Question

Choose the correct combination(s) of textural features of magmatic rocks with corresponding petrological processes from the following.

• A. ophitic texture in dolerite - peritectic crystallization
• B. perthite in granite - slow subsolidus cooling
• C. spinifex texture in komatiite - eruption of ultramafic lava
• D. orthopyroxene rim around olivine in peridotite - eutectic crystallization

Hint:

Magmatic textures such as ophitic, perthitic, and spinifex are key to understanding the cooling history and crystallization processes of igneous rocks.

Answer 1

The Correct Option is A

Step 1: Understanding the question.
This question asks about the relationship between magmatic textures and the processes that create them. Textures like ophitic and perthite are linked to specific petrological processes.
Step 2: Analyzing the options.
(A) ophitic texture in dolerite - peritectic crystallization: Correct — Ophitic texture is common in rocks that crystallized through peritectic crystallization.
(B) perthite in granite - slow subsolidus cooling: Correct — Perthite forms during slow cooling, often in granitic rocks, through exsolution.
(C) spinifex texture in komatiite - eruption of ultramafic lava: Correct — Spinifex texture is a characteristic feature of komatiites, which are ultramafic lava flows that cool rapidly.
(D) orthopyroxene rim around olivine in peridotite - eutectic crystallization: Incorrect — This texture is more related to the crystallization sequence in peridotites and is not a result of eutectic crystallization.
Step 3: Conclusion.
The correct answer is (A), (B), (C). These are correct combinations of textures and the petrological processes responsible for their formation.