Paleoproterozoic (1.9–1.8 Ga), syn-orogenic magmatism and sedimentation in the Ljusdal lithotectonic unit, Svecokarelian orogen

Karin Högdahl, Stefan Bergman

    Forskningsoutput: Kapitel i bok/konferenshandlingKapitelVetenskapligPeer review

    7 Citeringar (Scopus)

    Sammanfattning

    Ductile shear zones with dextral transpressive deformation separate the Ljusdal lithotectonic unit from the neighbouring units (Bothnia–Skellefteå and Bergslagen) in the 2.0–1.8 Ga Svecokarelian orogen. Sedimentation steered by regional crustal extension at c. 1.86–1.83 Ga was sandwiched between two separate phases of ductile strain with crustal shortening and predominantly high-grade metamorphism with plutonic activity. Metamorphism occurred under low-pressure, medium- to high-temperature conditions that locally reached granulite facies. The earlier shortening event resulted in the accretion of outboard sedimentary and c. 1.89 Ga volcanic rocks (formed in back- or inter-arc basin and volcanic arc settings, respectively) to a continental margin. Fabric development (D1), the earlier phase of low-pressure and variable temperature metamorphism (M1) and the intrusion of a predominantly granitic to granodioritic batholith with rather high εNd values (the Ljusdal batholith) occurred along this active margin at 1.87–1.84 Ga. Thrusting with westerly vergence, regional folding and ductile shearing (D2–3), the later phase of low-pressure and variable temperature metamorphism (M2), and the subsequent minor shear-related intrusion of granite, again with relatively high εNd values, prevailed at 1.83–1.80 Ga. Mineral deposits include epithermal Au–Cu deposits hosted by supracrustal rocks, V–Fe–Ti mineralization in subordinate gabbro and norite bodies inside the Ljusdal batholith, and graphite in metasedimentary rocks.
    OriginalspråkEngelska
    Titel på gästpublikationSweden: Lithotectonic Framework, Tectonic Evolution and Mineral Resources
    FörlagGeological Society of London
    ISBN (elektroniskt)9781786204707
    ISBN (tryckt)9781786204608
    DOI
    StatusPublicerad - 2020
    MoE-publikationstypA3 Del av bok eller annan forskningsbok

    Publikationsserier

    NamnGeological Society, London, Memoirs
    Volym50

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