The Evolution of the Rheic Ocean: From Avalonian-Cadomian Active Margin to Alleghenian-Variscan Collision
The assembly of West Gondwana—The view from the Rio de la Plata craton
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Published:January 01, 2007
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CiteCitation
Kerstin Saalmann, Léo A. Hartmann, Marcus V.D. Remus, 2007. "The assembly of West Gondwana—The view from the Rio de la Plata craton", The Evolution of the Rheic Ocean: From Avalonian-Cadomian Active Margin to Alleghenian-Variscan Collision, Ulf Linnemann, R. Damian Nance, Petr Kraft, Gernold Zulauf
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The southern Brazilian Shield comprises a number of tectonostratigraphic blocks representing two terranes. The São Gabriel block consists of relics of two Brasiliano juvenile magmatic arcs; the Porongos belt located on the Encantadas block formed in a passive margin setting. Plate tectonic evolution started with opening of an oceanic basin to the east of the Rio de la Plata craton since at least 0.9–1.0 Ga. An intra-oceanic island arc formed due to eastward subduction and was subsequently accreted to the eastern margin of the Rio de la Plata craton. Westward subduction beneath the newly formed active continental margin occurred between ca. 850 and 700 Ma. At the same time, the Porongos basin formed on stretched continental crust of the Encantadas passive margin. Collision of the two terranes took place at ca. 700–660 Ma followed by left-lateral ductile shear along the Dorsal de Canguçu Shear Zone between 670 and 620 Ma and 630- to 610-Ma sinistral shearing in the Dom Feliciano belt farther east. The episodic character of orogenic evolution can be observed throughout Brazil. The Brasiliano belts cannot be directly linked with pan-African belts in southwestern Africa because main deformation in the latter occurred 50–70 Ma later. The assembly of Gondwana comprises a series of collisions of cratons and microcontinents over a time span of nearly 400 Ma; however, a number of orogenic episodes can be discriminated. Their synchroneity suggests that temporally equivalent episodes are coupled with the global plate tectonic framework, which, however, is far from resolved.
- alkaline earth metals
- basement
- basins
- block structures
- Brasiliano Orogeny
- Brazil
- Brazilian Shield
- continental drift
- correlation
- cratons
- deformation
- Dom Feliciano Belt
- faults
- geochemistry
- Gondwana
- granites
- igneous rocks
- isotope ratios
- isotopes
- lithostratigraphy
- metals
- metamorphic belts
- metamorphic rocks
- microcontinents
- Neoproterozoic
- orogeny
- paleogeography
- Pan-African Orogeny
- passive margins
- plate convergence
- plate tectonics
- plutonic rocks
- Precambrian
- Proterozoic
- Rio de la Plata Craton
- Rio Grande do Sul Brazil
- sedimentary basins
- South America
- Sr-87/Sr-86
- stable isotopes
- strontium
- subduction
- systems
- tectonics
- terranes
- upper Precambrian
- Sao Gabriel Block
- Cambai Complex
- Porongos Belt
- Palma Group
- Passo Feio Formation
- Encantadas Complex
- Porongos Complex
- Encantadas Block
- Capane Gneiss