Abstract
Geochemical and oxygen isotopic data on the Neoproterozoic granulite facies rocks (enderbites, charnockite and charnokitic augen gneisses) of Guaxupé, 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 composition for charnockitic gneisses and mafic granulites yield δ 18O values in the range of +8.8 to +11‰ and fall in the range of quartzofeldspathic rocks of medium- to high-grade terrains elsewhere. A small-scale variation of δ 18O 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°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°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 Guaxupénappe in the Neoproterozoic Brasiliano cycle.
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