Question

In the Bowen's reaction series, which of the following mineral(s) is/are crystallized prior to amphibole?
A. Biotite
B. Clinopyroxene
C. K-feldspar
D. Forsterite

• A. A and B only
• B. A, B and D only
• C. B only
• D. B and D only

Hint:

Remember the order of the discontinuous series: Olivine -> Pyroxene -> Amphibole -> Biotite. A mnemonic could be "Old Pilots Are Boring".

Answer 1

The Correct Option is D

Step 1: Recall the discontinuous branch of Bowen's reaction series. Bowen's reaction series describes the temperature at which different silicate minerals crystallize from a cooling magma. The discontinuous series describes the formation of ferromagnesian minerals.

Step 2: List the minerals in the discontinuous series in order of decreasing crystallization temperature. The order is: 1. Olivine (e.g., Forsterite, D) - Highest Temperature 2. Pyroxene (e.g., Clinopyroxene, B) 3. Amphibole 4. Biotite mica (A) - Lowest Temperature

Step 3: Identify the minerals that crystallize before (at a higher temperature than) amphibole. According to the series, both Olivine (Forsterite) and Pyroxene (Clinopyroxene) crystallize before amphibole.

Step 4: Check the other minerals. - Biotite (A) crystallizes after amphibole. - K-feldspar (C) is on the continuous branch and crystallizes at lower temperatures than amphibole. Conclusion: The minerals that crystallize prior to amphibole are Clinopyroxene (B) and Forsterite (D).