| 1. |
- Carter, Isabel S. M., et al.
(författare)
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Cambrian ages for metavolcanic rocks in the Lower Köli Nappes, Swedish Caledonides: implications for the status of the Virisen arc terrane
- 2023
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 180:6
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Tidskriftsartikel (refereegranskat)abstract
- The Köli Nappe Complex (KNC) of the Scandinavian Caledonide orogen originated as oceanic terranes within the Iapetus Ocean. These terranes have characteristics of magmatic arcs and associated forearc or back-arc basins and underwent several periods of rifting and magmatism prior to their accretion to the Baltican margin. We present new U–Pb zircon ages from the Lower Köli Ankarede Volcanite Formation in Västerbotten, Sweden. U–Pb ages of magmatic zircon grains from metamorphosed dacitic to andesitic rocks show ages of 512 ± 3.5, 497 ± 2, 491 ± 1 and 488 ± 4 Ma. The three younger ages fit with previous ages for Lower Köli volcanic rocks, but the 512 Ma age is older than any previous age for this unit. These dates constrain the age of magmatism in an ensimatic arc system within Iapetus. We compare this evolution with published information from the other Köli nappes. Magmatic ages within the KNC overlap with ages for an early episode of ultrahigh-pressure (UHP) metamorphism within the underlying Seve Nappe Complex (SNC), supporting the hypothesis that attributes UHP metamorphism within the SNC to subduction beneath the island arc now preserved within the Lower Köli Nappes.
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| 2. |
- Faehnrich, Karol, et al.
(författare)
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Geochronological constraints on Caledonian strike-slip displacement in Svalbard, with implications for the evolution of the Arctic
- 2020
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 32:4, s. 290-299
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Tidskriftsartikel (refereegranskat)abstract
- The timing of Svalbard's assembly in relation to the mid-Paleozoic Caledonian collision between Baltica and Laurentia remains contentious. The Svalbard archipelago consists of three basement provinces bounded by N-S-trending strike-slip faults whose displacement histories are poorly understood. Here, we report microstructural and mineral chemistry data integrated with Ar-40/Ar-39 muscovite geochronology from the sinistral Vimsodden-Kosibapasset Shear Zone (VKSZ, southwest Svalbard) and explore its relationship to adjacent structures and regional deformation within the circum-Arctic. Our results indicate that strike-slip displacement along the VKSZ occurred in late Silurian-Early Devonian and was contemporaneous with the beginning of the main phase of continental collision in Greenland and Scandinavia and the onset of syn-orogenic sedimentation in Silurian-Devonian fault-controlled basins in northern Svalbard. These new-age constraints highlight possible links between escape tectonics in the Caledonian orogen and mid-Paleozoic terrane transfer across the northern margin of Laurentia.
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| 3. |
- Wala, Virginia T., et al.
(författare)
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Neoproterozoic stratigraphy of the Southwestern Basement Province, Svalbard (Norway) : Constraints on the Proterozoic-Paleozoic evolution of the North Atlantic-Arctic Caledonides
- 2021
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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 358
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic archipelago of Svalbard, Norway, plays an important role in tectonic reconstructions of the Cambrian-Devonian Caledonian orogen in the North Atlantic and circum-Arctic regions. To elucidate the Proterozoic geological history of the Southwestern Basement Province of Svalbard and place its origin and displacement history in the context of regional tectono-stratigraphic events, we present new geological mapping, stratigraphic assignments, carbonate carbon (delta C-13(carb)) and strontium (Sr-87/Sr-86) isotope chemostratigraphy, and detrital/igneous zircon U-Pb geochronology coupled with Hf isotope geochemistry from Neoproterozoic rocks exposed in southwestern Spitsbergen. The examined metasedimentary successions include a Tonian mixed carbonate-siliciclastic succession (the Nordbukta/Deilegga groups) that is regionally truncated by a Cryogenian (<650 Ma) angular unconformity (the Torellian unconformity), the age of which is confirmed herein by field relationships and re-analysis of previously reported detrital monazite data. New detrital zircon U-Pb data from the Nordbukta Group yield ca. 1030-1170, 1280-1400, 1430-1510, and 1580-1680 Ma age populations that are typical of North Atlantic (e.g., North and East Greenland, Scotland, and the Scandinavian Caledonides) Mesoproterozoic-Neoproterozoic sedimentary successions. Overlying Cryogenian-Ediacaran strata of the Sofiebogen, Dunderbukta, and Kapp Lyell (Bellsund) groups record rift-related sedimentation and host chemostratigraphic data that provide ties to the ca. 640(?)-635 Ma Marinoan snowball Earth glaciation. Detrital zircon U-Pb data from the Cryogenian Slyngfjellet, Jens Erikfjellet, and Konglomeratfjellet formations yield similar age spectra to the underlying Nordbukta and Deilegga groups, while younger Ediacaran strata of the Hoferpynten and Gashamna formations record a prominent shift to bimodal ca. 1850 and 2850 Ma U-Pb age populations. Integrating these data with previously published geochemical and geochronological datasets from Svalbard and other circum-Arctic Mesoproterozoic-Neoproterozoic successions, we propose that the Southwestern Basement Province represents a composite terrane composed of multiple peri-Baltican (Wedel Jarlsberg-Oscar II, Berzeliuseggene-Eimfjellet, and Prins Karls Forland terranes) and peri-Laurentian (Hornsund terrane) crustal fragments that were likely initially juxtaposed and/or amalgamated during the Caledonian orogeny. These terranes were subsequently complexly deformed and modified during the younger Devonian-Carboniferous Ellesmerian and Paleogene-Eocene Eurekan orogenic events that affected western Svalbard.
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| 4. |
- Walczak, Katarzyna, et al.
(författare)
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Late Neoproterozoic extended continental margin development recorded by the Seve Nappe Complex of the northern Scandinavian Caledonides
- 2022
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Ingår i: Lithos. - : Elsevier. - 0024-4937 .- 1872-6143. ; 416
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Tidskriftsartikel (refereegranskat)abstract
- The Scandinavian Caledonides comprise nappe stacks of far-travelled allochthons that record the opening and closure of the Iapetus Ocean, culminating with the collision of Baltica and Laurentia. The Seve Nappe Complex (SNC) of the Scandinavian Caledonides comprises relics of the outermost Baltoscandian passive margin that were subducted to mantle depths during ocean closure. Subduction of these rocks overprinted much of the Neoproterozoic record for Iapetus Ocean formation, and as a result, much of the work conducted in the SNC has focused solely on the Caledonian orogenic history.& nbsp;In this study, we combined petrological and geochronological work to expand the knowledge about the Neoproterozoic metamorphic history of the Baltoscandian margin in the understudied Vaivancohkka-Salmmecohkat region of the northern Scandinavian Caledonides. The work focused on rocks that belong to the upper gneiss unit, which constitutes part of SNC in the region. The unit comprises migmatitic paragneisses and garnet-mica schist containing metamafic bodies. U-Pb zircon and Th-U-total Pb monazite dating of the migmatitic paragneiss yielded consistent age of metamorphism in 602 +/- 5 Ma and 599 +/- 3 Ma, respectively. A similar U-Pb age of 604 +/- 8 Ma was obtained for the zircon from the leucocratic vein transecting the amphibolite within the studied gneiss. Interestingly, no Caledonian ages were identified. Likewise, no evidence for high or ultra-high pressure conditions was found, neither in the gneisses/schists nor in the metamafic rocks. Petrographic observations and calculated metamorphic P-T conditions indicate that rocks belonging to upper gneiss unit underwent upper-amphibolite facies metamorphism in a melt stability field; 8.0-10.5 kbar at 750-790 degrees C.& nbsp;Since the studied rocks underwent high-grade metamorphism in the Ediacaran and lack obvious evidence for Caledonian high-pressure metamorphism, the studied part of the SNC offers an extraordinary insight into the Late Neoproterozoic history of the hot, extended Baltoscandian margin.
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| 5. |
- Ziemniak, Grzegorz, et al.
(författare)
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Defining tectonic boundaries using detrital zircon signatures of Precambrian metasediments from Svalbard's Southwestern Caledonian Basement Prtovince
- 2019
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Ingår i: Geological Society of America, Special Paper. - : Geological Society of America. - 0072-1077.
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Tidskriftsartikel (refereegranskat)abstract
- Detrital zircon provenance studies of Precambrian metasedimentary rocks inWedel Jarlsberg Land and Sørkapp Land, Svalbard’s Southwestern Caledonian Base-ment Province, were conducted to evaluate local stratigraphic correlations and therole of long-distance strike-slip displacements in assembling the basement of the Arc-tic Caledonides. The detrital zircon U-Pb age spectra of the late Mesoproterozoic toNeoproterozoic metasediments revealed mainly Mesoproterozoic to Paleoproterozoic age signatures characteristic for a Grenville–Sveconorwegian orogen provenance.These results confi rmed a stratigraphic correlation between basement units of south-ern Sørkapp Land and the Isbjørnhamna Group of Wedel Jarlsberg Land and suggestrelocation of the tectonic boundary between the Eimfjellet Complex and the Isbjørn-hamna Group above the Eimfjellbreane Formation. Moreover, the results supportthe Vimsodden Kosibapasset Shear Zone (VKZ) as a major tectonic boundary andhighlight the inhomogeneity in the Southwestern Caledonian Basement Province. Thedetrital zircon age signatures north of the VKZ bear similarities with coeval metased-iments of the Northwestern Caledonian Basement Province of Svalbard and otherlocalities in the Greenland and Scandinavian Caledonides. In contrast, the detritalzircon age spectra south of the VKZ are comparable with the high Arctic Neoprotero-zoic sediments of Baltican affi nity. In conjunction with previous studies, the resultssuggest that the basement units may continue across the traditional boundaries of theSvalbard’s Caledonian basement provinces.
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| 6. |
- Ziemniak, Grzegorz, et al.
(författare)
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Th–U–total Pb monazite geochronology records Ordovician (444 Ma) metamorphism/partial melting and Silurian (419 Ma) thrusting in the Kåfjord Nappe, Norwegian Arctic Caledonides
- 2019
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Ingår i: Geologica Carpathica. - Bratislava : Walter de Gruyter GmbH. - 1335-0552 .- 1336-8052. ; 70:6, s. 494-511
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Tidskriftsartikel (refereegranskat)abstract
- The northern extent of the Scandinavian Caledonides includes the Skibotn Nappe Complex of still debatedstructural position. This paper is focused on part of this complex and presents new U–Th–total Pb monazite dating resultsfor the migmatitic gneiss of the Kåfjord Nappe. The rocks show mineral assemblage of garnet + plagioclase + biotite +white mica + kyanite + rutile ± K-feldspar ± sillimanite. Thermodynamic modelling suggests that garnet was stable at P–Tconditions of ca. 680–720 °C and 8–10 kbars in the stability field of kyanite and the rocks underwent partial meltingduring exhumation following a clockwise P–T path. This episode is dated to 444 ± 12 Ma using chemical Th–U–total Pbdating of the Y-depleted monazite core. Second episode highlighted by growth of secondary white mica resulted fromsubsequent overprint in amphibolite and greenschist facies. Fluid assisted growth of the Y-enriched monazite rim at419 ± 8 Ma marks the timing of the nappe emplacement. Age of migmatization and thrusting in the Kåfjord Nappe issimilar to the Kalak Nappe Complex, and other units of the Middle Allochthon to the south. Nevertheless, the obtainedresults do not allow for unambiguous definition of the tectonostratigraphic position of the Skibotn Nappe Complex.
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