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When I was young!!!

When I was young!!!. Metamorphic rocks are formed from other rocks Which are changed by heat and pressure. Metamorphic Rocks generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following: Pressure Temperature Mineral Rich Fluids

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When I was young!!!

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  1. When I was young!!!

  2. Metamorphic rocks are formed from other rocks Which are changed by heat and pressure

  3. Metamorphic Rocks • generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following: • Pressure • Temperature • Mineral Rich Fluids • The type of metamorphic rock is determined by the parent rock, and the P/T conditions. Metamorphism causes: Growth of new minerals Deformation and rotation of mineral grains Recrystallization of minerals as larger grains

  4. Metamorphic Minerals • Chlorite • Talc • Graphite • Asbestos • Kyanite • Staurolite • Siliminite • Corundum

  5. Contact Metamorphic Rocks generated mainly by temperature at the margins of igneous intrusions..

  6. Index Minerals • Minerals associated with the grade of metamorphism.

  7. Limestone into Marble • Texture - granular. • Grain size - medium grained; can see interlocking calcite • crystals with the naked eye.Hardness - hard, although component mineral is soft (calcite is 3 on Moh's scale of hardness). • Colour - variable - pure marble is white but marble exists in a wide variety of colours all the way through to black • Mineralogy - calcite. • Other features - generally gritty to touch.

  8. Sandstone to Limestone Texture - granular. Grain size - medium grained; can see interlocking quartz crystals with the naked eye. Hardness - hard. Colour - variable - pure quartzite is white but quartzite exists in a wide variety of colours. Mineralogy - quartz. Other features - generally gritty to touch. • Quartzite

  9. Mudstone - hornfels • Texture - granular. • Grain size - medium grained; can see interlocking crystals with the naked eye. • Hardness - hard. • Colour – greys - blacks • Mineralogy – no specific composition. • Other features - generally gritty to touch.

  10. Regional Metamorphism

  11. Foliation • Foliation is formed by the orientation in the rocks. • Foliation is seen as banding in the rocks.

  12. Metamorphic Grades

  13. Slaty • Texture - foliated, foliation on a mm scale. • Grain size - very fine-grained; crystals not visible to the naked eye. • Hardness - hard and brittle.Colour - variable - black, shades of blue, green, red, brown and buff. • Mineralogy - contains mica minerals (biotote, chlorite, muscovite) which typically impart a sheen on foliation surfaces; can contain cubic pyrite porphyroblasts.

  14. Schistose texture • Texture - foliated, foliation on mm to cm scale.Grain size - fine to medium grained; can often see crystals with the naked eye.Hardness - generally hard.Colour - variable - often alternating lighter and darker bands, often shiny.Mineralogy - mica minerals (biotite, chlorite, muscovite), quartz and plagioclase often present as monomineralic bands, garnetporphyroblasts common.

  15. Gneiss texture • Texture - foliated, foliation on a scale of cm or more. • Grain size -medium to coarse grained; can see crystals with the naked eye. • Hardness - hard. • Colour - variable - generally alternating lighter and darker sub-parallel discontinuous bands. • Mineralogy - felsic minerals such as feldspar (orthoclase, plagioclase) and quartz generally form the light coloured bands; mafic minerals such as biotite, pyroxene (augite) and amphibole (hornblende) generally form the dark coloured bands; garnet porphyroblasts common. • Large banding. • Distinct dark and light bending.

  16. Amphibolite • Made mainly of Amphibole. • Other minerals hornblende, Plagioclase and Garnet • Formed when Basalt undergoes high pressure and temperature. • Foliations present

  17. Greenschist • Low grade • Chlorite, epidote, actinolite. • Green in colour. • Changes from the original mafic minerals as water reacts with the minerals

  18. Dynamic Metamorphism

  19. Mylonite • Fine grained rock • Thin laminations • Large porphyrblasts of garnet and k feldspar during metamorphism. • Recrystalised quartz and Mica • Banding is called a ribbon texture

  20. Fault Breccia • Cataclastic rock • Formed by fault movement • Cemented by minerals.

  21. a-sedimentary rocks b-contact metamorphic c-burial metamorphic d-regional metamorphic e-igneous rock

  22. What does metamorphis do? • High Temperatures – Re-crystallisation of the rocks • High Pressure – minerals re-align causing a change in texture

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