Accumulation of organo-metallic complexes in laterites and the formation of Aluandic Andosols in the Nilgiri Hills (southern India) : similarities and differences with Umbric Podzols

摘要: We have investigated the speciation and distribution of iron (Fe) aluminium (Al) between minerals organic species in A B horizons two Aluandic Andosols with X-ray diffraction, thermal analyses, visible diffuse reflectance Fourier transform infrared (FTIR) spectroscopies, together selective total chemical extractions. The Nilgiri Highlands (south India) formed at expense intensively weathered lateritic formations Eocene. Data revealed that Al Fe were predominantly stored end-weathering products laterites, mainly as gibbsite (hydr)oxides Andosols. These secondary are gradually replaced by organo-metallic complexes topsoil exhibiting andic properties. then indicate formation results from weathering dominant crystalline Al- Fe-(hydr)oxides mediated ligands complexation polyvalent metals following accumulation matter. Such mechanisms therefore similar to those recently ascribed deferralitization freely drained Umbric Podzols (Humus-Podzols) upper Amazon Basin. In present case, large supplies both Fe-bearing provide metal:carbon ratios prevent mobility induce rather than Podzols.