A quantitative analysis by derivative thermogravimetry based on the difference of reactivity in oxygen of Mn2+ ions of iron manganite spinels Mn3-xFexO4 with 0 < x < 1.50 in relation to the occupied site (octahedral B site or tetrahedral A site) permits a cation distribution to be proposed. Kinetics studies on the oxidation process of Mn2+ ions show that the oxidation proceeds by way of a diffusion-controlled reaction for Mn2+ ions located at B sites and by a nucleation-growth mechanism for Mn2+ ions located at A sites. The difference in the kinetics behavior has been attributed to a structural change cation-deficient spinel into multi-phase oxides induced by oxidation temperature.