Dissolution of kaolinites and accumulation of iron oxides in lateritic-ferruginous nodules: Mineralogical and microstructural transformations
1986; Elsevier BV; Volume: 37; Issue: 2 Linguagem: Inglês
10.1016/0016-7061(86)90025-x
ISSN1872-6259
Autores Tópico(s)Geochemistry and Elemental Analysis
ResumoIn-situ geochemical and structural microanalysis of non-disturbed samples of laterite and mineralogical identifications of microsamples demonstrate an orderly succession of mineralogical and structural transformations. These transformations result in the formation of Fe-nodules. They start from a micaceous phase whose micropores are occupied by hematite. Because the source of iron is external to micas this hematite corresponds to an absolute accumulation (in the meaning of Brewer, 1964). The following transformations constitute a succession of three mineral phases corresponding to relative accumulations with the removal of some components and in-situ reutilization of residual materials. (1) Phase of Fe-kaolinite accumulation during which the structures inherited from micas are preserved. (2) Phase of Al-hematite accumulation resulting from a dissolution of Fe-kaolinite, with development of pedoplasma and vesicular porosity. (3) Phase of accumulation of more or less aluminous goethite which ultimately results in the crystallization of geodes at the borders of voids.
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