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  • 101.
    Axelsson, Mikael D.
    Luleå tekniska universitet.
    Multielemental analysis of geological and biological samples using laser ablation ICP-SFMS2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The analytical performance of laser ablation (LA) for multielemental determination of geological and biological samples has been investigated. In the present study, LA has been used for sample introduction in inductively coupled plasma sector field mass spectrometry (ICP-SFMS). Although LA can provide semi-quantitative results rapidly and easily, the calibration process still remains the "Achilles heel" of the technique. The major goal of this study has been to investigate the capabilities of LA-ICP-SFMS for qualitative and quantitative analysis of various solid materials. LA was used for analyses of coal were calibration was performed by using coal powder doped with analyte elements. This was done by adding solution standards (including analyte and internal standard elements) to the coal, drying and finally homogenising, followed by pressing tablets. LA results were compared with data obtained by conventional solution nebulisation (SN) after preparation of coal samples using microwave (MW) digestion or fusion. In spite of a relatively poor agreement for elements such as As, Se, Sn, Re, Te, and Tl, accuracy obtained with LA in the present study is otherwise generally superior to previously reported data for LA and slurry nebulisation. For about 50 elements, results obtained with LA fall within 20% of those obtained by SN. The study shows the potential of LA quantification, based on solution-doped powders. However, the necessity of sample grinding and homogenising results in loss of spatial distribution information and makes the approach more vulnerable to sample contamination. The possibilities of sulphide minerals analysis by ICP-SFMS have been investigated. Seven elements (Co, Fe, Cd, Ag, Mn, Cu and S) have been quantitatively determined in sphalerite samples from the Zinkgruvan mine, using Zn as internal standard (IS). A straightforward calibration procedure allows on-line correction for possible Fe impurities at percent levels. Consequently, the use of complimentary techniques for determination of actual Zn content in the samples is avoided. The LA-ICP-SFMS results were compared with data from conventional SN introduction of sample solutions following acid digestion. Good agreement was found between the methods. For homogeneously distributed elements the overall precision for LA was found to be better than 10% RSD. A method for total mineral dissolution of five sulphides (sphalerite, pyrite, galena, pyrrhotite and chalcopyrite) has been developed, followed by multielemental analysis by ICP-SFMS. By performing this mineral characterisation the intention was to determine whether the analysed bulk mineral samples could be used as in-house LA calibration standards. The use of LA was focused towards elucidating whether the observed deviations in results obtained by ICP-SFMS for the two reference material powders used were caused by sample inhomogeneity or by inefficient matrix dissolution. It was found that the reference materials showed lack of accuracy in recommended concentrations for many trace and ultra trace elements, as well as possible inhomogeneity when using 50 mg sample amounts. The sulphide minerals studied appears to be suitable as matrix matched calibration standards for the determination of about 20 trace and ultra trace elements by LA. Laser ablation was also used for analysing element to sulphur ratios in washed human nails. The element ratios were then used to display the effectiveness of the applied washing method applied prior to MW digestion and analysis by ICP-SFMS. Based on the LA analysis, it was found that, even after the applied nail washing procedure, many elements are enriched in the surface of the nail.

  • 102.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Baxter, Douglas
    Ingri, Johan
    Öhlander, Björn
    High spatial resolution analysis of ferromanganese concretions by LA-ICP-MS2002In: Geochemical Transactions, ISSN 1467-4866, E-ISSN 1467-4866, Vol. 3, no 5, p. 40-47Article in journal (Refereed)
    Abstract [en]

    A procedure was developed for the determination of element distributions in cross-sections of ferromanganese concretions using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The effects of carrier flow rates, rf forward power, ablation energy, ablation spot size, repetition rate and number of shots per point on analyte intensity were studied. It is shown that different carrier gas flow rates are required in order to obtain maximum sensitivities for different groups of elements, thus complicating the optimisation of ICP parameters. On the contrary, LA parameters have very similar effects on almost all elements studied, thus providing a common optimum parameter set for the entire mass range. However, for selected LA parameters, the use of compromise conditions was necessary in order to compensate for relatively slow data acquisition by ICP-MS and maintain high spatial resolution without sacrificing the multielemental capabilities of the technique. Possible variations in ablation efficiency were corrected for mathematically using the sum of Fe and Mn intensities. Quantification by external calibration against matrix-matched standards was successfully used for more than 50 elements. These standards, in the form of pressed pellets (no binder), were prepared in-house using

  • 103.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Determination of major and trace elements in sphalerite using laser ablation double focusing sector field ICP-MS2001In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 72, no 2, p. 81-89Article in journal (Refereed)
    Abstract [en]

    The analytical performance of laser ablation (LA) for the determination of Co, Fe, Cd, Ag, Mn, Cu and S in sphalerite was evaluated using double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS). Samples were collected from Zinkgruvan, situated in the south central Sweden. The use of Zn for internal standardisation, together with correction for FeS impurities in sphalerite, allows straightforward quantification without using external methods for the determination of the actual Zn content. LA-ICP-SFMS results were compared with data obtained by conventional pneumatic nebulisation introduction of sample solutions following acid digestion. Good agreement between the two methods was obtained for homogeneously distributed elements. For the majority of the elements under consideration, LA-ICP-SFMS precision was better than 10% RSD.

  • 104.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilya
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Multielemental analysis of Mn-Fe nodules by ICP-MS: optimisation of analytical method2002In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 127, no 1, p. 76-82Article in journal (Refereed)
    Abstract [en]

    Two acid digestion procedures (microwave-assisted and room temperature) were developed for the quantitative analysis of ferromanganese nodules by inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS). Different compositions of the acid mixture, dilution factors and corrections for spectral interferences were tested. A combination of nitric, hydrochloric and hydrofluoric acids is necessary for complete sample digestion, with lowest acid to sample ratios (v/m) of 15 and 1.5. respectively, for the last two acids. Sample dilution factors higher than 2 X 104 should be used in order to decrease matrix effects and provide robust long-term instrumental operation. In spite of high dilution. method detection limits in the sub-mug g(-1) range were obtained for 54 out of 71 elements tested. due to the high detection capability of ICP-SFMS, as well as the special care taken to ensure the purity of reagents, to clean the instrument sample introduction system and to minimise sample handling. Owing to the presence of unresolved (at the resolution available) spectral interferences, accurate determination of Au, Hg, Os, Pd, Re and Rh is impossible without matrix separation. The accuracy of the entire analytical method was tested by the analysis of two nodule reference materials. The results generated agreed to within +/-2% for about 10, within +/-10% for more than 40 and within +/-20% for about 50 of 53 elements for which certified, recommended or literature values are available. A precision better than 3%, expressed as the between-digestion relative standard deviation (n=4). was obtained for the majority of elements, except in cases limited by low analyte concentrations

  • 105.
    Bagherbandi, Mohammad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Tenzer, Robert
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Moho depth uncertainties in the Vening-Meinesz Moritz inverse problem of isostasy2014In: Studia Geophysica et Geodaetica, ISSN 0039-3169, E-ISSN 1573-1626, Vol. 58, no 2, p. 227-248Article in journal (Refereed)
    Abstract [en]

    We formulate an error propagation model based on solving the Vening Meinesz-Moritz (VMM) inverse problem of isostasy. The system of observation equations in the VMM model defines the relation between the isostatic gravity data and the Moho depth by means of a second-order Fredholm integral equation of the first kind. The corresponding error model (derived in a spectral domain) functionally relates the Moho depth errors with the commission errors of used gravity and topographic/bathymetric models. The error model also incorporates the non-isostatic bias which describes the disagreement, mainly of systematic nature, between the isostatic and seismic models. The error analysis is conducted at the study area of the Tibetan Plateau and Himalayas with the world largest crustal thickness. The Moho depth uncertainties due to errors of the currently available global gravity and topographic models are estimated to be typically up to 1-2 km, provided that the GOCE gravity gradient observables improved the medium-wavelength gravity spectra. The errors due to disregarding sedimentary basins can locally exceed similar to 2 km. The largest errors (which cause a systematic bias between isostatic and seismic models) are attributed to unmodeled mantle heterogeneities (including the core-mantle boundary) and other geophysical processes. These errors are mostly less than 2 km under significant orogens (Himalayas, Ural), but can reach up to similar to 10 km under the oceanic crust.

  • 106.
    Bagherbandi, Mohammad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. University of Gävle, Sweden.
    Tenzer, Robert
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Abrehdary, Majid
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    On the residual isostatic topography effect in the gravimetric Moho determination2015In: Journal of Geodynamics, ISSN 0264-3707, E-ISSN 1879-1670, Vol. 83, p. 28-36Article in journal (Refereed)
    Abstract [en]

    In classical isostatic models, a uniform crustal density is typically assumed, while disregarding the crustal density heterogeneities. This assumption, however, yields large errors in the Moho geometry determined from gravity data, because the actual topography is not fully isostatically compensated. Moreover, the sub-crustal density structures and additional geodynamic processes contribute to the overall isostatic balance. In this study we investigate the effects of unmodelled density structures and geodynamic processes on the gravity anomaly and the Moho geometry. For this purpose, we define the residual isostatic topography as the difference between actual topography and isostatic topography, which is computed based on utilizing the Vening Meinesz-Moritz isostatic theory. We show that the isostatic gravity bias due to disagreement between the actual and isostatically compensated topography varies between 382 and 596 mGal. This gravity bias corresponds to the Moho correction term of 16 to 25 km. Numerical results reveal that the application of this Moho correction to the gravimetrically determined Moho depths significantly improves the RMS fit of our result with some published global seismic and gravimetric Moho models. We also demonstrate that the isostatic equilibrium at long-to-medium wavelengths (up to degree of about 40) is mainly controlled by a variable Moho depth, while the topographic mass balance at a higher-frequency spectrum is mainly attained by a variable crustal density.

  • 107.
    Baken, Stijn
    et al.
    KU Leuven, Belgium.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Geochemistry and Ecotechnology.
    Smolders, Erik
    KU Leuven, Belgium.
    The association between iron and carbon in freshwater colloids2013Conference paper (Refereed)
    Abstract [en]

    Iron and carbon are important constituents of natural colloids, which intimately links the fate of these two elements in riverine systems. Iron may strongly affect the binding of trace metals by organic matter, e.g. through competition for binding sites, which highlights the importance of a correct appreciation of the Fe speciation in surface waters. However, the chemistry of Fe and C in natural colloids is complex and depend on many factors including the pH, the Fe:C ratio, and the redox speciation of Fe [1-3]. Two areas with a contrasting Fe chemistry were studied: a lowland area with widespread seepage of iron-rich groundwater, and an upland peat area. Samples of ten oxic, well-mixed streams were subjected to cascade filtration using conventional filtration (1.2 µm, 0.45 µm, 0.1 µm) and cross-flow ultrafiltration (CFF; 5 kDa). The colloidal fraction, here operationally defined as between 0.45 µm and 5 kDa, was isolated by CFF and subsequently freeze-dried. The speciation of colloidal Fe was determined by EXAFS spectroscopy at the Fe K-edge (MAX-lab, Lund, Sweden). In the rivers draining upland peat, Fe and C were predominantly recovered in the fraction between 5 kDa and 0.1 µm. Conversely, in the rivers draining the lowland with extensive seepage of iron-rich groundwater, Fe was most abundant in the > 0.1 µm fraction, whereas C was predominantly present < 0.1 µm. The EXAFS data reveal that colloidal Fe speciation is different in both study areas. It exists as mononuclear Fe complexed by dissolved organic matter, as colloidal hydrous ferric oxides (likely stabilized by adsorbed organic matter), or as a mixture of these. The colloidal Fe concentrations show considerable seasonal variability. Overall, this study contributes to a better understanding of colloidal Fe speciation and of its interaction with organic C.

  • 108. Baken, Stijn
    et al.
    Sjöstedt, Carin
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Seuntjens, Piet
    Desmet, Nele
    De Schutter, Jan
    Smolders, Erik
    Characterisation of hydrous ferric oxides derived from iron-rich groundwaters and their contribution to the suspended sediment of streams2013In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 39, p. 59-68Article in journal (Refereed)
    Abstract [en]

    When Fe(II) bearing groundwaters surface in streams, particulate authigenic Fe-rich material is produced by oxidation. Such freshly precipitated Fe minerals may be transported as suspended sediment and have a profound impact on the fate of trace metals and nutrients in rivers. The objective of this study was to monitor changes in mineralogy and composition of authigenic material from its source to streams of increasing order. Groundwaters, surface waters, and suspended sediment in streams of different order were sampled in the Kleine Nete catchment (Belgium), a lowland with Fe-rich groundwaters (3.5-53.8 mg Fe/L; pH 6.3-6.9). Fresh authigenic material (>0.45 mu m) was produced by oxidising filtered (<0.45 mu m) groundwater and surface water. This material contained, on average, 44% Fe, and smaller concentrations of C, P, and Ca. Iron EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy showed that the Fe was present as poorly crystalline hydrous ferric oxides with a structure similar to that of ferrihydrite. The Fe concentration in the suspended sediment samples decreased to 36-40% (stream order 2), and further to 18-26% (stream order 4 and 5). Conversely, the concentrations of organic C, Ca, Si, and trace metals increased with increasing stream order, suggesting mixing of authigenic material with suspended sediment from a different source. The Fe speciation in the suspended sediment was similar to that in fresh authigenic material, but more Fe-Fe interactions were observed, i.e. it was increasingly hydrolysed, suggesting ageing reactions. The suspended sediment in the streams of order 4 and 5 is estimated to contain between 31% and 59% of authigenic material, but more data are needed to refine this estimate. The authigenic material is an important sink for P in these streams which may alleviate the eutrophication risk in this catchment.

  • 109. Balic-Zunic, Tonci
    et al.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Katerinopoulou, Anna
    Schmith, Johan Haagen
    Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques2013In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 98, no 1, p. 41-52Article in journal (Refereed)
    Abstract [en]

    Feldspar crystals typically show a range of exsolution and polysynthetic twinning textures that can present problems for their full characterization, but at the same time give important information about their genesis. We present an integrated procedure for the micro-texture analysis, twin law identification plus crystal structure refinement of all components in a feldspar intergrowth. This procedure was applied to perthitic intergrowths in feldspars from two different pegmatites in the Larvik plutonic complex in the southern part of the Oslo region, Norway. It revealed that the two starting high-temperature (HT) feldspars had similar global chemical compositions but underwent significantly different cooling histories, with cooling times probably differing by over an order of magnitude. Powder X-ray diffraction with Rietveld refinement was used for a preliminary identification of the mineral components and concluding quantitative phase analysis. Electron microprobe analysis was used to bracket the chemical compositions of the constituents. Electron backscatter diffraction was used to reveal the texture of the samples, twin laws and spatial distribution and crystallographic orientation of the crystal domains. Single-grain X-ray diffraction recorded by an area detector was applied for a simultaneous integration of reflection intensities for all crystallographic domains with different orientations and severe diffraction overlaps. The crystal structures were refined using the program JANA2006 that allows a simultaneous calculation for structurally different components. Combined results of various methods helped improve accuracy and resolve ambiguities that arise from the application of a single technique. The approach is widely applicable to the study of mineral intergrowths and bridges an existing gap in the routinely accessible data on the structural characteristics of rock constituents.

  • 110. Baresel, Christian
    et al.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Uncertainty-Accounting Environmental Policy and Management of Water Systems2007In: Environmental Science & Technology, Vol. 41, no 10, p. 3653–3659-Article in journal (Refereed)
    Abstract [en]

    Environmental policies for water quality and ecosystem

    management do not commonly require explicit stochastic

    accounts of uncertainty and risk associated with the

    quantification and prediction of waterborne pollutant loads

    and abatement effects. In this study, we formulate and

    investigate a possible environmental policy that does require

    an explicit stochastic uncertainty account. We compare

    both the environmental and economic resource allocation

    performance of such an uncertainty-accounting environmental

    policy with that of deterministic, risk-prone and riskaverse

    environmental policies under a range of different

    hypothetical, yet still possible, scenarios. The comparison

    indicates that a stochastic uncertainty-accounting

    policy may perform better than deterministic policies over

    a range of different scenarios. Even in the absence of

    reliable site-specific data, reported literature values appear

    to be useful for such a stochastic account of uncertainty.

  • 111.
    Barker, Abigail
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, SE-75236 Uppsala, Sweden.
    Hansteen, Thor H.
    GEOMAR Helmholtz Ctr Ocean Res Kiel, Wischhofstr 1-3, D-24148 Kiel, Germany.
    Nilsson, David
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Unravelling the Crustal Architecture of Cape Verde from the Seamount Xenolith Record2019In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 9, no 2, article id 90Article in journal (Refereed)
    Abstract [en]

    The Cape Verde oceanic plateau hosts 10 islands and 11 seamounts and provides an extensive suite of alkaline lavas and pyroclastic rocks. The volcanic rocks host a range of crustal and mantle xenoliths. These xenoliths provide a spectrum of lithologies available to interact with magma during transport through the lithospheric mantle and crust. We explore the origin and depth of formation of crustal xenoliths to develop a framework of magma-crust interaction and a model for the crustal architecture beneath the Cape Verde oceanic plateau. The host lavas are phononephelinites to phonolites and the crustal xenoliths are mostly mafic plutonic assemblages with one sedimentary xenolith. REE profiles of clinopyroxene in the host lavas are light rare-earth element (LREE) enriched whereas clinopyoxene from the plutonic xenoliths are LREE depleted. Modelling of REE melt compositions indicates the plutonic xenoliths are derived from mid-ocean ridge basalt (MORB)-type ocean crust. Thermobarometry indicates that clinopyroxene in the host lavas formed at depths of 17 to 46 km, whereas those in the xenoliths formed at 5 to 20 km. This places the depth of origin of the plutonic xenoliths in the oceanic crust. Therefore, the xenoliths trace magma-crust interaction to the MORB oceanic crust and overlying sediments located beneath the Cape Verde oceanic plateau.

  • 112.
    Barker, Abigail
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Holm, Paul Martin
    Unniversity of Copenhagen.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    The role of eclogite in the mantle heterogeneity at Cape Verde2014In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 168, no 3, p. 1052-Article in journal (Refereed)
    Abstract [en]

    The Cape Verde hotspot, like many other Ocean Island Basalt provinces, demonstrates isotopic heterogeneity on a 100–200 km scale. The heterogeneity is represented by the appearance of an EM1-like component at several of the southern islands and with a HIMU-like component present throughout the archipelago. Where the EM1-like component is absent, a local DMM-like component replaces the EM1-like component. Various source lithologies, including peridotite, pyroxenite and eclogite have been suggested to contribute to generation of these heterogeneities; however, attempts to quantify such contributions have been limited. We apply the minor elements in olivine approach (Sobolev et al. in Nature 434:590–597, 2005; Science, doi:10.1126/science.1138113,2007), to determine and quantify the contributions of peridotite, pyroxenite and eclogite melts to the mantle heterogeneity observed at Cape Verde. Cores of olivine phenocrysts of the Cape Verde volcanics have low Mn/FeO and low Ni*FeO/MgO that deviate from the negative trend of the global array. The global array is defined by mixing between peridotite and pyroxenite, whereas the Cape Verde volcanics indicate contribution of an additional eclogite source. Eclogite melts escape reaction with peridotite either by efficient extraction in an area of poor mantle flow or by reaction of eclogite melts with peridotite, whereby an abundance of eclogite can seal off the melt from further reaction. Temporal trends of decreasing Mn/FeO indicate that the supply of eclogite melts is increasing. Modelling suggests the local DMM-like end-member is formed from a relatively peridotite-rich melt, while the EM1-like end-member has a closer affinity to a mixed peridotite–pyroxenite–eclogite melt. Notably the HIMU-like component ranges from pyroxenite–peridotite-rich melt to one with up to 77 % eclogite melt as a function of time, implying that sealing of melt pathways is becoming more effective.

  • 113.
    Barker, Abigail
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Carracedo, Juan Carlos
    Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Nicholls, Peter A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    The magma plumbing system for the 1971 Teneguía eruption on La Palma, Canary Islands2015In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 170, no 5-6, article id 54Article in journal (Refereed)
    Abstract [en]

    The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcanomagmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma.

    The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and Aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20 to 45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25 to 45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30 to 50 km.

    Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity. 

  • 114.
    Barnes, Christopher
    et al.
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Jarosław, Majka
    Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Schneider, David
    Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Canada.
    Walczak, Katarzyna
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Bukała, Michał
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Kośmińska, Karolina
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Tokarski, Tomasz
    Academic Center for Materials and NanotechnologyAGH University of Science and TechnologyKrakówPoland.
    Karlsson, Andreas
    Swedish Museum of Natural History, Department of Geology.
    High-spatial resolution dating of monazite and zircon reveals the timing of subduction–exhumation of the Vaimok Lens in the SeveNappe Complex (Scandinavian Caledonides)2019In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, no 1, article id 5Article in journal (Refereed)
    Abstract [en]

    In-situ monazite Th–U–total Pb dating and zircon LA–ICP–MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th–U–total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 ± 16 Ma Neoproterozoic cores surrounded byrims that formed at 498 ± 10 Ma. Monazite rim formation was facilitated via dissolution–reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formedby dissolution–reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, ± Y, and ± Sr. Rims also have subdued Eu anomalies (Eu/Eu* ≈ 0.6–1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 ± 22 Ma; 475 ± 26 Ma; and 479 ± 38 Ma. These results show that both monazite and zircon experienced dissolution–reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.

  • 115.
    Barnes, Christopher
    et al.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Schneider, David
    Univ Ottawa, Dept Earth & Environm Sci, Ottawa, ON, Canada.
    Walczak, Katarzyna
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Bukala, Michal
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Kosminska, Karolina
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Tokarski, Tomasz
    AGH Univ Sci & Technol, Acad Ctr Mat & Nanotechnol, Krakow, Poland.
    Karlsson, Andreas
    Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden.
    High-spatial resolution dating of monazite and zircon revealsthe timing of subduction-exhumation of the Vaimok Lens in the Seve Nappe Complex (Scandinavian Caledonides)2019In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, no 1, article id 5Article in journal (Refereed)
    Abstract [en]

    In-situ monazite Th-U-total Pb dating and zircon LA-ICP-MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th-U-total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 +/- 16 Ma Neoproterozoic cores surrounded by rims that formed at 498 +/- 10 Ma. Monazite rim formation was facilitated via dissolution-reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formed by dissolution-reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, +/- Y, and +/- Sr. Rims also have subdued Eu anomalies ( Eu/Eu* approximate to 0.6-1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 +/- 22 Ma; 475 +/- 26 Ma; and 479 +/- 38 Ma. These results show that both monazite and zircon experienced dissolution-reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.

  • 116.
    Barrientos, Natalia
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios: Implications for bottom water palaeothermometry2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.

    The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).

    The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.

  • 117.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Lear, Caroline
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mg/Ca ratios in late Quaternary benthic foraminifera from the central Arctic OceanManuscript (preprint) (Other academic)
  • 118.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lear, Caroline
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Muschitiello, Francesco
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    de Boer, Agatha
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cronin, Thomas
    Semiletov, Igor
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Late Holocene variability in Arctic Ocean Pacific Water inflow through the Bering StraitManuscript (preprint) (Other academic)
  • 119.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Miller, Clint
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Johansson, Carina
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Post-recovery dissolution of calcareous microfossils in sediments from a highly productive Arctic marine environmentManuscript (preprint) (Other academic)
  • 120.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lear, Caroline H.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cronin, Thomas M.
    Gukov, Aleksandr Y.
    Coxall, Helen K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arctic Ocean benthic foraminifera Mg/Ca ratios and global Mg/Ca-temperature calibrations: New constraints at low temperatures2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 236, p. 240-259Article in journal (Refereed)
    Abstract [en]

    We explore the use of Mg/Ca ratios in six Arctic Ocean benthic foraminifera species as bottom water palaeothermometers and expand published Mg/Ca-temperature calibrations to the coldest bottom temperatures (<1 °C). Foraminifera were analyzed in surface sediments at 27 sites in the Chukchi Sea, East Siberian Sea, Laptev Sea, Lomonosov Ridge and Petermann Fjord. The sites span water depths of 52–1157 m and bottom water temperatures (BWT) of −1.8 to +0.9 °C. Benthic foraminifera were alive at time of collection, determined from Rose Bengal (RB) staining. Three infaunal and three epifaunal species were abundant enough for Mg/Ca analysis. As predicted by theory and empirical evidence, cold water Arctic Ocean benthic species produce low Mg/Ca ratios, the exception being the porcelaneous species Quinqueloculina arctica. Our new data provide important constraints at the cold end (<1 °C) when added to existing global datasets. The refined calibrations based on the new and published global data appear best supported for the infaunal species Nonionella labradorica (Mg/Ca = 1.325 ± 0.01 × e^(0.065 ± 0.01 × BWT), r2 = 0.9), Cassidulina neoteretis (Mg/Ca = 1.009 ± 0.02 × e^(0.042 ± 0.01 × BWT), r2 = 0.6) and Elphidium clavatum (Mg/Ca = 0.816 ± 0.06 + 0.125 ± 0.05 × BWT, r2 = 0.4). The latter is based on the new Arctic data only. This suggests that Arctic Ocean infaunal taxa are suitable for capturing at least relative and probably semi-quantitative past changes in BWT. Arctic Oridorsalis tener Mg/Ca data are combined with existing O. umbonatus Mg/Ca data from well saturated core-tops from other regions to produce a temperature calibration with minimal influence of bottom water carbonate saturation state (Mg/Ca = 1.317 ± 0.03 × e^(0.102 ± 0.01 BWT), r2 = 0.7). The same approach for Cibicidoides wuellerstorfi yields Mg/Ca = 1.043 ± 0.03 × e^(0.118 ± 0.1 BWT), r2 = 0.4. Mg/Ca ratios of the porcelaneous epifaunal species Q. arctica show a clear positive relationship between Mg/Ca and Δ[CO32−] indicating that this species is not suitable for Mg/Ca-palaeothermometry at low temperatures, but may be useful in reconstructing carbonate system parameters through time.

  • 121. Barão, Lúcia
    et al.
    Vandevenne, Floor
    Clymans, Wim
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Ragueneau, Olivier
    Meire, Patrick
    Conley, Daniel J.
    Struyf, Eric
    Alkaline-extractable silicon from land to ocean: A challenge for biogenic silicon determination2015In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, p. n/a-n/aArticle in journal (Refereed)
    Abstract [en]

    The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction.

  • 122.
    Basapuram, Laxmi Gayatri Devi
    Linköping University, Department of Thematic Studies, Tema Environmental Change.
    Lake Victoria - Carbon, Nitrogen, Phosphorus and Stable Isotope (δ13C) comparison between lake and catchment sediments2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 123.
    Bastviken, David
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Teresia
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Karlsson, Susanne
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Sandén, Per
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Öberg, Gunilla
    IRES, UBC, Canada.
    Temperature sensitivity indicates enzyme controlled chlorination of soil organic matter2009In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 10, p. 3569-3573Article in journal (Refereed)
    Abstract [en]

    Old assumptions that chloride is inert and that most chlorinated organic matter in soils is anthropogenic have been challenged by findings of naturally formed organochlorines. Such natural chlorination has been recognized for several decades, but there are still very few measurements of chlorination rates or estimates of the quantitative importance of terrestrial chlorine transformations. While much is known about the formation of specific compounds, bulk chlorination remains poorly understood in terms of mechanisms and effects of environmental factors. We quantified bulk chlorination rates in coniferous forest soil using 36Cl-chloride in tracer experiments at different temperatures and with and without molecular oxygen (O2). Chlorination was enhanced by the presence of O2 and had a temperature optimum at 20 °C. Minimum rates were found at high temperatures (50 °C) or under anoxic conditions. The results indicate (1) that most of the chlorination between 4 and 40 °C was biotic and driven by O2 dependent enzymes, and (2) that there is also slower background chlorination occurring under anoxic conditions at 20 °C and under oxic conditions at 50 °C. Hence, while oxic and biotic chlorination clearly dominated, chlorination by other processes including possible abiotic reactions was also detected.

  • 124.
    Bastviken, David
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Teresia
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Sandén, Per
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Kylin, Henrik
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Chlorine cycling and fates of 36Cl in terrestrial environments2013Report (Other academic)
    Abstract [en]

    Chlorine-36 (36Cl), a radioisotope of chlorine (Cl) with a half-life of 301,000 years, is present in some types of nuclear waste and is disposed in repositories for radioactive waste. As the release of 36Cl from such repositories to the near surface environment has to be taken into account it is of interest to predict possible fates of 36Cl under various conditions as a part of the safety assessments of repositories for radioactive waste. This report aims to summarize the state of the art knowledge on Cl cycling in terrestrial environments. The view on Cl cycling in terrestrial environments is changing due to recent research and it is clear that the chloride ion (Cl) is more reactive than previously believed. We group the major findings in three categories below according to the amount of data in support of the findings.

    From the result presented in this report it is evident that:

    • There is an ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems.
    • The abundance of naturally formed chlorinated organic compounds (Clorg) frequently exceeds the abundance of Cl, particularly in soils. Thereby Clorg in many cases dominates the total Cl pool.
    • This has important implications for Cl transport. When reaching surface soils Cl will not be a suitable tracer of water and will instead enter other Cl pools (Clorg and biomass) that prolong residence times in the system.
    • Cl dominates import and export from terrestrial ecosystems while Clorg and biomass Cl can dominate the standing stock Cl within terrestrial ecosystems.
    • Both Cl and Clorg pools have to be considered separately in future monitoring programs addressing Cl cycling.

    Further, there are also indications (in need of confirmation by additional studies) that:

    • There is a rapid and large uptake of Cl by organisms and an accumulation in green plant parts. A surprisingly large proportion of total catchment Cl (up to 60%) can be found in the terrestrial biomass.
    • Emissions of total volatile organohalogens could be a significant export pathway of Cl from the systems.
    • Some of the Clorg may be very persistent and resist degradation better than average organic matter. This may lead to selective preservation of some Clorg (with associated low bioavailability).
    • There is a production of Clorg in tissues of e.g. plants and animals and Cl can accumulate as
    • chlorinated fatty acids in organisms.

    Most other nevertheless important aspects are largely unknown due to lack of data. Key unknowns include:

    • The development over time of major Cl pools and fluxes. As long as such data is lacking we cannot assess net changes over time.
    • How the precesses behind chlorination, dechlorination and transport patterns in terrestrial systems are regulated and affected by environmental factors.
    • The ecological roles of the chlorine cycling in general.
    • The ecological role of the microbial chlorination in particular.
    • The chlorine cycling in aquatic environments – including Cl and Clorg pools in sediment and water, are largely missing.

    Given the limited present information available, and particularly the lack of data with a temporal dimension and the lack of process understanding, predictive models are challenging. We also summarize currently available methods to study Cl in the environment.

  • 125.
    Bastviken, David
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Geokemi.
    Thomsen, Frida
    Karlsson, Susanne
    Svensson, Teresia
    Sanden, Per
    Shaw, George
    Matucha, Miroslav
    Öberg, Gunilla
    Chloride retention in forest soil by microbial uptake and by natural chlorination of organic matter2007In: Geochimica Cosmochimica Acta, ISSN 0016-7037, Vol. 71, no 13, p. 3182-3192Article in journal (Refereed)
    Abstract [en]

    Inorganic chlorine (i.e. chloride; Cl-in) is generally considered inert in soil and is often used as a tracer of soil and ground water movements. However, recent studies indicate that substantial retention or release of Cl-in can occur in soil, but the rates and processes responsible under different environmental conditions are largely unknown. We performed Cl-36 tracer experiments which indicated that short-term microbial uptake and release of Cl-in, in combination with more long-term natural formation of chlorinated organic matter (Cl-org), caused Cl-in imbalances in coniferous forest soil. Extensive microbial uptake and release of Cl-in occurred over short time scales, and were probably associated with changes in environmental conditions. Up to 24% of the initially available Clin within pore water was retained by microbial uptake within a week in our experiments, but most of this Cl-in, was released to the pore water again within a month, probably associated with decreasing microbial populations. The natural formation of Clorg resulted in a net immobilization of 4% of the initial pore water Clin over four months. If this rate is representative for the area where soil was collected, Clorg formation would correspond to a conversion of 25% of the yearly wet deposition of Cl-in. The study illustrates the potential of two Clin retaining processes in addition to those previously addressed elsewhere (e.g. uptake of chloride by vegetation). Hence, several processes operating at different time scales and with different regulation mechanisms can cause Clin imbalances in soil. Altogether, the results of the present study (1) provide evidence that Cl-in cannot be assumed to be inert in soil, (2) show that microbial exchange can regulate pore water Cl-in, concentrations and (3) confirm the controversial idea of substantial natural chlorination of soil organic matter.

  • 126. Bauer, Friederike U.
    et al.
    Glasmacher, Ulrich A.
    Ring, Uwe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Karl, Markus
    Schumann, Andreas
    Nagudi, Betty
    Tracing the exhumation history of the Rwenzori Mountains, Albertine Rift, Uganda, using low-temperature thermochronology2013In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 599, p. 8-28Article in journal (Refereed)
    Abstract [en]

    The Rwenzori Mtns form a striking feature within the Albertine Rift of the East African Rift System. They are made up of a dissected Precambrian metamorphic basement block reaching heights of more than 5 km. Applying low-temperature therrnochronology a complex exhumation history becomes evident, where rock and surface uplift can be traced from Palaeozoic to Neogene times. Fission-track and (U-Th-Sm)/He cooling ages and derived cooling histories allow distinguishing different blocks in the Rwenzori Mtns. In the central part a northern and a southern block are separated by a putative NW-SE trending fault; with the northern block showing distinctly younger apatite fission-track ages (similar to 130 Ma) than the southern block (similar to 300 Ma). Cooling ages in both blocks do not vary significantly with elevation, despite considerable differences in elevation. Thermal history modelling reflects protracted cooling histories. Modelled t-T paths show decoupled blocks that were relocated separately along distinct fault planes, which reactivated pre-existing structures, inherited from Palaeozoic folding and thrusting. Initial cooling affected the Rwenzori area in Silurian to Devonian times, followed by Mesozoic and Cainozoic cooling events. Pre-Neogene evolution seems to be triggered by tectonic processes like the opening of the Indian Ocean and the south Atlantic. From thermochronological data the formation of a Mesozoic Albertine high is conceivable. In Cainozoic times the area was affected by rifting, resulting in differentiated surface uplift. Along the western flank of the Rwenzori Mtns, surface uplift was more pronounced. This is also reflected in their recent topography, formed by accelerated rock uplift in the near past (Pliocene to Pleistocene). Erosion could not compensate for this most recent uplift, resulting in apatite He ages of Oligocene to Miocene age or even older.

  • 127.
    Bauer, Susanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Some transition metals and metalloids occur primarily as oxyanions in natural waters including antimony, arsenic, chromium, molybdenum, tungsten and vanadium. These oxyanions can pass through cell walls along the same pathways as phosphate or sulfate. Some of these oxyanions are essential for life, but in high concentrations they become all toxic. Recent studies showed that tungsten probably is posing a risk to human health. The growing use of tungsten in industrial and military applications probably leads to an increased release of tungsten to the environment. It has also been shown that the use of studded winter tires in Sweden significantly increases tungsten concentrations in road runoff. Still, little is known about the geochemical cycling of tungsten in the environment as it has been considered to be a more or less inert element. Only a few studies deal with tungsten in natural waters. For example, for the Baltic Sea no concentration data have been published before this work and data on the suspended particulate fraction of tungsten in terrestrial and marine waters are scarce.

    This thesis contributes to the understanding of the distribution and behavior of tungsten, molybdenum and vanadium in natural waters under changing redox conditions, varying pH and different seasons. Particular attention is paid to the suspended particulate fraction of these elements, which is often neglected even though it can be of great importance. Tungsten, molybdenum and vanadium primarily occur as oxyanions in solution and can be adsorbed to particles, which determines their mobility.

    Molybdenum usually is very mobile, while vanadium has a tendency to adsorb to iron oxyhydroxides or to form organic complexes. Tungsten has many similarities with molybdenum, but it seems to be less mobile than molybdenum in natural waters.

    Tungsten and molybdenum have a similar abundance in the upper continental crust, but in the ocean molybdenum is almost 2000 times more abundant. A strong fractionation of these two elements occurs from land to the ocean, indicating a removal of W during mixing of river and seawater.

    This study comprises data from small streams in the boreal landscape of northern Sweden, major rivers (Kalix River and Råne River) and their estuaries discharging into the Baltic Sea. In the marine environment, sediment cores from the Bothnian Bay and water profiles at the stratified Landsort Deep have been studied. Apart from the spatial distribution, the temporal behavior of tungsten, molybdenum, and vanadium in was investigated. In the boreal environment snowmelt is playing a major role for their transport.

    All water samples were filtered through 0.22 pore size filters to define dissolved and suspended particulate fractions. The particulate fraction of all studied elements increases from streams to rivers. Especially during spring flood, particle transport becomes even more important. About 80% tungsten, 70% vanadium and 30% molybdenum occur in the particulate fraction during this event. During estuarine mixing, tungsten and molybdenum are released from the particles again. However, vanadium seems to be removed in both fractions, probably due to a different adsorption behavior. In the dissolved fraction molybdenum increased and vanadium decreased from land to the sea, while tungsten showed small variation in all surface waters.

    All three elements are affected by manganese redox cycling at the transition zone between oxic and sulfidic water at the Landsort Deep in the Baltic Sea. Adsorption of these oxyanions to the freshly formed manganese oxides plays an important role for their transport to the sulfidic zone. In contrast to molybdenum, dissolved tungsten is accumulated in the sulfidic environment. There is no effective removal mechanisms like for molybdenum, which is adsorbed to sulfides. Also in the sediment, redox cycling of manganese and iron affects the distribution of tungsten and molybdenum close to the water-sediment interface.

  • 128.
    Bauer, Susanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Role of manganese redox cycling for trace metals in the Baltic Sea2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Redox zones are defined by steep gradients of changing concentrations and changing redox potential. They form a transition zone between oxic and anoxic/sulfidic conditions, where nitrate, manganese and iron reduction occurs. These redox zones can be situated in the sediment as well as in the water column. In the Baltic Sea both types are found. In the Bothnian Bay, the northernmost part of the Baltic Sea, the water column is well oxygenated and the redox zone lies within the uppermost sediment (approximately 2 cm in extend). In the Baltic Proper several of the deeper basins are stratified with the redox zone hanging between 75 and 100 m in the water column reaching up to 20 m.The redox-sensitive trace metal manganese can be both electron donor and acceptor in redox zones depending on its oxidation state. Manganese is transformed between the dissolved Mn(II),(III) and the particulate Mn(III/IV). Hence, Mn plays an important role in trace metal cycling across redox zones in natural environments. Manganese particles serve as a carrier for adsorbed trace metals towards the anoxic/sulfidic zone in the water column and as a barrier in the sediment, which restricts dissolved trace elements from diffusing to the oxic zone.In this study water samples (dissolved fraction, <0.22 μm, and particulate fraction, >0.22 μm) from the pelagic redox zone in Landsort Deep, Baltic proper were analyzed. Furthermore, a sedimentary redox zone from the Bothnian Bay has been investigated. A Mn particle peak is detected within the pelagic redox zone at Landsort Deep. A strong correlation between these Mn particles and several oxyanions as Mo, V and W is observed. The oxyanions are adsorbed onto the freshly formed Mn particles in the redox zone, settle with the particles and are released when Mn particles are reduced to Mn2+ and dissolve. This mechanism can act as a pump for trace metals to the sulfidic zone, where the trace metals either can be enriched in the dissolved fraction or form sulfid particles.In the sediment Mn redox cycling leads to enrichment of trace metals in the top layer. The formation of a barrier of Mn-Fe hydroxides restricts trace metal exchange between bottom water and sediment. Freshening of the Bothnian Bay basin has led to an increased sequestering of trace metals in the uppermost sediment. Trace metal proxies show that primary production in the Bothnian Bay has decreased starting approximately 2500 years BP. That led to a shift in the deposition of sulfide forming elements mainly due to the lower input of reactive organic carbon from plankton and to the recent enrichment of elements together with Mn-Fe hydroxides.

  • 129.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Blomqvist, Sven
    Department of Ecology, Environment and Plant Sciences, Stockholm University.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Distribution of dissolved and suspended particulate molybdenum, vanadium, and tungsten in the Baltic Sea2017In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 196, p. 135-147Article in journal (Refereed)
    Abstract [en]

    In natural waters, dissolved oxyanions often dominate over the particle-bound element fraction. Still, the scavenging of oxyanions by suspended particles might contribute significantly to their dynamic cycling and distribution. To investigate how oxyanions are affected by manganese (Mn) redox cycling, detailed depth profiles across the pelagic redox zone at the Landsort Deep, Baltic Sea, were collected for molybdenum (Mo), vanadium (V), and tungsten (W), for both dissolved (<0.22 µm) and suspended particulate (>0.22 µm) fractions.

    All three oxyanions show a non-conservative behavior in the stratified Landsort Deep. Strong linear correlations with Mn in the particulate fraction in the redox zone of the Landsort Deep suggest that Mn redox cycling influences their distribution. In the dissolved fraction, Mo, V, and W exhibited rather different behavior. Molybdenum was depleted below the redox zone, while V was depleted only within the redox zone. Tungsten concentrations increased within the redox zone, being three times higher in the sulfidic zone than in the surface water. Unlike Mo, W shows no tendency for adsorption or co-precipitation under the prevailing weak sulfidic conditions in the deep water of the Landsort Deep and is, therefore, not exported to the underlying sediment.

    The Landsort Deep data were compared with data from the northern Baltic Sea (Bothnian Bay, Kalix River and Råne River estuaries), where particulate iron (Fe) occurs in high abundance. The particulate fractions of Mo, V, and W decreased during mixing in these estuaries. Vanadium showed the most drastic reduction, with a decrease in dissolved and particulate fractions, indicating that different processes influence the distribution of these oxyanions.

  • 130.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geochemistry of tungsten and molybdenum during fresh water transport and estuarine mixingManuscript (preprint) (Other academic)
    Abstract [en]

    The geochemistry of tungsten (W) in the environment is still poorly studied. Tungsten is little mobile and usually occurs in low concentrations in natural waters. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fraction of two boreal estuaries during different seasons. Additionally, we sampled first-order streams, draining different landscape types, and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to get a comprehensive overview of the distribution of W and Mo in a boreal environment.

    Both elements showed different distribution patterns during different seasons. While they decreased in dissolved concentrations during spring discharge, their concentrations were elevated in winter and exhibited non-conservative behavior along the salinity gradient in the estuaries. In the particulate fraction, we found an opposing behavior for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

    Molybdenum and W underwent fractionation from land to sea, indicating different mobility for these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations. 

  • 131.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geochemistry of tungsten and molybdenum during freshwater transport and estuarine mixing2018In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 93, p. 36-48Article in journal (Refereed)
    Abstract [en]

    The geochemistry of tungsten (W) in the environment is poorly studied. Tungsten usually occurs in low concentrations in natural waters and is not very mobile. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fractions of two boreal estuaries during different seasons. Additionally, we sampled first-order streams that drain different landscape types and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to obtain a comprehensive overview of the distribution of W and Mo in a boreal environment.

    Both elements showed different distribution patterns during different seasons. While they decreased in the dissolved fraction during spring discharge, in winter, their concentrations were elevated. Molybdenum exhibited non-conservative behavior along the salinity gradient in winter, which was probably caused by its release from underlying sediments. In the particulate fraction, we found opposite behaviors for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

    Molybdenum and W underwent fractionation from land to sea, indicating the different mobilities of these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration, as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations.

  • 132.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Seasonal behavior of molybdenum, vanadium, and tungsten in boreal riversManuscript (preprint) (Other academic)
  • 133.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The geochemistry of tungsten in the Baltic Sea2015Conference paper (Other academic)
  • 134.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Role of Mn for cycling of oxyanions (Mo, V and W) across the pelagic redox zone, Landsort Deep2015Conference paper (Other academic)
    Abstract [en]

    The Landsort Deep in the Baltic Sea is a stratified basin with a pelagic redox zone separating the oxic water from the sulphidic water below. In this zone redox cycling of Mn plays an important role for the distribution of trace elements. Freshly formed Mn oxide acts as carrier for trace elements across the redox zone. In the underlying sulphidic zone the adsorbed trace elements are released when Mn is reduced and the Mn particles dissolve. Mn oxide has a negative surface charge at seawater pH conditions. Oxyanions would most likely adsorb on Fe oxides instead of Mn oxide due to the surface charge. The particulate Fe concentration in the redox zone of the Landsort Deep is 10-40 times lower than the concentration of particulate Mn. Therefore the Landsort Deep is an excellent place to study the role of Mn for cycling of oxyanions. This study shows uptake of Mo, V and W on Mn particles in the redox zone. Insights from this study may also be applicable for other oxyanion forming elements as P. The Landsort Deep in the Baltic Sea was sampled over a two-year period. Detailed profiles for the dissolved (<0.22 m) and particulate (>0.22 m) fraction were taken across the pelagic redox zone. While the pattern of dissolved Mn is constant during the sampling period maxima for particulate Mn vary in concentration and depth. Throughout the sampling period Mo, V and W are following Mn in the particulate fraction within the redox zone.

  • 135.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Älvtransporterade spårmetaller till Bottenviken: Genomgång av monitoringdata2012Report (Other academic)
    Abstract [sv]

    Data visar att det är svårt att karakterisera och ta fram en ”typ-älv” för spårmetalltransportentill Bottenviken. Det är stora skillnader i transporten av spårmetaller mellan kustnära vattendrag,som dränerar sediment som tidigare avsatts i Bottenviken, skogsälvar och fjällälvar. Dessutom ärskillnaderna stora mellan älvar av samma typ. Trots att Kalixälv och Torneälv dränerar samma typav berggrund och lösa avlagringar är kemin olika för flera spårmetaller. Skillnaderna är i grundenberoende på vittringsförhållanden i dräneringsområdet och vattenföringen, men späds på av analyssvårigheteroch avsaknaden av filtrerade prov.I stort sett visar järn, krom, aluminium och totalt organiskt kol liknade mönster, även om de iblandinte är korrelerade i varje älv. Zink, kadmium, kobolt och nickel är korrelerade till mangan, meni flera älvar är inte sambandet uppenbart. Arsenik är linjärt korrelerat till järn söder om Piteälven.Halterna av järn är låga i utbyggda älvar, vilket indikerar att järntransporten minskar när en älvbyggs ut. Zinkvärdena i monitoringdata verkar vara påverkade av kontamination. De flesta kadmiumvärdenligger nära detektionsgränsen och överlag är kadmiumhalterna inte tillförlitliga.Övervakningsprogrammet bygger på ofiltrerade syrasatta vattenprov. Problemet med sådana provär att analysvärdena ”hoppar”. Syrasättningen löser inte upp bergartsfragment men löser järnmanganoxidhydroxidpartiklar.Partiklar påverkar med andra ord analysen på ett oregelbundet sätteftersom mängden, och typen a partiklar, varierar kraftigt speciellt vid höga flöden.Proven bör filtreras i fält, enklast genom sprutfiltrering. Filtren kan sparas för analys eller baralagras. Oberoende om filtren analyseras eller inte blir den lösta fraktionen bättre definierad än utanfiltrering. Filtrering förändrar inte nämnvärt provtagningskostnaden och analyskostnaden blir densamma (utan filteranalys). Filtrering bör införas omgående. För att kunna jämföra med tidigare årbör både ofiltrerad och filtrerad fas analyseras under ett eller två år.I vissa system bör även den partikulära fasen bestämmas. Detta är speciellt viktigt för att förståförändringar i järn och mangantransporten, eftersom dessa grundämnen styr flera spårmetaller ochfosfor. Brunifieringen av svenska vattendrag är tydlig i flera större och mindre vattendrag. Brunifieringenberor på förhöjda halter av bla. järn och mangan. För att förstå orsakerna till brunifieringmåste både filtrerade prov och partiklar analyseras.Markanvändning och dess betydelse för transporten av järn och mangan är en viktig forskningsfråga.Dels för att det finns gränsvärden uppsatta för säker mänsklig konsumtion, dels för attdessa grundämnen styr biotillgängligheten av fosfor i Östersjön, via en serie av komplicerade biogeokemiskaprocesser. Detaljerade kunskaper, på molekylnivå, om järn-mangan oxidhydroxideroch deras biogeokemi är viktig.Eftersom det är järn-mangan oxidhydroxider som till stor del reglerar utbytet mellan vatten ochsediment blir tillgången av dessa grundämnen central. Källorna för både järn och mangan är påland. Hanteringen av markfrågor kan med andra ord direkt påverka tillflödet av järn och mangan.Kopplingen mellan marktyp-markanvändning och utflödet av järn och mangan är idag litestuderat. Fosfortransporten i sötvatteninflödet är också starkt korrelerad till järnoxidhydroxider.Biotillgängligheten av den tillförda fosforn är lite studerat. Nya data antyder att fosforn inte ärdirekt biotillgänglig. Detta kan bero på ett komplext samspel mellan fosfor-järn-fotoreduktion, enkoppling som inte studerats i Östersjön.2Höga halter fosfor sitter bundet i ytsediment i Bottniska viken. En sänkning av redoxnivån skullefrigöra fosforn och systemet skulle snabbt bli eutroft. Tröskelvärdet för hur mycket näringsämnensom kan tillföras utan att förändra syreförhållandena är okänt. Bottenhavet och Bottenvikenär idag viktiga sänkor för fosfor. Hur stabila dessa sänkor är för miljöförändringar blir därför enviktig fråga. Eftersom Bottenhavet i stort sett saknar Mn-barriären så är denna bassäng troligenkänsligare för förändringar jämfört med Bottenviken.Kadmium visar en stigande trend i sedimentdata från Bottenviken. Inga andra metaller, förutombly, visar en sådan klar förändring. Orsaken till förändringen kan bero på landhöjningen (exponeringav sulfidleror på land) och oligotrofieringen av Bottenviken, men mekanismen är inte klarlagdoch bör studeras i detalj.

  • 136.
    Bax, Gerhard
    et al.
    Stockholms Universitet.
    Lundén, B.
    Stockholms Universitet.
    Wester, K.
    Stockholms Universitet.
    Romer, Rolf L.
    Luleå tekniska universitet.
    Remote sensing techniques as mineral exploration tools in the Scandinavian Caledonides and their Fennoscandian foreland1991In: IGARSS 91: remote sensing: global monitoring for earth managementt : Espoo, Finland, June 3-6, 1991, New York: IEEE Communications Society, 1991, p. 2061-2064Conference paper (Refereed)
  • 137. Baxter, Douglas
    et al.
    Faarinen, Mikko
    ALS Scandinavia AB.
    Österlund, Helene
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Rodushkin, Ilya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Christensen, Morten
    ALS Scandinavia AB, Täby.
    Serum/plasma methylmercury determination by isotope dilution gas chromatography: inductively coupled plasma mass spectrometry2011In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 701, no 2, p. 134-138Article in journal (Refereed)
    Abstract [en]

    A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with 198Hg-labelled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L−1 could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L−1 was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L−1, 0.35 μg L−1 and 2.8 μg L−1, with recoveries in the range 82% to 110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03–0.19) μg L−1. This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.

  • 138. Baxter, Douglas
    et al.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Engström, Emma
    Malinovskiy, Dmitry
    Revised exponential model for mass bias correction using an internal standard for isotope abundance ratio measurements by multi-collector inductively coupled plasma mass spectrometry2006In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 21, no 4, p. 427-430Article in journal (Refereed)
    Abstract [en]

    An internal standard (IS) can be used to account for moderate, matrix-related shifts in mass bias using multi-collector inductively coupled plasma mass spectrometry through the empirical, linear relationship between measured isotope abundance ratios for different elements in ln-ln space. Unfortunately, erroneous mass bias corrected isotope abundance ratios may be returned by the model, requiring artificial adjustment of the true isotope abundance ratio of the IS. Although inadequate correction for peak tailing has been convincingly used to explain this problem, our analysis of the literature describing the development of the mass bias correction model using an IS reveals the presence of a source of systematic error. The origin of this error is purely mathematical and is eliminated in the revised model presented, in which mass bias corrected isotope abundance ratios are independent of the isotopic composition of the IS. An expression for computing the total combined uncertainty in the corrected ratio, incorporating contributions from the linear model, the isotopic reference material, and measurements of analyte element and IS in the sample, is also derived.

  • 139. Baxter, Douglas
    et al.
    Rodushkin, Ilya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Engström, Emma
    Klockare, Dennis
    ALS Analytica AB, Luleå.
    Waara, Hans
    ALS Analytica AB, Luleå.
    Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods2007In: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 53, no 1, p. 111-116Article in journal (Refereed)
    Abstract [en]

    Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.

  • 140.
    Bellucci, Jeremy
    Swedish Museum of Natural History, Department of Geology.
    Pb Isotopic Composition of Panamanian Colonial Majolica by LA-ICP-MS2016In: Recent Advances in Laser Ablation ICP-MS for Archaeology / [ed] L. Dussubieux, Springer Berlin/Heidelberg, 2016Chapter in book (Refereed)
    Abstract [en]

    Panama ́ Viejo, founded in 1519 by the Spanish explorer Pedrarias Da ́vila, was the first permanent European settlement on the Pacific Ocean, and became a city, by royal decree, in 1521. Shortly after its creation, the city became an important base for trade with Spain. In 1671, the English pirate Henry Morgan waged an attack on Panama ́ Viejo, which resulted in a fire that destroyed the entire city. A new settlement built a few miles west, called Casco Antiguo or San Felipe, is now the historic district of modern Panama City. The Pb isotopic compositions of the glazes on the surface of sixteenth to seventeenth century majolica pottery sherds from Panama Viejo and Casco Antiguo (both in Panama), and Lima (Peru) were determined via non-destructive laser ablation multi-collector ICP-MS (LA-MC-ICP-MS). The contrast in Pb isotopic compositions in the glazes on ceramics recovered in different locations demonstrate that early majolica pottery production during this period used Pb obtained from the Andes. However, the Pb used in later majolica production in Panama is of Spanish origin. After Panama ́ Viejo was burned to the ground, Panamanian majolica production ended.

  • 141.
    Bellucci, Jeremy
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Nemchin, Alexander
    Swedish Museum of Natural History, Department of Geology.
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Ross, Kielman
    Swedish Museum of Natural History, Department of Geology.
    Snape, Joshua
    Swedish Museum of Natural History, Department of Geology.
    Pidgeon, Robert
    Geochronology of Hadean zircon grains from the Jack Hills, Western Australia constrained by quantitative scanning ion imaging2018In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 476, p. 469-480Article in journal (Refereed)
    Abstract [en]

    Five Hadean (> 4 Ga) aged zircon grains from the Jack Hills metasedimentary belt have been investigated by a secondary ion mass spectrometry scanning ion image technique. This technique has the ability to obtain accurate and precise full U-Pb systematics on a scale < 5 μm, as well as document the spatial distribution of U, Th and Pb. All five of the grains investigated here have complex cathodoluminescence patterns that correlate to different U, Th, and Pb concentration domains. The age determinations for these different chemical zones indicate multiple reworking events that are preserved in each grain and have affected the primary crystalized zircon on the scale of < 10 μm, smaller than conventional ion microprobe spot analyses. In comparison to the spot analyses performed on these grains, these new scanning ion images and age determinations indicate that almost half of the spot analyses have intersected several age and chemical domains in both fractured and unfractured parts of the individual crystals. Some of these unfractured, mixed domain spot analyses have concordant ages that are inaccurate. Thus, if the frequency of spot analyses intersecting mixed domains here is even close to representative of all other studies of the Jack Hills zircon population, it makes the interpretation of any trace element, Hf, or O isotopic data present in the literature tenuous. Lastly, all of the grains analysed here preserve at least two distinguishable 207Pb/206Pb ages. These ages are preserved in core-rim and/or complex internal textural relationships in unfractured domains. These secondary events took place at ca. 4.3, 4.2, 4.1, 4.0, 3.7, and 2.9 Ga, which are coincident with previously determined statistically robust age peaks present in this zircon population.

  • 142.
    Bellucci, Jeremy
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Nemchin, Alexander
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Snape, Joshua
    Swedish Museum of Natural History, Department of Geology.
    Bland, Phil
    Benedix, Gretchen
    Roszjar, Julia
    Pb evolution in the Martian mantle2018In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 485, p. 79-87Article in journal (Refereed)
    Abstract [en]

    The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm–Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (238U/204Pb) obtained for these two different stages of Pb growth are μ1 of 1.8 and a range of μ2 from 1.4–4.7, respectively. The μ1-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sri, γ187Os, ε143Nd, and ε176Hf), the second stage mantle evolution range in observed mantle μ-values display excellent linear correlations (r2 > 0.85) and represent a spectrum of Martian mantle mixing-end members (depleted, intermediate, enriched).

  • 143.
    Bellucci, Jeremy
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Snape, Joshua
    Swedish Museum of Natural History, Department of Geology.
    Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars2017In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 458, p. 192-202Article in journal (Refereed)
    Abstract [en]

    The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive d37Cl anomalies (+1.1 to +2.5 ‰).  These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative d37Cl anomalies (-0.2 to -5.6 ‰).  Phosphates with the largest negative d37Cl anomalies display zonation where the rims of the grains are enriched in all halogens and have significantly more negative d37Cl anomalies indicating interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average d37Cl of -0.6 ‰, which suggests a similar Cl isotope composition between Mars, the Earth, and the Moon. The only process known to fractionate Cl isotopes, both positively and negatively, is formation of perchlorate, which has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have also been observed on the Martian surface, has been active throughout Martian history. 

  • 144.
    Belonoshko, Anatoly B.
    et al.
    Royal Institute Technology KTH, Sweden.
    Lukinov, Timofei
    Royal Institute Technology KTH, Sweden.
    Fu, Jie
    Royal Institute Technology KTH, Sweden; Dalian University of Technology, Peoples R China.
    Zhao, Jijun
    Dalian University of Technology, Peoples R China.
    Davis, Sergio
    Chilean Comm Nucl Energy CCHEN, Chile.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Stabilization of body-centred cubic iron under inner-core conditions2017In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 10, no 4, p. 312-+Article in journal (Refereed)
    Abstract [en]

    The Earths solid core is mostly composed of iron. However, despite being central to our understanding of core properties, the stable phase of iron under inner-core conditions remains uncertain. The two leading candidates are hexagonal close-packed and body-centred cubic (bcc) crystal structures, but the dynamic and thermodynamic stability of bcc iron under inner-core conditions has been challenged. Here we demonstrate the stability of the bcc phase of iron under conditions consistent with the centre of the core using ab initio molecular dynamics simulations. We find that the bcc phase is stabilized at high temperatures by a diffusion mechanism that arises due to the dynamical instability of the phase at lower temperatures. On the basis of our simulations, we reinterpret experimental data as support for the stability of bcc iron under inner-core conditions. We suggest that the diffusion of iron atoms in solid state may explain both the anisotropy and the low shear modulus of the inner core.

  • 145.
    Benaiges-Fernandez, Robert
    et al.
    Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Catalonia, Spain. Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Palau, Jordi
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain. Department of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, Barcelona, Catalonia, Spain.
    Offeddu, Francesco G.
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Cama, Jordi
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Urmeneta, Jordi
    Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Catalonia, Spain. Biodiversity Research Institute (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain.
    Soler, Josep M.
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Dold, Bernhard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Sustainable Mining Research & Consultancy EIRL, San Pedro de La Paz, Chile.
    Dissimilatory bioreduction of iron(III) oxides by Shewanella loihica under marine sediment conditions2019In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291Article in journal (Refereed)
    Abstract [en]

    Shewanella is a genus of marine bacteria capable of dissimilatory iron reduction (DIR). In the context of deep-sea mining activities or submarine mine tailings disposal, dissimilatory iron reducing bacteria may play an important role in biogeochemical reactions concerning iron oxides placed on the sea bed. In this study, batch experiments were performed to evaluate the capacity of Shewanella loihica PV-4 to bioreduce different iron oxides (ferrihydrite, magnetite, goethite and hematite) under conditions similar to those in anaerobic sea sediments. Results showed that bioreduction of structural Fe(III) via oxidation of labile organic matter occurred in all these iron oxides. Based on the aqueous Fe (II) released, derived Fe(II)/acetate ratios and bioreduction coefficients seem to be only up to about 4% of the theoretical ones, considering the ideal stoichiometry of the reaction. A loss of aqueous Fe (II) was caused by adsorption and mineral transformation processes. Scanning electron microscope images showed that Shewanella lohica was attached to the Fe(III)-oxide surfaces during bioreduction. Our findings suggest that DIR of Fe(III) oxides from mine waste placed in marine environments could result in adverse ecological impacts such as liberation of trace metals in the environment.

  • 146.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Lundberg, Angela
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Starius, Göran
    Luleå tekniska universitet.
    Beskrivning av vattenrörelser i den omättade markzonen: litteraturgenomgång, numerisk modell, simuleringar1982Report (Other academic)
  • 147.
    Beranek, Luke P.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    van Staal, Cees R.
    McClelland, William C.
    Israel, Steve
    Mihalynuk, Mitch G.
    Detrital zircon Hf isotopic compositions indicate a northern Caledonian connection for the Alexander terrane2013In: Lithosphere, ISSN 1941-8264, E-ISSN 1947-4253, Vol. 5, no 2, p. 163-168Article in journal (Refereed)
    Abstract [en]

    Various plate reconstructions predict that the Alexander terrane, a Neoproterozoic-Jurassic crustal fragment now located in the North American Cordillera, evolved in proximity to the northern Appalachian-Caledonian convergent margin during assembly of supercontinent Laurussia. To test stratigraphic connections with Laurussia that are implied by these plate reconstructions, we measured the Hf isotopic compositions of 176 detrital zircons from two relevant sedimentary sequences of the Alexander terrane. An older, Upper Silurian-Lower Devonian terrestrial to shallow-marine molasse sequence yields 405-490 Ma detrital zircons with negative epsilon(Hf(t)) values and Mesoproterozoic to Paleoproterozoic Hf model ages. In combination with paleomagnetic and biogeographic constraints, these Hf data argue for the molasse strata to be now-displaced equivalents of the Old Red Sandstone and primarily sourced from crustally contaminated granitoids in the Greenland, Svalbard, or British Caledonides. Late Silurian-Early Devonian orogenesis in the Alexander terrane is therefore likely related to the Scandian-Salinic phase of Appalachian-Caledonian mountain building. Younger, Middle Devonian sequences of the Alexander terrane are endowed in 390-490 Ma detrital zircons with positive epsilon(Hf(t)) values and Neoproterozoic Hf model ages. These isotopic signatures are consistent with the erosion of local basement rocks during the opening of the Slide Mountain-Angayucham backarc rift and tectonic separation of the Alexander terrane from northern Laurussia.

  • 148.
    Berg, Sylvia E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland.
    Silicic Magma Genesis in Basalt-dominated Oceanic Settings: Examples from Iceland and the Canary Islands2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understanding of magmatic processes and formation of the earliest continental crust. Particularly significant is magma-crust interaction that can modify the composition of magma and the dynamics of volcanism. This thesis investigates silicic magma genesis on different scales in two ocean island settings. First, volcanic products from a series of voluminous Neogene silicic centres in northeast Iceland are investigated using rock and mineral geochemistry, U-Pb geochronology, and oxygen isotope analysis. Second, interfacial processes of magma-crust interaction are investigated using geochemistry and 3D X-ray computed microtomography on crustal xenoliths from the 2011-12 El Hierro eruption, Canary Islands.

    The results from northeast Iceland constrain a rapid outburst of silicic magmatism driven by a flare of the Iceland plume and/or by formation of a new rift zone, causing large volume injection of basaltic magma into hydrated basaltic crust. This promoted crustal recycling by partial melting of the hydrothermally altered Icelandic crust, thereby producing mixed-origin silicic melt pockets that reflect the heterogeneous nature of the crustal protolith with respect to oxygen isotopes. In particular, a previously unrecognised high-δ18O end-member on Iceland was documented, which implies potentially complex multi-component assimilation histories for magmas ascending through the Icelandic crust. Common geochemical traits between Icelandic and Hadean zircon populations strengthen the concept of Iceland as an analogue for early Earth, implying that crustal recycling in emergent rifts was pivotal in generating Earth’s earliest continental silicic crust.

    Crustal xenoliths from the El Hierro 2011-2012 eruption underline the role of partial melting and assimilation of pre-island sedimentary layers in the early shield-building phase of ocean islands. This phenomenon may contribute to the formation of evolved magmas, and importantly, the release of volatiles from the xenoliths may be sufficient to increase the volatile load of the magma and temporarily alter the character and intensity of an eruption.

    This thesis sheds new light on the generation of silicic magma in basalt-dominated oceanic settings and emphasises the relevance of magma-crust interaction for magma evolution, silicic crust formation, and eruption style from early Earth to present.

  • 149.
    Berg, Sylvia E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Riishuus, Morten
    Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Harris, Chris
    Dept. of Geological Sciences, University of Cape Town.
    Whitehouse, Martin
    Department of Geosciences, Swedish Museum of Natural History.
    Krumbholz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Gústafsson, Ludvik
    Samband Islenskra Sveitarfélag.
    Rapid generation of high-silica magmas in basalt-dominated rift settingsManuscript (preprint) (Other academic)
  • 150.
    Berg, Sylvia E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ellis, Ben
    Inst. f. Geochemie und Petrologie, ETH.
    Riishuus, Morten
    Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland.
    Meade, Fiona
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Zircons from northeast Iceland analogous to those from early EarthManuscript (preprint) (Other academic)
1234567 101 - 150 of 1671
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