The assemblage of albite, chlorite, actinolite, and calcite is most characteristic of which metamorphic facies?

• A. Greenschist facies
• B. Blueschist facies
• C. Amphibolite facies
• D. Granulite facies

Answer: (A)

Greenschist facies. This low-grade metamorphism is defined by minerals stable at relatively low temperatures and pressures, where chlorite is a hallmark mineral that gives the green tint. The assemblage here—chlorite with albite (a plagioclase), calcite, and a low-grade amphibole like actinolite—fits the greenschist range, where calc-silicate and plagioclase-bearing rocks can still host chlorite and actinolite. In higher-grade metamorphism, you’d see minerals like hornblende or pyroxenes (amphibolite) or garnet and pyroxenes (granulite), and blueschist would feature glaucophane and lawsonite at high pressure, low temperature. Hence this assemblage points to greenschist facies.