The diagnostic amphibole in a blueschist facies metabasalt is
Show Hint
- hornblende
- anthophyllite
- glaucochane
- actinolite
The Correct Option is C
Solution and Explanation
Step 1: Understanding blueschist facies metamorphism:
Blueschist facies represents high-pressure, low-temperature metamorphism, typically occurring in subduction zones where oceanic crust is rapidly buried to great depths without significant heating.
Step 2: Evaluating each option:
(A) Hornblende: Common amphibole in amphibolite facies (medium-grade metamorphism). Not diagnostic of blueschist facies
(B) Anthophyllite: An orthorhombic amphibole. Not characteristic of high-pressure conditions
(C) Glaucophane: Sodium-rich blue amphibole. The presence of glaucophane is diagnostic of blueschist facies
(D) Actinolite: Calcium-magnesium amphibole. Not diagnostic of blueschist facies
Answer: (C) glaucophane
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