1. Metamorphic Rocks Change in mineralogy, texture or both of a pre-existing rock by application of heat and pressure Pre-existing rock can be either igneous, Sedimentary, or metamorphic

2. Figure C 01 Rock cycle Metamorphic Rock Metamorphic rock derived from igneous rock, metamorphic rock or sedimentary rock

3. Metamorphic Agents heat – essential agent to form new minerals pressure – reduce space and reorient minerals lithostatic = uniform directed via tectonic fluids – promote chemical reactions time

4. Application of HEAT Low Pressure < 3 kb (kilobar) of pressure 1 kb approx 3.3 km of average density crust Variable Temperature called Contact Metamorphism

5. Figure 8-23

6. called Regional Metamorphism Where does the pressure come from? - burial - plate tectonic stresses Application of PRESSURE (and heat)

7. Page 250 Figure 8.26 Metamorphic rocks correlate with plate tectonic boundaries and processes Contact And High pressure Low T meta Regional High temp and pressure Convergent - collision Convergent - subduction

8. Products of Metamorphism Original Rock Metamorphic Rock minerals texture original minerals original texture new minerals new texture some combination depending on grade

9. Chemical Changes Physical changes recrystallization remobilization Pressure solution deformation rotation shearing

10. Diagenesis <~ 100 o C Low Grade <~ 300 o C High Grade >~ 600 o C Metamorphic grade level of temperature and pressure or “intensity of metamorphism”

11. Figure 8.17a diagenesis METAMORPHIC GRADES DIAGENESIS

14. Figure 8.18 The geothermal gradient in a given tectonic environment determines the progression of metamorphic rocks Metamorphic facies Assemblage of minerals similar to grade

15. Figure 8-6c Metamorphic textures from PRESSURE -response to directed pressure/differential stress -produces foliation (layering) slaty cleavage, schistosity, gneissic banding

16. Figure 8.9 Figure 8.8a Figure 8.8b

17. slate phyllite

18. schist

19. gneiss

20. There are progressive changes related to metamorphic grade when starting with a single composition of rock Figure 8.19

21. Application of just HEAT (contact metamorphism) - Recrystallization with random fabric

22. Quartzite (from sandstone)

23. Marble (from limestone)

24. Q: What do you call a can of pop found in a conglomerate? A: Coca-Cola Clastic Two Geologists are walking across a granite outcrop one day. The first says to the second "Hey, this terrain is unmetamorphosed". Replies the second one, "No Schist". The more you try to be gneiss, the more you get taken for granite.

25. Stretched pebble conglomerate

26. boudin

29. mylonite