Message #14405

[Rebecca]

Blueschist Metamorphism:
Low Temp./High Pressure

Typical Rocks: blueschist
     Blueschist metamorphism occurs at convergent plate boundaries in subduction zones, either under volcanic arcs, or under continents (cordilleran type). Here cold oceanic crust and sediment is rapidly subducted. Pressure increases quickly because of depth, but the temperature lags behind because the rock is being buried faster than it can heat up. Rocks in outcrop appear blue from amphibole mineral glaucophane.