2014-07-092014-07-092007-02LEMOS, Vanda Porpino et al. Vivianite and siderite in lateritic iron crust: an example of bioreduction. Química Nova, São Paulo, v. 30, n. 1, p. 36-40, jan./fev. 2007. Disponível em: <http://www.scielo.br/pdf/qn/v30n1/07.pdf>. Acesso em: 28 fev. 2014. <http://dx.doi.org/10.1590/S0100-40422007000100008>.0100-4042https://repositorio.ufpa.br/handle/2011/5284Lateritic iron crust (LIC) samples from Padauari (AM) were analysed by XRD, optical microscopy and SEM-EDS. The equilibrium of iron minerals (IM) was studied using Eh-pH diagram. It was shown that the minerals of the LIC are goethite (a-FeOOH), vivianite [Fe3(PO4)2.8H2O] and siderite (FeCO3). Carbonate grains are a solid solution of FeCO3-MnCO3. The LIC presents textures and structures of dissolution of IM. The siderite and vivianite are stable from Eh =-0.3 to 0.0 V and pH=5.0-7.5. These results indicate that vivianite and siderite are products of bioreduction through biogenic dissolution of IM, the new conditions of ecosystems of the Amazon region.engAcesso AbertoMinérios de ferroVivianiteSideritaFerro lateríticoBioreduçãoDifração de raio XMicroscopia óticaGoetiteAmazônia brasileiraArtigo de Periódico