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|Type:||Artigo de periódico|
|Title:||Petrology and geochemistry of the Neoproterozoic Guaxupe granulite facies terrain, southeastern Brazil|
|Abstract:||Geochemical and oxygen isotopic data on the Neoproterozoic granulite facies rocks (enderbites, charnockite and charnokitic augen gneisses) of Guaxupe, Brazil are assembled. Geochemical discrimination function calculations show an igneous origin for majority of the rock types in the area. Major and trace element data, especially REE, are similar to tonalite and granodiorite. Oxygen isotope corn-position for charnockitic gneisses and mafic granulites yield delta(18)O values in the range of +8.8 to +11 parts per thousand and fall in the range of quartzofeldspathic rocks of medium- to high-grade terrains elsewhere. A small-scale variation of delta(18)O values, compatible with the chemical data, imply the preservation of pre-metamorphic oxygen isotope compositions. Minimum peak pressure-temperature conditions are 8.5 kbar and 850 degrees C. The high-grade metamorphism did not appear to have altered significantly the geochemical and oxygen isotope compositions of the protoliths. Approximately 2.5 kbar of pressure decrease accompanied by 200 degrees C cooling has been recorded for a portion of the cooling path. The P-T path is consistent with a single event, namely the formation and uplift of the Guaxupe nappe in the Neoproterozoic Brasiliano cycle.|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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