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Previous issue date: 2016-11-11 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A Faixa Paraguai Norte, localizada a SE do Cráton Amazônico foi estabelecida durante os
estágios finais do Ciclo Brasiliano (940-620 Ma.) marcado por colisões entre os crátons
Amazônico, São Francisco e Rio de La Plata para compor o Supercontinente Gondwana
Oeste. Este segmento tectônico é formado por rochas metassedimentares do Grupo Cuiabá
(720 Ma.), provenientes de bacias marinhas profundas em margens passivas no contexto
extensional da fragmentação do Supercontinente Rodínia (1,0 Ga.). Estas bacias foram
afetadas por inversão tectônica, devido aos esforços advindos da Orogenia Brasiliana,
promovendo metamorfismo regional e deformação cujo nível crustal dúctil está hoje
aflorante. Subsequentemente, este orógeno foi soerguido, exposto à erosão e submetido a
eventos extensionais, embasando bacias intracratônicas que compreende as rochas
sedimentares da Formação Puga (635 Ma.), Grupo Araras (627±32), Formação Raizama
(645±15 Ma.) e Formação Diamantino (541±7 Ma.) de ambiente plataformal moderadamente profundo a raso, com influência de tempestades, ambiente transicional com influência de sedimentares são relacionadas a eventos de reativações transtensivas de estruturas antigas, e
estão relacionadas à geração de dobras de arrasto e grábens pós-paleozóicos afetando as
bacias sedimentares dos Parecis e do Paraná. Veios de quartzo tardios ocorrem encaixados
somente em rochas do Grupo Cuiabá. Os dados apresentados indicam que as rochas da Faixa
Paraguai Norte foram afetadas por no mínimo dois episódios tectônicos: o primeiro
relacionado ao estabelecimento do Orógeno Brasiliano composto somente por rochas do
Grupo Cuiabá metamorfizadas e deformadas; e o segundo ligado a reativações transtensivas,
responsáveis pelo estabelecimento de bacias sedimentares fanerozóicas e deformação rúptil
por dobras e falhas normais nas rochas sedimentares da Formação Puga, Grupo Araras,
Formação Raizama e Formação Diamantino. / The Northern Paraguay Belt, located at Southeast of Amazonian Craton, was established
during the final stages of Brasiliano Cycle (940-620 My.) marked by the collisions among
Amazonian, San Francisco and Rio de La Plata cratons to assembly the Gondwana West
Supercontinent. The Northern Paraguay Belt consists mainly of metasedimentary rocks of the
Cuiabá Group (720 My.), assigned to passive margins basins in an extensional context during
the break-up of Supercontinent Rodinia (1.0 Gy.). These basins were affected by tectonic
inversion by Brasiliano Orogeny, causing regional metamorphism and ductile crustal level
deformation. Subsequently, the orogen had been uplifted, exposed to erosion and subjected to
extensional episodes, developing intracratonic basin where sedimentary rocks of the Puga
Formation (635 My.), Araras Group (627 ± 32 My.), Raizama Formation (645 ± 15 My.) and
Diamantino Formation (541 ± 7 Ma.) were unconformably deposited in moderately deep to
shallow storm influenced plataformal environment, tidal affected transitional environment
and, lacustrine deltaic environment, respectively. These rocks are classically assigned to a
Foreland Basin, however, ancient suture zones usually exposes the orogen roots, and these
basins are currently not well preserved. These intracratonic or plataformal basin sedimentary
rocks show considerable thicknesses and outcrop in Northeast-Southwest aligned trending
mountain ranges. The São Vicente Granite (518 My.) and the Tapirapuã Formation basalts
(197 My.) occur as intrusive rocks in the studied area along the Northern Paraguay Belt. The
geological contacts between the metasedimentary rocks of the Cuiabá Group with
sedimentary rocks of Puga Formation, Araras Group and Alto Paraguay Group, is interpreted
as non-conformity. The Cuiabá Group rocks (720 My.) are mainly composed by quartz,
plagioclase, muscovite, biotite and phengite and correspondent to greenschist facies affecting
a low grade pelitic protolith. These rocks were deformed by ductile shear zone trending
Northeast-Southwest, with strain partitioning, described as Transpressional Structural Domain
D1, which was divided into two deformation facies: (1) D1-A and (2) D1-B. (1) The D1-A
features a fine continuous foliation and stretching mineral lineation, with a rake of 40º,
moderately inclined to recumbent, “S” type asymmetrical flexural folds; ductile-brittle thrustfaults
and late strike-slip dextral ductile-brittle shear bands; (2) The D1-B is marked by a
mylonitic foliation, with its stretching mineral lineation, with a 15º rake. These deformational
facies comprises a mainly transpressional sinistral flow mostly dominated by simple shear and
influenced by the strain partitioning. All structures indicate tectonic vergence from Northwest
toward Southeast, as a result of the collisional setting of the Brasiliano Orogeny (620 Ma.). The sedimentary rocks were deformed under brittle crustal level conditions. Consequently
they show inclined to subvertical, asymmetric "Z" type drag folds indicating dextral
movement, besides normal faults and cataclastic foliation. The drag folds in the sedimentary
rocks indicate tectonic vergence toward both Southeast and Southwest, therefore they were
not generated under directed tectonic effort. Normal faults which deform sedimentary rocks
are related to later transtensional reactivation episodes of ancient structures forming drag
folds and Post-Paleozoic grabens affecting both the Parecis and Parana sedimentary basins.
Late quartz veins occur emplaced only in the Cuiabá Group rocks. In conclusion, the Northern
Paraguay Belt rocks were affected for at least two main tectonic episodes: (1) The Brasiliano
Orogeny, only represented by Cuiabá Group rocks which show metamorphism and ductile
deformation; (2) and transtensional reactivation that had been responsible for the
establishment of the sedimentary basins followed by brittle deformation of Puga Formation,
Araras Group, Raizama and Diamantino Formation.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufpa.br:2011/9344 |
| Date | 11 November 2016 |
| Creators | SANTOS, Iara Maria dos |
| Contributors | NOGUEIRA, Afonso César Rodrigues, PINHEIRO, Roberto Vizeu Lima |
| Publisher | Universidade Federal do Pará, Programa de Pós-Graduação em Geologia e Geoquímica, UFPA, Brasil, Instituto de Geociências |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFPA, instname:Universidade Federal do Pará, instacron:UFPA |
| Rights | info:eu-repo/semantics/openAccess |
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