1. Metamorphic Rocks and Rock Cycle
Shmulik Marco

2. Three Basic Types of Rocks
Igneous Rocks formed by solidification of molten rock (magma). Examples: basalt, granite.
Sedimentary Rocks formed as layers of sediments accumulate. Examples: sandstone, limestone.

3. 3. Metamorphic Rocks Lithostatic Pressure Differential Pressure
Formed by transformation of preexisting rocks in the solid state under high pressures and temperatures
Lithostatic Pressure
Differential Pressure

4. Metamorphism: Processes of generating metamorphic rocks
Metamorphism: Processes of generating metamorphic rocks. Rocks undergo mineralogical and physical changes in solid state

5. Metamorphic Textures Foliation
set of flat or wavy parallel surfaces produced by deformation
define a preferred orientation, usually perpendicular to directed pressure and parallel to shear
often expressed in orientation of “platy” minerals such as micas

6. Schist – Preferred Orientation Foliation

7. Foliated Rock: Schist
5 cm
10 cm

8. Metamorphic Textures: Foliation and Cleavage
set of flat or wavy parallel surfaces produced by deformation
define a preferred orientation, usually perpendicular to directed pressure and parallel to shear
often expressed in orientation of “platy” minerals such as micas and chlorite

9. Granite – Equidimensional Crystals, No Preferred Orientation

10. Gneiss with Lineation

11. Gneiss – Preferred Orientation Lineation

12. Metamorphic Textures
Lineation

13. Ductile Deformation: Folds

14. No preferred orientation
Quartzite
No preferred orientation

16. Metamorphic Minerals
Grow in rocks only during metamorphism (solid state!)
Indicative of pressure and temperature
Do not form from cooling magma

17. Contact Metamorphism: The main metamorphic agent is heat.

18. Pressure & Temperature Regimes

19. Pressure & Temperature Regimes
Increases with depth at about 1/3 kilobar per kilometer
Does not vary much with geographic position or plate-tectonic setting

20. Pressure & Temperature Regimes
Temperature: Increases with depth at a rate that varies substantially with plate-tectonic setting
20ºC per kilometer in stable continental crust
40ºC per kilometer in orogenic belts
60ºC per kilometer in volcanic regions

21. Pressure & Temperature Regimes
Deformation stress
Direction varies substantially with plate-tectonic setting
Magnitude limited by strength of rocks to be less than 1 kilobar

22. Metamorphic Grade
Geologists determine pressure and temperature from mineral assemblages
geothermometers
geobarometers
60º/km
40º/km
20º/km

23. Types of Metamorphism Regional metamorphism
caused by large-scale lithospheric movements
Contact metamorphism
caused by high temperatures near magmatic intrusions
Deformation metamorphism
caused by faulting, tight folding, and shearing
Hydrothermal metamorphism
caused by circulation of hot fluids
Burial metamorphism
caused by subsidence and burial of sediments

24. t0 t5 t1 t4 t2 t3 PTt Path T P Original rock forms: t0
Burial, pressure and temperature increase, metamorphism, : t1 - t3
Exhumation: t4 - t5 T t0 t5 t1 t4 P t2 t3

25. Rock Cycle סלעים מגמתיים סלעים מטמורפיים סלעים סדימנטריים מטמורפוזה
התכה
התכה
סלעים מטמורפיים
אירוזיה
אירוזיה
מטמורפוזה
סלעים סדימנטריים

26. Rock Cycle