Metamorphic Rocks

Understanding the key characteristics of metamorphic rocks.

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  • Created by: Caitlin
  • Created on: 19-05-13 12:44
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  • Metamorphic Rocks
    • Foliated - minerals have a preferred alignment
      • Slate
        • Parent Rock - Shale
        • Clay minerals, Muscovite, Mica, Chlorite, Quartz
        • Fine grained <1mm
        • Low Grade Metamorphism - Low Pressure and Temp
        • Regional Metamorphism
        • Grey, Purple, Green or Black in colour
        • Slaty Cleavage
      • Schist
        • Parent Rock - Shale
        • Medium Grained 1 - 5mm
        • Silvery Sheen
        • Mica crystals at 90 degrees to pressure - Schistocity
        • Medium Grade Metamorphism - Medium Pressure and Temp
        • Regional Metamorphism
        • Muscovite and Biotite Mica, Quartz, Garnet, Kyanite
        • Garnets often form Porphyroblasts
      • Gneiss
        • Parent Rock - Shale
        • High Grade Metamorphism - Highest Pressure and Temp
        • Regional Metamorphism
        • Coarse Grained >5mm
        • Gneissose Banding - segregation of light and dark minerals
        • Biotite Mica, Quartz, K Feldspar, Silimanite, Mafic Minerals
    • Unfoliated - no platy minerals to align
      • Quartzite
        • Parent Rock - Orthoquartzite
        • Quartz grains recrystalise
        • Interlocking crystals formed
        • Crystals are equidimensional = no foliation
        • Granobalstic
        • Sedimentary structure are destroyed
        • Grey or White in colour
        • Other minerals in original rock will change colour
        • Contact or Regional Metamorphism
      • Marble
        • Parent Rock - Marble
        • Calcite crystals grow
        • Granoblastic
        • Medium Graine 1 - 5mm
        • Interlocking Calcite Crystals
        • Pure Limestone results in White Marble
        • Clay Minerals in Limestone results in green or red minerals
        • Sand Grains present in Limestone results in Wollastonite
        • Wollastonite - light green, pinkish, brown, red or yellow
        • Contact or Regional Metamorphism
      • Spotted Rock
        • Contact Metamorphism
        • No  Pressure, High Temp = No Foliation
        • Spots = only partially recrystallised rock
        • Parent Rock - Slate or Shale
        • Slate is the parent = Foliation or Relict Bedding
        • Clay minerals, mica
        • Poorly formed minerals mica, andalusite,graphite) in spots
        • Slaty Cleavage is Slate is the parent rock
        • Fine Grained <1mm
        • Grey, Purple, Green or Black with Darker Spots

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