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Metamorphism – transformation of one rock type into another<br /><ul><li> Metamorphic rocks – produced from pre-existing s...
 Parent rock – origin of a metamorphic rock</li></ul>See next slides for samples of metamorphic rocks<br />
Norway<br />
China<br />
Lake Huron, Ontario, Canada<br />
Michigan, North America<br />
California, North America<br />
California, North America<br />
Metamorphism leads to changes in:<br /><ul><li> Mineral content
 Texture
 Chemical composition</li></ul>Metamorphic agents are:<br /><ul><li> Heat
 Pressure
 Chemically active fluids</li></li></ul><li>Metamorphism occurs from a few km into the crust all the way down to the upper...
Degrees of metamorphism<br /><ul><li> Low-grade metamorphism : little change in the parent rock
 High-grade metamorphism : identity of parent rock becomes hard to distinguish
 Remember : parent rock should not melt, if it does, then igneous processes (not metamorphic) become involved</li></li></u...
Example of high-grade metamorphism: from shale (top) to slate (top right) to gneiss (right)<br />
Degrees of metamorphism<br />Agents of metamorphism<br />Time<br />low-grade<br />LOW<br />SHORT<br />Heat<br />Pressure<b...
Heat as an agent of metamorphism<br />Heat provides the energy of activation for the chemical transformation in metamorphi...
formation of new minerals </li></ul>Chemical changes are all based on the increased kinetic energies of the ions.<br />
Heat as an agent of metamorphism<br />Temperatures increase with depth at a rate known as the geothermal gradient.<br />He...
The deepest mine in the world<br />The Western Deep Levels Mine in South Africa at 4 km is the deepest in the world.<br />...
What heats up the Earth?<br /><ul><li> Primordial heat – trapped when Earth’s crust first cooled
 Radioactivity – energy released when subatomic particles are spontaneously emitted by radioactive elements
 Solar radiation – absorbed and converted to thermal energy by the Earth’s surface</li></li></ul><li>Primordial heat<br />...
Solar radiation – the Earth’s crust absorbs about 50% of the Sun’s energy<br />
The absorbed solar radiation is distributed unevenly.  The greatest concentration occurs in the tropical belt (red zone).<...
Radioactivity<br />Radioactive elements contribute to Earth’s internal heat.  Background radiation (not enough to harm) ex...
Pressure as an agent of metamorphism<br />Two types of pressure:<br /><ul><li> Confining pressure – experienced by buried ...
 Differential stress – forces are unequal in different directions</li></li></ul><li>Confining pressure is evenly distribut...
 produces a more compact, denser rock</li></li></ul><li>Confining pressure produces rock layers that are undeformed.<br />
Directonial stress deforms rock layers as shown in C.  (the series shows the deformation of sediments deposited in a river...
The layers of rock shown below have been deformed by directional stress.  Such pressure is most active in convergent plate...
Rocks in shallow depths are pulverized when subjected to differential stress. At greater depths, on the other hand, rocks ...
Heat and pressure<br />Heat increases with increasing pressure.  This means that areas of mountain building (continental v...
METAMORPHIC ROCKS<br /><ul><li> definition
 degrees of metamorphism
 agents of metamorphism</li></li></ul><li>Where does metamorphism occur?<br /><ul><li> contact metamorphism
 regional metamorphism
 dynamic metamorphism</li></li></ul><li>Contact metamorphism<br />
Contact metamorphism<br />
Contact metamorphism<br />
Contact metamorphism<br />
Contact metamorphism<br />Granite<br />Gneiss<br />
From limestone to marble<br />
From igneous rocks to marble<br />Syenite<br />(igneous)<br />marble<br />
From sediments to metamorphic rocks<br />
Regional metamorphism<br />Mountain-building:<br /><ul><li> plate tectonics (convergent boundaries)
 directional stresses are involved
 greatest volume of metamorphic rocks are produced in this way</li></li></ul><li>Review of plate tectonics<br />
Regional metamorphism<br />
Regional vs contact metamorphism<br />
Textural changes<br />Texture – size, shape, and distribution of particles that constitute a rock<br /><ul><li> foliated
 non-foliated</li></li></ul><li>Textural changes (foliation)<br />
Types of foliation:<br /><ul><li> rock or slaty cleavage – minute crystals
 schistosity – larger crystals
 gneissic texture – segregation of minerals</li></li></ul><li>Rock or Slaty cleavage<br />
Rock or <br />Slaty cleavage<br />
Rock or Slaty cleavage<br />
Schistocity<br />mica schist – most abundant schist type<br />
Schistocity<br />mica schist<br />
Schistocity<br />
Schistocity<br />
Schistocity<br />
Schistocity<br />
Schistocity<br />talc schist<br />
Schistocity<br />talc schist<br />
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Metamorphism

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Transcript of "Metamorphism"

  1. 1. Metamorphism – transformation of one rock type into another<br /><ul><li> Metamorphic rocks – produced from pre-existing sedimentary, igneous and metamorphic rocks
  2. 2. Parent rock – origin of a metamorphic rock</li></ul>See next slides for samples of metamorphic rocks<br />
  3. 3. Norway<br />
  4. 4. China<br />
  5. 5. Lake Huron, Ontario, Canada<br />
  6. 6. Michigan, North America<br />
  7. 7. California, North America<br />
  8. 8. California, North America<br />
  9. 9. Metamorphism leads to changes in:<br /><ul><li> Mineral content
  10. 10. Texture
  11. 11. Chemical composition</li></ul>Metamorphic agents are:<br /><ul><li> Heat
  12. 12. Pressure
  13. 13. Chemically active fluids</li></li></ul><li>Metamorphism occurs from a few km into the crust all the way down to the upper mantle.<br />
  14. 14. Degrees of metamorphism<br /><ul><li> Low-grade metamorphism : little change in the parent rock
  15. 15. High-grade metamorphism : identity of parent rock becomes hard to distinguish
  16. 16. Remember : parent rock should not melt, if it does, then igneous processes (not metamorphic) become involved</li></li></ul><li>Example of low-grade metamorphism (from shale to slate)<br />Shale (sedimentary rock)<br />Slate (metamorphic rock)<br />
  17. 17. Example of high-grade metamorphism: from shale (top) to slate (top right) to gneiss (right)<br />
  18. 18. Degrees of metamorphism<br />Agents of metamorphism<br />Time<br />low-grade<br />LOW<br />SHORT<br />Heat<br />Pressure<br />Chemical activity<br />HIGH<br />high-grade<br />LONG<br />
  19. 19. Heat as an agent of metamorphism<br />Heat provides the energy of activation for the chemical transformation in metamorphic rocks.<br />Chemical reactions result in:<br /><ul><li>recrystallization of existing minerals
  20. 20. formation of new minerals </li></ul>Chemical changes are all based on the increased kinetic energies of the ions.<br />
  21. 21. Heat as an agent of metamorphism<br />Temperatures increase with depth at a rate known as the geothermal gradient.<br />Hence, degree of metamorphism increases as depth increases.<br />
  22. 22. The deepest mine in the world<br />The Western Deep Levels Mine in South Africa at 4 km is the deepest in the world.<br />At these depths, the rock is actually hot enough to burn human skin. Miners work in pairs- one digging, the other operating a large fan to keep cool.<br />
  23. 23. What heats up the Earth?<br /><ul><li> Primordial heat – trapped when Earth’s crust first cooled
  24. 24. Radioactivity – energy released when subatomic particles are spontaneously emitted by radioactive elements
  25. 25. Solar radiation – absorbed and converted to thermal energy by the Earth’s surface</li></li></ul><li>Primordial heat<br />Earth initially formed as a molten ball of rock. When the surface cooled to become the crust, the heat became trapped.<br />This trapped heat now drives the convection cells in the mantle and the movement of the molten outer core round the inner core.<br />
  26. 26. Solar radiation – the Earth’s crust absorbs about 50% of the Sun’s energy<br />
  27. 27. The absorbed solar radiation is distributed unevenly. The greatest concentration occurs in the tropical belt (red zone).<br />
  28. 28. Radioactivity<br />Radioactive elements contribute to Earth’s internal heat. Background radiation (not enough to harm) exists all around us. Shown at right is a geologist measuring background radiation with a portable Geiger counter.<br />
  29. 29. Pressure as an agent of metamorphism<br />Two types of pressure:<br /><ul><li> Confining pressure – experienced by buried rocks; forces are applied equally in all directions
  30. 30. Differential stress – forces are unequal in different directions</li></li></ul><li>Confining pressure is evenly distributed.<br /><ul><li> squeezes out the spaces between mineral grains
  31. 31. produces a more compact, denser rock</li></li></ul><li>Confining pressure produces rock layers that are undeformed.<br />
  32. 32. Directonial stress deforms rock layers as shown in C. (the series shows the deformation of sediments deposited in a river flood plain)<br />
  33. 33. The layers of rock shown below have been deformed by directional stress. Such pressure is most active in convergent plate boundaries.<br />
  34. 34. Rocks in shallow depths are pulverized when subjected to differential stress. At greater depths, on the other hand, rocks are more ductile and are compressed and elongated rather than crushed.<br />A sample of conglomerate becomes metaconglomerate when subjected to differential stress at depth (note the elongated rock fragments).<br />
  35. 35. Heat and pressure<br />Heat increases with increasing pressure. This means that areas of mountain building (continental vs continental convergent plates) are hotter due to greater pressure.<br />
  36. 36. METAMORPHIC ROCKS<br /><ul><li> definition
  37. 37. degrees of metamorphism
  38. 38. agents of metamorphism</li></li></ul><li>Where does metamorphism occur?<br /><ul><li> contact metamorphism
  39. 39. regional metamorphism
  40. 40. dynamic metamorphism</li></li></ul><li>Contact metamorphism<br />
  41. 41. Contact metamorphism<br />
  42. 42. Contact metamorphism<br />
  43. 43. Contact metamorphism<br />
  44. 44. Contact metamorphism<br />Granite<br />Gneiss<br />
  45. 45. From limestone to marble<br />
  46. 46. From igneous rocks to marble<br />Syenite<br />(igneous)<br />marble<br />
  47. 47. From sediments to metamorphic rocks<br />
  48. 48. Regional metamorphism<br />Mountain-building:<br /><ul><li> plate tectonics (convergent boundaries)
  49. 49. directional stresses are involved
  50. 50. greatest volume of metamorphic rocks are produced in this way</li></li></ul><li>Review of plate tectonics<br />
  51. 51.
  52. 52. Regional metamorphism<br />
  53. 53. Regional vs contact metamorphism<br />
  54. 54. Textural changes<br />Texture – size, shape, and distribution of particles that constitute a rock<br /><ul><li> foliated
  55. 55. non-foliated</li></li></ul><li>Textural changes (foliation)<br />
  56. 56. Types of foliation:<br /><ul><li> rock or slaty cleavage – minute crystals
  57. 57. schistosity – larger crystals
  58. 58. gneissic texture – segregation of minerals</li></li></ul><li>Rock or Slaty cleavage<br />
  59. 59. Rock or <br />Slaty cleavage<br />
  60. 60. Rock or Slaty cleavage<br />
  61. 61. Schistocity<br />mica schist – most abundant schist type<br />
  62. 62. Schistocity<br />mica schist<br />
  63. 63. Schistocity<br />
  64. 64. Schistocity<br />
  65. 65. Schistocity<br />
  66. 66. Schistocity<br />
  67. 67. Schistocity<br />talc schist<br />
  68. 68. Schistocity<br />talc schist<br />
  69. 69. Schistocity<br />talc schist<br />
  70. 70. Gneissic texture<br />
  71. 71. Gneissic texture<br />
  72. 72. Gneissic texture<br />
  73. 73. Gneissic texture<br />
  74. 74. Nonfoliated texture<br />marble<br />
  75. 75. Nonfoliated texture<br />
  76. 76. Nonfoliated texture<br />
  77. 77. Nonfoliated texture<br />
  78. 78. Nonfoliated texture<br />quartzite<br />
  79. 79. Nonfoliated texture<br />quartzite<br />
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