Question

Which of the following ore types form(s) by magmatic differentiation?

• A. Gold in quartz vein
• B. Titaniferous magnetite in anorthosite
• C. Columbite-Tantalite in pegmatite
• D. Chromite-Pentlandite in pyroxenite

Hint:

Magmatic differentiation is responsible for the formation of mineral deposits like titaniferous magnetite in anorthosites and chromite-pentlandite in pyroxenites, which crystallize from cooling magma.

Answer 1

The Correct Option is B, D

Magmatic differentiation is the process by which different minerals crystallize from a cooling magma, leading to the formation of distinct mineral deposits.
In this process, minerals crystallize in a specific sequence based on their melting points and chemical composition, which can lead to the formation of distinct ore types.
Step 1: Understanding each option.
- Option (A): Gold in quartz vein: Gold is typically deposited in quartz veins through hydrothermal processes, not by magmatic differentiation. This option is incorrect.
- Option (B): Titaniferous magnetite in anorthosite: Titaniferous magnetite is a mineral that forms in magmatic environments through differentiation, especially in igneous rocks like anorthosite. This is the correct answer.
- Option (C): Columbite-Tantalite in pegmatite: While columbite-tantalite is often found in pegmatites, this mineral group forms through fractional crystallization and is not a direct result of magmatic differentiation.
It forms more specifically in the later stages of crystallization in an evolving magma body, so this is not a primary example of magmatic differentiation.
- Option (D): Chromite-Pentlandite in pyroxenite: Chromite and pentlandite are both typical products of magmatic differentiation in ultramafic rocks like pyroxenites. This is another correct answer.

Step 2: Conclusion.
The correct ore types that form by magmatic differentiation are titaniferous magnetite in anorthosite (B) and chromite-pentlandite in pyroxenite (D). Therefore, the correct answer is (B), (D).
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