Question

Which one of the following is produced by a closed-system metamorphic reaction between muscovite and quartz?

• A. orthoclase + sillimanite
• B. orthoclase + biotite
• C. plagioclase + biotite
• D. plagioclase + sillimanite

Hint:

In closed-system metamorphic reactions, muscovite and quartz commonly produce orthoclase and sillimanite when subjected to high pressure and temperature.

Answer 1

The Correct Option is A

Step 1: Understanding metamorphic reactions.
The question asks about the closed-system metamorphic reaction between muscovite and quartz. In such reactions, muscovite (a mica) reacts with quartz to form orthoclase and sillimanite under high pressure and temperature conditions.

Step 2: Analyzing the options.
(A) orthoclase + sillimanite: This is the correct answer as it matches the typical products of this metamorphic reaction.
(B) orthoclase + biotite: This is incorrect, as biotite would not form in this specific reaction.
(C) plagioclase + biotite: This is incorrect because plagioclase and biotite are not the products of this reaction.
(D) plagioclase + sillimanite: This is also incorrect because plagioclase is not involved in the reaction between muscovite and quartz.

Step 3: Conclusion.
The correct answer is (A) orthoclase + sillimanite.