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Unformatted text preview: RE . Concord . . Boston . Albany NEW YORK MASSACHUSETTS . Hartford Binghamton . R.I. CONNECTICUT . PENNSYLVANIA Scranton r NEW JERSEY i ATLANTIC OCEAN . ft l va l ey Providence Low grade Long Medium Island grade Newark High grade Unmetamorphosed Chlorite/muscovite zone Biotite zone Garnet zone Staurolite zone Sillimanite zone Increasing pressure and temperature DIAGENESIS LOW GRADE HIGH GRADE INTERMEDIATE GRADE Chlorite and muscovite Biotite Garnet Staurolite MELTING Sillimanite Metamorphic Environments Metamorphic grade or Facies A group of minerals that form in a particular P-T environment Can be used to deduce T-P conditions of formation Metamorphic Environments in Subduction Zones We can look at minerals in Metamorphic Rocks and determine where they formed. Water facilitates metamorphic reactions by allowing movement of atoms and ions Greenschist Hand Sample Greenschist Thin Section Chl­Ep Blueschist glaucophane Amphibolite Common metamorphic rocks Common metamorphic rocks Nonfoliated rocks: the Field Geologist’s Nonfoliated friend friend Quartzite – Formed from a parent rock of quartz-rich Formed sandstone sandstone – Quartz grains are fused together – Forms in intermediate T, P conditions Sample of quartzite Thin section of quartzite Field Geologists are grateful for quartzites. They don’t foliate, so you can see the folds. Mudrocks foliate; much harder to map. Flattening of quartz grains in quartzite 7_18 Fracture Sandstone: grains and cement Fracture Quartzite: grains interlock Common metamorphic rocks Common metamorphic rocks Nonfoliated rocks (cont.) Marble – Coarse, cryst...
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