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  • Barnes, Christopher
    et al.
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Jarosław, Majka
    Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Schneider, David
    Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Canada.
    Walczak, Katarzyna
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Bukała, Michał
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Kośmińska, Karolina
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Tokarski, Tomasz
    Academic Center for Materials and NanotechnologyAGH University of Science and TechnologyKrakówPoland.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    High-spatial resolution dating of monazite and zircon reveals the timing of subduction–exhumation of the Vaimok Lens in the SeveNappe Complex (Scandinavian Caledonides)2019Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, nr 1, artikel-id 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-situ monazite Th–U–total Pb dating and zircon LA–ICP–MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th–U–total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 ± 16 Ma Neoproterozoic cores surrounded byrims that formed at 498 ± 10 Ma. Monazite rim formation was facilitated via dissolution–reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formedby dissolution–reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, ± Y, and ± Sr. Rims also have subdued Eu anomalies (Eu/Eu* ≈ 0.6–1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 ± 22 Ma; 475 ± 26 Ma; and 479 ± 38 Ma. These results show that both monazite and zircon experienced dissolution–reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.