Viser treff 196-215 av 711

    • Evolution of metal-bearing fluids at the Nussir and Ulveryggen sediment-hosted Cu deposits, Repparfjord Tectonic Window, northern Norway 

      Mun, Yulia; Strmic Palinkas, Sabina; Kullerud, Kåre; Nilsen, Kjell S.; Neufeld, Kai; Bekker, Andrey (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-13)
      The Palaeoproterozoic greenstone belts of Fennoscandia are metamorphosed and deformed volcanic and sedimentary rocks that formed in basins with a high base-metal ore potential. One of these, the Repparfjord Tectonic Window (RTW), is exposed in the Caledonides of northern Norway and contains several sediment-hosted Cu deposits including Nussir and Ulveryggen. The RTW is composed of mafic metavolcanic ...
    • Evolution of ore-forming fluids in a post-collisional porphyry Cu-Au system: A case study from the Bučim deposit, Republic of North Macedonia 

      Strmic Palinkas, Sabina; Perkovic, Ivor; Čobić, Andrea; Jurkovic, Iva; Tasev, Goran; Serafimovski, Todor; Spangenberg, Jorge E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-27)
      The Bučim porphyry Cu-Au deposit is situated in the westernmost part of the Serbo-Macedonian Massif, Republic of North Macedonia. The deposit is hosted by Precambrian gneisses with tectonically imbedded rare lenses of Palaeozoic amphibolites. The mineralization is spatially associated with intrusions of andesitic to trachyandesitic magmatic bodies. The geochemical signature of the intrusions and ...
    • Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics 

      Orvik, Alf Andre; Slagstad, Trond; Sørensen, Bjørn Eske; Millar, Ian; Hansen, Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-05)
      The Karasjok–Central Lapland Greenstone Belt is one of the largest Palaeoproterozoic greenstone belts in the Fennoscandian Shield and includes multiple (ultra)mafic intrusions, some with notable ore reserves, formed during three episodes at 2.44, 2.22 and 2.05 Ga. This study presents new mineralogical, geochronological and isotopic data for the Gállojávri ultramafic intrusion, in the Karasjok ...
    • Evolution of ultrapotassic volcanism on the Kaapvaal craton: deepening the orangeite versus lamproite debate 

      Tappe, Sebastian; Shaikh, Azhar M.; Wilson, Allan H.; Stracke, Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-02)
      Orangeites are a significant source of diamonds, yet ambiguity surrounds their status among groups of mantle-derived potassic rocks. This study reports mineralogical and geochemical data for a c. 140 Ma orangeite dyke swarm that intersects the Bushveld Complex on the Kaapvaal craton in South Africa. The dykes comprise distinctive petrographic varieties that are linked principally by olivine ...
    • Exceptions to bed-controlled ice sheet flow and retreat from glaciated continental margins worldwide 

      Greenwood, Sarah L.; Simkins, Lauren M; Winsborrow, Monica; Bjarnadóttir, Lilja Rún (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-13)
      Projections of ice sheet behavior hinge on how ice flow velocity evolves and the extent to which marine-based grounding lines are stable. Ice flow and grounding line retreat are variably governed by the coupling between the ice and underlying terrain. We ask to what degree catchment-scale bed characteristics determine ice flow and retreat, drawing on paleo-ice sheet landform imprints from 99 sites ...
    • Excess water storage induced by viscous strain localization during high-pressure shear experiment 

      Précigout, Jacques; Stünitz, Holger; Villeneuve, Johan (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-05)
      Strain localization in viscously deformed rocks commonly results in fine-grained shear zones where massive fluid circulation is regularly observed. Recently attributed to strain-induced pumping, this phenomenon may have major implications for the distribution of ores deposits and rock rheology. However, although grain size reduction and/or creep cavitation have been proposed as important processes, ...
    • Exhumation of the High‐Pressure Tsäkkok Lens, Swedish Caledonides: Insights From the Structural and White Mica 40Ar/39Ar Geochronological Record 

      Barnes, C.J.; Jeanneret, P.; Kullerud, Kåre; Majka, J.; Schneider, D.A.; Bukala, M.; Klonowska, I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)
      Integrated structural, geochemical, and geochronological investigations were conducted on metasedimentary rocks in the eclogite-bearing Tsäkkok Lens of the Seve Nappe Complex (Scandinavian Caledonides) to resolve its exhumation history. Three deformation events are defined. D1 is likely related to the prograde to peak-metamorphic stages, represented by a locally preserved S1. D2 resulted in vertical ...
    • Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature 

      Fukuda, Junichi; Raimbourg, Hugues; Shimizu, Ichiko; Neufeld, Kai; Stünitz, Holger (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)
      Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 ∘C. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of <i>d<sup>n</sup>−d<sup>n</sup><sub>0</sub>=k</i><sub>0</sub><i>f<sup>r</sup><su ...
    • Experimental investigation of the brittle-viscous transition in mafic rocks – Interplay between fracturing, reaction, and viscous deformation 

      Marti, Sina; Stunitz, Holger; Heilbronner, Renée; Drury, Martyn; Plümper, Oliver; Drury, Martyn (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-03)
      Rock deformation experiments are performed on fault gouge fabricated from ‘Maryland Diabase’ rock powder to investigate the transition from dominant brittle to dominant viscous behaviour. At the imposed strain rates of γ = 3 • 10⁻⁵ − 3 • 10⁻⁶ s-1 the transition is observed in the temperature range of (600 °C < T < 800 °C) at confining pressures of (0.5 GPa ≤ Pc ≤ 1.5 GPa). The transition thereby ...
    • Exploring late Pleistocene bioturbation on Yermak Plateau to assess sea-ice conditions and primary productivity through the Ethological Ichno Quotient 

      Singh, Akanksha; O’Regan, Matt; Coxall, Helen K.; Forwick, Matthias; Löwemark, Ludvig (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-13)
      Central Arctic, interglacial intervals have traditionally been associated with diverse and intense bioturbation, and abundant foraminifera, interpreted as indicating relatively low sea-ice concentrations and productive surface waters, while glacial intervals, typically barren, support the inverse. In this respect, the Yermak Plateau is anomalous. Biomarker studies suggest that glacial intervals were ...
    • Exploring the teaching environment in a higher education geoscience programme 

      Malm, Rie Hjørnegaard; Martens, Iver (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-19)
      This paper explores the teaching environment among the teaching staff in thegeoscience programme at UiT The Arctic University of Norway. The findings in this paper are based on a large baseline study conducted in 2018. This paper operationalises the teaching culture by analysing the teachers’ ideas, collaborations, and attitudes towards teaching. In-depth interviews ...
    • Extensive release of methane from Arctic seabed west of Svalbard during summer 2014 does not influence the atmosphere 

      Myhre, Cathrine Lund; Ferré, Benedicte; Platt, Stephen Matthew; Silyakova, Anna; Hermansen, Ove; Allen, Grant; Pisso, Ignacio; Schmidbauer, Josef Norbert; Stohl, Andreas; Pitt, Joseph R.; Jansson, Pær; Greinert, Jens; Percival, Carl; Fjæraa, Ann Mari; O'Shea, Sebastian J.; Gallagher, Martin; Le Breton, Michael; Bower, Keith N.; Bauguitte, Stéphane Jean-Bernard; Dalsøren, Stig Bjørløw; Vadakkepuliyambatta, Sunil; Fisher, Rebecca E.; Nisbet, Euan G.; Lowry, David; Myhre, Gunnar; Pyle, John Adrian; Cain, Michelle; Mienert, Jurgen (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-07)
      We find that summer methane (CH4) release from seabed sediments west of Svalbard substantially increases CH4 concentrations in the ocean but has limited influence on the atmospheric CH4 levels. Our conclusion stems from complementary measurements at the seafloor, in the ocean, and in the atmosphere from land-based, ship and aircraft platforms during a summer campaign in 2014. We detected high ...
    • Extraordinary runoff from the Greenland ice sheet in 2012 amplified by hypsometry and depleted firn retention 

      Mikkelsen, A.B.; Hubbard, Alun Lloyd; MacFerrin, Mike; Box, Jason Eric; Doyle, Sam H.; Fitzpatrick, Andrew; Hasholt, Bent; Bailey, Hannah L.; Lindbäck, Katrin; Pettersson, Rickard (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-30)
      It has been argued that the infiltration and retention of meltwater within firn across the percolation zone of the Greenland ice sheet has the potential to buffer up to  ∼  3.6 mm of global sea-level rise (Harper et al., 2012). Despite evidence confirming active refreezing processes above the equilibrium line, their impact on runoff and proglacial discharge has yet to be assessed. Here, we compare ...
    • The extreme yet transient nature of glacial erosion 

      Patton, Henry; Hubbard, Alun; Heyman, J.; Alexandropoulou, Nikolitsa; Lasabuda, Amando P. E.; Stroeven, A.P.; Hall, A.M.; Winsborrow, Monica; Sugden, David E.; Kleman, J.; Andreassen, Karin Marie (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-30)
      Ice can sculpt extraordinary landscapes, yet the efficacy of, and controls governing, glacial erosion on geological timescales remain poorly understood and contended, particularly across Polar continental shields. Here, we assimilate geophysical data with modelling of the Eurasian Ice Sheet — the third largest Quaternary ice mass that spanned 49°N to 82°N — to decipher its erosional footprint during ...
    • Factors controlling the net ecosystem production of cryoconite on Western Himalayan glaciers 

      Shamurailatpam, Monica S.; Telling, Jon; Wadham, Jemma Louise; Ramanathan, A. L.; Yates, Christopher A.; Raju, N. Janardhana (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-07)
      In situ experiments were conducted to determine the net ecosystem production (NEP) in cryoconite holes from the surface of two glaciers (Patsio glacier and Chhota Shigri glacier) in the Western Himalaya during the melt season from August to September 2019. The study aimed to gain an insight into the factors controlling microbial activity on glacier surfaces in this region. A wide range of parameters, ...
    • Fast and slow components of interstadial warming in the North Atlantic during the last glacial 

      Margari, Vasiliki; Skinner, Luke C.; Menviel, Laurie; Capron, Emilie; Rhodes, Rachael H; Mleneck-Vautravers, Maryline J.; Ezat, Mohamed; Martrat, Belen; Grimalt, Joan O.; Hodell, David A; Tzedakis, Polychronis (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)
      The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short ...
    • The fate of plastic in the ocean environment – a minireview 

      Wayman, Chloe; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-14)
      The presence of plastics in the marine environment poses a threat to ocean life and has received much scientific and public attention in recent years. Plastics were introduced to the market in the 1950s and since then, global production figures and ocean plastic littering have increased exponentially. Of the 359 million tonnes (Mt) produced in 2018, an estimated 14.5 Mt has entered the ocean. In ...
    • Fault-controlled asymmetric landscapes and low-relief surfaces on Vestvågøya, Lofoten, North Norway: inherited Mesozoic rift-margin structures? 

      Bergh, Steffen G; Liland, Kristian; Corner, Geoffrey D.; Henningsen, Tormod; Lundekvam, Petter (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-20)
      The Lofoten Ridge is an integral basement horst of the hyperextended continental rift-margin off northern Norway. It is a key area for studying onshore–offshore rift-related faults, and for evaluating tectonic control on landscape development along the North Atlantic margin. This paper combines onshore geomorphological relief/aspect data and fault/fracture analysis with offshore bathymetric and ...
    • Fault-controlled fluid circulation and diagenesis along basin-bounding fault systems in rifts - Insights from the East Greenland rift system 

      Salomon, Eric; Rotevatn, Atle; Kristensen, Thomas Berg; Grundvåg, Sten-Andreas; Henstra, Gijs Allard; Meckler, Anna Nele; Albert, Richard; Gerdes, Axel (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-05)
      In marine rift basins, deep-water clastics (>200 m) in the hanging wall of rift- or basin-bounding fault systems are commonly juxtaposed against crystalline “basement” rocks in the footwall. A distinct feature of such fault systems is therefore the juxtaposition of relatively highly permeable, unconsolidated sediments against relatively low-permeable basement rocks. Due to limited surface exposure ...
    • Feasibility of using the P-Cable high-resolution 3D seismic system in detecting and monitoring CO2 leakage 

      Waage, Malin; Singhroha, Sunny; Bünz, Stefan; Planke, Sverre; Waghorn, Kate Alyse; Bellwald, Benjamin (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-23)
      The P-Cable technology is an acquisition principle for high-resolution and ultra-high-resolution 3D seismic data. Many 3D seismic datasets have been acquired over the last decade, but the application in time-lapse studies for monitoring of CO2 storage is a new and intriguing topic. High-resolution 3D (HR3D) seismic has the potential to detect and monitor CO2 leakage at carbon capture and storage ...