Paleoproterozoic, Mesoproterozoic, and Paleozoic sedimentary successions of the Southwestern Amazonian craton: geochemistry, provenance, and post-sedimentary events

Abstract

The Amazonian Craton is home to many Statherian to Calymmian taphrogenesis events that evolved over Large Igneous Provinces. The NW-SE faults on the Western Amazonian Igneous Belt (1.82–1.74Ga) and their reactivations, which facilitated the deposition of the Beneficente Group (1.76–1.60Ga), Prainha Formation (1.46Ga), and Alto Tapajós Group (Silurian-Devonian), are associated with these events in the southwest Amazonian Craton. Mineralogical composition, whole-rocks geochemistry, and Nd-Sr-Pb isotopic data show that the three sedimentary successions originated in the provinces of Rondônia-Juruena and Tapajós Parima, particularly during two rift stages. Beneficente Group deposition is associated with Paleoproterozoic Rift 1, while the Prainha Formation represents the post-rift 1, and Alto Tapajós Group deposition is associated with Paleozoic Rift 2. In addition, the Prainha Formation also received sediment supply from the Sunsás Province. These three sedimentary successions have an intrinsic relationship with the reworking of the local basement and their own reworking that occurred from the Paleoproterozoic to the Paleozoic. Autochthonous reworking, particularly in the Colíder and Beneficente groups, is demonstrated by Ti-magnetite grains, volcanic and arenite fragments in the Prainha Formation sublitharenite, and by angular microcline grains, high Au content, a Pb whole-rock isochron yielding the 1.796±0.096Ga age, and by ${\epsilon }_{\mathit{Sr}\left(0\right)}$ vs 1/Rb relationship in Alto Tapajós Group. ${\epsilon }_{\mathit{Nd}\left(\mathit{t}\right)}$ and flat REE patterns and some positive Eu anomalies in the Prainha Formation and Alto Tapajós Group record the influence of the mafic rocks of the Mata-Matá suite. A Pb-Pb whole-rock isochron allowed hydrothermal activity recognition at 1.32Ga in the Vila do Carmo Formation. This event was ratified by positive Eu/Eu* (1.3–1.43), Ce/Ce* (1.24–2.84), and Gd/Gd*(~1.5) anomalies. Finally, Nd model ages, geochemistry, and Sr isotopes allow for correlating the local basement and the overlaying sedimentary successions along the Columbia and Gondwana boundaries.

Graphical abstract

KEYWORDS:

• Rift basin
• post-depositional events
• isotopic data
• sorting

Acknowledgments

The authors thank the Universidade de Brasilia, CAPES for scholarship granting to the first author and CNPq for financial support (process n ° 471971/2010-3 and 473359/2012) and research grants to the second and third authors. The authors also thank CPRM (Brazilian Geological Survey) for samples of the basement rocks to perform Pb isotopes. In memoriam to Davi Albuquerque and Valdemar Albuquerque, victims of COVID-19. We also thank the anonymous referees that provided helpful suggestions for improving the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2266754.

Additional information

Funding

The work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [471971/2010-3 and 473359/2012]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior .