Iron pedogenic

Schwertmann U (1985) The effect of pedogenic environments on iron oxide minerals. Adv Soil Sci 1 171-200... 

Terrestrial- pedogenic supergene massive vesicular pisolithic Gt, Hm, Fh soils Laterite Bog iron Ferricrete... 

Almost all rocks contain at least some iron. The more important minerals, in which Fe is a major constituent, are given with their Fe contents in Table 16.1. In all of these minerals except magnetite, iron is exclusively or predominantly in the bivalent state. During weathering, the iron is released from these minerals and secondary , pedogenic iron minerals are formed. The most important ones are Fe-contain-ing clay silicates and Fe oxides but under reducing conditions, Fe carbonates, sulphides and phosphates may also be formed. 

Fe(OH), using Mdssbauer spectroscopy, optical spectroscopy and transmission electron microscopy. Phy. Chem. Min. 22 11-20 McCreadie, H. Blowes, D.W. (2000) Influence of reduction reactions and solid-phase composition on porewater concentrations of arsenic. Environ. Sd. Tedm. 34 3159-3166 McFadden, L.D. Hendricks, D.M. (1985) Changes in the content and composition of pedogenic iron oxyhydroxides in a chronose-quence of soils in Southern Cahfomia. Quart. Res. 23 189-204... 

Schwertmann, U. Kampf, N. (1983) Oxidos de ferro jovens em ambientes pedogeneticos Brasileiros. (Young iron oxides in Brazilian pedogenic environments). Rev. bras. Ci. Solo. 7 251-255... 

Grygar T, van Oorschot IFIM (2002) Voltammetric identification of pedogenic iron oxides in paleosol and loess. Electroanalysis 14 339-344. 

Buffle, J., Zali, O., Zumstein, J. and De Vitre, R.R. (1987) Analytical methods for the direct determination of inorganic and organic species seasonal changes of iron, sulfur, and pedogenic and aquogenic organic constituents in the eutrophic Lake Bret, Switzerland. Sci. Total Environ., 64, 41-59. 

Other molar weathering ratios can be devised to reflect leaching (Ba/Sr), oxidation (Fe0/Fe203), calcification (CaO + MgO/AlaOs), and salinization (Na20/K20). Two of these ratios reflect differential solubility of chemically comparable elements, but calcification ratio quantifies the accumulation of pedogenic calcite and dolomite, and the ratio of iron of different valence gives reactant and product of iron oxidation reactions. In the Precambrian paleosol illustrated (Figure 4), these molar ratios indicate that the profile was oxidized and well drained, but little leached, calcified or salinized. 

Fitzpatrick, R, W. (1988) Iron compounds as indicators of pedogenic processes Examples from the southern hemisphere. In Stucki J. W. et al. (Eds.) Iron in soils and clay minerals. Reidel Publ. Co. Dordi echt Holland, NATO ASI Ser. 217 351-396. 

Stiles, C.A., Mora, C.I. Driese, S.G. (2001) Pedogenic iron-manganese modules in Vertisols a new proxy for paleoprecipitation Geology 29, 943-946. 

Figure 12.3 Possible pathways of Fe(III) oxide formation under near pedogenic conditions. Adapted from U. Schwertmann and R. M. Taylor, Iron oxides, in Minerals in soil environments, ed. J. B. Dixon and S. B. Weed. Copyright 1989 by Soil Science Society of America. Used by permission.

Iron oxides are the most abundant metallic oxides in soils (Schwertmann and Taylor, 1989 Cornell and Schwertmann, 1996 Bigham etal., 2002). Iron oxides usually form via solution from Fe + ions released from Fe(II)-bearing silicates and sulfide minerals on weathering (Oades, 1963 Schwertmann and Taylor, 1989 Cornell and Schwertmann, 1996). Once formed in soil and other natural environments, the mineral phase, composition, and distribution of iron oxides can be continually modified by the alteration of their environments (Schwertmann and Taylor, 1989). Therefore, the formation and transformation of pedogenic iron oxide mineral phases depend on the pedo-environmental conditions under which they have formed. 

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