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Metamorphic Rocks “If something is gneiss, don’t take it for granite.”

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Presentation on theme: "Metamorphic Rocks “If something is gneiss, don’t take it for granite.”"— Presentation transcript:

1 Metamorphic Rocks “If something is gneiss, don’t take it for granite.”


3 Metamorphic Agents Pressure (>1,000 times atmospheric pressure) Temperature (>300 degrees C) Chemical Fluids (mineral saturated hot water)

4 Metamorphic Environments Contact (thermal) – intrusion by magma Hydrothermal – ion-rich hot water circulates through cracks Mountain Building – regional metamorphism

5 Metamorphic Changes - Rocks adjust to new conditions by: Changes in texture Changes in mineralogy

6 Changes in Texture Compaction Recrystallization - may cause –Foliation –Lineation

7 Changes in Minerology Recrystallization – small crystals reform into larger crystals of the same mineral Formation of new minerals – elements recombine to form new minerals –Garnet, Chlorite and others found only (or mostly) in metamorphic rock

8 Grades of Metamorphosis Low Grade – Low temperature and pressure results in slate and phyllite –“Rock cleavage” in slate –Foliated –Fine grained –Slate looks dull, phyllite is shiny

9 Grades of Metamorphosis (cont.) Intermediate Grade – higher temperatures and pressures than Low Grade –Schist Foliated Mica, garnet

10 Grades of Metamorphosis (cont.) High temperatures and pressures –Gneiss and Migmatite Dark & light banding of mica (dark), quartz & feldspar (light)

11 Foliated Metamorphic Rock Sequence Slate – parent rock is shale (sedimentary) Phyllite – parent rock is slate Schist – parent rock is phyllite Gneiss – parent rock is schist Migmatite – parent rock is gneiss

12 Non-Foliated Metamorphic Rocks & Their Parent Rocks Marble – Parent rock is limestone or dolostone (calcite, reacts with acid) Quartzite – Parent rock is sandstone Anthacite – Parent rock is bituminous coal Hornfels – Parent rock is any rock type

13 Metamorphic Rock Dichotomous Key Proceed to Dichotomous Key Activity

14 View in slide show, then click to view: Dichotomous Metamorphic Key

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