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vol.46 suppl.1The tectonic significance of the Cabo Frio Tectonic Domain in the SE Brazilian margin: a Paleoproterozoic through Cretaceous saga of a reworked continental margin author indexsubject indexarticles search
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Brazilian Journal of Geology

Print version ISSN 2317-4889On-line version ISSN 2317-4692


CORDANI, Umberto Giuseppe; SATO, Kei; SPROESSNER, Walter  and  FERNANDES, Fabiana Santos. U-Pb zircon ages of rocks from the Amazonas Territory of Colombia and their bearing on the tectonic history of the NW sector of the Amazonian Craton. Braz. J. Geol. [online]. 2016, vol.46, suppl.1, pp.5-35. ISSN 2317-4889.

Here we report the results of several U-Pb zircon ages, made to generate an integrated history for the Rio Negro-Juruena tectonic province, for the northwestern part of the Amazonian ­Craton. This region comprises granitoid rocks, described as calc-alkaline syntectonic gneisses, granites and migmatites, affected by medium level amphibolite facies metamorphism. The new measurements, with the available Rb-Sr and K-Ar ages, indicate the formation of these rocks within a series of essentially juvenile magmatic arcs, that are closely related with subduction. Sm-Nd analyses indicate that all samples, regardless of their zircon ages, yielded TDM model ages roughly between 1.9 and 2.2 Ga, suggesting the absence of a much older source material. In the northeastern part (areas of Puerto Inírida and San Carlos), the Atabapo belt comprises rocks formed within a period of about 60 Ma, from 1800 to 1740 Ma. In the southwestern region, including the towns of Mitú and Iauaretê, the granitoids formed in the Vaupés belt between 1580 and 1520 Ma. Finally, the available K-Ar measurements indicate the onset of the Nickerie-K'Mudku intraplate heating event, with temperature above 300oC within the entire region at 1200 - 1300 Ma.

Keywords : Amazonian Craton; Rio Negro-Juruena province; geochronology; zircon ages; tectonic history.

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