Blue amphibole-albite-chlorite assemblages from Fuscaldo (S Italy) and the role of glaucophane in metamorphism
✍ Scribed by Emond W. F. Roever; Frank F. Beunk
- Publisher
- Springer
- Year
- 1976
- Tongue
- English
- Weight
- 809 KB
- Volume
- 58
- Category
- Article
- ISSN
- 0010-7999
No coin nor oath required. For personal study only.
✦ Synopsis
The Fuscaldo assemblages show that in metabasites suitable for the production of glaucophane at higher pressures, amphibole poor(er) in Gl-molecule + albite +Al-rich chlorite is formed at lower pressure. Blue amphibole formed together with albite, chlorite and a Ca-silicate appears to have a fixed content of the Gl-molecule and of Ca 2+, apart from the FEZ+/ R 2+ ratio, which varies with host rock chemistry. The constant Gl-content indicates attainment of equilibrium, and is a function of T and especially P, so it may be used as a geobarometer. Glaucophane generally forms at the cost of albite+chlorite. In a P-T diagram the reaction is probably situated somewhat below the reaction albite~jadeite+quartz, and has a smaller slope than the latter. The concomitant high-pressure character of glaucophane justifies reintroduction of Eskola's glaucophane-schist facies, of which glaucophane is critical.