1. Metamorphic Rocks

2. Rock Cycle

4. Objectives
14 – Describe the types of changes associated with metamorphic rocks.
15 – Contrast regional and contact metamorphism.

5. Metamorphic Rocks
Pre-existing rocks changed by heat and pressure

6. Different Types of Changes
Compaction
Grains move closer.
Rock becomes more dense.
Porosity reduced.
Example: clay to shale to slate
Recrystallization-
Growth of new crystals.
No changes in overall chemistry.
New crystals grow from the minerals already present
Foliation
Minerals separate into bands
New minerals form from heat and pressure

7. Types of Metamorphism: Contact
Contact (thermal)
Small scale
Associated with igneous intrusions

8. Types: Regional Metamorphism
Regional (dynamic)
Large scale
Associated with mountain building

9. Foliated vs. Non-foliated
Foliated – has bands or layers
Non-foliated -
No banding
Form from rocks made up of single minerals

10. Rank
The degree of metamorphism required to change a rock

12. Quartzite Non-foliated Visible minerals grains Low-high metamorphisis
Parent - Sandstone

13. Marble Non-foliated Usually visible grains – granular
Will effervesce in HCl
Calcite
Parent - Limestone

14. Anthracite Non-foliated Black color Metamorphosed Coal Peat→Lignite→
Bituminous coal→ Anthracite

15. Slate Foliated Small grain size Low metamorphism Visible layering
A metamorphosed shale

16. Phylite Foliated Small-visible grains Low-medium metamorphism Sheen
Crenulations- slight wavy appearance
A metamorphosed slate

17. Schist Foliatied Visible grain size Medium metamorphism
Biotite, Garnet
A metamorphosed phylite
Basalt may change into schist

18. Gneiss Foliated Large visible grains High degree of metamorphism
Definite banding and recrystallization
Horneblende, Quartz
Metamorphosed schist