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  • 1.
    Beranek, Luke
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pease, Victoria
    Hadlari, Thomas
    Dewing, Keith
    Silurian flysch successions of Ellesmere Island, Arctic Canada, and their significance to northern Caledonian palaeogeography and tectonics2015In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 172, no 2, p. 201-212Article in journal (Refereed)
    Abstract [en]

    Detrital zircon provenance studies of Silurian flysch units that underlie the Hazen and Clements Markham fold belts of Ellesmere Island, Arctic Canada, were conducted to evaluate models for northern Caledonian palaeogeography and tectonics. Llandovery flysch was deposited along an active plate margin and yields detrital zircons that require northern derivation from the adjacent Pearya terrane. If Pearya originated near Svalbard and NE Greenland, it was transported by strike-slip faults to Ellesmere Island by the Early Silurian. Wenlock to Ludlow turbidites yield Palaeozoic-Archaean detrital zircons with dominant age-groupings c. 650, 970, 1150, 1450 and 1650 Ma. These turbidite systems did not fill a flexural foreland basin in front of the East Greenland Caledonides, but rather an east-west-trending trough that was probably related to sinistral strike-slip faulting along the northern Laurentian margin. The data support provenance connections with the Svalbard Caledonides, especially Baltican-affinity rocks of SW Spitsbergen that were proximal to NE Greenland during the Baltica-Laurentia collision. Pridoli flysch has sources that include Pearya, the East Greenland Caledonides and the Canadian Shield. Devonian-Carboniferous molasse in Arctic Canada has analogous detrital zircon signatures, which implies recycling of Silurian flysch during mid-Palaeozoic (Ellesmerian) collisional tectonism or that some collisional blocks were of similar Baltican-Laurentian crustal affinities.

  • 2.
    Pease, V.
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Scott, R.
    Crustal affinities in the Arctic Uralides, northern Russia: Significance of detrital zircon ages from Neoproterozoic and early Paleozoic sediments in Novaya Zemlya and Taimyr2009In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 166, p. 1-11Article in journal (Refereed)
  • 3.
    Pease, Victoria L.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kuzmichev, Alexander B.
    Danukalova, Maria K.
    The New Siberian Islands and evidence for the continuation of the Uralides, Arctic Russia2015In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 172, p. 1-4Article in journal (Refereed)
    Abstract [en]

    U–Pb detrital zircon results from New Siberian Islands sandstones illuminate the long-lived controversy regarding the continuation of the Uralian orogen into the Arctic region. A dominant age peak of c. 285 Ma from Permian sandstone requires proximal derivation from Taimyr’s Carboniferous–Permian granites, thought to reflect syn- to post-tectonic Uralian magmatism. The provenance of Devonian sandstone has Baltica affinities. The data record a dramatic change in provenance between Devonian and Permian time, from Baltica to a mixed Baltica + Uralian source. Our results confirm that the Uralian foreland basin extended from Taimyr to the New Siberian Islands.

  • 4.
    Pettersson, Carl Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Tebenkov, A.
    Larionov, A.
    Andresen, A.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Timing of migmatization and granite genesis of the Northwestern Terrane, Svalbard2009In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 166, p. 147-158Article in journal (Refereed)
    Abstract [en]

    U–Pb ion microprobe investigations of zircons from gneisses, granites and migmatites of the pre-Devonian Smerenburgfjorden and Richarddalen Complexes constrain the tectonic evolution and origin of Svalbard's Northwestern Terrane. Field relationships combined with U–Pb age data indicate that a late Meso- to Neoproterozoic metapelitic protolith was intruded by Tonian (c. 960 Ma) granitoids and suggest that the entire Northwestern Terrane is underlain by early Neoproterozoic granitoids intruding older metasediments. Both rock types were later involved in Caledonian deformation, with subsequent migmatization and granite genesis at c. 435–420 Ma. Ages of inherited zircons in granites and migmatites reflect anatexis of this late Meso- to Neoproterozoic protolith, with zircon xenocrysts ranging in age from c. 1030 to 1820 Ma. Pronounced lithological, geochronological and tectonothermal similarities to NE Svalbard (Nordaustlandet) and the Krummedal supracrustal sequence of East Greenland suggest a strong correlation between Svalbard and East Greenland prior to Caledonian orogenesis.

  • 5.
    Pitcairn, Iain K.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skelton, Alasdair D. L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arghe, Fredrik
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boyce, Adrian
    Structurally focused fluid flow during orogenesis: the Islay Anticline, SW Highlands, Scotland2010In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, no 4, p. 659-674Article in journal (Refereed)
    Abstract [en]

    Displacement of isotopic compositions at boundary layers across strata of contrasting composition is commonly used to investigate hydrothermal fluid flow during orogeny. This study investigates whether hydrothermal fluid flow was focused along the Islay Anticline, Islay, SW Highlands of Scotland, as shown in the axial zone of the neighbouring Ardrishaig Anticline. Four localities from the limb to the axial plane of the Islay Anticline were investigated for isotopic homogenization of metacarbonate units to silicate values. At Mull of Oa on the limb of the anticline, metacarbonate samples show limited isotopic resetting and the fluid flux is estimated to be <1 m(3) m(-2). Within the axial zone of the Islay Anticline, metacarbonate units from Port a' Chotain and Bagh an Da Dhoruis show complete isotopic homogenization to silicate values indicating higher fluid fluxes. Fluid flow was enhanced along localized parasitic folds such as at Port an t-Sruthain, where metacarbonates have been isotopically reset, and there are abundant quartz-carbonate veins that precipitated during D-1-D-2 deformation. Metamorphic fluid flow was higher in the axial zone of the Islay Anticline and in localized antiformal structures. Fluid fluxes are estimated to be considerably lower than at the neighbouring Ardrishaig Anticline.

  • 6.
    Ring, Uwe
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hampton, Sam
    Faulting in Banks Peninsula: tectonic setting and structural controls for late Miocene intraplate volcanism, New Zealand2012In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 169, no 6, p. 773-785Article in journal (Refereed)
    Abstract [en]

    An analysis of faulting in the late Miocene volcanic rocks of Banks Peninsula, South Island, New Zealand, shows that the formation of the volcanic edifice was largely controlled by NE-SW-striking dextral-oblique strike-slip faults. The data show a variable component of west-east-or NW-SE-oriented shortening and north-south or NE-SW extension. Synvolcanic faults reactivated Cretaceous normal faults and are interpreted to have formed a local pull-apart basin that controlled volcanism. Further east, the geometry of Akaroa Harbour is controlled by a north-south-striking oblique reverse fault. Limited fault-slip data collected from sub-recent loess deposits are not significantly different from the data collected in the volcanic rocks and appear to show that the kinematic field did not change significantly over the last c. 10 Ma. The overall kinematic field causing the recent series of earthquakes in the greater Christchurch region is also not fundamentally different from the one that controlled the eruption of the volcanic rocks. We conclude that the inherited Cretaceous faults controlled the development of the late Miocene volcanism on Banks Peninsula and largely provided a major anisotropy along which the recent faults ruptured.

  • 7.
    Skelton, Alasdair
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arghe, Fredrik
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pitcairn, Iain
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Regional mapping of pre-metamorphic spilitization and associated chemical mobility in greenschist-facies metabasalts of the SW Scottish Highlands2010In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, no 5, p. 1049-1061Article in journal (Refereed)
    Abstract [en]

    Both spilitic and non-spilitic metabasaltic sills are hosted by greenschist-facies metasediments in the SW Scottish Highlands. Spilitization is mainly characterized by enrichment in Na2O, elevated modal plagioclase and epidote segregations. Mapping of the spatial distribution of spilitic metabasalts reveals an ancient sub-sea-floor fluid cell centred on the extrusive Tayvallich Volcanics. Fluid circulation was most extensive at shallow levels where most sills were spilitized. We attribute this to pervasive flow of saline fluid, which was thermally driven by the cooling suite of lava flows and sills. Spilitization below this lithostratigraphic depth was restricted to only a few sills. Their spilitization is largely unrelated to specific properties of these sills (e. g. width, chemistry or host lithology). We conclude that fluid channelling was an intrinsic property of sub-sea-floor fluid flow either at deeper levels or earlier during fluid circulation. By profiling of the size distributions of relic phenocrysts in a partly spilitized sill, we conclude that spilitization proceeds with the symmetric propagation of a spilitization front from the sill margins towards the sill interior. Based on chemical profiling across the margin of an epidote segregation, we conclude that spilitization is associated with chemical transport on scales ranging from 0.1 to 10 m.

  • 8. Toro, J.
    et al.
    Miller, E. L.
    Prokopiev, A. V.
    Zhang, Xiaojing
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Veselovskiy, R.
    Mesozoic orogens of the Arctic from Novaya Zemlya to Alaska2016In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 173, no 6, p. 989-1006Article in journal (Refereed)
    Abstract [en]

    Mesozoic orogenic belts fringe the Alaska and eastern Russia portion of the Arctic Basin. From west to east, these include the fold belts of Novaya Zemlya, Taimyr Peninsula, northern Verkhoyansk-Kolyma, Chukotka and the Brooks Range, as well as their continuations onto the continental shelves. The Taimyr and Novaya Zemlya structures were traditionally interpreted as the continuation of the late Palaeozoic Uralian orogenic belt. This is probably correct for Taimyr, but not for Novaya Zemlya, where shortening post-dates Uralian deformation. The Mesozoic tectonic evolution of the Verkhoyansk-Kolyma, Chukotka and Brooks Range orogens relates to the accretion of numerous continental and arc terranes to the Siberian and North American margins starting in the Late Jurassic and driven by palaeo-Pacific dynamics. This history is complicated by the opening of the Amerasia Basin of the Arctic, which displaced the Arctic Alaska-Chukotka microplate from a position adjacent to Arctic Canada towards the palaeo-Pacific. Although the Chukotka fold belt and the Brooks Range both formed along the southern edge of Arctic Alaska-Chukotka, most shortening took place prior to Amerasia Basin opening. The remoteness of this region and the complexity of its geology has left numerous questions regarding its tectonic evolution unresolved, providing rich avenues for future research.

  • 9. Virtasalo, Joonas J.
    et al.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Papunenen, Heikki
    Kotilainen, Aarno T.
    Whitehouse, Martin J.
    Pyritic and baritic burrows and microbial filaments in postglacial lacustrine clays in the northern Baltic Sea2010In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, no 6, p. 1185-1198Article in journal (Refereed)
    Abstract [en]

    Holocene postglacial lacustrine clays in the northern Baltic Sea were studied for ichnofossils,petrography, and microscale elemental and 34S/32S composition to understand the impact of benthos-producedorganic matrices on the early diagenesis of sediments. X-radiographs of these clays display intense burrowmottling with discrete Palaeophycus, ‘Mycellia’ and rare Arenicolites. Small burrow-like and irregularlyshaped concretions were separated from these clays. The burrow-like concretions are composed of framboidalpyrite and poorly crystalline FeS2 cement. They formed within worm-produced burrows by the decompositionof mucous coatings on the burrow walls by sulphate reduction. 34SCDT composition of the framboidsindicates saline inflows from the North Sea as the sulphate source. The irregular concretions are microcrystallinepyritic masses that formed in pore spaces with less reactive organic compounds. Their 34SCDT valuesreflect precipitation from the ambient porewater sulphate by sulphate reduction. The burrow-like and irregularconcretions are microcrystalline barite in the lower parts of the clays. ‘Mycellia’ are mineral-replacedfilaments produced by large sulphur-oxidizing bacteria or mycelial fungi. They concentrate in monosulphidebands in the lower substrate levels, but are associated with organic patches upward. This study demonstratesthat substantial amounts of pyrite formed within organic matrices close to the sediment–water interface. Thisdiffers from previous studies that proposed a deeper-burial origin and allochthonous sulphur source.

  • 10.
    Yeshanew, Fitsum Girum
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Pease, Victoria
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Abdelsalam, Mohamed G.
    Whitehouse, Martin J.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Zircon U-Pb ages, delta O-18 and whole-rock Nd isotopic compositions of the Dire Dawa Precambrian basement, eastern Ethiopia: implications for the assembly of Gondwana2017In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 174, no 1, p. 142-156Article in journal (Refereed)
    Abstract [en]

    New high spatial resolution secondary ion mass spectrometry (SIMS) zircon dating from the Dire Dawa Precambrian basement yields crystallization ages at c. 790 Ma and 600 - 560 Ma. Two of the youngest samples are pervasively deformed, indicating that orogenesis continued until c. 560 Ma. SIMS delta O-18(zrn) shows bimodality, with the oldest sample (c. 790 Ma) and inherited zircons of that age in the younger samples having values of 7.8 - 9.6%, whereas the Ediacaran samples have delta O-18(zrn) values of 4.9 - 7.2%. These delta O-18(zrn) ratios are higher than mantle values and indicate a supracrustal input to the source of the Dire Dawa granitoids. All samples have unradiogenic epsilon(Nd)(t) values of -10.3 to -5.8 and Nd model ages of 1.72-1.42 Ga. These attributes suggest that the Dire Dawa granitoids were mostly derived from reworking of long-lived crustal sources. The occurrence of c. 580 - 550 Ma orogenesis in both the Dire Dawa basement and the juvenile Western Ethiopian Shield and the confinement of c. 630 Ma metamorphism to only the latter indicate that these two lithospheric blocks of contrasting isotopic compositions amalgamated at c. 580 - 550 Ma. This suggests that the Mozambique Ocean, which separated these two lithospheric blocks, was completely consumed during the late Ediacaran to early Cambrian.

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