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  • 301.
    Døssing, Arne
    et al.
    DTU Space, National Space Institute, Technical University of Denmark.
    Hopper, John R.
    Geological Survey of Denmark and Greenland (GEUS), Copenhagen.
    Olesen, Arne Vestergaard
    DTU Space, National Space Institute, Technical University of Denmark.
    Rasmussen, Thorkild Maack
    Geological Survey of Denmark and Greenland (GEUS), Copenhagen.
    Halpenny, John F.
    Natural Resources Canada, Ottawa, ON.
    New aero-gravity results from the Arctic: Linking the latest Cretaceous-early Cenozoic plate kinematics of the North Atlantic and Arctic Ocean2013In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 14, no 10, p. 4044-4065Article in journal (Refereed)
    Abstract [en]

    The tectonic history of the Arctic Ocean remains poorly resolved and highly controversial. Details regarding break up of the Lomonosov Ridge from the Barents-Kara shelf margins and the establishment of seafloor spreading in the Cenozoic Eurasia Basin are unresolved. Significantly, the plate tectonic evolution of the Mesozoic Amerasia Basin is essentially unknown. The Arctic Ocean north of Greenland is at a critical juncture that formed at the locus of a Mesozoic three-plate setting between the Lomonosov Ridge, Greenland, and North America. In addition, the area is close to the European plate, resulting in complicated interactions between all these areas that are difficult to resolve. In 2009, the 550,000 km2 LOMGRAV aero-geophysical survey produced the first collocated gravity and magnetic measurements over the area, significantly increasing the data coverage. We present an interpretation of a new free-air gravity compilation, which reveals a regionally consistent structural grain across the Lomonosov Ridge, the Ellesmere and Lincoln Sea shelves, and the Alpha Ridge. We interpret the grain as evidence of latest Cretaceous (∼80 Ma) regional extension in response to the northward propagation of Atlantic and Labrador Sea opening into the Arctic, west of Greenland. This interpretation is consistent with coincident alkaline volcanic activity evident in the borderlands of the Lincoln Sea. We further suggest that Eurekan crustal shortening contributed to the formation of the distinct Lomonosov Ridge plateau against an important fault zone north of Greenland. Our results provide new constraints for Cretaceous-Cenozoic plate reconstructions of the Arctic. Key Points Presentation of the largest aero-gravity survey acquired over the Arctic Ocean Plate tectonic link between Atlantic and Arctic spreading west of Greenland New plate reconstruction models are presented for the area north of Greenland

  • 302.
    Døssing, Arne
    et al.
    DTU Space, National Space Institute, Technical University of Denmark.
    Jackson, H. Ruth
    Geological Survey of Canada Atlantic (GSCA), Halifax.
    Matzka, Jürgen
    National Space Institute, DTU Space.
    Einarsson, Indridi
    National Space Institute, DTU Space.
    Rasmussen, Thorkild Maack
    Geological Survey of Denmark and Greenland (GEUS) .
    Brozena, John M.
    Naval Research Laboratory.
    On the origin of the Amerasia Basin and the High Arctic Large Igneous Province-Results of new aeromagnetic data2013In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 363, p. 219-230Article in journal (Refereed)
    Abstract [en]

    The history of the 2.5 million km2 Amerasia Basin (sensu lato) is in many ways the least known in the global tectonic system. Radically different hypotheses proposed to explain its origin are supported only by inconclusive and/or indirect observations and several outstanding issues on the origin of the Basin remain unaddressed. The difficulty lies in the geodynamic evolution and signature of the Basin being overprinted by excess volcanism of the Alpha-Mendeleev Ridge complex, part of the High Arctic Large Igneous Province (HALIP) and one of the largest (>1 million km2) and most intense magmatic and magnetic complexes on Earth. Here, we present the results of a 550,000km2 aerogeophysical survey over the poorly explored Lomonosov Ridge (near Greenland) and adjoining Amerasia and Eurasia Basins that provides the first direct evidence for consistent linear magnetic features between the Alpha and Lomonosov Ridges, enabling the tectonic origin of both the Amerasia Basin and the HALIP to be constrained. A landward Lower Cretaceous ( ~ 138 - 125(120) Ma) giant dyke swarm (minimum 350×800km2) and tentative oceanward Barremian (or alternatively lower Valanginian-Barremian) seafloor spreading anomalies are revealed. Prior to Cenozoic opening of the Eurasia Basin the giant dyke swarm stretched from Franz Josef Land to the southern Alpha Ridge and possibly further to Queen Elisabeth Islands, Canada. The swarm points towards a 250-km-wide donut-shaped anomaly on the southern Alpha Ridge, which we propose was the centre of the HALIP mantle plume, suggesting that pronounced intrusive activity, associated with an Alpha Ridge mantle plume, took place well before the Late Cretaceous Superchron and caused continental breakup in the northern Amerasia Basin. Our results imply that at least the southern Alpha Ridge as well as large parts of the area between the Lomonosov and southern Alpha Ridges are highly attenuated continental crust formed by poly-phase breakup with LIP volcanic addition. Significantly, our results are consistent with an early ( ~ pre-120 Ma) overall continental scale rotational opening of the Amerasia Basin in which the Eurasian continental margin is rifted from the Canadian-southern Alpha Ridge margin about one or more poles in the Mackenzie Delta (Alaska). The findings provide a key to resolving Arctic plate reconstructions and LIPs in the Mesozoic.

  • 303.
    Eastwood, J. P.
    et al.
    Imperial Coll London, Blackett Lab, London, England..
    Mistry, R.
    Imperial Coll London, Blackett Lab, London, England..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Schwartz, S. J.
    Imperial Coll London, Blackett Lab, London, England.;Univ Colorado, Dept Astrophys & Planetary Sci, LASP, Boulder, CO 80309 USA..
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, LASP, Boulder, CO 80309 USA..
    Drake, J. F.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA.;Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA..
    Oieroset, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England..
    Goldman, M. V.
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA..
    Haggerty, C.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.;Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA..
    Shay, M. A.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Gershman, D. J.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Torbert, R. B.
    Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA.;Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Guide Field Reconnection: Exhaust Structure and Heating2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 10, p. 4569-4577Article in journal (Refereed)
    Abstract [en]

    Magnetospheric Multiscale observations are used to probe the structure and temperature profile of a guide field reconnection exhaust similar to 100 ion inertial lengths downstream from the X-line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near 1 edge of the exhaust and containing electron flow toward the X-line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust, but within the cavity, electron cooling and enhanced parallel ion heating were found. This is explained in terms of the parallel electric field, which inhibits electron mixing within the cavity on newly reconnected field lines but accelerates ions. Consequently, guide field reconnection causes inhomogeneous changes in ion and electron temperature across the exhaust.

  • 304.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    Lebreton, J. -P
    Gasc, S.
    Rubin, M.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gill, Reine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Erik P. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Carr, C. M.
    Cupido, E.
    Glassmeier, K. -H
    Goldstein, R.
    Koenders, C.
    Mandt, K.
    Nemeth, Z.
    Nilsson, H.
    Richter, I.
    Wieser, G. Stenberg
    Szego, K.
    Volwerk, M.
    Spatial distribution of low-energy plasma around comet 67P/CG from Rosetta measurements2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 11, p. 4263-4269Article in journal (Refereed)
    Abstract [en]

    We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be approximate to 1-210(-6), at a cometocentric distance of 10km and at 3.1AU from the Sun. A clear 6.2h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260km from the nucleus falls off with radial distance as approximate to 1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet.

  • 305. Edfelt, Åsa
    et al.
    Sandrin, Alessandro
    Luleå tekniska universitet.
    Evins, Paul
    EGRU, School of Earth Sciences, James Cook University.
    Jeffries, Teresa
    Natural History Museum, London.
    Storey, Craig
    Open University, Walton Hall, Milton Keynes.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stratigraphy and tectonic setting of the host rocks to the Tjårrojåkka Fe-oxide Cu-Au deposits, Kiruna area, northern Sweden2006In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 128, no 3, p. 221-232Article in journal (Refereed)
    Abstract [en]

    The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially and possibly genetically related Fe-oxide and Cu-Au occurrences in the area. The bedrock is dominated by intermediate and basic extrusive and intrusive rocks. An andesite constrains the ages of these rocks with a U-Pb LA-ICPMS age of 1878±7 Ma. They are cut by dolerites, which acted as feeder dykes for the overlying basalts. Based on geochemistry and the obtained age the andesites and basaltic andesites can be correlated with the 1.9 Ga intermediate volcanic rocks of the Svecofennian Porphyrite Group in northern Sweden. They formed during subduction-related magmatism in a volcanic arc environment on the Archaean continental margin above the Kiruna Greenstone Group. Chemically the basalts and associated dolerites have the same signature, but cannot directly be related to any known basaltic unit in northern Sweden. The basalts show only minor contamination of continental crust and may represent a local extensional event in a subaquatic back arc setting with extrusion of mantle derived magma. The intrusive rocks range from gabbro to quartz-monzodiorite in composition. The area is metamorphosed at epidote-amphibolite facies and has been affected by scapolite, K-feldspar, epidote, and albite alteration that is more intense in the vicinity of deformation zones and mineral deposits. Three events of deformation have been distinguished in the area. D1 brittle-ductile deformation created NE-SW-striking steep foliation corresponding with the strike of the Tjårrojåkka-Fe and Cu deposits and was followed by the development of an E-W deformation zone (D2). A compressional event (D3), possible involving thrusting from the SW, produced folds in the central part of the area and a NNW-SSE striking deformation zone in NE.

  • 306.
    Edlmann, K.
    et al.
    Univ Edinburgh, Grant Inst, Sch Geosci, Kings Bldg,James Hutton Rd, Edinburgh EH9 3FE, Midlothian, Scotland..
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bensabat, J.
    EWRE, Haifa, Israel..
    Haszeldine, R. S.
    Univ Edinburgh, Grant Inst, Sch Geosci, Kings Bldg,James Hutton Rd, Edinburgh EH9 3FE, Midlothian, Scotland..
    McDermott, C. I.
    Univ Edinburgh, Grant Inst, Sch Geosci, Kings Bldg,James Hutton Rd, Edinburgh EH9 3FE, Midlothian, Scotland..
    Mineralogical properties of the caprock and reservoir sandstone of the Heletz field scale experimental CO2 injection site, Israel; and their initial sensitivity to CO2 injection2016In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 48, p. 94-104Article in journal (Refereed)
    Abstract [en]

    This paper presents the initial database of the mineralogy of the caprock and reservoir sandstones of the Heletz field scale experimental CO2 injection site, Israel. The XRD mineralogy results show that the Heletz caprock has K-feldspar as the primary mineral (40%) followed by kaolinite (15%) and plagioclase feldspar (12%) then illite (6%) and muscovite (6%) with minor quartz, calcite, pyrite, chlorite and ankerite with traces of siderite. The Heletz reservoir rock is primarily quartz (70%) followed by K-feldspar (12%) and plagioclase feldspar (4%) with minor illite, kaolinite, muscovite, chlorite ankerite and pyrite with traces of dolomite, calcite and siderite. "Cook and look" bench experiments were conducted on the Heletz caprock and reservoir sandstone samples to identify if there was any immediate mineral reactivity that would influence permeability on exposure to CO2 that may cause concerns during well completion and initial injection of CO2 at Heletz. The sandstone exhibited reactivity under brine dis-equilibrium which was observed in the field with loss of injectivity which was restored by injecting KCL into the well and performing 20 swab-suctions. The caprock revealed no reactivity of immediate concern to the well completion and injection strategy and will retain its integrity.

  • 307.
    Ehsan, Siddique Akhtar
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Re-processing and Interpretation of 2D Seismic Line in the Kristineberg Mining Area, Northern Sweden2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Skellefte district, 1.90 to 1.80 Ga, is one of the most important base metal mining districts of Sweden with over 85 volcanic-hosted massive sulfide (VHMS) deposits. The study area focuses on the western part of the Skellefte district which contains volcanic, metasedimentary and intrusive rocks. In 2003, seismic data acquisition was carried out in the western part of the Skellefte district in the vicinity of the Kristineberg mine. Two parallel seismic lines were acquired about 8 km apart from each other. Profile 1 is about 22 km long and selected for the re-processing and interpretation in this thesis. The acquisition geometry, low fold coverage, the complex tectonic history and fewer outcrops in the area make the data processing and interpretation quite challenging and required a careful processing design to obtain interpretable seismic image. The re-processed Profile 1 is correlated with two other newly acquired seismic lines in the area for the purpose of possible 3D visualization and interpretation. The re-processing work includes a careful velocity analysis along with a series of iterations in residual statics, poststack and prestack migrations and cross dip analysis. The re-processed seismic section clearly shows a north dipping reflector which truncates against the Revsund Granites at depth. The possible interpretation for this reflector is a structural basement to the Skellefte Group constituting Bothnian Basin or a fault zone within the Viterliden intrusion. The Kristineberg mine is situated on the northern limb of a synform structure with prominent southwards dipping reflections. The major lithological contacts between different rock units are series of latest thrust faults. The prominent reflectivity within and at the contact with the Viterliden intrusion may suggest deep seated mineralized horizons. The cross dip analysis helps finding the eastward dipping component for the shallow horizons. The re-processed image is also compared with the previous processed seismic section and improvements in reflectors are evident.

  • 308.
    Ekeberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. ABB Schweiz AG, Corporate Research, CH-5405 Baden-Dättwil, Switzerland.
    Stasiewicz, Kristof
    Swedish Institute of Space Physics, P.O. Box 537, SE-751 21 Uppsala, Sweden.
    Wannberg, Gudmund
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Sergienko, Tima
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Eliasson, Lars
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Incoherent scatter ion line enhancements and auroral arc-induced Kelvin-Helmholtz turbulence2015In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 122, p. 119-128Article in journal (Refereed)
    Abstract [en]

    We present two cases of incoherent-scatter ion line enhancements in conjunction with auroral arcs drifting through the radar beam. The up- and downshifted ion line shoulders as well as the spectral region between them are enhanced equally and simultaneously. The power enhancements are one order of magnitude above the thermal level and are concentrated in less than 15 km wide altitude ranges at the ionospheric F region peak. The auroral arc passages are preceded by significantly enhanced ion temperatures in the E region, which are shown to generate high velocity shears. We use a Hall MHD model of velocity shears perpendicular to the geomagnetic field and show that a Kelvin-Helmholtz instability will grow for the two presented cases. We assess the possibility that the subsequently generated low frequency turbulence can explain the observed spectrally uniform ion line power enhancements.

  • 309.
    Eken, Tuna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Plomerová, Jaroslava
    Geophysical Institute, Czech Acad. Sci..
    Roberts, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Vecsey, Ludek
    Geophysical Institute, Czech Acad. Sci..
    Babuška, Vladislav
    Geophysical Institute, Czech Acad. Sci..
    Shomali, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bodvarsson, Reynir
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Seismic anisotropy of the mantle lithosphere beneath the Swedish National Seismological Network (SNSN)2010In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 480, no 1-4, p. 241-258Article in journal (Refereed)
    Abstract [en]

    Body-wave analysis – shear-wave splitting and P-travel time residuals - detect anisotropic structure of the upper mantle beneath the Swedish part of Fennoscandia. Geographic variations of both the splitting measurements and the P-residual spheres map regions of different fabrics of the mantle lithosphere. The fabric of individual mantle domains is internally consistent, usually with sudden changes at their boundaries. Distinct back-azimuth dependence of SKS splitting excludes single-layer anisotropy models with horizontal symmetry axes for the whole region. Based upon joint inversion of body-wave anisotropic parameters we instead propose 3D self-consistent anisotropic models of well-defined mantle lithosphere domains with differently oriented fabrics approximated by hexagonal aggregates with plunging symmetry axes. The domain-like structure of the Precambrian mantle lithosphere, most probably retaining fossil fabric since the domains’ origin, supports the idea of the existence of an early form of plate tectonics during formation of continental cratons already in the Archean. Similarly to different geochemical and geological constraints, the 3D anisotropy modelling and mapping of fabrics of the lithosphere domains contribute to tracking plate tectonics regimes back in time.

  • 310.
    Eken, Tuna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Shomali, Zaher Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Roberts, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hieronymus, Christoph F.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bödvarsson, Reynir
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    S and P velocity heterogeneities within the upper mantle below the Baltic Shield2008In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 462, no 1-4, p. 109-124Article in journal (Refereed)
    Abstract [en]

    Upper mantle structure beneath the Baltic (Fennoscandian) Shield is investigated using non-linear tomographic inversion of relative arrival-time residuals. 52 selected teleseismic earthquakes recorded by 45 broadband stations of the Swedish National Seismological Network (SNSN) provide 1532 good quality S-wave relative arrival times. SV and SH arrival-time residuals were initially analyzed independently, providing two separate models. These reveal several consistent major features, many of which are also consistent with P-wave results. Lateral velocity variations of ± 3–4% are observed to depths of at least 470 km. The correlation between the SH and SV models is investigated and shows a pattern of minor but significant differences down to around 150–200 km depth, below which the models are essentially similar. Direct cell by cell comparison of the model velocities reveals a similar pattern, with velocity differences between the models of up to 4%. Numerical tests show that differences in the two S-wave models can only be partially attributed to noise and limited resolution, and some features are attributed to the effect of large scale anisotropy. One of the significant and sharp discrepancies between the S models coincides with a presumed boundary between Archean and Proterozic domains, suggesting different anisotropic characteristics in the two regions.

  • 311.
    Ekman, Annica
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Engström, Anders
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    de Reus, Marian
    Max Planck Institute for Chemistry, Mainz, Germany.
    Williams, Jonathan
    Max Planck Institute for Chemistry, Mainz, Germany.
    Andreae, Meinrat
    Max Planck Institute for Chemistry, Mainz, Germany.
    Do organics contribute to small particle formation in the Amazonian upper troposphere?2008In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 35, no L17810, p. 5-Article in journal (Refereed)
    Abstract [en]

    3-D cloud-resolving model simulations including explicit aerosol physics and chemistry are compared with observations of upper tropospheric (12 km) aerosol size distributions over the Amazon Basin. The model underestimates the aerosol number concentration for all modes, especially the nucleation mode (d < 18 nm). We show that a boundary layer SO2 mixing ratio of approximately 5 ppb would be needed in order to reproduce the high nucleation mode number concentrations observed. This high SO2 mixing ratio is very unlikely for the pristine Amazon Basin at this time of the year. Hence, it is suggested that vapours other than H2SO4 participate in the formation and growth of small aerosols. Using activation nucleation theory together with a small (0.4–10%) secondary organic aerosol mass yield, we show that isoprene has the potential of substantially increasing the number of small particles formed as well as reducing the underestimate for the larger aerosol modes.

  • 312.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Papadopoulos, K.
    Departments of Physics and Astronomy, University of Maryland, College Park, Maryland, USA.
    Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, p. A10301-A10314Article in journal (Refereed)
    Abstract [en]

    The penetration of extremely low frequency (ELF) transient electromagnetic fields and associated currents in the Earth's equatorial E-region plasma is studied theoretically and numerically. In the low-frequency regime, the plasma dynamics of the E-region is characterized by helicon waves since the ions are viscously coupled to neutrals while the electrons remain mobile. For typical equatorial E-region parameters, the plasma is magnetically insulated from penetration of very long timescale magnetic fields by a thin diffusive sheath. Wave penetration driven by a vertically incident pulse localized in space and time leads to both vertical penetration and the triggering of ELF helicon/whistler waves that carry currents obliquely to the magnetic field lines. The study presented here may have relevance for ELF wave generation by lightning discharges and seismic activity and can lead to new concepts in ELF/ULF injection in the earth-ionosphere waveguide.

  • 313.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A palaeomagnetic study and K-Ar age determinations of tertiary rocks in Nicaragua1998In: Geoscientific research in Nicaragua: a Swedish-Nicaraguan joint project during the period 1981-1991, Luleå: Luleå tekniska universitet, 1998, p. 1-19Chapter in book (Other academic)
  • 314.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A palaeomagnetic study of Svecokarelian basic rocks from northern Sweden1985In: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 107, no 1, p. 17-35Article in journal (Refereed)
    Abstract [en]

    This palaeomagnetic investigation comprises basic rocks from six localities from the Svecokarelian zone in northern Sweden. Most of the pole positions in this study and other reported poles of Svecokarelian and post-Svecokarelian rocks fall within an approximately 12 degrees wide band running from east to west representing ages of magnetizations from 1880-1700 to ∼ 1530 Ma. Thermal demagnetizations of specimens of the probably oldest massifs indicate a possible backward continuation of the polar wandering path. Mineralogical studies of thin sections of the rocks show ore symplectites and myrmekitic textures indicating a slow rate of cooling at least at the end of the rock formation. Signs of metamorphism are demonstrated by the existence of secondary minerals, including magnetite, not related to late magmatic alterations. The distribution of site means as well as the change of directions of the remanence vectors during thermal demagnetization can be explained by a slow rate of cooling and where signs of metamorphism exist by partial remagnetization of the rock. This study has, apart from the palaeomagnetic results, demonstrated the difficulty of correlating radiometric ages with ages of magnetization

  • 315.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Basic dykes and dyke swarms in central and northern Sweden and the plate tectonic evolution of Fennoscandia: palaeomagnetic and Ar39/Ar40 studies2005In: "Dyke swarms - time markers of crustal evolution": Fifth International Dyke Conference, Pohtimolampi Wilderness Hotel, Polar Circle, Rovaniemi, Finland, 31 June - 3 August 2005 ; abstracts and programme / [ed] Jouni Vuollo; Satu Mertanen, Espoo: Geological Survey of Finland , 2005, p. 11-Conference paper (Other academic)
    Abstract [en]

    Palaeomagnetic and Ar39/Ar40 studies have been performed on basic dykes and dyke swarms in central and northern Sweden. At least five different generations of dykes have been defined and will be discussed in a plate tectonic context. Reliable palaeomagnetic data have been obtained from a big gabbro diabase and a geographically related dyke swarm in the northern part of Sweden from which poles similar to those calculated from Svecofennian gabbros (ca 1.86 Ga) are defined. In another swarm of palaeomagnetically similar age, just north of the Skellefte district, partially remagnetized dykes indicate a possible Subjotnian or Caledonian regional remagnetization. The dykes are younger when moving towards the south and in the central part there is a significant dyke swarm with at least two generations of dykes (ca. 1.7 and 1.6 Ga, respectively), one of which is related with rapakivi magmatism. Palaeomagnetic and anisotropy of magnetic susceptibility (AMS) data from the huge ca 1.25 Ga sill complexes in central Sweden and western Finland and from basic intrusions in Greenland suggest that Baltica and Laurentia were joined at that time. The similar stress field as indicated by the AMS data and the tensional regime reflected by the sill complexes is interpreted related to the break up of Baltica from Laurentia. New data from ca 1.1 Ga dykes in central Sweden confirms a clockwise rotation of Fennoscandia between 1.25 and 1.1 Ga, a rotation that is not seen for Laurentia.

  • 316.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Density and magnetic properties of rocks in the Caledonides of Jämtland, Sweden1980In: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 102, no 4, p. 439-453Article in journal (Refereed)
    Abstract [en]

    Density and magnetic properties were determined on some 1350 rock samples, taken from the different lithologies in the Caledonides of Jmtland, Sweden. The density determinations showed a strong trend of increasing density when moving from east to west in the investigated area. There was also a general increase in density upwards in the tectono-stratigraphy from the autochthon to the Seve of the Seve-Kli Nappe Complex. The determination of magnetic properties showed that east of the Caledonian Front the dominating high-susceptibility rock was the Rtan granite. In the Eastern Complex, west of the Caledonian Front, high-susceptibility rocks were found in the parautochthonous and allochthonous crystalline basement, whereas in the Western Complex the Ottfjllet dolerite in the Srv Nappe was the dominating high-susceptibility rock.

  • 317.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Evidence for early Proterozoic plate tectonics from seismic reflection profiles in the Baltic Shield1990In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 348, p. 34-38Article in journal (Refereed)
    Abstract [en]

    Plate tectonics provides the linking framework for all tectonic and magmatic activity seen today, but it is not known when plate tectonics first developed on Earth. New deep seismic reflection and coincident refraction profiles across an exposed, 1.89-Gyr-old volcanic arc complex show a 10-km-thick offset in the Moho and bivergent reflectors in the crust, which were most probably created by plate convergence, subduction and accretion during the Early Proterozoic. Hence, plate tectonic models seem to be applicable for at least the second half of Earth's history.

  • 318.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geological modelling based on gravity data from the central part of the Swedish caledonides1988In: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 110, no 4, p. 317-327Article in journal (Refereed)
    Abstract [en]

    Gravimetric measurements have been carried out within a c. 500 km2 area of western Jämtland in the Swedish Caledonides. Using different types of regional-residual gravity field separations, various geological models have been tested to fit the measured gravity data. Information on the geology and density of the rocks have reduced the number of possible models which are presented along two profiles. These models confirm the existence of antiforms and synforms running approximately parallel to the mountain range. The main profile crosses the two synforms over which positive anomalies are identified. Both in the western Tnnfors Synform and the eastern re Synform this is explained by the presence of high density Seve rocks, in the former case occurring beneath a cover of Kli Nappes. The depth to the base of the Seve Nappe units in the Tnnfors Synform is calculated at 4.5 km and in the re Synform at 3 km. The maximum depth to the interface between Kli and Seve rocks in the Tnnfors district is 3.2 km. Gravimetric models of the basement rocks in the windows, and difference in physical properties between the crystalline rocks of the windows and those of the autochthonous basement east of the Caledonian thrust front, imply that the basement exposed in the antiforms is allochthonous. A gravity minimum east of the re Synform is interpreted as a southern continuation of low density granites related to the Olden Complex. The inferred thickness of these low density rocks suggests that it may be a part of the autochthonous basement.

  • 319.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geological modelling based on gravity data from the central part of the Swedish Caledonides1991In: Vol. 113, no 2-3, p. 257-258Article in journal (Other academic)
  • 320.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Integrated seismic studies of the Baltic shield using data in the Gulf of Bothnia region1993In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 112, no 3, p. 305-324Article in journal (Refereed)
    Abstract [en]

    In the autumn of 1989 a co-operative experiment involving 12 research institutions in northwestern Europe collected 2268 km of deep seismic reflection profiles in the Gulf of Bothnia and the Baltic Sea. the 121 litre airgun array used for this profiling was also recorded by 62 muiticomponent land stations to provide coincident refraction surveys, fan-spreads, and 3-D seismic coverage of much of the Gulf of Bothnia. We thus have potentially both high-resolution impedance contrast images as well as more regional 3-D velocity models in both P- and S-waves. In the Bothnian Bay a south-dipping, non-reflective zone coincides with the conductive Archaean-Proterozoic boundary onshore in Finland. Between the Bothnian Bay and Bothnian Sea observed reflectivity geometries and velocity models at Moho depths suggest structures inherited from a 1.9Ga subduction zone; the upper crust here appears to have anomalously low velocity. Within the Bothnian Sea, reflectivity varies considerably beneath the metasedimentary/granitoid rocks of the Central Svecofennian Province (CSP) and the surrounding metavolcanic-arc rocks. Numerous dipping reflectors appear throughout the metavolcanic crust, whereas the CSP has little reflectivity. Wide-angle reflections indicate that the metasedimentary crust of the Bothnian Basin is 10 km thicker than the neighbouring Svecofennian subprovinces. Near the Åland archipelago Rapakivi granite plutons exhibit bright reflections, a contrast to the usual non-reflective plutons elsewhere in western Europe. Additional dipping reflections deep in the crust of this area may support models of rifting and crustal thinning during emplacement of the 1.70-1.54 Ga Rapakivi granites. Coeval gabbroic/anorthositic magmatism may explain the high reflectivity and high velocity of these plutons. the c. 1.25 Ga mafic sills and feeder dykes of the Central Scandinavian Dolerite Group also produce clear reflections on both near- and far-offset seismic sections. Continued modelling will produce better velocity models of the crust and better constrained contour maps of crustal thickness in this part of the Baltic shield.

  • 321.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Magnetic properties of pyrrhotite1981In: Vol. 19, no 2, p. 144-Article in journal (Other academic)
  • 322.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Palaeomagnetism of Precambrian rocks in northern Sweden and its correlation to radiometric data1994In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 69, no 1-4, p. 61-79Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic study has been performed on Palaeo- to Mesoproterozoic basic intrusions and volcanic rocks from the Fennoscandian shield in northern Sweden. Three, possibly four, different generations of magnetizations were identified, the oldest assigned to a Svecofennian age (1.86-1.89 Ga). A second generation is related to the intrusion of granitoids of 1.80-1.76 Ga. In this geological event probably also the third group of directions has its origin. These different magnetizations may indicate that there are at least two different generations of basic intrusions in northern Sweden. A fourth group of directions is isolated as overprints. This magnetization is interpreted to be a Subjotnian magnetization, reflecting a previously unrecognized regional Subjotnian metamorphic event in the northwestern part of the Fennoscandian shield. The drift history for the Fennoscandian shield during the period 1.88-1.50 Ga has been defined based on these new palaeomagnetic data

  • 323.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Recording marine airgun shots at offsets between 300 and 700 km1991In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 18, no 4, p. 645-648Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates that - under favorable conditions - by using multichannel recording and subsequent stacking of adjacent records marine airgun shots have been detected at offset distances up to 700 km, the maximum offset at which the authors attempted to record data.^Besides a powerful airgun array, a low noise environment at the recording site and the elimination of static shifts are the prerequisites to obtain refracted and reflected arrivals from the crust and upper mantle at such large offsets.^Primary arrivals detected at offsets between 400 and 700 km image the upper mantle from 70 to about 120 km depth.^Stacking of neighboring shots and/or receivers successfully increases the signal-to-noise ratio, if the traces have been corrected for offset differences, which requires knowledge of the apparent phase velocities.^The data presented here were collected in autumn 1989 during the BABEL Project on the Baltic Shield.

  • 324.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Research in rock magnetism and palaeomagnetism with reference to Caledonian and Precambrian rocks in Sweden1982Doctoral thesis, comprehensive summary (Other academic)
  • 325.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Subjotnian metamorphism in northern Sweden: a palaeomagnetic analysis of rocks from the northern svecofennian province and the Skellefte district1993In: Abstracts of lectures and posters: 21:a Nordiska geologiska vintermötet 10-13 Januari 1994 Luleå / [ed] Jan-Anders Perdahl, Luleå: Högskolan i Luleå , 1993, p. 44-Conference paper (Other academic)
  • 326.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The definition of the southern extension of the Chortis block: a palaeomagnetic and regional geophysical study in Nicaragua1993In: Abstracts of lectures and posters: 21:a Nordiska geologiska vintermötet 10-13 Januari 1994 Luleå / [ed] Jan-Anders Perdahl, Luleå: Högskolan i Luleå , 1993, p. 45-Conference paper (Other academic)
  • 327.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Bylund, Göran
    Palaeomagnetism and the Siljan impact structure, central Sweden1991In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 105, no 3, p. 757-770Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic study of rocks, from inside and outside the impact structure has been carried out, with the aim of identifying natural remanent magnetizations (NRMs) related to the impact event. Three different directions of magnetizations, not recognized elsewhere, were identified within the central part of the structure. These three magnetizations are defined in terms of coercivity and blocking temperature. The implications of the results are discussed in relation to ages obtained from Ar-Ar dating of impact melt

  • 328.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Bylund, Göran
    Lund University.
    Paleomagnetism and the Siljan impact structure, central Sweden1990In: Programme and abstracts: symposium Fennoscandian impact structures, may 29-31, 1990, Espoo and Lappajärvi, Finland / [ed] L.J. Pesonen; H. Niemisara, Geological Survey of Finland , 1990, p. 25-Conference paper (Other academic)
  • 329.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Bylund, göran
    Lund University.
    Paleomagnetism and the Siljan impact structure, Central Sweden1992In: Vol. 114, no 1, p. 158-Article in journal (Other academic)
  • 330.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    D'Agrella-Filho, M.S.
    Universidade de São Paulo.
    Page, L.M.
    University of Lund.
    Tohver, E.
    School of Earth and Geographical Sciences, University of Western Australia, Crawley.
    Trindade, R. I. F.
    Universidade de São Paulo.
    Pacca, I.I.G.
    Universidade de São Paulo.
    Geraldes, M.C.
    Faculdade de Geologia, Universidade do Estado do Rio de Janeiro.
    Teixeira, W.
    Instituto de Geociências, Universidade de São Paulo.
    A palaeomagnetic and Ar-40/Ar-39 study of late precambrian sills in the SW part of the Amazonian craton: Amazonia in the Rodinia reconstruction2009In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 178, no 1, p. 106-122Article in journal (Refereed)
    Abstract [en]

    A new key palaeomagnetic pole (Plat. = 64.3°S, Plon. = 271.0°E, N = 14, A95= 9.2°; Q = 5) is calculated from a primary magnetization isolated in early Neoproterozoic Aguapei basic sills and dykes hosted by 1.3-1.0 Ga sedimentary rocks from the southwestern part of the Amazon craton. The characteristic remanence carried by stable, pseudo-single domain titanomagnetite shows two antipodal polarities that pass a reversals test. Magnetic anisotropy for most sites shows fabric orientations that are typical of sills, with horizontal magnetic foliations concordant to the flat-lying bedding of the host sedimentary rocks. 40Ar/39Ar analyses for one of the sills reveal a well-defined plateau age at 981 ± 2 Myr. A tectonic reconstruction for Amazonia relative Laurentia based on this new pole 'is consistent with' a position of the present northwestern part of Amazonia attached with eastern Laurentia close to Greenland at ca. 981 Ma. On basis of palaeomagnetic and geological data, we propose a scenario where Amazonia moved northeastwards along the present southeast coast of Laurentia from ca. 1200 to 980 Ma. By 980 Ma, Amazonia is placed alongside Laurentia and Baltica, in a position similar to other reconstructions of Rodinia but with a significantly different orientation.

  • 331.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Enmark, Thomas
    Widenfalk, Lennart
    A combined geological petrophysical and geophysical investigation of the Notträsk gabbro, northern Sweden1983In: Vol. 105, no 4, p. 386-387Article in journal (Refereed)
  • 332.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jensen, Mai-Britt Mose
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A correlation of AMS and rock quality in crystalline and sedimentary rocks in the Kiirunavaara hanging wall2012In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 86, p. 54-69Article in journal (Refereed)
    Abstract [en]

    A study of the magnetic fabric and rock quality has been performed on crystalline and sedimentary rocks from the hanging wall of the Kiirunavaara iron ore deposit, northern Sweden. The rock samples were taken from 12 outcrops and three oriented drillcores and consist of quartzite, siltstone, conglomerate, porphyritic basalts, quartz-bearing porphyry and mylonite.Anisotropy of magnetic susceptibility (AMS) was used to determine the texture of the rocks by defining the shape of the magnetic susceptibility ellipsoids, the orientation of the magnetic foliation planes and the degree of magnetic anisotropy. AMS data from the outcrops as well as data from the uppermost part of two of the drillcores was used to produce a surface contour map which indicates that both the dip of the magnetic foliation plane and the degree of magnetic anisotropy decreases towards the east. These two parameters thus generally follow the major structural features of the Kiruna region.Two classical rock mechanical parameters, RQD (Rock Quality Designation) and F/m (fractures pr. meter), were used to quantify the amount of discontinuities and fractures in the drill cores. RQD and F/m was subsequently correlated with the AMS data, and a correlation was observed, with the correlation coefficient r varying between 0.6142-0.7557. The correlation was limited to just one of the drillcores however it could be traced across rock type boundaries. The correlation indicates that AMS may be used as an indicator tool of the rock mechanical properties in both crystalline and sedimentary rocks.

  • 333.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kravchenko, S. N.
    National Academy of Sciences of Ukraine.
    Layer, P.
    University of Alaska.
    Rusakov, O. M.
    National Academy of Sciences of Ukraine.
    Glevasskaya, A. M.
    National Academy of Sciences of Ukraine.
    Mikhailova, N. P.
    National Academy of Sciences of Ukraine.
    Bachhtadse, V.
    Ludwig-Maximilians-University.
    Palaeomagnetism and AR-40/AR-39 age determinations of the Ediacaran traps from the southwestern margin of the East European Craton, Ukraine: relevance to the Rodinia break-up2007In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 164, no 5, p. 969-982Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic study and age determinations have been performed on Ediacaran basalts from the northwestern Ukraine. Whole-rock ^sup 40^Ar/^sup 39^Ar age determination revealed plateau ages at 590-560 Ma and 393 Ma, the latter probably reflecting a resetting of the radiometric system. Palaeomagnetic poles have been calculated from five basalt flows, two of which (A poles) are considered reliable with ages that range from 580 to 560 Ma. Tentative poles (B poles), calculated from most probably primary magnetizations, have ages estimated at 580-545 Ma. Secondary magnetizations, possibly of late Ediacaran or Devonian age, have also been isolated (C poles). Based on the new poles, Baltica drifted together with Laurentia from an equatorial position at c. 750 Ma to occupy high southern latitude positions at c. 580 Ma. Baltica during that time period was joined to Laurentia in a similar relative position to that at 750 Ma. The two shields then split up from each other and from c. 550 Ma Baltica drifted at moderately high latitudes and rotated some 180° during the final opening of the Iapetus ocean. This reconstruction suggests that during the Ediacaran glaciation Baltica occupied high-latitude positions, which contradicts the high-obliquity model to explain low-latitude Neoproterozoic glaciations

  • 334.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kravchenko, Svetlana
    Geophysical Institute, Academy of Sciences of Ukraine, Kiev.
    A palaeomagnetic study of Mesoproterozoic basic dykes from the Ukrainian Shield and the amalgamation of the shield with Fennoscandia2005In: "Dyke swarms - time markers of crustal evolution": Fifth International Dyke Conference, Pohtimolampi Wilderness Hotel, Polar Circle, Rovaniemi, Finland, 31 June - 3 August 2005 ; abstracts and programme / [ed] Jouni Vuollo; Satu Mertanen, Espoo: Geological Survey of Finland , 2005, p. 12-Conference paper (Other academic)
    Abstract [en]

    A palaeomagnetic study has been performed on Palaeo-Mesoproterozoic basic intrusions from three crustal blocks of the Ukrainian Shield. At least three different generations of dykes has been identified and positive field tests can be demonstrated for some of them. A sequence of 2.1 to 1.72 Ga apparent polar wander has been defined on basis of the new palaeomagnetic and Ar/Ar data presented here and on basis of old data from anorthosites. The calculated poles are significantly different from poles of similar age from the Fennoscandian Shield. Although the poles are not perfectly coeval the tectonic reconstructions demonstrate that the Ukrainian Shield collided with Fennoscandia at 1.80-1.85 Ga and then rotated some 45° into its present relative position.

  • 335.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kravchenko, Svetlana
    Institute of Geophysics, Acadamy of Science, Kiev.
    Mikhailova, Ninel
    Geophysical Institute, Academy of Sciences of Ukraine, Kiev.
    The consolidation of the East European Craton: a palaeomagnetic analysis of Proterozoic rocks from the Ukrainian and Fennoscandian shields1999In: Vol. 4, no 1, p. 151-Article in journal (Other academic)
  • 336.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Layer, P.
    Geophysical Institute, University of Alaska.
    Ubieta, K.
    Centro de Investigaciones Geoscientificas (CIGEO), the Autonomous University of Nicaragua (UNAN), Managua.
    A palaeomagnetic study and age determinations of Tertiary rocks in Nicaragua, Central America2001In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 147, no 2, p. 294-309Article in journal (Refereed)
    Abstract [en]

    Palaeomagnetic, K-Ar and Ar40/Ar39 measurements have been made to elucidate Nicaragua's plate tectonic history. These show that the Nicaraguan Highland rotated 90° counterclockwise between 30 and 18 Myr ago, but the Pacific Coastal Plain has not rotated.A lack of data has prevented a direct comparison with the tectonic history of adjacent areas, in particular, the Chortis Block, which is the part of the Caribbean Plate that is geologically most closely related to the Nicaraguan Highland. However, our data suggest that the Caribbean Plate in this part of Central America was not consolidated until c. 15 Ma.

  • 337.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Layer, Paul
    Geophysical Institute, University of Alaska Fairbanks.
    Söderlund, Ulf
    Department of Geology, Lund University.
    Cooling history and age of magnetization of a deep intrusion: a new 1.7 Ga key pole and Svecoffennian-post Svecofennian APWP for Baltica2018In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433Article in journal (Refereed)
    Abstract [en]

    A paleomagnetic and chronogical study has been performed on the Turinge gabbro-diabase formation and on a cross cutting basic dyke in central Sweden and on the Joulovaara gabbro intrusion in northern Sweden in the Fennoscandian Shield. U-Pb age of baddeleyite and 40Ar/ 39Ar ages of hornblende and biotite reveal a cooling history of the deep gabbro-diabase intrusion in Turinge. The cooling is suggested to have taken place in two stages, one related to the time of intrusion in temperature down to ca 500 °C with a cooling rate up to 46 - 59°/Ma and another at a lower rate of ca 2.9 °C/Ma, which is suggested to be related with uplift. From this cooling history it can be concluded that the magnetization age of the diabase, ca 1695 – 1700 Ma is close to the crystallization age and the 40Ar/39Ar age of hornblende. Applying a similar cooling history for the other studied deep intrusion, the ca 1800 Ma gabbro of Joulovaara gabbro, it is estimated that the magnetization age of the gabbro should be close to that of the U-Pb age of the formation, although the pole of the Joulovaara gabbro is less reliable.

    The cooling history presented here for the Turinge gabbro-diabase has implications for estimations of magnetization ages also for other deep intrusions.

    The new pole (Plat. = 51.6°, Plon. = 220.2°; A95= 4.8°) of the Turinge gabbro-diabase passes most of the reliability criteria and is considered a new key pole for Fennoscandia.

    The Basic dyke that cuts the Turinge gabbro-diabase was here dated at ca 1200 Ma (whole rock, 40Ar/ 39Ar) and the virtual geomagnetic pole calculated from its primary magnetization falls into the expected trend of APWP for Baltica.

    The new Turinge key pole prolong the time of overlapping poles for Fennoscandia, indicating only small movements of the shield between ca. 1870 to 1700 Ma.

  • 338.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Leino, M.A.H.
    Pesonen, L.J.
    Khramov, A.N.
    Bylund, G.
    Mertanen, S.
    Krasnova, A.F.
    Terho, M.
    Drift history of Fennoscandia2009In: A continent revealed: the European geotraverse, Cambridge: Cambridge University Press, 2009Chapter in book (Other academic)
  • 339.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maokhar, M.O.
    Razi University, Department of Physics, Faculty of Basic Sciences.
    Layer, P.
    University of Alaska, Institute for Geophysics, Fairbanks.
    Donadini, F.
    Scripps Institution of Oceanography, La Jolla, United States of America.
    Uplift deduced from remanent magnetization of a proterozoic basic dyke and the baked country rock in the Hoting area, central Sweden: a palaeomagnetic and Ar-40/Ar-39 study2009In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 179, no 1, p. 59-78Article in journal (Refereed)
    Abstract [en]

    Remanent magnetization in dyke contact zones in the Hoting area of the Fennoscandian Shield in the central part of Sweden has been studied in order to establish the ambient temperature of the host rock and the depth of burial of the present erosion surface at the time of intrusion. A positive baked contact test for two Subjotnian dykes demonstrates the primary nature of the dyke magnetization. From the magnetic properties and the palaeomagnetic data, it can be concluded that the overprinting in the hybrid zone of one of the basic dykes is a partial thermoremanent magnetization. Reliable results were also obtained from a palaeointensity study of samples from the hybrid zone in the baked host rock. The study was performed in the laboratories at Luleå and at Scripps and a mean intensity of the Earth's magnetic field of 5.8 ± 1.9 μT was determined. The maximum temperature due to the dyke intrusion in the hybrid zone has been defined and from that an ambient temperature of 375 °C in the host rock at the time of intrusion has been calculated. This calculated temperature is not contradicted by the 40Ar/39Ar data. A palaeothermal gradient in the crust at ca. 1.6 Ga is calculated at ca. 34 °C km-1 and yields a depth of burial of the present erosion surface at ca. 10.4 km. This implies an uplift rate of 0.65 km (100 Ma)-1. A slow cooling of the gabbroic host rock (ca. 3.5 °C Ma-1) has been calculated from the difference in the U-Pb age of zircon (1.786 ± 0.010 Ga) and the 40Ar/39Ar biotite ages (1.648 ± 0.012 Ga; 1614 ± 0.024 Ga) of this study. This slow cooling resulted in a palaeomagnetic age of ca. 1.7 Ga for the gabbro, which is also the age of the determined palaeointensity. The calculated ca. 1.614 Ga palaeomagnetic pole from the basic dykes fulfils most of the criteria for a reliable pole and may be regarded as a new key-pole for Fennoscandia.

  • 340.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mattsson, Håkan
    Luleå tekniska universitet.
    Post Jotnian basic intrusions in the Fennoscandian Shield, and the break up of baltica from Laurentia: a palaeomagnetic and AMS study2001In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 108, no 3-4, p. 215-236Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic and anisotropy of magnetic susceptibility (AMS) study has been performed on dolerite sills of the Central Scandinavian Dolerite Group (CSDG) in the Fennoscandian Shield. The dolerites occur in four previously known complexes in central Sweden and Finland and from the results of this palaeomagnetic study another complex has been identified in northern Sweden. These complexes cover an area of at least 100 000 km2 and the palaeomagnetic data suggest a small difference in time between the intrusion of the dolerites. The measurements of anisotropy of magnetic susceptibility reveal a magnetic fabric with almost horizontal foliation planes and lineations that indicate fairly uniform ca NW or SE directed magma flows. The dolerites of the CSDG are geochemically rather uniform and have compositions typical of mantle derived melts formed in continental tensional settings. In a palaeomagnetic reconstruction of Baltica versus Laurentia at ca 1.27 Ga the two continents were joined, with NE Greenland attached to NW Baltica. AMS data from a few dolerites and a basalt in NE Greenland indicate magma flow directions that in the tectonic reconstruction are more or less parallel to the flow of the dolerites in Sweden. This may suggest a common magma source located at the reconstructed contact between Baltica and Laurentia. Both the dolerites in Greenland and those in Sweden are of tholeitic composition indicating an intraplate origin, which supports the interpretation of joined continents at that time. The tensional regime, that is reflected by the huge sill complexes, is in our interpretation related to the break up of Baltica from Laurentia at ca 1.27 Ga ago.

  • 341.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mattsson, Håkan J.
    Luleå tekniska universitet.
    A paleomagnetic and AMS study of the Rätan granite of the Transscandinavian Igneous Belt, central Sweden2001In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 123, no 4, p. 205-215Article in journal (Refereed)
    Abstract [en]

    The 1.85-1.67 Ga Transscandinavian Igneous Belt (TIB) forms a major Paleoproterozoic igneous complex in the western part of the Fennoscandian Shield. Different tectonic models propose that the TIB was formed in a tectonic regime governed either by compression or by extension. This paper presents an analysis of anisotropy of magnetic susceptibility (AMS) and paleomagnetic data from the Rätan granite (1.70 Ga), which forms a large pluton in the central part of the TIB. The major aim of the study is to test the existing tectonic models and to define a paleomagnetic pole position for the Rätan granite. Three contrasting magnetic fabric domains are identified. In the eastern and western domains the AMS fabric is characterized by NW-SE to N-S trending subvertical foliation planes and a girdle distribution of the maximum and intermediate anisotropy axes. The central domain is characterized by subhorizontal magnetic foliation planes and lineations that cluster in a NW-SE trending direction. We suggest that the Rätan granite was emplaced in a tectonic regime governed by NW-SE directed extension and that the pluton was fed obliquely with a magma source situated to the present northwest. A positive baked contact test is demonstrated for a basic dyke suggesting that the Rätan granite has not been remagnetized since c. 1.6 Ga. A paleomagnetic formation mean direction is defined for the granite (decl. = 2°, incl. = 59°) that yields a paleopole position of Plat = 67° and Plon = 190°.

  • 342.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mikhailnova, N.P.
    Ukrainian Academy of Sciences.
    Kravchenko, S.
    Ukrainian Academy of Sciences.
    Palaeomagnetism of Proterozoic rocks from the Ukrainian Shield and the consolidation of the East European Craton1998In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 16, no Suppl. 1, p. 103-Article in journal (Other academic)
  • 343.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mikhailova, N. P.
    Geophysical Institute, Academy of Sciences of Ukraine, Kiev.
    Kravchenko, S.
    Geophysical Institute, Academy of Sciences of Ukraine, Kiev.
    Palaeomagnetism of Proterozoic rocks from the Ukrainian shield: new tectonic reconstructions of the Ukrainian and Fennoscandian shields2001In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 339, no 1-2, p. 19-38Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic study has been performed on Palaeo-Mesoproterozoic rocks from three crustal blocks of the Ukrainian Shield, southern Sarmatia. Primary remanent magnetizations have been isolated in 2.0 Ga monzonite, 2.0-1.8 Ga sandstone, 1.77-1.72 Ga anorthosite and from mafic dykes of probably Palaeo-Mesoproterozoic ages. On basis of these results a sequence of 2.0-1.72 Ga apparent polar wander has for the first time been defined for the Ukrainian Shield. Palaeomagnetic and geological data indicate that there has probably not been any large scale tectonic movements within Sarmatia since the Mesoproterozoic. This suggests that tectonic reconstructions for the Ukrainian Shield may also include Sarmatia. The calculated pole positions for the Ukrainian Shield are significantly different from poles of similar age from the Fennoscandian Shield. The tectonic reconstructions demonstrate that the relative position and orientation of the Ukrainian Shield as a part of Sarmatia in the time interval 2.0-1.78 Ga was different from its present position relative to Fennoscandia. One pole from the Ukrainian Shield falls on the ca. 1.6 or 1.3 Ga part of the Fennoscandian APWP. This pole may represent a time when Fennoscandia was already accreted to Ukrainia. Contemporaneous rifting of the two cratons at ca. 1.35 Ga indicates that they were already joined to each other at that time, which means that the final accretion should have taken place sometimes after ca. 1.8 Ga ago.

  • 344.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mikhailova, N. P.
    Institute of Geophysics, Acadamy of Science, Kiev.
    Kravchenko, S. N.
    Geophysical Institute, Academy of Sciences of Ukraine, Kiev.
    Consolidation of the East European craton: a paleomagnetic analysis of proterozoic rocks from the Ukrainian shield and tectonic reconstructions versus fennoscandia1998In: Geophysical Journal, ISSN 0275-9128, Vol. 20, no 4, p. 71-74Article in journal (Refereed)
  • 345.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Moakhar, Mohsen Oveisy
    Luleå University of Technology.
    A palaeomagnetic analysis of rapakivi intrusions and related dykes in the Fennoscandian Shield1999In: Vol. 4, no 1, p. 686-Article in journal (Other academic)
  • 346.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Moakhar, Mohsen Oveisy
    Razi University, Kermanshah.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A palaeomagnetic and geochemical study of basic intrusions in northern Sweden2004In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 126, no 2, p. 243-252Article in journal (Refereed)
    Abstract [en]

    A palaeomagnetic and geochemical study has been performed on basic dykes in northern Sweden. The dykes and a gabbro formation were sampled in 28 sites and characteristic magnetizations could be defined in 23 of them. The dykes form a part of a swarm that trends in NE-SW to E-W. From differences in palaeomagnetic signatures and composition it is concluded that this swarm is composed of two generations of dykes, group A and B, trending in similar directions. The dykes of group A have compositions that are similar to rapakivi related dykes, while those of group B are different from most rapakivi dykes in Fennoscandia. The calculated pole positions may suggest that the group B dykes are older than those of group A and both groups intruded within the time span 1.77 Ga to 1.50 Ga. The trend of the dykes is more or less parallell to a palaeo-compressional stress field that may be expected from the collisional tectonics related to the Gothian orogeny. The intrusion of the rapakivi formations in Fennoscandia has been suggested to be related with the Gothian orogeny and the intrusion of the dykes may thus be guided by the stress field generated by the collisional tectonics.

  • 347.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pesonen, L. J.
    Leino, M. A. H.
    Khramov, A. N.
    Mikhailova, N. P.
    Krasnova, A. F.
    Merlanen, S.
    Bylund, G.
    Terho, M.
    The drift of the Fennoscandian and Ukrainian Shields during the Precambrian: a Palaeomagnetic analysis1993In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 223, no 3-4, p. 177-198Article in journal (Refereed)
    Abstract [en]

    A revised Precambrian (2.85-0.6 Ga) Apparent Polar Wander Path (APWP) for the Fennoscandian Shield, based on a new compilation and analysis of data, is presented. In fitting the APW path to successive Grand Mean Palaeomagnetic poles (GMPs), we applied the spherical spline technique originally developed by Jupp and Kent in 1987. The position and orientation of the Fennoscandian Shield during 2.85-0.6 Ga was determined from the GMPs. Major palaeoclimatological findings are used to constrain the palaeomagnetic interpretation of palaeolatitudes. The general drift of Fennoscandia, from relatively high latitudes in the late Archaean-Early Proterozoic to nearly equatorial latitudes in the Middle Proterozoic, correlates with palaeoclimatological indications that a period of cold climate was followed by one of warm climate during this time interval. From the continuous APWP the APW velocities and latitudinal drift velocities of the shield were calculated. An accumulated APW curve was also calculated. The palaeomagnetic data are irregularly distributed and some periods are rather poorly represented. This means that the calculated velocities can sometimes be artifacts of sampling. Late Archaean and Early Proterozoic (2.85-1.90 Ga) data are too sparse to make these calculations meaningful and velocity calculations are therefore restricted to data of 1.90 Ga and younger ages. The accumulated APW curve shows a number of linear segments with varying slopes, indicating sudden changes in drift rate. During the Middle Proterozoic (1.90-1.35 Ga) there was a period when the rate of APW was constant and low and that of latitudinal drift also was low. This pattern changed at ca. 1.35 Ga, and the following Middle-Late Proterozoic period can be described by rapid APW and strongly fluctuating drift velocities. Jotnian rifting and the intrusion of numerous dyke swarms (at ca. 1.25 Ga) correlate with this shift in rate. These changes are attributed to changes in plate configuration. A new database for the Ukrainian Shield is also presented, and GMPs in the 2.32-1.20 Ga range are defined. The database is still inadequate and the comparison of the Ukrainian and Fennoscandian drift histories is therefore tentative. Similarities in position, latitudinal drift and rotation during the Early-Middle Proterozoic are, nevertheless, evident. A close relationship between the shields in this period is consistent with the low APW rate of Fennoscandia, indicating that Fennoscandia may have been part of a larger continent, including the Ukraine, at that time. At ca. 1.2 Ga, the latitudinal position of Ukraine differed significantly from that of Fennoscandia, suggesting that the large shield split up between ca. 1.35 and 1.2 Ga. This would explain the change in APW rate at 1.35 Ga. The subsequent increase in rate was due to a reduction in the size of the shield. The discrepancy in palaeopositions of Fennoscandia and Ukraine at 1.2 Ga led Mikhailova and Kravchenko to suggest a late Precambrian time (1.07-0.57 Ga) for the accreation of Fennoscandia to the East European Platform (EEP). This may be correct as the rate of APW for Fennoscandia decreased in the late Precambrian, reflecting such a consolidation.

  • 348.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pesonen, Lauri
    Division of Atmospheric Sciences and Geophysics, Department of Physics, University of Helsinki.
    Recent developments in paleomagnetism and geomagnetism2009In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 90, no 51, p. 502-Article in journal (Other academic)
  • 349.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pesonen, L.J.
    Bylund, G.
    The continental drift of the Fennoscandian Shield during the Precambrian: a palaeomagnetic analysis1993In: Vol. 5, no Suppl. 1, p. 1-2Article in journal (Other academic)
  • 350.
    Elming, Sten-åke
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pesonen, L.J.
    Mertanen, S.
    DÁgrella-Filho, M.
    Continental assemblies during the proterozoic and tectonic relations between Fennoscandia and Amazonia: a palaeomagnetic reconstruction2001In: Workshop on Geology of the SW Amazonian Craton: State-of- the-art. Abstracts, Instituto de Geociências-USP , 2001, p. 150-Conference paper (Other academic)
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