Iron oxides in burozems on red-colored deposits in European Russia and the color differentiation of soils

摘要

The composition, content, and color-forming role of iron and manganese (hydr)oxide minerals in the profiles of weakly differentiated soils on Permian red-colored deposits in the northern and southern taiga zones of European Russia (clay-illuvial burozem on leached heavy clays, podzolized raw-humus burozem on red-brown loamy sands, and calcareous raw-humus burozem on carbonate aleurites) were studied. It was found that the differences in the color of genetic horizons of finely textured calcareous and clay-illuvial burozems on red-colored deposits are determined by the content of hematite, the main iron-bearing pigment. The portion of hematite calculated from the spectral characteristics of soils averages 68 and 79% of total iron (hydr)oxides in calcareous and clay-illuvial burozems, respectively. The color of coarse-textured podzolized burozem does not depend on the content of hematite. The active development of iron oxidogenesis occurs presently in podzolized raw-humus burozem. It is manifested in the formation of ferrihydrite 2Fe(2)O(3) . FeOOH . 4H(2)O and feroxyhite delta-FeOOH in the upper part of the profile.