Retrieving "Metamorphic Grade" from the archives

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1. Gabbro

   Linked via "metamorphic conditions"

   Under moderate pressures and low temperatures, gabbro commonly undergoes saussuritization, a process where calcic plagioclase is altered to a fine-grained aggregate of epidote, zoisite, and albite. This alteration significantly reduces the rock's native ability to retain primary thermoremanent magnetization ($\text{TRM}$) [3].
   Under higher metamorphic conditions, gabbro can transform into [am…