Orosirian calc-alkaline volcanism ana the Orocaima eventn in the Northern Amazonian Craton, Eastern Roraima State, Brazil

• Autor(a) principal: REIS, Nelson Joaquim
• Data de Publicação: 2000
• Outros Autores: FARIA, Mário Sérgio Gomes de, FRAGA, Lêda Maria Barreto, HADDAD, Regina Clélia
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional de Geociências - RIGEO
• Texto Completo: https://rigeo.cprm.gov.br/handle/doc/504
• topic: GEOCRONOLOGIA; GEOQUÍMICA; PETROGRAFIA; PROTEROZOICO; VULCANISMO; BRASIL; RORAIMA

In the eastern portion of the Brazilian state of Roraima there are two main volcanic terranes of Paleoproterozoic age: the Surumu Group to the north and the Iricoumé Group to the south. The Central Guyana Belt is located between these groups. Geochemical and|geochronological data point to a dissociation with the anorogenic granitoids related to Saracura and Mapuera suites, presently grouped into the Uatumã Supergroup (Uatumã Event, 1.90-1.70Ga). Chemical characteristics of volcanic rocks are very similar to those observed in the calcalkaline|granitoids such as the Pedra Pintada and Água Branca suites (1.96-1.91Ga) pointing to a post-collisional setting, related to the end of Trans-Amazonian Orogeny. The Surumu Group is usually metamorphosed in the lower greenschist facies, with steep foliation and open folding|The Surumu – Iricoumé groups represent a series of acidic to intermediate volcanics, metaluminous and calc-alkaline affinities, similar to those observed in modern magmatic arcs. The REE pattern shows two characteristic groups of volcanics, suggesting distinctive magmatic evolution|Both volcanic-plutonic associated Surumu - Pedra Pintada and Iricoumé - Água Branca and previous molassic sedimentary covers show a new geological framework and are postulated to the Orocaima Event (1.98-1.88 Ga), Orosirian Period