Question

In Bowen’s Reaction Series, which mineral is the first to crystallize from a cooling silicate magma?

• A. Quartz
• B. Olivine
• C. Biotite
• D. Muscovite

Hint:

In Bowen’s Reaction Series, remember the order of the discontinuous branch: {Olivine → Pyroxene → Amphibole → Biotite}. The mineral that crystallizes first from magma is {Olivine}.

Answer 1

The Correct Option is B

Concept: Bowen’s Reaction Series describes the order in which minerals crystallize from a cooling magma. As magma cools, minerals form at different temperatures depending on their chemical composition. The series is divided into two main branches:

• Discontinuous series: Olivine → Pyroxene → Amphibole → Biotite
• Continuous series: Calcium-rich plagioclase → Sodium-rich plagioclase

Minerals at the top of the series crystallize at the highest temperatures. Minerals toward the bottom crystallize at lower temperatures.
Step 1: Understanding the highest temperature mineral.
At very high temperatures (about \(1200^\circ C\)), the first mineral to crystallize from a cooling silicate magma is Olivine. It is rich in magnesium and iron and forms early during magma cooling.
Step 2: Position of other minerals in the series.

• Quartz: Crystallizes at the lowest temperatures.
• Biotite: Forms later in the discontinuous branch.
• Muscovite: Forms at relatively low temperatures.

Since Olivine crystallizes first at the highest temperature, it is the correct answer.