Why is the regional metamorphism of ocean crust in a subduction zone considered separately from regular regional metamorphism?
A)The ocean crust has no hydrous minerals to destroy or recrystallize.
B)Both the basaltic composition and very low geothermal gradient (Low T, Hi P)are unique and lead to different facies than seen in continental rocks.
C)Unlike regular regional metamorphism, this does not occur along plate margins.
D)Because this setting does not involve any strain deformation.

Question

Quizplus · Accepted Answer

The basaltic composition and very low geothermal gradient (Low T, Hi P) in ocean crust subducted in a subduction zone lead to different facies than seen in continental rocks during regional metamorphism. This is because the ocean crust undergoes a unique type of metamorphism due to its composition and the conditions it experiences in the subduction zone.

Why Is the Regional Metamorphism of Ocean Crust in a Subduction