|Ferromanganese nodules on the seafloor. USGS|
Ferromanganese nodules are found more then a mile beneath the oceans where they are usually found in vast quantities on the abyssal plains. Most of these nodules are about the size of the potato although an occasional nodule may be found this the size of your kitchen table. At other times the modules have combined to make a pavement on the ocean floor. For the most part these nodules are composed of iron and manganese oxide, but they can also contain cobalt, copper, and other elements including gold and other precious metals. How these nodules form is actually poorly understood, but they are found in all the oceans of the world as well as its large lakes.
Because these modules are slow growing it takes about 1 million years to add a millimeter to their size, or about the thickness of the wire used in a small paperclip. When an ocean closes the nodules are swept down in the subduction zone to be recycled as new mineral deposits such as the deposits that are associated with all the earth’s suture zones. In the process of being recycled the various minerals are separated from each other forming different kinds of deposits including gold.
|Ferromanganese nodules from the Pacific floor.|
Photo by Marsin Zych
Altogether it is estimated that over millions of years these nodules have produced several billion tons of metal oxides. During the 1970s arose several nations that gave these nodules and a long hard look as a source of metals, but because they are submerged in the depth of 1 to 2 miles they quickly realized that the nodules were not an economic ore deposit.
The recent jump in commodity prices however has created a new interest in mining this resource. By using some technology borrowed from the undersea petroleum industry a company named “Nautilus Minerals Inc.” is the first company to explore the economic recovery of these resources; only their target is not modules is the deposits that are laid down by black smokers. There are other ventures that are now being undertaken in the
Pacific Ocean that are also aimed to commercially mining these undersea resources.
It remains to be seen if any of these ventures are commercially viable, but time will tell!