Sapphirine has recently been found to be abundant throughout Proterozoic (1.7−1.6 Ga) granulite facies quartzofeldspathic paragneiss in central Labrador. The pressure-temperature (P-T) trajectory of metamorphism culminated at 900 °C and 9 kbar and was succeeded by nearly isobaric cooling. The paragneiss has δ18O enrichment and chemical compositions, which suggest that the protolith was probably highly oxidized shale. Chemical constraints render the involvement of partial melting during the formation of the paragneiss unlikely.

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