dynamic metamorphism

• Dynamic metamorphism is found along major fault planes, due to shearing and are altered. Only forms due to pressure. 

  • Very localised, just 1 or 2 meters next to the fault plane. 
  • Cataclasis involves crushing and grinding of rock into fragments. 
• Fault breccia and fault gouge is low grade dynamic metamorphism, brittle deformation of competent rock. 
• Fault breccia and gouges erode easily if they don’t become cemented and lead to gullies forming where faults are present. There is some conflict between geologists as to whether this is a true metamorphic 
• Mylonite is medium and high grade:

  • At greater depths the pressure and increased temperature along major fault planes produces larger changes. 
  • Mylonite forms by ductile deformation during intense shearing 
  • Common on thrust planes 
• Mylonite:

  • Broken material is drawn into lens shaped fragments that need to be magnified 
  • Surrounded by finer grained matrix made of very fine particles which may have recrystallisation