The prehnite-pumpellyite facies is a metamorphic facies typical of subseafloor alteration of the oceanic crust around mid-ocean ridge spreading centres.
It is a metamorphic grade transitional between zeolite facies and greenschist facies representing a temperature range of 250 to 350 °C and a pressure range of approximately two to seven kilobars.
The mineral assemblage is dependent on host composition.
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