Question

Select the correct statement(s).

• A. Phenocrysts are found in igneous rocks whereas porphyroblasts are found in metamorphic rocks
• B. Phenocrysts are indicators of crystallization history whereas porphyroblasts indicate metamorphic history
• C. Porphyroblasts are relict grains, relatively larger than matrix minerals in deformed igneous rocks
• D. Poikiloblastic texture is found in igneous rocks whereas poikilitic texture is found in metamorphic rocks

Hint:

Understanding the textures of minerals in rocks provides insight into their formation process, whether igneous or metamorphic.

Answer 1

The Correct Option is A, B

Step 1: Understanding Crystal Textures.
- Phenocrysts are large crystals found in igneous rocks, while porphyroblasts are large crystals found in metamorphic rocks (A).
- Phenocrysts indicate the crystallization history of magma, while porphyroblasts provide information about the metamorphic history (B).
- Porphyroblasts can be relict grains that are larger than the surrounding matrix in deformed rocks (C).
- Poikiloblastic texture is associated with metamorphic rocks, not igneous rocks (D is incorrect).
Step 2: Conclusion.
The correct answer is (A), (B), and (C).