1. Metamorphism

2. Metamorphic Rocks & the Rock Cycle

3. Types of Metamorphism Mineral Assemblages in Metamorphic Rocks Metamorphic Textures Factors affecting type of metamorphic rock Index Minerals Patterns of Metamorphic Grade METAMORPHIC ROCKS Phase Diagrams

4. Metamorphic Rocks By the end of this lesson you will be able to: Classify metamorphic rocks into two groups. Explain the concept of metamorphic grade. Describe the causes of the different types of metamorphism. Explain how metamorphic reactions occur during metamorphism.

5. Metamorphic Rocks spotted rock hornfels marble metaquartzite slate phyllite schist gneiss List down as many metamorphic rocks as you can remember:

6. Metamorphic Rocks spotted rock hornfels marble metaquartzite slate phyllite schist gneiss unfoliated foliated Which ones are foliated and which ones are unfoliated?

7. Metamorphic Rocks spotted rock hornfels marble metaquartzite slate phyllite schist gneiss unfoliated foliated Which can be formed due to contact metamorphism & which can be formed due to regional metamorphism? Contact metamorphism Regional metamorphism mylonite/fault breccia Dynamic metamorphism

8. Metamorphic Processes Mineral alignment Recrystallisation New minerals formed from metamorphic reactions

9. Metamorphic Reactions muscovite + quartz =feldspar + sillimanite + water vapour reactants products temp by 550 °C (increase in metamorphic grade) PROGRADE REACTION temp by 550 °C (decrease in metamorphic grade) RETROGRADE REACTION reactantsproducts Low temperature mineralsHigh temperature minerals Low temperature minerals Change in stability

10. Metamorphic Reactions muscovite + quartz =feldspar + sillimanite + water vapour reactants products temp by 550 °C (increase in metamorphic grade) PROGRADE REACTION Low temperature mineralsHigh temperature minerals Change in stability Escapes from rock Metamorphic mineral

11. Phase Diagrams Andalusite stability field. Kyanite stability field. Sillimanite stability field. Phase boundary All have same formula but each mineral has a different crystal structure = POLYMORPH Al 2 SiO 5

12. Metamorphism & Metamorphic Reactions 1.Define metamorphism. 2.What does the term metamorphic grade mean? 3.Why do metamorphic reactions occur? 4.What do these reactions typically form? 5.Explain prograde and retrograde reactions using the muscovite + quartz metamorphic reaction. 6.In reality most metamorphic reactions do not return to their original starting point. Why? 7.Metamorphic reactions are slow. What could cause them to speed up and how is this done? 8.What is a phase diagram and what does it show? (note: explain these words - phase/phase transformation/ stability field - using the kyanite, andalusite & sillimanite example) 9.Why might a mineral be termed metastable? 10.Describe the differences between the three types of metamorphism.

13. Metamorphic Rocks The intended learning outcomes from last lesson were to be able to: Classify metamorphic rocks into two groups. Explain the concept of metamorphic grade. Describe the causes of the different types of metamorphism. Explain how metamorphic reactions occur during metamorphism.

14. Put these metamorphic rocks into 2 groups – unfoliated & foliated. Classify metamorphic rocks into two groups. schist mylonite fault breccia spotted rock hornfels slate phyllite marble gneiss metaquartzite migmatite Unfoliated 1. Fault breccia 2. Spotted rock 3. Hornfels 4. Marble 5. Metaquartzite Foliated 1. Schist 2. Mylonite 3. Slate 4. Phyllite 5. Gneiss 6.Migmatite

15. Classify metamorphic rocks into two groups. Put these metamorphic rocks into a Venn diagram to show whether they are formed by contact metamorphism or regional metamorphism, or by both. schist mylonite fault breccia spotted rock hornfels slate phyllite marble gneiss metaquartzite migmatite ContactRegional Schist Slate Phyllite Gneiss Migmatite Spotted rock Hornfels Marble Metaquartzite Dynamic Fault Breccia Mylonite

16. Explain the concept of metamorphic grade. Put these regional metamorphic rocks into a linear order to show increasing metamorphic grade. schist slate phyllite migmatite gneiss slate phylliteschistgneissmigmatite Increasing metamorphic grade

17. Describe the causes of the different types of metamorphism. Write the cause of the metamorphic change next to the types of metamorphism below. Dynamic metamorphism - Contact metamorphism - Regional metamorphism - Localised deformation along fault zones. Heat from igneous intrusions. Heat & pressure due to orogenesis.

18. Explain how metamorphic reactions occur during metamorphism. Use clay & its polymorph andalusite to show how metamorphic reactions occur. Prograde reaction Retrograde reaction ClayAndalusite Clay

19. Metamorphic Rocks By the end of this lesson you will be able to: Identify & describe the metamorphic textures associated with the different types of metamorphism. Explain how these metamorphic textures form.

20. Dynamic Metamorphism Fault Breccia Mylonite elongation of minerals foliation large, angular fragments (fault breccia) fine-grained matrix (fault gouge)

21. Contact Metamorphism A B CDE F G

22. A B CD E G H HDBF Interlocking coarse calcite crystals (granoblastic) Interlocking quartz grains (granoblastic) Interlocking quartz, feldspar & mica grains (granoblastic) Partially recrystallised clay minerals (unfoliated) Cordierite minerals (porphyroblastic) Recrystallised mica minerals (unfoliated) E F

23. Metamorphic Texture Recrystalline Interlocking Medium-grained Granoblastic Non-foliated Metamorphic Minerals Quartz Feldspar Mica Sillimanite

24. Metamorphic Texture Recrystalline Interlocking Medium-grained Granoblastic Non-foliated Metamorphic Minerals Calcite

25. Schist Increasing metamorphic grade Slate Phyllite Regional Metamorphism Schistosity (foliation) Slaty cleavage (foliation) Clay & mica

26. Metamorphic Texture Partially recrystalline Fine-grained Foliated Slaty cleavage (porphyroblastic) Metamorphic Minerals Quartz Clay Mica Pyrite (porphyroblasts)

27. Metamorphic Texture Partially recrystalline Fine-grained Foliated Slaty cleavage Metamorphic Minerals Quartz Clay Chlorite Mica

28. Metamorphic Texture Recrystalline Interlocking Medium-grained Foliated Schistosity Porphyroblastic Metamorphic Minerals Quartz Feldspar Mica Garnet

29. Gneiss Migmatite Granite Increasing metamorphic grade Regional Metamorphism Gneissose Banding (foliation)

30. Metamorphic Texture Recrystalline Interlocking Coarse-grained Foliated Gneissose banding Metamorphic Minerals Quartz Feldspar Hornblende Augite

32. Metamorphic Rock Identification Checklist for describing metamorphic rocks A – H: 1.Texture Recrystalline Interlocking Grain size (coarse >2mm, medium 2mm-0.05mm, fine <0.05mm) Granoblastic Porphyroblastic Foliated (slaty cleavage, schistosity, gneissose banding) 2.Mineralogy Quartz, feldspar, hornblende, augite Chlorite mica, muscovite mica, biotite mica, andalusite, garnet

33. A.B.C. D.E.F.

34. Metamorphic Rocks The intended learning outcomes from last lesson were to be able to: Identify & describe the metamorphic textures associated with the different types of metamorphism. Explain how these metamorphic textures form.

35. Thin section of a metamorphic rock Identify & describe the metamorphic textures associated with the different types of metamorphism. 1. Describe the texture of this rock. 2mm 2. Name this rock. 3. How did this rock form?

36. Andalusite Cordierite Identify & describe the metamorphic textures associated with the different types of metamorphism. 1. Describe the texture of this rock. 2. Name this rock. 3. How did this rock form? Thin section of a metamorphic rock Clay

37. Metamorphic Rocks By the end of this lesson you will be able to: Interpret pressure-temperature graphs. Recognise the type of metamorphism from the patterns of changing metamorphic grade. Use index minerals to indicate the direction of increasing metamorphic grade & the location of metamorphic mineral isograds.

38. P-T Graph Slate Phyllite Schist Gneiss Igneous Spotted Rock Hornfels CONTACT METAMORPHISM Fault-breccia Mylonite DYNAMIC METAMORPHISM REGIONAL METAMORPHISM

39. Metamorphic Mineral Isograds Chlorite Biotite Garnet Staurolite Kyanite Key: isograd Increasing metamorphic grade Index minerals North Chlorite zone Biotite zoneGarnet zone Staurolite zone Kyanite zone

40. Contact Metamorphism concentric metamorphic zones associated with a batholith index minerals (andalusite, cordierite & sillimanite) hornfels at contact (granoblastic texture) GRANITE Metamorphic aureole UNALTERED COUNTRY ROCKS Increasing metamorphic grade andalusite cordierite sillimanite

41. Regional Metamorphism Increasing metamorphic grade linear metamorphic zones not associated with a batholith index minerals (muscovite mica, chlorite mica, biotite mica, garnet, staurolite, kyanite & sillimanite) foliated textures (slaty cleavage, schistosity & gneissose banding) Increasing metamorphic grade

42. Phase Diagrams Using the phase diagram: 1.Which mineral is stable at 700°C and 400 Mpa? 2.At what temperature do andalusite & sillimanite coexist in equilibrium at a pressure of 200 Mpa? 3.Which mineral is high temperature, low pressure metamorphic mineral? 4.Which mineral is high pressure, low pressure?

44. Metamorphic Rocks By the end of this unit you should now be able to: Classify metamorphic rocks into two groups. Explain the concept of metamorphic grade. Describe the causes of the different types of metamorphism. Explain how metamorphic processes occur during metamorphism. Identify & describe the metamorphic textures associated with the different types of metamorphism. Explain how these metamorphic textures form. Name metamorphic rocks from their metamorphic texture. Interpret P-T graphs and phase diagrams. Recognise the type of metamorphism from the patterns of changing metamorphic grade. Use index minerals to indicate the direction of increasing metamorphic grade & the location of metamorphic mineral isograds.