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Type: Artigo de periódico
Title: Mechanisms Of Retrograde Changes In Oxide Minerals From The Proterozoic Serrote Da Laje Deposit, Northeastern Brazil
Author: Amcoff O.
Figueiredo B.R.
Abstract: Retrograde textural and chemical changes in oxide minerals from the Proterozoic Serrote da Laje deposit, northeastern Brazil, have been investigated. The deposit is situated in a mafic-ultramafic layered sill. Oxidation and cooling leading to successively decreasing diffusion rates resulted in disequilibrium on the microscale. Pleonaste in particular shows a rapid change in composition between (a) coarse grains in a granoblastic magnetite host, indicating metamorphic peak conditions, (b) coarse lamellae in magnetite, indicating commencement of exsolution, and (c) composite pleonaste - ilmenite lamellae in magnetite, which indicate oxidation exsolution. Barren rock layers cooled under more oxidized conditions compared with oxide-rich layers. Formation of pleonaste- and ilmenite lamellae in magnetite and ilmenite - hematite relations are discussed. © 1990 Springer-Verlag.
Editor: Springer-Verlag
Rights: fechado
Identifier DOI: 10.1007/BF00199002
Date Issue: 1990
Appears in Collections:Unicamp - Artigos e Outros Documentos

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