@article{fdi:010040743,
  title = {{I}ron-bearing phases in a peat-derived duricrust from {B}razil},
  author = {{V}arajao, {A}fdc and {D}a {C}osta, {G}. {M}. and {V}arajao, {C}. {A}. {C}. and {M}eunier, {J}. {D}. and {C}olin, {F}abrice},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he formation of aluminium-substituted iron-minerals is still subject to debate. {W}e report a case study in a {H}umic {G}leysol soil profile, developed on a sedimentary saprolite, from a basin floor on the {U}beraba {P}lateau ({M}inas {G}erais {S}tate, {B}razil) where iron-phases are crystallized by a ferruginization process. {T}he mineralogical and chemical properties were investigated by {X}-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and {M}ossbauer spectroscopy. {T}he specific surface area ({BET} method) and cation exchange capacity ({CEC}) were also determined. {T}he soil profile is mainly composed of gibbsite, kaolinite and amorphous alumino-silicate phases, the latter being more frequent in the {H} horizon where the organic carbon content is greater. {T}he surface area and {CEC} values are also greater in the {H} horizon (58.6 m(2)g(-1) and 4.65 mol(c)kg(-1), respectively) which indicates an increase in porosity caused by the presence of 20.8% of organic matter and amorphous materials. {G}oethite occurs as a secondary mineral in the {H} horizon and as the main mineral in the duricrust in association with haematite. {T}he omnipresence of aluminium in the environment (24.6-46.2% of {A}l2{O}3) resulted in {A}l-substitution in all iron-bearing phases but the goethite from the {H} horizon has the greatest {A}l-for-{F}e substitution, with at least 20 mole per cent of aluminium. {I}n spite of the greater microporosity and wetness of the {H} horizon, the immediate contact with the richest {A}l-source (gibbsite) favours the precipitation of unusually greatly {A}l-substituted goethite instead of haematite in this horizon.},
  keywords = {},
  booktitle = {},
  journal = {{E}uropean {J}ournal of {S}oil {S}cience},
  volume = {58},
  numero = {5},
  pages = {1096--1106},
  ISSN = {1351-0754},
  year = {2007},
  DOI = {10.1111/j.1365-2389.2007.00891.x},
  URL = {https://www.documentation.ird.fr/hor/fdi:010040743},
}