The early proterozoic greenstone belt of the Northern Guiana Shield,South America |
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Authors: | Asit Choudhuri |
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Affiliation: | Departamento de Mineralogia e Recursos Minerais, UNESP, 13.500 Rio Claro, S.P. Brazil |
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Abstract: | A large part of the northern Guiana Shield is underlain by metavolcanic and metasedimentary sequences steeply folded and metamorphosed in the greenschist facies during the 2000 Ma old Trans-Amazonian orogeny. It is suggested that this extensive early Proterozoic belt represents a back-arc basin environment marginal to a supercontinent; that is to say, this belt was possibly intercratonic with respect to existing Archaean basements, whereas elsewhere in the interior of the continent, as in Brazil, fold belts of identical age were intracratonic. The formation of the volcano-sedimentary pile and subsequent orogeny to which the Guiana belt was subjected are ascribed to plate convergence and subduction. This interpretation is supported by the nature of the volcanic pile and the presence of a possible fossil suture in northern Guiana. |
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