Manganese nodules and crusts

There are also three principal modes of formation of these deposits. Hydrogenous deposits form directly from seawater in an oxidizing enviromnent. They are characterized by slow growth (about 2 mm Ma ) Manganese nodules tend to form on red clays and 

---

The best known forms of these precipitates are Bog ore, hydrothermal incrustations of manganese and iron, desert hamish, marine manganese nodules and crusts and marine red or brown clay. 

For long timescales the fluctuations in °Be flux are damped out by bioturbation in slowly accumulating sediments or averaged out in very slowly growing manganese nodules and crusts as discussed below. 

Mullineaux, L.S. (1987) Organisms living on manganese nodules and crusts distribution and abundance at three North Pacific sites. Deep-Sea Research, 34, 165-184. 

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... 

Deep-sea Mn nodnles and crusts are amongst the slowest growing minerals on Earth (Manheim 1986). They have a minimum growth rate of 0.8 mm Ma (Puteanus and Halbach 1988) which is eqnivalent to the formation of about one unit cell every year. Shallow-water concretions grow about 10 times faster. Several methods have been used to date deep-sea manganese nodules and crusts (Ku 1977 Mangini 1988). 

Mangini, A., 1988. Growth rates of manganese nodules and crusts. In Halbach, R, Friedrich, G. and von Stackelberg,... 

Table 18.2 Manganese Minerals in Marine Mn Nodules and Crusts. ... 

Let us now consider the effects of Eh-pH conditions on the speciation state and solubility of manganese in aqueous solutions. Manganese complexes have been carefully studied in the last decade, owing to the discovery on ocean ffoors of economically important metalliferous deposits (nodules and crusts) in which Mn compounds are dominant. 

Ferromanganese Nodules and Crusts Table 3 Manganese minerals in marine Mn nodules and crusts. 

---