Ändra sökning
Avgränsa sökresultatet
1 - 15 av 15
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Augustsson, Anna
    et al.
    Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
    Uddh-Söderberg, Terese
    Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
    Filipsson, Monika
    Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
    Helmfrid, Ingela
    Occupational and Environmental Medicine Centre, Department of Clinical and Experimental Medicine Linköping University, Linköping, Sweden.
    Berglund, Marika
    Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
    Karlsson, Helen
    Occupational and Environmental Medicine Centre, Department of Clinical and Experimental Medicine Linköping University, Linköping, Sweden.
    Hogmalm, Johan
    Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Alriksson, Stina
    Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
    Challenges in assessing the health risks of consuming vegetables in metal-contaminated environments2018Ingår i: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 113, s. 269-280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A great deal of research has been devoted to the characterization of metal exposure due to the consumption of vegetables from urban or industrialized areas. It may seem comforting that concentrations in crops, as well as estimated exposure levels, are often found to be below permissible limits. However, we show that even a moderate increase in metal accumulation in crops may result in a significant increase in exposure. We also highlight the importance of assessing exposure levels in relation to a regional baseline. We have analyzed metal (Pb, Cd, As) concentrations in nearly 700 samples from 23 different vegetables, fruits, berries and mushrooms, collected near 21 highly contaminated industrial sites and from reference sites. Metal concentrations generally complied with permissible levels in commercial food and only Pb showed overall higher concentrations around the contaminated sites. Nevertheless, probabilistic exposure assessments revealed that the exposure to all three metals was significantly higher in the population residing around the contaminated sites, for both low-, median- and high consumers. The exposure was about twice as high for Pb and Cd, and four to six times as high for As. Since vegetable consumption alone did not result in exposure above tolerable intakes, it would have been easy to conclude that there is no risk associated with consuming vegetables grown near the contaminated sites. However, when the increase in exposure is quantified, its potential significance is harder to dismiss – especially when considering that exposure via other routes may be elevated in a similar way.

  • 2.
    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
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    High-spatial resolution dating of monazite and zircon reveals the timing of subduction–exhumation of the Vaimok Lens in the SeveNappe Complex (Scandinavian Caledonides)2019Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, nr 1, artikel-id 5Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Biagioni, Cristian
    et al.
    Università di Pisa, Italy..
    Hålenius, Ulf
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Pasero, Marco
    Università di Pisa, Italy..
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Bosi, Ferdinando
    Sapienza Università di Roma, Italy.
    Hydroxylhedyphane, Ca2Pb3(AsO4)3(OH), a new member of the apatite supergroup from Långban, Sweden2019Ingår i: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 31, nr 5-6, s. 1007-1014Artikel i tidskrift (Refereegranskat)
  • 4.
    Drake, Henrik
    et al.
    Department of Biology and Environmental Science, Linnaeus University, 39231 Kalmar, Sweden.
    Mathurin, Frédéric A.
    Department of Biology and Environmental Science, Linnaeus University, 39231 Kalmar, Sweden.
    Zack, Thomas
    Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
    Schäfer, Thorsten
    Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, 76021 Karlsruhe, Germany.
    Nick MW, Roberts
    NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham NG12 5GG, U.K..
    Whitehouse, Martin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Broman, Curt
    Department of Geological Sciences, Stockholm University, Stockholm 106 91, Sweden.
    Mats E., Åström
    Department of Biology and Environmental Science, Linnaeus University, 39231 Kalmar, Sweden.
    Incorporation of Metals into Calcite in a Deep Anoxic Granite Aquifer2018Ingår i: Environmental Science and Technology, ISSN 1086-931X, E-ISSN 1520-6912, Vol. 52, nr 2, s. 293-502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding metal scavenging by calcite in deep aquifers in granite is of importance for deciphering and modeling hydrochemical fluctuations and water–rock interaction in the upper crust and for retention mechanisms associated with underground repositories for toxic wastes. Metal scavenging into calcite has generally been established in the laboratory or in natural environments that cannot be unreservedly applied to conditions in deep crystalline rocks, an environment of broad interest for nuclear waste repositories. Here, we report a microanalytical study of calcite precipitated over a period of 17 years from anoxic, low-temperature (14 °C), neutral (pH: 7.4–7.7), and brackish (Cl: 1700–7100 mg/L) groundwater flowing in fractures at >400 m depth in granite rock. This enabled assessment of the trace metal uptake by calcite under these deep-seated conditions. Aquatic speciation modeling was carried out to assess influence of metal complexation on the partitioning into calcite. The resulting environment-specific partition coefficients were for several divalent ions in line with values obtained in controlled laboratory experiments, whereas for several other ions they differed substantially. High absolute uptake of rare earth elements and U(IV) suggests that coprecipitation into calcite can be an important sink for these metals and analogousactinides in the vicinity of geological repositories.

  • 5.
    Hogmalm, Johan K.
    et al.
    Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
    Zack, Thomas
    Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Sjökvist, Axel S.L.
    Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
    Garbe-Schönberg, Dieter
    CAU Kiel University, Institute of Geosciences, Ludewig-Meyn-Strasse 10, D-24118 Kiel, Germany .
    In situ Rb–Sr and K–Ca dating by LA-ICP-MS/MS: an evaluation of N2O and SF6 as reaction gases2017Ingår i: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 32, s. 305-313Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In situ dating of K-rich minerals, e.g. micas and K-feldspar, by the Rb–Sr isotopic system is a new development made possible by the ICP-MS/MS technique. Online chemical separation of Rb and Sr is possible in an O2-filled reaction cell, wherein a portion of the Sr reacts to SrO+ while simultaneously no RbO+ is formed. O2 reactions provide stable analytical conditions sufficient for precise and accurate determination of Rb/Sr and Sr/Sr isotopic ratios using 80 micron laser ablation spots. However, to date <10% of the Sr reacts with O2 as reaction gas, leaving room for improvement using more potent reaction gases. With a more efficient reactive transfer, it should be possible to obtain similar results with a smaller laser spot size, hence gaining higher spatial resolution. In this study, we have evaluated N2O and SF6 as reaction gases since they have previously been shown to react strongly with Sr+, without affecting Rb+. Analytical conditions, including cell parameters and reaction gas flow rate were optimized while ablating NIST SRM 610. The main reaction product is SrO+ for N2O reaction and SrF+ for SF6 reaction. Both gases show significantly higher reaction product formation compared to O2 with >85% of Sr reacting with N2O and >70% Sr reacting with SF6; Rb does not react with either gas. As a result, the sensitivity for Sr reaction products is ∼10 times higher with N2O and ∼8 times higher with SF6 compared to O2. With these more reactive gases, the error of mica isochron ages, calibrated against a newly developed nano-particulate pressed powder tablet of mica–Mg, is ∼1% using a 50 μm laser spot. Our tests show that both N2O and SF6 form interfering reaction products, e.g., SrOH (N2O), SiF3 and TiF3 (SF6) that are difficult to handle using single mass spectrometer instruments, but which can be overcome using MS/MS. Using SF6 combined with H2, it is possible to measure 40Ca+ as 40Ca19F+, free from interference of 40Ar+ and 40K+. This facilitates the dating of micas by the K–Ca isotopic system; we present the first in situ K–Ca age determination.

  • 6.
    Holtstam, Dan
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Cámara, Fernando
    Università degli Studi di Milano.
    Skogby, Henrik
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Hjalmarite, a new Na-Mn member of the amphibole supergroup, from Mn skarn in the Långban deposit, Värmland, Sweden.2019Ingår i: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 31, s. 565-574Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hjalmarite, ideally ANaB(NaMn)CMg5TSi8O22W(OH)2, is a new root-name member of the amphibole supergroup, discovered in skarn from the Långban Fe-Mn-(Ba-As-Pb-Sb-Be-B) deposit, Filipstad, Värmland, Sweden (IMA-CNMNC 2017-070). It occurs closely associated with mainly rhodonite and quartz. It is grayish white with vitreous luster and non-fluorescent. The crystals are up to 5 mm in length and display splintery fracture and perfect cleavage along {110}. Hjalmarite is colorless (non-pleochroic) in thin section and optically biaxial (-), with α = 1.620(5), β = 1.630(5), γ = 1.640(5). The calculated density is 3.12 Mg/m3. Average VHN100 is 782, corresponding to circa 5½ Mohs. An empirical formula, derived from EPMA analyses in combination with crystal structure refinements, is (Na0.84K0.16)Σ1(Na1.01Mn0.55Ca0.43Sr0.01) Σ2(Mg3.83Mn1.16Al0.01) Σ5(Si7.99Al0.01) Σ8O22(OH1.92F0.08)Σ2. An infra-red spectrum of hjalmarite shows distinct absorption bands at 3673 cm-1 and 3731 cm-1 polarized in the α direction. The eight strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 3.164, 100, (310); 2.837, 50, (330); 8.50, 44, (110); 3.302; 40, (240); 1.670, 34, (461); 1.448, 32, (-661); 2.727, 30, (151); 2.183, 18 (261).

    Single-crystal X-ray diffraction data were collected at 298 K and 180 K. The crystal structure was refined in space group C2/m to R1=2.6% [I>2(I)], with observed unit-cell parameters a = 9.9113(3), b = 18.1361(4), c = 5.2831(5) Å, β=103.658(5)° and V = 922.80(9) Å3 at ambient temperature. The A and M(4) sites split into A(m) (K+), A(2) (Na+), and M(4’) (Mn2+) subsites, respectively. Among the octahedrally coordinated C group cations, Mn2+ orders strongly at the M(2) site. No significant violation of C2/m symmetry or change in the structure topology is detected at low temperature (R1=2.1%). The hjalmarite-bearing skarn formed at peak regional metamorphism, T  ≥ 600°C, at conditions of high SiO2 activity and relatively low oxygen fugacity. The mineral name honors the Swedish geologist and mineralogist S.A. Hjalmar Sjögren (1856–1922).

  • 7.
    Holtstam, Dan
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Cámara, Fernando
    Università degli Studi di Milano.
    Skogby, Henrik
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Langhof, Jörgen
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Recognition and approval of potassic-richerite, an amphibole supergroup mineral, from the Pajsberg mines, Filipstad, Sweden.2019Ingår i: Mineralogy and Petrology, ISSN 0930-0708, E-ISSN 1438-1168, Vol. 113, s. 7-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Potassic-richterite, ideally AKB(NaCa)CMg5TSi8O22W(OH)2, is recognized as a valid member of the amphibole supergroup (IMA CNMNC 2017–102). Type material is from the Pajsberg Mn-Fe ore field, Filipstad, Värmland, Sweden, where the mineral occurs in a Mn-rich skarn, closely associated with mainly phlogopite, jacobsite and tephroite. The megascopic colour is straw yellow to grayish brown and the luster vitreous. The nearly anhedral crystals, up to 4 mm in length, are pale yellow (non-pleochroic) in thin section andoptically biaxial (−), with α = 1.615(5), β = 1.625(5), γ = 1.635(5). The calculated density is 3.07 g·cm−1. VHN100 is in the range 610–946. Cleavage is perfect along {110}. EPMA analysis in combination with Mössbauer and infrared spectroscopy yields the empirical formula (K0.61Na0.30Pb0.020.93(Na1.14Ca0.79Mn0.07)Σ2(Mg4.31Mn0.47Fe3+0.20)Σ5(Si7.95Al0.04Fe3+0.01)Σ8O22(OH1.82F0.18)Σ2 for a fragmentused for collection of single-crystal X-ray diffraction data. The infra-red spectra show absorption bands at 3672 cm−1 and 3736 cm−1 for the α direction. The crystal structure was refined in space group C2/m to R1=3.6% [I >2σ(I)], with resulting cellparameters a = 9.9977(3) Å, b = 18.0409(4) Å, c = 5.2794(2) Å, γ = 104.465(4)°, V = 922.05(5) Å3 and Z=2. The A and M(4) sites split into A(m) (K+), A(2/m) (Na+), A(2) (Pb2+), and M(4′) (Mn2+) subsites, respectively. The remaining Mn2+ is strongly ordered at theoctahedrally coordinated M(2) site, possibly together with most of Fe3+. The skarn bearing potassic-richterite formed at peak metamorphism, under conditions of low SiO2 and Al2O3 activities and relatively high oxygen fugacities.

  • 8.
    Johansson, Åke
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Hurgammal är Stockholmsgraniten? Vad säger forskningen och vad säger folket?2019Ingår i: Geologiskt forum, nr 101, s. 22-25Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 9.
    Karlsson, Andreas
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Holtstam, Dan
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Bindi, Luca
    Dipartimento di Scienze della Terra, Università degli Studi di Firenze.
    Bonazzi, Poala
    Dipartimento di Scienze della Terra, Università degli Studi di Firenze.
    Konrad-Schmolke, Matthias
    Department of Earth Sciences, University of Gothenburg.
    Adding complexity to the garnet supergroup: monteneveite, Ca3Sb5+2(Fe3+2Fe2+)O12, a new mineral from the Monteneve mine, Bolzano Province, Italy2020Ingår i: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 32, nr 1, s. 77-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Monteneveite, ideally Ca3Sb5+2(Fe3+2Fe2+)O12, is a new member of the garnet supergroup (IMA2018-060). The mineral was discovered in a small specimen belonging to the Swedish Museum of Natural History coming from the now abandoned Monteneve Pb–Zn mine in Passiria Valley, Bolzano Province, Alto Adige (South Tyrol), Italy. The specimen consists of mainly magnetite, sphalerite, tetrahedrite-(Fe) and oxycalcioroméite. Monteneveite occurs as black, subhedral crystals with adamantine lustre. They are equidimensionaland up to 400 μm in size, with a subconchoidal fracture. Monteneveite is opaque, grey in reflected light,and isotropic under crossed polars. Measured reflectance values (%) at the four COM wavelengths are 12.6 (470 nm), 12.0 (546 nm), 11.6 (589 nm) and 11.4 (650 nm). The Vickers hardness (VHN100) is 1141 kg mm-2, corresponding to H = 6.5–7, and the calculated density is 4.72(1) g cm-3. A mean of 10 electron microprobe analyses gave (wt %) CaO 23.67, FeO 3.75, Fe2O3 29.54, Sb2O5 39.81, SnO2 2.22, ZnO 2.29, MgO 0.15, MnO 0.03 and CoO 0.03. The crystal chemical formula calculated on the basis of a total of eight cations and 12 anions, and taking into account the available structural and spectroscopic data, is (Ca2.97Mg0.03)Σ=3.00(Sb5+1.73Sn4+0.10Fe3+0.17)Σ=2.00(Fe3+2:43Fe2+0.37Zn0.20)Σ=3.00O12. The most significant chemical variations encounteredin the sample are related to a substitution of the type YSn4+ + ZFe3+  YSb5+ + ZFe2+. Mössbauer data obtained at RT and 77K indicate the presence of tetrahedrally coordinated Fe2+. Raman spectroscopy demonstrates that there is no measurable hydrogarnet component in monteneveite. The six strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 4.45, 100, (220); 3.147, 60, (400); 2.814, 40, (420); 2.571, 80, (422); 1.993, 40, (620); 1.683, 60, (642). Monteneveite is cubic, space group Ia-3d, with a =12.6093(2) Å, V = 2004.8(1)Å3, and Z = 8. The crystal structure was refined up to R1 = 0.0197 for 305 reflections with Fo > 4σ (Fo) and 19 parameters. Monteneveite is related to the other Ca-, Sb- and Fe-bearing, nominally Si-free members of the bitikleite group, but it differs in that it is the only known garnet species with mixed trivalent and divalent cations (2:1) at the tetrahedral Z site. Textural and mineralogical evidence suggests that monteneveite formed during peak metamorphism (at ca. 600 ºC) during partial breakdown of tetrahedrite-(Fe) by reactions with carbonate, under relatively oxidizingconditions. The mineral is named after the type locality, the Monteneve (Schneeberg) mine.

  • 10.
    Kasapoğlu, Bülent
    et al.
    The Graduate School of Natural and Applied Sciences, Dokuz Eylül University, TR-35160 İzmir, Turkey.
    Ersoy, Yalçın E.
    Department of Geological Engineering, Dokuz Eylül University, TR-35160 İzmir, Turkey.
    Uysal, İbrahim
    Department of Geological Engineering, Karadeniz Technical University, TR-61080 Trabzon, Turkey.
    Palmer, Martin R.
    School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK.
    Zack, Thomas
    Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
    Koralay, Ersin O.
    Department of Geological Engineering, Dokuz Eylül University, TR-35160 İzmir, Turkey.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    The petrology of Paleogene volcanism in the Central Sakarya, Nallıhan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity2015Ingår i: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 246-247, s. 81-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zircon ages, mineral chemistry, whole-rock major and trace element compositions, as well as Sr–Nd isotopic ratios of basaltic (basanite, basalt, and hawaiite with MgO = 3.90–10.06 and SiO2 = 43.18–48.16) to andesitic (SiO2 = 50.86–61.27) and rhyolitic (SiO2 = 71.11–71.13) volcanic rocks (E-W emplaced Nallıhan volcanics) in the Lower Eocene terrestrial sedimentary units in the Central Sakarya Zone were studied and compared with those of the northerly located E-W-trending Eocene volcanic rocks (the Kızderbent Volcanics with 52.7–38.1 Ma radiometric ages) that are thought to be related to slab break-off process following the continental collision in the NW Anatolia. Zircon U–Pb ages of the Nallıhan volcanics vary from 51.7 ± 4.7 to 47.8 ± 2.4 Ma.

    Clinopyroxene from the basaltic and andesitic rocks record crystallization conditions from ~ 7–8 kbars (~ 23 km) and ~ 1210 °C, to 4.5–1.5 kbars (~ 14–1.5 km) and 1110–1010 °C crystallization conditions, respectively. The olivine-bearing, high-MgO (up to 10 wt%) basaltic rocks of the Nallıhan volcanics have nepheline-normative and Na-alkaline compositions, while the andesitic to rhyolitic rocks show calc-alkaline affinity with mainly sodic character. This is the first time this type of volcanic rock has been described in this region. The initial Sr isotopic ratios of both basaltic and andesitic–rhyolitic samples from the Nallıhan volcanics are similar (~ 0.7040–0.7045), indicating that fractional crystallization processes were not accompanied by crustal contamination and that the magma chambers were likely stored within ophiolitic units. Trace element ratios suggest that the Nallıhan volcanics were derived from E-MORB- or OIB-like enriched mantle sources, while the Kızderbent volcanics had N-MORB-like depleted mantle sources. Both volcanic units were produced by partial melting of spinel-bearing (shallow) mantle sources that had undergone subduction-related enrichment processes, with the degree of enrichment having been greater for the Kızderbent volcanics.

    The geochemical features of both the Nallıhan and Kızderbent volcanics are best explained as the result of slab break-off, in which the Nallıhan volcanics (located closer to the original subduction front) were produced mainly by the melting of upwelling asthenospheric mantle. Further back from the subduction front, the upwelling interacted with more highly metasomatized sub-arc mantle that underwent partial melting to produce the Kızderbent volcanics. This geodynamic scenario can be used for understanding other post-collisional slab break-off-related magmatic activities.

  • 11.
    Kenny, Gavin
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Schmieder, Martin
    Whitehouse, Martin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Nemchin, Alexander
    Bellucci, Jeremy
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Recrystallization and chemical changes in apatite in response to hypervelocity impact2020Ingår i: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 48, nr 1, s. 19-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Despite the wide utility of apatite, Ca5(PO4)3(F,Cl,OH), in the geosciences, including tracing volatile abundances on the Moon and Mars, little is known about how the mineral responds to the extreme temperatures and pressures associated with hypervelocity impacts. To address this deficiency, we here present the first microstructural analysis and chemical mapping of shocked apatite from a terrestrial impact crater. Apatite grains from the Paasselkä impact structure, Finland, display intragrain crystal-plastic deformation as well as pervasive recrystallization—the first such report in terrestrial apatite. A partially recrystallized grain offers the opportunity to investigate the effect of shock recrystallization on the chemical composition of apatite. The recrystallized portion of the fluorapatite grain is depleted in Mg and Fe relative to the remnant non-recrystallized domain. Strikingly, the recrystallized region alone hosts inclusions of (Mg,Fe)2(PO4)F, wagnerite or a polymorph thereof. These are interpreted to be a product of phase separation during recrystallization and to be related to the reduced abundances of certain elements in the recrystallized domain. The shock-induced recrystallization of apatite, which we show to be related to changes in the mineral’s chemical composition, is not always readily visible in traditional imaging techniques (such as backscattered electron imaging of polished interior surfaces), thus highlighting the need for correlated microstructural, chemical, and isotopic studies of phosphates. This is particularly relevant for extraterrestrial phosphates that may have been exposed to impacts, and we urge the consideration of microstructural data in the interpretation of the primary or secondary nature of elemental abundances and isotopic compositions.

    Publikationen är tillgänglig i fulltext från 2021-01-01 12:00
  • 12. Larsen, Alf Olav
    et al.
    Langhof, Jörgen
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Fantehullet på Oteröy - lokaliteten for Tellef Dahlls angivelige nye grunnstoff norvegium2019Ingår i: Norskt Mineralsymposium 2019 / [ed] Alf Olav Larsen & Torfinn Kjaernet, 2019, s. 93-101Konferensbidrag (Övrigt vetenskapligt)
  • 13.
    Stockmann, Gabrielle
    Department of Geological Sciences, Stockholm University, Sweden.
    Skelton, Alasdair (Medarbetare/bidragsgivare)
    Department of Geological Sciences, Stockholm University, Sweden.
    Brüchert, Volker (Medarbetare/bidragsgivare)
    Department of Geological Sciences, Stockholm University, Sweden.
    Balic-Zunic, Tonci (Medarbetare/bidragsgivare)
    Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark.
    Langhof, Jörgen (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Skogby, Henrik (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Control of a calcite inhibitor (phosphate) and temperature on ikaite precipitation in Ikka Fjord, southwest Greenland2018Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 89, s. 11-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ikaite (CaCO3·6H2O) forms submarine tufa columns in Ikka Fjord, SW Greenland. This unique occurrence is thought to relate to aqueous phosphate concentration and low water temperatures (<6 °C). Phosphate ions are well-known inhibitors of calcite precipitation and Ikka Fjord has a naturally high-phosphate groundwater system that when mixing with seawater leads to the precipitation of ikaite. In the study presented here, experiments simulating conditions of Ikka Fjord show that a) the formation of ikaite is unrelated to the aqueous phosphate concentration (0–263 μmol/kg PO43−) in 0.1 M NaHCO3/0.1 M Na2CO3 solutions mixing with seawater at 5 °C and pH 9.6–10.6, and b) ikaite forms at temperatures up to 15 °C without phosphate and in open beakers exposed to air. Instead, supersaturation of ikaite and the seawater composition are the likely factors causing ikaite to precipitate in Ikka Fjord. This study shows that adding Mg2+ to a NaHCO3/Na2CO3 – CaCl2 mixed solution leads to the formation of ikaite along with hydrated Mg carbonates, which points to the high Mg2+ concentration of seawater, another known inhibitor of calcite, as a key factor promoting ikaite formation. In experiments at 10 and 15 °C, increasing amounts of either nesquehonite (Mg(HCO3)(OH)·2H2O) or an amorphous phase co-precipitate with ikaite. At 20 °C, only the amorphous phase is formed. In warming Arctic seawater, this suggests Mg carbonate precipitation could become dominant over ikaite in the future.

  • 14.
    Stockmann, Gabrielle
    Department of Geological Sciences, Stockholm University, Sweden.
    Brüchert, Volker (Medarbetare/bidragsgivare)
    Department of Geological Sciences, Stockholm University, Sweden.
    Skelton, Alasdair (Medarbetare/bidragsgivare)
    Department of Geological Sciences, Stockholm University, Sweden.
    Balic-Zunic, Tonci (Medarbetare/bidragsgivare)
    Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark.
    Langhof, Jörgen (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Skogby, Henrik (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas (Medarbetare/bidragsgivare)
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Control of a calcite inhibitor (phosphate) and temperature on ikaite precipitation in Ikka Fjord, southwest Greenland2018Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 89, s. 11-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ikaite (CaCO3·6H2O) forms submarine tufa columns in Ikka Fjord, SW Greenland. This unique occurrence is thought to relate to aqueous phosphate concentration and low water temperatures (<6 °C). Phosphate ions are well-known inhibitors of calcite precipitation and Ikka Fjord has a naturally high-phosphate groundwater system that when mixing with seawater leads to the precipitation of ikaite. In the study presented here, experiments simulating conditions of Ikka Fjord show that a) the formation of ikaite is unrelated to the aqueous phosphate concentration (0–263 μmol/kg PO43−) in 0.1 M NaHCO3/0.1 M Na2CO3 solutions mixing with seawater at 5 °C and pH 9.6–10.6, and b) ikaite forms at temperatures up to 15 °C without phosphate and in open beakers exposed to air. Instead, supersaturation of ikaite and the seawater composition are the likely factors causing ikaite to precipitate in Ikka Fjord. This study shows that adding Mg2+ to a NaHCO3/Na2CO3 – CaCl2 mixed solution leads to the formation of ikaite along with hydrated Mg carbonates, which points to the high Mg2+ concentration of seawater, another known inhibitor of calcite, as a key factor promoting ikaite formation. In experiments at 10 and 15 °C, increasing amounts of either nesquehonite (Mg(HCO3)(OH)·2H2O) or an amorphous phase co-precipitate with ikaite. At 20 °C, only the amorphous phase is formed. In warming Arctic seawater, this suggests Mg carbonate precipitation could become dominant over ikaite in the future.

  • 15.
    Stockmann, Gabrielle
    et al.
    Department of Geological Sceinces, Stockholm University.
    Tollefsen, Elin
    Department of Geological Sceinces, Stockholm University.
    Skelton, Alasdair
    Department of Geological Sceinces, Stockholm University.
    Brüchert, Volker
    Department of Geological Sceinces, Stockholm University.
    Balic-Zunic, Tonci
    Department of Geosceinces and Natural Resource Management, University of Copenhagen.
    Langhof, Jörgen
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Skogby, Henrik
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Control of calcite inhibitor (phosphate) and temperature on ikaite precipitation in Ikka Fjord, southwest Greenland2018Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 89, s. 11-22Artikel i tidskrift (Refereegranskat)
1 - 15 av 15
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf