Discussion
The characteristic assemblage of granulite facies is :
Answer: D
The characteristic granulite-facies assemblage is orthopyroxene-plagioclase-garnet.
The granulite facies represents high temperatures (above about 700°C) and moderate to high pressures in the deep crust, where hydrous minerals break down. In mafic and intermediate rocks this gives anhydrous assemblages with orthopyroxene (hypersthene), plagioclase, garnet and clinopyroxene; orthopyroxene is the diagnostic mineral.
Omphacite-garnet-lawsonite indicates eclogite or blueschist conditions of high pressure and low temperature. Hornblende-plagioclase-garnet is an amphibolite-facies assemblage, and scapolite-plagioclase-quartz reflects metasomatism of calcareous rocks rather than a facies.
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