Question

Which of the following deposits is/are linked to magmatic-hydrothermal fluids derived from granitic plutons?

• A. Mississippi Valley-type (MVT) Pb-Zn deposit
• B. Ophiolite-hosted chromite deposit
• C. Komatiite-hosted Ni-Cu sulfide deposit
• D. Greisen related Sn-W deposit

Hint:

Think about which deposit type forms directly from late-stage fluids released by a crystallizing granite, not from mafic or ultramafic magma or basinal brines.

Answer 1

The Correct Option is D

Step 1: Recall what a magmatic-hydrothermal fluid is.
As a granite pluton cools, the last bit of melt is rich in water and other volatiles. This fluid escapes into the surrounding rock and carries metals with it.

Step 2: Sort the four deposits by their parent magma.
MVT Pb-Zn deposits sit in carbonate rocks and come from warm brines moving through sedimentary basins, with no granite involved. Ophiolite chromite and komatiite Ni-Cu deposits both come from mafic to ultramafic magma, not from granite.

Step 3: Match greisen deposits to granite fluids.
Greisen Sn-W deposits form when the fluid squeezed out of a cooling granite alters the rock around it into a mica and quartz rich rock called greisen, and drops tin and tungsten minerals as it does so. This is a textbook magmatic-hydrothermal deposit from a granitic source.

Step 4: Conclude.
Since only the greisen Sn-W case comes from granite derived fluid, the answer is option D alone.
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