Paleomagnetic Study of Mucajai AMG Complex Rocks, Northern Amazonian Craton, Guiana Shield (Roraima, Brazil): Paleogeographic Implications for Columbia Supercontinent

In recent years, there has been a significant increase in the paleomagnetic data of the Amazonian Craton, with important geodynamic and paleogeographic implications of this unit in the Columbia Supercontinent during Paleo-Mesoproterozoic. However, many issues still emerge about Columbia's longevity and the geodynamic processes that have resulted in its formation. In this sense, a paleomagnetic study was performed on rocks from the 1540 Ma AMG (Anortosite-Mangerite-rapakivi Granite) Mucajai Complex located in the Roraima State (Brazil), northern portion of the Amazonian Craton, Guiana Shield. Thermal and AF treatments revealed northwestern/southeastern directions with upward/downward inclinations. Magnetic mineralogy experiments indicate that the characteristic remanent magnetization (ChRM) of the Mucajai Complex is probably carried by magnetite and titanomagnetite minerals. Site mean directions cluster around the mean, Dm=136.5°; Im=36.1° (N=12; α₉₅=14.8°) which yielded a paleomagnetic pole located at 357.3°E, 41.5°S (α₉₅=14.4°) for the Mucajai Complex, whose age is probably 1540 Ma. The Mucajaí pole favors the SAMBA (South AMerica-BAltica) link in a configuration formed by Laurentia, Baltica, Amazonia and West Africa. Also, the present paleomagnetic data predict a long life for this nucleus of the Columbia Supercontinent, which remained stable at least since 1780 Ma up to 1420 Ma.