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