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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|
|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.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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