Figure 2
pH-Eh mineral stability diagram of different iron-bearing mineral phases and various clays. The blue arrows trace several diagenetic pathways starting in different Fe-bearing protoliths (e.g., sulfates and nanophase oxides), passing by an intermediate phase such as goethite (FeOOH), and ending in hematite (Fe2O3). The diagram shows that mineral maturation toward iron oxides requires hydrolysis and dehydration, which are controlled by changes in pH and Eh. The red arrows trace weathering pathways in the clays forming sedimentary deposits at the surface and subsurface of Rio Tinto.
