Question

The diagnostic amphibole in a blueschist facies metabasalt is

• A. hornblende
• B. anthophyllite
• C. glaucochane
• D. actinolite

Hint:

Blueschist facies is characterized by minerals like hornblende and glaucophane, which form under high-pressure, low-temperature conditions.

Answer 1

The Correct Option is C

Step 1: Understanding Blueschist Facies.
Blueschist facies is a high-pressure, low-temperature metamorphic facies characterized by the presence of minerals like glaucophane, actinolite, and hornblende. Hornblende is often a diagnostic mineral in blueschist facies metabasalt.

Step 2: Analyzing the options.
(A) hornblende: Correct — Hornblende is commonly found in blueschist facies and is a diagnostic amphibole in metabasalt.
(B) anthophyllite: This is a magnesium-rich amphibole, but it is not typical in blueschist facies.
(C) glaucochane: This is a mineral associated with blueschist but not typically an amphibole.
(D) actinolite: Actinolite is a green amphibole but is less diagnostic of blueschist facies compared to hornblende.

Step 3: Conclusion.
The correct answer is (A) hornblende, which is a diagnostic amphibole found in blueschist facies metabasalt.