1. Subduction Zone and High Pressure Rocks

2. Granulite Facies High T, P Base of Crust T > 700 C Very anhydrous
Dry conditions inhibit melting

3. About 600 C

4. About 680 C

5. About 700 C

6. About 750 C

7. Subduction Zone Rocks

8. Steinmann Trinity (1905) Serpentinite Pillow Basalt Radiolarian Cherts
Characteristic of ophiolite settings
Other Distinctive Rocks
Graywacke and Flysch
Blueschist

9. Bedded Chert

10. Serpentinite

11. Serpentinite

12. Magnesite Mines in Serpentinite

13. Pillow Lava

14. Pillow Lava

15. Pillow Lava

16. Blueschist

17. Graywacke

18. Flysch

19. Melange

22. Melange

23. Coesite in Quartz Not very dramatic Rare
Relict in inclusions, often in garnet
Mostly reverts to quartz
Distinctive “palisade” texture in quartz
Radial fractures due to 10% volume increase

24. Coesite in Gneiss

25. Palisade Texture in Quartz

26. Garnets Pyralspite series (Mg-Fe-Mn) Ugrandite Series (Ca + Fe-Al-Cr)
Pyrope Mg3Al2Si3O12
Almandine Fe3Al2Si3O12
Spessartite Mn3Al2Si3O12
Ugrandite Series (Ca + Fe-Al-Cr)
Gossularite Ca3Al2Si3O12
Andradite Ca3(Fe, Ti)2Si3O12
Uvarovite Ca3Cr2Si3O12

27. Eclogite Start with Basalt: Labradorite (An + Ab) + Diopside + Olivine
Ab breaks down to Jadeite + Quartz
Jadeite + Diopside = Omphacite
Anorthite + Olivine = Garnet
Final composition: Omphacite + Garnet + Quartz
Plagioclase no longer stable

28. Types of Eclogite
Type A: kimberlites, dunites, volcanic pipes (Py 70%, Alm 20% T>900 C)
Metamorphism of mantle rocks
Type B: high-pressure gneiss terranes (Py 45%, Alm 40% T= C)
Crustal thickening and deep metamorphism
Type C: blueschists (Py 10%, Alm 60% T<500 C)
Next stage after blueschist metamorphism

29. Eclogite