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- Total number of questions : 2
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Mining Geology [ Question No: 1 To 2 ] :
Which one of the following mineral associations is diagnostic of the highly-oxidized zone of a weathered primary base metal vein?
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 |
Total number of questions : 2
Number of answered questions : 0
Number of unanswered questions : 2
Mining Geology [ Question No: 1 To 2 ] :
Which one of the following mineral associations is diagnostic of the highly-oxidized zone of a weathered primary base metal vein?
Your Answer : (Not Answered)
Correct Answer : A
The association diagnostic of the highly oxidized zone is smithsonite, malachite, anglesite.
Above the water table, oxygenated water breaks down the primary sulphides of a base metal vein, and zinc, copper and lead are re-deposited as oxidized minerals: smithsonite (ZnCO3), malachite (Cu2CO3(OH)2) and anglesite (PbSO4). All three are secondary oxidation products of the very metals a base metal vein carries.
Calcite, fluorite and pyrite are primary vein gangue and sulphide, unaltered. Chalcocite belongs to the supergene enrichment zone below the water table, which is reducing, and realgar is a sulphide. Goethite is an oxidation product, but orpiment is an arsenic sulphide and boehmite is an aluminium hydroxide of bauxites, not of base metal veins.
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 |
Your Answer : (Not Answered)
Correct 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.
Marks
Total number of questions : 2
Number of answered questions : 0
Number of unanswered questions : 2