Metamorphic rocks

Metamorphic rocks

1. metamorphism

   • the alteration in mineralogy, chemical composition and/or texture
   • types
     • Regional: result of change in pressure and heat
     • Contact: caused only by heat, only effects rocks along that point
     • Dynamic: caused by faulting and pressure

2. types of metamorphic rocks

   • Greenschist facies
     • form at high temperatures and high pressures
     • examples
       • Slate
         • fine grained non coarse rock, it is dark grey to black in colour and is the lowest grade foliated rock
       • phylitte
         • higher grade of foliation. it has very similar characteristics to slate, but has slightly larger crystals, glossy and splits into sheets
   • amphibolite facies
     • relatively high temperatures and moderate pressures
     • example
       • schist
         • rich in both quartz and feldspar, the high temperatures cause larger crystals to form but the minerals are often too small to be seen
   • granulite facies
     • form at low temperatures and low pressures
     • example
       • gneiss
         • light in colour, very coarse grained rock with poor foliation, granular minerals

3. Foliation

   • this is the deformation of igneous or sedimentary rocks due to pressure casing flat or curvy cleavage planes