Browsing by Subject "Amazonian craton"

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  • Bispo-Santos, Franklin; D’Agrella-Filho, Manoel S.; Pesonen, Lauri J.; Salminen, Johanna M.; Reis, Nelson J.; Silva, Julia Massucato (2020)
    In recent years, there has been a significant increase in the paleomagnetic data of the Amazonian Craton, with important geodynamic and paleogeographic implications for the Paleo-Mesoproterozoic Columbia supercontinent (a.k.a., Nuna, Hudsoland). Despite recent increase of paleomagnetic data for several other cratons in Columbia, its longevity and the geodynamic processes that resulted in its formation are not well known. A paleomagnetic study was performed on rocks from the similar to 1535 Ma AMG (Anorthosite-Mangerite-Rapakivi Granite) Mucajai Complex located in the Roraima State (Brazil), in the northern portion of the Amazonian Craton, the Guiana Shield. Thermal and AF treatments revealed northwestern/southeastern directions with upward/downward inclinations for samples from twelve sites. This characteristic remanent magnetization is mainly carried by Ti-poor magnetite and in a lesser amount by hematite. Site mean directions were combined with previous results obtained for three other sites from the Mucajai Complex, producing the dual polarity mean direction: Dm = 132.2 degrees; Im = 35.4 degrees (N = 15; alpha(95) = 12.7 degrees; k = 10.0) and a paleomagnetic pole located at 0.1 degrees E, 38.2 degrees S (A(95) = 12.6 degrees; K = 10.2). The Mucajai pole favours the SAMBA (South AMerica-BAltica) link in a configuration formed by Amazonia and Baltica in Columbia. Also, there is geological and paleomagnetic evidence that the juxtaposition of Baltica and Laurentia at 1.76-1.26 Ga forms the core of Columbia. The present paleomagnetic data predict a long life 1.78-1.43 Ga SAMBA connection forming part of the core of the supercontinent. (c) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.