UnB - Instituto de Geociências - Produção Científica
RESUMOS/ABSTRACTS
PROTEROZOIC CRUST-FORMING EVENTS IN SOUTH AMERICA
Fuck, R.A.
Pimentel, M.M.
In: International Geological Congress, 31, 2000, Rio de Janeiro,Brazil. Abstracts Volume (CD-ROM)
Most of the South American Platform was built during Proterozoic crust-forming events. Exceptions are the Archean basement exposed in the Amazon and São Francisco cratons, and small reworked blocks within Brasiliano fold belts. Even in many parts of the sialic basement of the Andes, Proterozoic rocks are present and have been correlated with rock units in eastern Laurentia.During the Transamazonian orogeny (ca. 2.0-2.2 Ga) juvenile crust was formed in island arc settings which were accreted to the northeastern border of the Archean Central Amazônia block. In the São Francisco Craton, low and high-grade orogenic belts containing juvenile components resulted from the assembly of the Gavião and other Archean blocks, also between ca. 2.0-2.2 Ga. The sialic basement of the Rio de la Plata, Luís Alves, and São Luiz cratons, as well as other crustal fragments exposed within Neoproterozoic orogens, were also accreted during the Paleoproterozoic. These latter were strongly reworked during the Neoproterozoic (Brasiliano) orogeny. Juvenile terrains were accreted to the western margin of Central Amazônia during Paleo- and Mesoproterozoic events at ca. 1.8-2.0 Ga, 1.6-1.8 Ga, and 1.3-1.5 Ga. These new additions were partially reworked during the evolution of the late Mesoproterozoic Sunsas belt, within the framework of Rodinia amalgamation. Finally, much of central/eastern South America was built during the Brasiliano orogeny. Many continental fragments dispersed after Rodinia break up were reassembled in the complex array of Brasiliano collisional belts. This was achieved through destruction of Adamastor, Goiás, and other ocean basins during Western Gondwana assembly. Neoproterozoic crustal accretion episodes are represented by island arc terrains in central Brazil (Brasília Belt) and, to a lesser extent, in the Dom Feliciano Belt, southern Brazil.