How Did Large Iron Deposits, Called Banded Iron Formations, Form

Multiple Choice

How did large iron deposits, called banded iron formations, form?

A) hot water circulates along the margins of a caldera
B) groundwater mixes with seawater in the subsurface
C) magma releases metal-rich fluids that replace reactive rocks
D) an increase in oxygen in Earth's atmosphere caused seas to precipitate beds of iron-rich minerals