Metamorphic P-T conditions and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland

K. Aoki, B. F. Windley, S. Maruyama, S. Omori

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The metamorphic P-T conditions and associated relationships of the Barrovian zones near Glen Muick were re-examined by focusing on the petrology and thermodynamics of rocks at Cairn Leuchan, where garnetite lenses and layers occur in surrounding garnet amphibolite in the highest-grade sillimanite zone. The representative mineral assemblages in the garnet-rich lenses and garnet amphibolite are garnet + quartz + clinopyroxene + plagioclase + amphibole ± epidote, and garnet + amphibole + quartz + plagioclase ± clinopyroxene ± epidote, respectively. The chemical compositions of constituent minerals are the same in both garnetite and garnet amphibolite. The metamorphic P-T conditions of these rocks were estimated by thermodynamic calculations. The results show that the rocks underwent high-pressure granulite facies metamorphism at P = c. 1.2-1.4 GPa and T = c. 770-800°C followed by amphibolite facies metamorphism at P = c. 0.5-0.8 GPa and T = c. 580-700°C. Integration of our new results with previously published data suggests that the retrograde P-T trajectory of the highest-grade Barrovian metamorphic rocks marks a temperature decrease during decompression from a crustal depth of the high-pressure granulite facies, which is much deeper than previously considered.

Original languageEnglish
Pages (from-to)559-571
Number of pages13
JournalGeological Magazine
Volume151
Issue number3
DOIs
Publication statusPublished - 2014
Externally publishedYes

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Keywords

  • Barrovian zones
  • P-T condition
  • pseudosection
  • retrograde path

ASJC Scopus subject areas

  • Geology

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