Question

Which one of the following statements is CORRECT?

• A. Banded Iron Formations are of chemogenic origin
• B. Porphyry-type deposits are formed purely by sedimentary processes
• C. Quartz-Pebble Conglomerate hosted gold deposits are formed by supergene enrichment
• D. Fullerene is formed by residual concentration process

Answer 1

The Correct Option is A

To determine the correct statement among the given options, we need to understand certain geological concepts underlying the formation processes of various types of mineral deposits and rock formations.

1. Banded Iron Formations are of chemogenic origin: Banded Iron Formations (BIFs) are sedimentary rocks consisting of alternating layers of iron-rich minerals and silica (or chert). They are formed through chemical processes in the water column in ancient marine settings, primarily during the Precambrian era. These formations are considered to have a chemogenic origin because they are believed to form as a result of chemical reactions, typically involving the precipitation of iron from ocean water, possibly influenced by biological processes like photosynthesis of early microorganisms. Hence, this statement is correct.
2. Porphyry-type deposits are formed purely by sedimentary processes: Porphyry-type deposits are large, disseminated systems of sulfides and are primarily associated with magmatic processes, particularly related to intrusive igneous activity. These deposits form from the cooling of hydrothermal fluids that originate from magmatic sources, making this statement incorrect as it attributes the formation to sedimentary processes rather than magmatic processes.
3. Quartz-Pebble Conglomerate hosted gold deposits are formed by supergene enrichment: Quartz-pebble conglomerate deposits are often the source of placer gold, formed due to erosion and mechanical weathering processes. Supergene enrichment typically refers to the secondary enrichment of minerals at or near the Earth's surface through meteoric waters, which is not how these gold deposits are primarily formed. This makes the statement incorrect as well.
4. Fullerene is formed by residual concentration process: Fullerenes are a form of carbon molecule with a cage-like structure, first discovered in laboratory settings. While natural occurrences of fullerenes exist, they are not formed through residual concentration, which is a process associated with the accumulation of resistant minerals after the removal of more soluble components. Therefore, this statement is incorrect as well.

Based on this analysis, the statement "Banded Iron Formations are of chemogenic origin" is the correct option.