Question:medium
Which of the following ore types form(s) by magmatic differentiation?
Which of the following ore types form(s) by magmatic differentiation?
Show 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.
Updated On: Jun 1, 2026
- Gold in quartz vein
- Titaniferous magnetite in anorthosite
- Columbite-Tantalite in pegmatite
- Chromite-Pentlandite in pyroxenite
Show Solution
The Correct Option is B, D
Solution and Explanation
Step 1: What magmatic differentiation is.
As magma cools, minerals crystallize in turn and settle out. Ores that form this way grow straight from the cooling melt, often in mafic or ultramafic rocks.
Step 2: Check the magnetite.
Titaniferous magnetite in anorthosite separates out as the magma cools, a clear differentiation product. So B counts.
Step 3: Check the chromite group.
Chromite and pentlandite in pyroxenite settle from cooling ultramafic magma, again by differentiation. So D counts.
Step 4: Reject the others.
Gold in quartz veins comes from hot water fluids, not melt settling. Columbite tantalite in pegmatite forms in the late watery stage, not by simple differentiation. So A and C are out.
Step 5: Final choice.
The magmatic differentiation ores are B and D.
\[ \boxed{\text{B, D}} \]
As magma cools, minerals crystallize in turn and settle out. Ores that form this way grow straight from the cooling melt, often in mafic or ultramafic rocks.
Step 2: Check the magnetite.
Titaniferous magnetite in anorthosite separates out as the magma cools, a clear differentiation product. So B counts.
Step 3: Check the chromite group.
Chromite and pentlandite in pyroxenite settle from cooling ultramafic magma, again by differentiation. So D counts.
Step 4: Reject the others.
Gold in quartz veins comes from hot water fluids, not melt settling. Columbite tantalite in pegmatite forms in the late watery stage, not by simple differentiation. So A and C are out.
Step 5: Final choice.
The magmatic differentiation ores are B and D.
\[ \boxed{\text{B, D}} \]
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