Metamorphism

Metamorphism

1. Contact

   • High temperatures
     • 200-800°C
   • Low pressure
     • less than 2Kb
   • Found in igneous intrusions (especially batholiths)
     • Zone of changed rock is called a metamorphic aureole
   • minerals have a random orientation
     • spotted slate or hornfels

2. Regional

   • High temperature
     • 200-800°C
   • High pressure
     • 2Kb-8Kb
   • Takes place at destructive plate margins
   • Grade of rock varies
     • Low grade
     • Medium grade
     • High grade
   • high pressures cause the minerals to line up 90° to the direction of pressure

3. Burial

   • High pressure
     • 2Kb-8Kb
   • Relatively low temperatures
     • 0-200°C
   • Takes place over long periods of time
   • Deep burial is an extension of diagenesis
   • Often involves the burial of ocean sediments at subduction zones