Osumilite and spinel + quartz from Sri Lanka: Implications for UHT conditions and retrograde P-T path

K. Sajeev, Yasuhito Osanai

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

We report here the occurrence of osumilite as fine isolated inclusions in garnet porphyroblasts from a granulite facies rock in the southwestern part of the Highland Complex in Sri Lanka. Garnet porphyroblasts in the matrix are partly rimmed by sillimanite-biotite-K-feldspar assemblage as well as cordierite-K-feldspar-quartz assemblage. Spinel coexisting with quartz is also observed in the same sample. The pressure-temperature condition must be above 950°C at around 7 kbar pressure, on the basis of osumilite stability in KFMASH system. The cooling and decompression continued down to 850°C, into the biotite-sillimanite-K-feldspar-quartz stability field. During decompression f o2 must have increased leading to the stability of Zn-rich-spinel with quartz after cordierite. Our findings provide direct evidence for ultrahigh-temperature (UHT) metamorphic conditions in southwestern Highland Complex, and also suggest the existence of a possible UHT zone within the high-grade terrane of Sri Lanka.

Original languageEnglish
Pages (from-to)320-327
Number of pages8
JournalJournal of Mineralogical and Petrological Sciences
Volume99
Issue number5
DOIs
Publication statusPublished - Dec 1 2004

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geology

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