What term describes bodies of apparent accumulation of Fe/Mn oxides?

The term that describes bodies of apparent accumulation of iron (Fe) and manganese (Mn) oxides is redox concentrations. This term refers to the presence of these oxides that often form in soil as a result of redox reactions, which involve the reduction and oxidation of minerals during the process of soil formation and in relation to water saturation and drainage conditions.

In wetland or poorly drained soils, the levels of water can fluctuate, leading to anaerobic conditions where Fe and Mn are reduced and then may be remobilized. When conditions change, particularly upon drainage, these reduced forms can oxidize and precipitate as oxides. The accumulation of Fe and Mn oxides brings a noticeable color change and is a key indicator used in soil science to identify certain soil types and conditions.

Other terms provided in the question signify different phenomena. Redox depletions refer to areas where iron has been leached away due to anaerobic conditions, while pore linings describe mineral deposits that form along soil pore spaces, and reduced matrix indicates a general state of soil where iron is in its reduced state but does not capture the specific accumulation of oxides as well as redox concentrations does.