What if we had staurolite and andalusite together What conditions would that indicate Epidote Group Sorosilicates paired silicate tetrahedra Include the mineral Epidote Ca2FeAl2Si3O12 OH Zoisite Ca2Al3Si3O12 OH and clinozoisite polymorph Garnets Garnet A2 3 B3 2 SiO4 3 Pyralspites B Al Pyrope Mg3 Al2 SiO4 3 Almandine Fe3 Al2 SiO4 3 Spessartine Mn3 Al2 SiO4 3 Ugrandites A Ca Uvarovite Ca3 Cr2 SiO4 3 Grossularite Ca3 Al2 SiO4 3 Andradite Ca3 Fe2 SiO4 3 Occurrence Mostly metamorphic Some high Al igneous Also in some mantle peridotites Garnet 001 view blue Si purple A turquoise B Staurolite Aluminosilicate Fe2Al9Si4O22 OH 2 Similar structure to kyanite with tetrahedrally coordinated Fe2 easily replaced by Zn2 and Mg2 Medium grade metamorphic mineral typically forms around 400 500 C chloritoid quartz staurolite garnet chloritoid chlorite muscovite staurolite biotite quartz water Degrades to almandine garnet at higher T staurolite muscovite quartz almandine aluminosilicate biotite water Metamorphic chain silicates Actinolite and tremolite are chain silicates derived from dolomite and quartz and common in low mid grade metamorphic rocks Riebeckite and Glaucophane are also chain silicates higher grade minerals often a blue color These minerals usually lower P higher T conditions Metamorphic Facies Where do we find these regimes of PT off of the typical continental isotherms How is the environment that forms a blueschist facies rock different from one forming a hornfels Metamorphic Facies Table 25 1 The definitive mineral assemblages that characterize each facies for mafic rocks Facies Series Miyashiro 1961 initially proposed five facies series most of them named for a specific representative type locality The series were 1 Contact Facies Series very low P 2 Buchan or Abukuma Facies Series low P regional 3 Barrovian Facies Series medium P regional 4 Sanbagawa Facies Series high P moderate T 5 Franciscan Facies Series high P low T Fig 25 3 Temperaturepressure diagram showing the three major types of metamorphic facies series proposed by Miyashiro 1973 1994 Winter 2001 An Introduction to Igneous and Metamorphic Petrology Prentice Hall Isograds Lines on a map or Surfaces in the 3D world marking the appearance or disappearance of the Index minerals in rocks of appropriate composition e g the garnet in isograd the stauroliteout isograd Complicated by the fact that most of these minerals are solid solutions Isograds for a single shale unit in southern Vermont Which side reflects a higher grade or higher P T environment Meteorite Comet Impacts P T space Energy of an impact Kinetic energy going from very fast to stopping is a BIG change in energy What happens to that energy Impactite any mineral formed as a result of this impact Shatter cone Materials indicating Meteorite Impacts Tektites Glass formed from impact Diaplectic Glass Glass formed through fusion of different minerals not melted but fused What Happens to minerals that are there but not melted Shock Quartz Lamellae retaining evidence of impact Diamonds Very small diamonds can form from impacts and are found in meteorite impact craters around the world Quartz Polymorphs Coesite and Stishovite found associated with impact craters
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