Question

The correct combination of textural feature of magmatic rocks with corresponding petrological process is

• A. Exsolution lamellae → Sub-solidus cooling
• B. Reaction rim → Eutectic crystallization
• C. Graphic intergrowth → Quenching of ultramafic lava
• D. Spinifex texture → Peritectic crystallization

Hint:

Exsolution lamellae are typically formed during sub-solidus cooling in magmatic rocks, a process that occurs after the magma has solidified.

Answer 1

The Correct Option is A

Step 1: Understanding the textures and processes.
Exsolution lamellae form when minerals separate at lower temperatures in magmatic rocks, a process known as sub-solidus cooling. This process typically occurs after the initial solidification of the magma.

Step 2: Analyzing the options.
(A) Exsolution lamellae → Sub-solidus cooling: Correct — Exsolution lamellae form during sub-solidus cooling, as minerals separate during cooling.
(B) Reaction rim → Eutectic crystallization: Reaction rims form due to reactions between different minerals, not related to eutectic crystallization.
(C) Graphic intergrowth → Quenching of ultramafic lava: Graphic intergrowths occur in certain types of igneous rocks, but they are not directly linked to quenching.
(D) Spinifex texture → Peritectic crystallization: Spinifex texture is related to rapid cooling of ultramafic lava, not peritectic crystallization.

Step 3: Conclusion.
The correct answer is (A) Exsolution lamellae → Sub-solidus cooling.