What is the difference between metamorphic grade and metamorphic facies?

Answer 1

A metamorphic grade takes into account only the change in temperature while a metamorphic facies is more specific by showing the change in temperature in relation to the change in pressure and depth. There are three grades: low (250°C-400°C), intermediate (400°C-600°C) and high (above 600°C). Although there are many facies, the major ones are zeolite, hornfels, greenschist, amphibolite, blueschist, eclogite, and granulite. This allows for geologist to easily locate where a metamorphic rock was formed.

Answer 2

Metamorphic grade refers to the intensity of metamorphism a rock has undergone, typically based on factors like temperature and pressure. Metamorphic facies, on the other hand, are specific mineral assemblages that represent a set of metamorphic conditions under which rocks form. In essence, metamorphic grade is the overall level of metamorphism, while metamorphic facies are more detailed representations of specific mineral groups formed under certain conditions.