| The micromorphology, compositions, surface chemical properties and element geochemical characteristics of iron-manganese cutans and matrix soils in yellow cinnamon soil, yellow brown earth and red soil were studied by chemical analyses, XRD, SEM and EPMA techniques in subtropical zone in China. Results showed:1. The micromorphological structure of iron-manganese cutan was a thin black film alternating with red and brown, and about 1 mm thick covering on soil particle.The structures of cutan materials were denser, and the boundarys between cutans and matrix soils were clearly. SEM/EPMA analyses showed that the line distributions of MnO2 and Fe2O3 contents in iron-manganese cutan profile were wave-like curves. There were manganese-rich region, iron-manganese-rich region and iron-rich region from outside to inside of iron-manganese cutans in yellow cinnamon soil and yellow brown earth, and they presented alternate belt structures of manganese cutan, iron-manganese cutan and iron cutan. But from outside to inside in the belt tructure of iron-manganese cutans in red soil, there were only iron-manganese-rich region and manganese-rich region.The manganese-rich regions in belt tructures were gradually obvious from south to north. The growth of cutans came from flooding-water environment, and they gradually grew in the oxidation-reduction process. The formation of belt tructure in iron-manganese cutans would probably undergo several great landscape and soil environment changes in yellow cinnamon soil, yellow brown earth and red soil.2. The pH, Feo/Fed, contents of clay, base ions, MnO2, Feo, Fed, Fe2O3, P2O5, Co, Pb, Li, Cu, Zn, Ni, Cd etc. in iron-manganese cutans were notable higher than those in corresponding matrix soils. Heavy metals enriched in iron-manganese cutans especially Co and Pb, this showed that these elements separated from matrix soils and enriched in cutans going with illuvial iron oxides and manganese oxides during the formation of cutans. In cutans, Ba, Co, Cu, Li, Ni, Pb mainly enriched in manganses minerals, and Zn, Cd, Cr and Mo mainly existed in iron minerals.3. The formations of three iron-manganese cutans were different because the difference of their material compositions, soil-forming climate and environment. The soil-forming processes were weak in yellow cinnamon soil, the element transformations of cutans mainly effected by MnO2 which enriched heavy metal elements of Co Pb Cu Cd Ni etc. In yellow brown earth, the effects of iron oxides inceased in addition to MnO2 in cutan formation, and the actions that influenced geochemical acts of heavy elements in cutans was close.The cutans in red soils were wet and acide.The acts that MnO2 enriched heavy elements decreased in the course of cutan formation in red soil, and effects of clay and iron oxide increased. From yellow cinnamon soil to yellow brown earth, the effects of influencing heavy element acts gradually get togather. These factors concentrated andinteracted more violently in iron-manganese cutans of yellow brown earth. But in cutans of red soil, these factors became more dispersed and little interacted.4. The cutans and matrix soils all contained hydromica, kaolinite and 1.4 nm mineral in tested samples. Both vermiculites and 1.4 nm intergrade minerals were present in matrix soils, whereas only vermiculites were detected in iron-manganese cutans in yellow cinnamon soil and yellow brown earth. The 1.4 nm minerals were all consisted of1.4 nm intergrade minerals(HIV) and vermiculites in cutans and matrixes in red soils. fThis suggested that the vermiculites in cutans mainly came from the vermiculites in clays illuviating from the topsoil or changes of 1.4 nm intergrade minerals in clays moving from the matrix soils around cracks in yellow cinnamon soil and yellow brown earth. The contents of organic matter, exchanged bases and pH value were different between cutans and matrix soils, so the factors in the microregions restrained the transforms of vermiculites to 1.4 nm intergrade minerals or led to the chan...
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