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Earth and Space Sciences · Glossary

What is Ultrahigh-pressure metamorphism?

Definition 11.11 University Earth and Space Sciences — Year 2 · Chapter 11 — Thermobarometry and P–T–t Paths

Ultrahigh-pressure metamorphism is metamorphism of crustal rocks at pressures high enough for coesite, or diamond, to grow.

Coesite in an eclogite, about 1\, mm across, in a thin section between crossed polarisers: the large central grain is coesite, the rim of small bright grains is quartz that grew from it as the pressure fell; the small coloured grain in the centre is a pyroxene inclusion. Photograph J. R. Smyth, CC BY-SA 1.0.
Coesite in an eclogite, about 1 mm1\,\mathrm{mm} across, in a thin section between crossed polarisers: the large central grain is coesite, the rim of small bright grains is quartz that grew from it as the pressure fell; the small coloured grain in the centre is a pyroxene inclusion. Photograph J. R. Smyth, CC BY-SA 1.0.
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