Zeolite facies describes the mineral assemblage resulting from the pressure and temperature conditions of low-grade metamorphism. The zeolite facies is generally considered to be transitional between diagenetic processes which turn sediments into sedimentary rocks, and prehnite-pumpellyite facies, which is a hallmark of subseafloor alteration of the oceanic crust around mid-ocean ridge spreading centres. The zeolite and prehnite-pumpellyite facies are considered burial metamorphism as the processes of orogenic regional metamorphism are not required.