Iron-manganese nodules formation

Table 18.5 Deep-Sea Iron-Manganese Nodule Modes of Formation. ...

Basalt, granite, manganese nodules, shale, flint clay, iron formation materials, phosphate rock, fertilizers Calcareous loam soil, loess, polluted farmland soil, sand soil... 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Giovanoli R. and Arrhenius G. (1988) Structural chemistry of marine manganese and iron minerals and synthetic model compounds. In The Manganese Nodule Belt of the Pacific Ocean Geological Environment, Nodule Formation, and Mining Aspects (ed. P. Halbach). Eerdinand Enke Verlag, pp. 20-37. 

The formation of huge quantities of manganese nodules and crusts on the deep-sea floor is a function of the fact that manganese and iron are relatively abundant in the Earth s crust and migrate from less... 

The stability field of Fe in seawater is best illustrated by the use of an Eh, pH diagram (Fig. 11.4). Solid Fe(OH)3 is shown as the metastable form of iron at the conditions prevalent in sea-water (Eh +0.4 V, pH 8). Actually, akageneite (P-FeOOH) is the more stable form found in deep-sea manganese nodules (see Sect. 11.4.8) but its free energy of formation has not been determined. 

In addition to the above direct contributions of microoi anisms to the formation of ferromanganese nodules, several indirect contributions may also be possible, and may indeed be essential to the formation of extensive ferromanganese deposits, especially those highly enriched in trace metals other th2in iron and manganese. For example, the most extensive deposit of... 

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