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Polymetallic nodules, also called manganese nodules, are mineral concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. As nodules can be found in vast quantities, and contain valuable metals, deposits have been identified as a potential economic interest. [ 1 ]
Nodule is also used for widely scattered concretionary lumps of manganese, cobalt, iron, and nickel found on the floors of the world's oceans. This is especially true of manganese nodules. Manganese and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are concretions instead of nodules ...
The nodules form in a manner similar to pearls; there is a central object around which concentric layers are slowly deposited, causing the nodule to grow over time. The composition of the nodules can vary somewhat depending on their location and the conditions of their formation, but they are usually dominated by manganese- and iron oxides.
Polymetallic nodules on the deep seabed in the CCZ Example of manganese nodule that can be found on the sea floor. Polymetallic nodules are found at depths of 4–6 km (2.5–3.7 mi) in all major oceans, but also in shallow waters like the Baltic Sea and in freshwater lakes. [23] [24] They are the most readily minable type of deep sea ore. [25]
An abundant resource of manganese in the form of manganese nodules found on the ocean floor. [65] These nodules, which are composed of 29% manganese, [66] are located along the ocean floor. The environmental impacts of nodule collection are of interest. [67] [68]
The term "polymetallic ore" also includes nodules, principally Manganese nodules, that do not form as terrestrial deposits but as concretions on the ocean floor. [3] [4] Rocks containing polymetallic ores are often altered or formed by hydrothermal processes — chloritization, sericitization and silicification.
Dorodango – Japanese art form in which earth and water are molded to create a delicate shiny sphere; Gypcrust – Hardened layer of soil with a high percentage of gypsum. CaSO 4 concretions in arid and semi-arid soils; Klerksdorp sphere – Natural nodule-like rock concretions; Martian spherules – Small iron oxide spherules found on Mars
Manganese precipitates in soils in the form of manganese-iron oxide minerals, which promote nutrient and organic matter accumulation due to their high surface area. Manganese is the tenth most abundant metal in the Earth's crust, making up approximately 0.1% of the total composition, or about 0.019 mol kg −1 , which is found mostly in the ...