84 12.3 Mineral Resources

Sea salts are generated from from seawater evaporated in ponds. About 1/3 of all table salt (NaCl) in the world comes from evaporation seawater. Other economically significant mineral derivative from seawater evaporation operations include gypsum and salts of potassium, magnesium, iodine, and bromine.

Iron-manganese nodules are hydrogenous rocks that precipitated from seawater. They form very slowing (taking millions of years to form fist-size nodules, Figure 12.3.1). However, large regions of abyssal plains in the deep ocean are covered with them, particularly in the southern Pacific Ocean.. Samples collected show that they are rich in iron, manganese, copper, nickel, and cobalt. Mining manganese nodules from the deep sea bed is not considered economically feasible at this time. Similarly, deposits around deep sea vents (black smokers) are also rich in valuable metals but mining them is not economically feasible. However, ancient back smoker and manganese nodule deposits have been discovered and mined on land.

Figure 12.3.1. Iron-manganese nodules on the seafloor on an abyssal plain in the South Pacific Ocean.