Occurrence of talc in soils with high iron content from the south-west of Spain

Abstract

The mineralogy of the clay fractions of 2 soil profiles classified as an Alfic Dystric Eutrochrept (Soil I) and a Xerochreptic Haploxeralf (Soil II) has been determined.

A notable feature of these soils is the presence of talc and the high iron content as goethite, hematite, lepidocrocite, and maghemite. Talc was the most abundant non-iron mineral of the clay fraction of Soil II. In Soil I, talc occurs as a residual phase from the parent material with its persistence in the profile aided by coatings of iron oxides, which inhibit further weathering.

In these soils there is a high proportion of goethite accompanied by hematite. In Soil I the proportion of iron oxides changes within the profile. Another notable feature of this profile is the presence of maghemite in the upper horizons where this is the predominant iron oxide mineral.