Ferromanganese nodules

Elemental Composition of Ferromanganese Nodules Collected from Freshwater and Marine Sediments 

Elemental Composition of Eerromanganese Nodules Collected from Soils 

A wide range of iron and manganese concentrations is reported for nodules collected from soils and sediments (Table 10.5). The accumulation of iron and manganese in nodules depends on the sources of ambient concentrations in soils. The flux of soluble Fe(ll) and Mn(ll) into aerobic environments and redox fluctuations in soils are mediated by hydroperiod. 

Unique characteristics of ferromanganese nodules and associated oxidation-reduction reactions have been used by soil scientists as morphological indicators to help identify hydric soils (see Chapter 3). These characteristics are termed by soil scientists as redoximorphic features however, various terms such as redox concentrations, redox depletions, and reduced matrix are synonymously used for the oxidation-reduction of iron and manganese and their respective concentrations. We prefer not to define these characteristics as redoximorphic features because oxidation-reduction reactions not only involve iron and manganese but also a range of elements that support biotic communities in the biosphere. 

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Ocean Nodules. A less conventional copper resource consists of deep-sea ferromanganese nodules. These nodules are primarily manganese, but some deposits contain over 1% copper. The nodules occur at many ocean sites, but the most valuable deposits are found in the Pacific Ocean. Although a number of companies are studying methods for recovering values from this source, copper resources from nodules must be considered tentative. World resources are estimated at 0.7 biUion metric tons (8) (see Ocean raw materials). 

Copper exists in crustal rocks at concentrations ranging from about 10 to a few hundred ppm, with 70 ppm being about average. In addition, at least 20 copper minerals have been identified, containing copper in the 0, +1, or -i-II oxidation state. These are primarily sulfides, hydroxides, and carbonates, of which chalcopyrite (CuFeS2), is most common. Copper is also foimd in relatively high concentrations in deep-sea ferromanganese nodules, in many cases at concentrations... 

KEYWORDS ferromanganese, nodules, lakes, trace metals, LA-ICP-MS... 

Ferromanganese nodules have been identified and described in temperate lakes around the world. These nodules were first described by Honeyman (1881) who thought they were fragments of prehistoric pottery. Further investigation showed that the nodules were composed of iron and manganese oxides (Honeyman 1881). 

Ferromanganese nodules found in freshwater lakes show concentric, alternating, iron- and manganese-rich bands radiating out from a central nucleus of detrital rock (e.g. Harriss Troup 1970). The nodules are found primarily in shallow (1-5 meters depth) regions of lakes, in regions with little to no finegrained sediment accumulation (e.g. Kindle 1935). 

Ferromanganese nodules found in Lake George, New Brunswick are the focus of this project. Lake George is situated approximately 35 km southwest of Fredericton (Fig. 1). 

Manganese is an important element in the aquatic environment. It is an essential micronutrient U 2) and is the subject of much interest because its oxides scavenge other heavy metals (3). Of particular interest are ferromanganese nodules, which are abundant in the aquatic environment. These nodules contain high concentrations of cobalt, nickel, copper and other heavy metals (4). 

Figure 6. Plot of the Zn/ Zn and Zn/ Zn ratios in delta notation for ferromanganese nodules from different localities in the ocean (Marechal et al. 2000). The dashed line represents the linear mass fractionation line going through the origin and has a slope of two.

Calvert SE, Price NB (1977) Geochemical variation in ferromanganese nodules and associated sediments from the Pacific Ocean. Mar Geochem 5 43-47... 

Variability of U and some trace elements in ferromanganese nodules of the Clarion-Clipperton zone (Pacific Ocean) and mechanism of their formation... 

We studied two sites of samples. Firstly, the element s distribution in the ferromanganese nodules and adjacent bottom sediments has been investigated after undisturbed sampling by grabs. Secondly, dimension distribution of discoid, plate, and ellipsoid nodules, as well its fragments and crusts discovered after seagoing dreged samples. 

The characters of each element s distribution in ferromanganese nodules and adjacent sediments are different and... 

The ferromanganese nodules sho w a marked increase (up to 10 - 100 times) in manganese, cobalt, nickel, zinc, and copper concentrations (Guliy 2004). In contrast, the U and Th contents in the nodules show a weak increase (less than 2 times). Manganese, iron, cobalt, nickel, zinc, lead, and copper in the nodules are subdivided on the basis of character of their correlation into two main groups Mn, Ni, Zn, Cu and Fe, Pb, and Co. However, our results do not show any strong correlation between these elements and U, Th, and Ra. 

Guliy, V. 2004. Peculiarities of morphology and composition of ferromanganese nodules and possible mechanism of their formation. Geologist of Ukraine, 3, 61-71. 

Koschinsky, a. 2008. Ferromanganese Nodule Deposits Distribution, Composition and Origin / International Symposium Shaping the Future Deep-Sea Minerals and Mining, (March 9-12, 2008), RWTH Aachen... 

Analysis of ferromanganese nodules from the Clarion-Clipperton zone show... 

Ostwald, J. (1984) Ferruginous vemadite in an Indian Ocean ferromanganese nodule. Geol. Mag. 121 483-488... 

Iron is a common constituent of marine sediments. Magnetite is found in beach sands and iron is coituuoti in glauconitic manne silicates. Iron oxides and sulfides occur where anaerobic conditions and elevated temperatures arc found, as in the hot. salty brines found near rifts. Iron is a major constituent of the ferromanganese nodules. 

Bums, R. G. (1976b) The uptake of cobalt into ferromanganese nodules, soils, and synthetic manganese(IV) oxides. Geochim. Cosmochim. Acta, 40,95-102. 

Dillard, J. G., Crowther, D. L. Murray, J. W. (1982) The oxidation states of cobalt and selected metals in Pacific ferromanganese nodules. Geochim. Cosmochim. Acta, 46,755-9. 

Manceau A, Tamura N, Celestre RS, MacDowell AA, Geoffroy N, Sposito G, Padmore HA. 2003. Molecular-scale speciation of Zn and Ni in soil ferromanganese nodules from loess soils of the Mississippi Basin. Environ Sci Technol 37 75-80. 

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