a metal zonation with (Mo+Cu+S) → (Zn+Pb±Au) → (As) from centre outwards. The host granitoid shows similarities with modern I-type granitoids, and the high primary content of Cu and Fe is possibly a discriminant factor for exploration for similar porphyry-type occurrences in Early Proterozoic volcanic arc terrains. Late shear zones adjacent to postmineral dykes have high Au contents (2-3 g/t), which are interpreted as gold mobilized from the porphyry-type deposit.

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