Metamorphic Facies Metamorphic Facies Best, Chapter 10 Metamorphic Grade Metamorphic Grade • Controlled by the temperature of metamorphism • Low-grade rocks contain hydrated and carbonated phases • High-grade rocks are dehydrated and decarbonized Metamorphic Zones Metamorphic Zones • Mappable metamorphic units of similar grade in a rock of distinct composition • Isograds are lines marking the first appearance of key minerals • Zones of Barrow – Biotite, garnet, staurolite, kyanite, sillimanite Metamorphic Reactions Metamorphic Reactions • Formation of talc in a siliceous dolomite Dol + Qtz + H 2 0 = Tlc + Cal + C0 2 • Controlled by the ratio of H 2 0/ C0 2 Metamorphic Facies Metamorphic Facies • The set of mineral assemblages occurring in rocks of diverse composition • Facies develop under restricted P,T conditions • Mineral assemblages may be plotted on ACF diagrams
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Metamorphic FaciesMetamorphic Facies
Best, Chapter 10
Metamorphic GradeMetamorphic Grade
• Controlled by the temperature of metamorphism
• Low-grade rocks contain hydrated and carbonated phases
• High-grade rocks are dehydrated and decarbonized
Metamorphic ZonesMetamorphic Zones
• Mappable metamorphic units of similar grade in a rock of distinct composition
• Isograds are lines marking the first appearance of key minerals
• Zones of Barrow– Biotite, garnet, staurolite, kyanite, sillimanite
Metamorphic ReactionsMetamorphic Reactions• Formation of talc in a siliceous dolomite
Dol + Qtz + H20 = Tlc + Cal + C02• Controlled by the ratio of H20/ C02
Metamorphic FaciesMetamorphic Facies
• The set of mineral assemblages occurring in rocks of diverse composition
• Facies develop under restricted P,T conditions
• Mineral assemblages may be plotted on ACF diagrams