Reviewing the puzzling intracontinental termination of the Aracuai-West Congo orogenic belt and its implications for orogenic development

Autor(es)

Cavalcante, Carolina ^[1] ; Fossen, Haakon ^[2] ; de Almeida, Renato Paes ^[3] ; Hollanda, Maria Helena B. M. ^[3] ; Egydio-Silva, Marcos ^[3]

Afiliação do(s) autor(es)

^[1] Univ Fed Parana, Dept Geol, Ave Coronel Francisco H dos Santos 100, BR-81531980 Curitiba, Parana - Brazil

^[2] Univ Bergen, Museum Nat Hist, Dept Earth Sci, Allegaten 41, N-5007 Bergen - Norway

^[3] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508900 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo de Revisão
• Fonte: Precambrian Research; v. 322, p. 85-98, MAR 2019.
• Citações Web of Science: 0

Resumo

Palinspastic reconstructions suggest that the late Proterozoic-Cambrian Brasiliano/Pan-African orogenic belt in southeast Brazil and west Congo terminated northwards into an embayment within the Sao Francisco-Congo cratonic unit. The orogenic shortening that created the Aracuai-West Congo orogen in this embayment has been explained by tightening of the horseshoe-shaped Sao Francisco-Congo craton in a fashion referred to as ``nutcracker tectonics{''}. We show that this model is incompatible with the general orogenic evolution proposed in recent literature, which involves (1) similar to 50 m.y. of subduction of oceanic crust and associated arc formation, followed by (2) collisional orogeny and crustal thickening. Quantitative considerations show that the original nutcracker model is too rigid to explain even the second, crustal thickening part, let alone any long pre-collisional history. To soften the model, we suggest that the so-called Sao Francisco - Congo bridge was broken by a similar to 150 km wide orogenic corridor along the current African Atlantic margin. This corridor adds sufficient mobility to the system to explain the orogenic thickening of the crust to 60-65 km. However, even with this additional softening the confined nature of this orogen is incompatible with prolonged arc development. We therefore suggest that oceanic crust was nonexistent or very limited in the Macaubas basin, and reject the widely published model involving similar to 50 m.y. of subduction of oceanic crust and related arc development. Instead, we find strong support for a hot intracontinental orogen model in the currently available P-T, geochronologic, petrographic and structural data. In this model, extensive melting and flow of the middle crust is likely to have caused spreading of the upper crust in an orogenic setting that was created by collisions along the N, W and S margins of the Sao Francisco craton from similar to 630 Ma. (AU)

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