Metamorphic hydrology at 13-km depth and 400-550 degrees C

The progressive metamorphism of a single stratigraphic unit of impure carbonate rock in south-central Maine from conditions of the chlorite zone to conditions of the sillimanite zone involved the following sequence of prograde reactions: muscovite + ankerite + albite --> biotite + calcite + quartz + anorthite component of plagioclase; ankerite + quartz + plagioclase --> calcic amphibole + calcite; biotite + calcite + quartz + amphibole --> diopside + clinozoisite + K-feldspar. The flow pattern of reactive metamorphic fluids through six large outcrops of metacarbonate rock in the chlorite, biotite, garnet, staurolite-andalusite and sillimanite zones was determined by calculating and mapping fluid-rock ratios for numerous samples within each outcrop.