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    The age of the lower crust of the central part of the Columbia supercontinent: a review of zircon data

    Koreshkova, M. and Downes, Hilary (2021) The age of the lower crust of the central part of the Columbia supercontinent: a review of zircon data. Gondwana Research 96 , pp. 37-55. ISSN 1342-937X.

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    Abstract

    We have compiled data on textures, trace element contents, Hf isotope compositions and U-Pb ages of zircons from lower crustal xenoliths from the central part of the Columbia supercontinent in Precambrian areas in North America, Siberia and Northern Europe to address the question of when the host rocks to the zircons became part of the lower continental crust. The time when the lower crust reached its current state, a layer of high-pressure granulite-facies rocks, is dated by zircons that have equilibrated with the observed metamorphic association. Magmatic zircons can provide the age of protolith crystallization, which did not necessarily occur within the lower crust. Those from within Archean cratonic areas of Columbia (the Slave, Wyoming, Superior, Siberian and Karelian cratons and the Archean Belomorian mobile belt in NW Russia) yield predominantly Archean ages (3.5–2.6 Ga). Addition of Proterozoic material is rarely recorded in dated magmatic zircons (2.50–2.47 and 1.64 Ga). The granulite-facies association formed in Archean times has been preserved in lower crustal rocks of the Slave and Superior cratons despite later re-heating events. In other Archean areas of Columbia, the lower crust was reworked during Paleoproterozoic orogenic events. At present, 1.9–1.7 Ga old granulitic lower crust predominates, formed during the assembly of the Columbia supercontinent. Nevertheless, sporadic surviving metamorphic zircons show that Archean lower crustal remnants are occasionally preserved. Mesoproterozoic and younger extensional events and anorogenic magmatism occurred across a wide area at the southern margins of the Superior and Wyoming cratons, in the Belomorian belt, Yavapai and Mazatzal provinces and the Cheyenne belt. These events caused significant reworking of the lower crust with migmatization and formation of the granulite-facies association. The main differences of upper and lower crustal metamorphic histories are slow cooling and long duration of thermal events in the lower crust.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): Lower crust, Metamorphic history, Protolith age, Hf isotopes, Xenoliths, Columbia supercontinent
    School: School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 01 Jul 2021 07:46
    Last Modified: 23 Apr 2022 00:10
    URI: https://eprints.bbk.ac.uk/id/eprint/44954

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