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Paleoproterozoic crustal evolution and Mesoproterozoic overprint in the Roosevelt-Guariba Transpressive Belt, Juruena Terrain, Southeastern Amazonas, Brazil

2022; Volume: 5; Issue: 3 Linguagem: Inglês

10.29396/jgsb.2022.v5.n3.5

2595-1939

Marcelo Esteves Almeida, Antonio Charles da Silva Oliveira, João Orestes Schneider Santos, Joseneusa Brilhante Rodrigues, Gilles Ruffet,

Geochemistry and Elemental Analysis

The Juruena Terrain (Rondônia-Juruena Province) in the southeastern Amazonas State shows a NW-SE dextral shear zones system denominated Roosevelt-Guariba Transpressive Belt (RGTB).The RGTB was generated in response to intracontinental crustal reworking, juxtaposing Paleoproterozoic Juruena granitic-gneiss and coeval supracrustal associations.This granitic-gneiss basement shows high-K calcalkaline (Teodósia Suite) to transitional I-to A-type (Igarapé das Lontras Suite) signatures, produced in a continental magmatic arc setting around 1760-1740 Ma (zircon, titanite; U-Pb SHRIMP, LA-ICP-MS).New geochronological data about of the deformation and metamorphic rocks in the RGTB were obtained from migmatite paragneisses, amphibolites, S-type leucogranite (Quatro Cachoeiras Complex and Itamaraty Suite; zircon U-Pb SHRIMP) and protomylonites and mylonites (Igarapé das Lontras and Teodosia protoliths; amphibole-muscovite-sericite Ar-Ar step heating).The results suggest that Southeastern Amazonas (northern Juruena Terrain) was metamorphosed/deformed during 1530-1460 Ma under temperatures of 900 o C (zircon) to 580 o C (hornblende) and 420 o C (muscovite).The geochronological data show that the granite-gneiss basement (continental magmatic arc) and supracrustal rocks (foreland basin) were reworked by a regional event with an age interval of 1530 Ma (high grade and anatexis) to 1460 Ma (medium grade).Finally, the Juruena Terrain is affected by a younger low-T event (1300 Ma, muscovite Ar-Ar step heating) with wide NE-trending structures (e.g.Buiuçu Shear Zone).This 1.3 Ga event suggests a continental reactivation caused by the pericratonic deformation related to Candeias/ Sunsás Orogeny during the Columbia Supercontinent break-up, before the Rodinia Supercontinent assembly.In summary, the Juruena Terrain in the southeast Amazonas shows a complex metamorphic and structural intracontinental evolution, involving polycyclic events from late Orosirian to Ectasian in a convergent tectonic setting.Therefore, the Juruena Terrain shows similar accretionary histories with other orogens and has apparent long-lived connections with Laurentia (Yavapai Province) and Baltica (Transscandinavian Igneous Belt), forming the core of the Columbia Supercontinent.Paleoproterozoic crustal evolution and Mesoproterozoic overprint in the Roosevelt-Guariba Transpressive Belt, Juruena Terrain, Southeastern Amazonas, Brazil