%0 Journal Article
%T Paleoproterozoic felsic volcanism of Iricoum¨¦ group, Erepecuru-Trombetas domain, Amazonian central province: Field and petrographic characterization and Pb-Pb zircon geochronology
%A Carla Joana Santos Barreto
%A Jean Michel Lafon
%A L¨²cia Travassos da Rosa Costa
%A Evandro Fernandes de Lima
%J Geologia USP : S¨¦rie Cient¨ªfica
%D 2013
%I Instituto de Geoci¨ºncias da USP
%R 10.5327/z1519-874x2013000100004
%X The Iricoum¨¦ group consists of very well preserved pyroclastic and effusive volcanic rocks as a part of an extensive volcano-plutonic event, which marked the central part of the Amazonian craton during the Orosirian. Such rocks occur in the southern part of the southwestern of Erepecuru-Trombetas Domain (NW of the Par¨¢ state), south of the Guyana Shield. Petrographic study allows distinction of two volcanic types. A dominant explosive volcanism is characterized by pyroclastic rocks (ignimbrites, rheoignimbrites, lapilli-tuff related to surge deposit, and co-ignimbrite fall tuff) while a subordinated effusive volcanism is represented by coherent lavas flows and hypabissal rocks (andesites, lamprophyres and latites). Most of the pyroclastic rocks exhibit features of deposition under high temperature suggesting formation in a caldera-related environment. Pb-Pb zircon ages of 1888 +-2.5 and 1889 +-2 Ma have been obtained for the formation of trachydacitic ignimbrites and confirm that the dominant volcanism is part of the Iricoum¨¦ group. The Pb-Pb zircon age of 1992 +-3 Ma yielded by an andesite points to the occurrence in the area of an older Orosirian magmatic episode, which has been previously recognized locally southward in the Tapaj¨®s domain. These new results constitute a further evidence of the wide extent of the Iricoum group and correlated volcanic rocks in the central part of the Amazonian craton, and reinforce the assumption that this volcanic episode and correlated magmatism may be considered as a silicic large igneous province (SLIP), as previously proposed by some authors.
%K Orosirian
%K Amazonian Craton
%K Iricoum¨¦ Group
%K Erepecuru-Trombetas Domain
%K Volcanic rocks.
%U http://ppegeo.igc.usp.br/pdf/guspsc/v13n1/04.pdf