1. Foliation and lineation Goal: To interpret some common types of foliation and lineation in deformed rocks

2. Typically forms in metamorphic rocks Combines mineral “Shape-preferred orientation” and compositional banding Foliation: mesoscopically penetrative subparallel alignment of planar fabric elements in a rock

3. A. Foliation nomenclature S 0 = bedding S 1 = first foliation S 2 = second foliation....

4. Continuous vs. discontinuous foliations

5. B. Continuous foliations 1.Slaty cleavage and phyllitic cleavage 2.Schistose foliation 3.Gneissic banding

6. 1. Slaty Cleavage

7. Pressure solution vs. rotation M-domains Q-F-domains Can have volume loss > 50%

8. Sample with discrete M-domains and Q-F-domains

9. 3. Schistose foliation Individual mineral grains are visible May see M-domains and Q-F-domains with naked eye. Metamorphic reactions help grow aligned minerals

10. 4. Gneissic foliation Shape-preferred alignment of minerals and compositional banding Requires compositional segregation... not fully understood –Pre-existing sedimentary –Metamorphic/igneous segregation

12. C. Discontinuous foliations 1.Spaced cleavage 2.Crenulation cleavage

13. 1. Spaced cleavage Array of anastomosing, fracture-like partings Generally weak deformation at low temps

14. 2. Crenulation cleavage mm- to cm-scale folding of a pre-existing foliation Marks a second phase of deformation

16. Part-II Lineations — Outline A.Lineation nomenclature B.Elongation lineations C.Intersection lineations D.Other linear elements

17. A. Nomenclature L 1 = first lineation L 2 = second lineation

18. B. Elongation lineations 1.Mineral lineations 2.Elongated clasts

19. Preferred alignment of tabular or acicular mineral grains Not always a true elongation lineation!!! 1. Mineral lineations

20. 2. Elongated clasts Cobbles Pebbles Sand grains Breccia clasts

21. C. Intersection lineations Form due to the intersection of two planar fabric elements (e.g. S 0 and S 1, S 1 and S 2....) Nomenclature — L 0x1 = S 0 crossed by S 1, L 1x2 = S 1 crossed by S 2....

23. D. Other linear elements 1.Boudinage 2.Mullion structure 3.Fold hinge lines 4.Slickenlines and ridge-in-groove lineations

24. 1. Boudinage Forms due to competency contrast between layers

25. Examples of boudinage

26. 2. Mullion structure Also forms due to competency contrast between layers... different layer orientations

27. Combined boudinage and mullion structure