Discussion

Match the metal associations in Column 1 to corresponding hosts in Column 2.

Column 1	Column 2
P. Cu, Co, Zn	i. Tectonized dunite and harzburgite
Q. Mn, Co, Ni	ii. MORB
R. Cr	iii. I-Type granite in volcanic arc
S. Cu, Mo, Pb	iv. Pelagic sediment

Answer: A

The correct matching is P-ii; Q-iv; R-i; S-iii.

Cu, Co, Zn: Cyprus-type volcanogenic massive sulphides formed at spreading ridges in MORB (ii).
Mn, Co, Ni: ferromanganese nodules and crusts that grow slowly on the deep sea floor among pelagic sediment (iv).
Cr: podiform chromite in the tectonized dunite and harzburgite of ophiolite mantle sections (i).
Cu, Mo, Pb: porphyry copper-molybdenum deposits, with base-metal veins around them, related to I-type granitoids in volcanic arcs (iii).

Option B swaps the ridge and pelagic settings, and options C and D put chromium outside its ultramafic host.

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