Phase equilibria among pumpellyite, lawsonite, epidote and associated minerals in low grade metamorphic rocks
✍ Scribed by E. H. Brown
- Publisher
- Springer
- Year
- 1977
- Tongue
- English
- Weight
- 757 KB
- Volume
- 64
- Category
- Article
- ISSN
- 0010-7999
No coin nor oath required. For personal study only.
✦ Synopsis
Phase relations of pumpellyite, epidote, lawsonite, CaCO3, paragonite, actinolite, crossite and iron oxide are analysed on an A1-Ca-Fe 3+ diagram in which all minerals are projected from quartz, albite or jadeite, chlorite and fluid. Fe 2 § and Mg are treated as a single component because variation in FeZ+/Mg has little effect on the stability of phases on the diagram. Comparison of assemblages in the Franciscan, Shuksan, Sanbagawa, New Caledonia, Southern Italian, and Otago metamorphic terranes reveals several reactions, useful for construction of a petrogenetic grid:
(1) lawsonite + crossite + paragonite = epidote + chlorite + albite+ quartz + H20
(2) lawsonite + crossite = pumpellyite + epidote + chlorite + albite+ quartz + H20
(3) crossite + pumpellyite + quartz = epidote + actinolite + albite § chlorite + H20
(4) crossite + epidote + quartz = actinolite + hematite + albite + chlorite + H20
(5) calcite + epidote + chlorite + quartz = pumpellyite + actinolite+ H20+CO2 (6) pumpellyite + chlorite + quartz = epidote + actinolite + H20