Types of Metamorphism

1. Types of Metamorphism Regional metamorphism • Large scale – large volume of rock is affected • Associated with convergent plate margins and mountain building • Folding and faulting increase thickness of the crust • Occurs over a range of temperatures and pressures • Fluids are also present • Low grade to high grade metamorphism • Will have zones of contact metamorphism

2. Regional Metamorphism

3. Metamorphic Grade

5. The following diagram illustrates the rock cycle. Match the lettered responses to the blank ovals on the diagram. (Note: some letters are used more than once.) • a) Cementation & Compaction (lithification) • b) Heat and Pressure • c) weathering, transportation, deposition • d) Cooling and solidification • e) Melting Magma 1 2 Metamorphic rock Igneous rock 3 4 6 5 7 Sedimentary Rock Sediment 8

6. Rock Cycle

7. Geologic Structure

8. Rock Deformation • Stress • Force applied to an area • Pressure • Differential stress – magnitude of stress is greater in one direction • Rock Strength • Rock’s resistance to deformation (stress)

9. Rock Deformation Cont. • Strain • A rock’s response to stress • Deformation resulting in change of shape or position • Elastic deformation • Deformation is reversible, after stress is removed, materials return to original shape, i.e. A rubber band • Plastic deformation • Deformation is permanent • Rock flow in response to stress • Need high pressures and temperatures, generally deep in earth’s interior, i.e. Taffy

10. Rock Deformation Cont. • Brittle deformation • Deformation is permanent • Rock break (fracture) or lose cohesion • Generally low temperature and low pressure, common in shallow crust, i.e. Peanut brittle

11. Types of Stress • Tensional (Extension) Stress • Compressional Stress • Shear Stress

12. Tension or Extensional Stress • Stress move away from each other (pull apart) • Rock lengthens • Common in divergent boundaries, but not sole locale • Ductile deformation – stretching and thinning of rock • Brittle deformation – fracturing and faulting

13. Compressional Stress • Stress presses (squeezes) rock together • Rock shortens • Common at convergent boundaries • Ductile deformation – shortening and thickening of rock – rock folds • Brittle deformation – fracturing and faulting

14. Shear Stress • Stress creates a lateral shift in the rock • Rock slides past other rock • Common at transform boundaries • Results in faults

15. Folds • Ductile deformation • Compressional stress • Horizontal rocks are deformed

16. Fold Terminology • Limb – the sides of the fold • Axial plane (hinge plane) – imaginary plane that divides the fold into two equal parts, marks location of maximum curvature • Fold axis (hinge line) – the line formed by the intersection of the hinge plane and a bedding plane

17. Syncline • A fold with the youngest beds in the middle • Generally trough shaped, with limbs dipping toward the center

19. Anticline • A fold with the oldest beds in the middle • Generally arched shaped, with limbs dipping away the center

21. Monocline • Folds with only one limb • Often Associated with faults

22. Symmetrical fold – limbs of the fold dip at the same angle Asymmetrical fold – limbs of the fold dip at different angles Fold Symmetry

23. Overturned Fold • Fold where one limb has been tilted beyond vertical

29. Daily Exercise-Complete the concept map Applied to a causes 1 2 3 At low T & P or high stress rate At high T & P or low stress rate 5 4 The material The material no displacement 7 6 8 • Joints • Folds • Anticline • Tension • Faults • Break • Plastic deformation • Syncline • Brittle deformation • Force/stress • Deformation • Normal • Reverse • Rock • Compression displacement Defined by oldest rock in middle Defined by youngest rock in middle 11 9 10 Each letter can be used only once, and it is possible that it will not be used.

30. Faults • A results of brittle deformation • Fractures in the Earth's crust where displacement has occurred

31. Footwall – block that lies above the fault plane Hanging wall – block that lies below the fault plane Fault Terminology

32. Dip-Slip Movement is primarily vertical Strike Slip Movement is along strike • Oblique-Slip • Movement is both vertical and along strike Classes of Faults

33. Extensional Stress Hanging wall moves down with respect to footwall Dip-Slip Fault – Normal Fault

34. FOOTWALL HANGINGWALL

36. Normal Fault • Horst – raised block of material bounded by two normal faults • Graben – trough (valley) bounded by two normal faults

38. Compressional Stress Hanging wall moves up with respect to footwall Dip-Slip Fault – Reverse Fault

40. Compressional Stress Low-angle reverse fault (fault plane < 45o) Displacement can be 100’s km (~60 miles) Typically associated with folds Dip-Slip Fault – Thrust Fault

42. Shear Stress No vertical movement Movement parallel to fault plane Left-lateral strike-slip faults: movement of opposite plate is to the left Strike-Slip Fault Right-lateral strike-slip faults: movement of opposite plate is to the right

44. Joints • Brittle deformation at low pressure • Tension fractures with NO DISPLACEMENT