Mineralogy and geochemistry of granulometric fractions as a tool for studying transformations of the solid phase of soils

A detailed study of mineralogy and geochemistry of bulk samples and granulometric fractions has been carried out <2, 2–5, 5–10, 10–50, 50–250 microns of typical chernozem (Stavropolregion) using a set of methodsincluding X-ray diffraction analysis(XRD), Mossbauer, X-ray fluorescence (XRF)spectroscopy, as an example of the development of instrumental approaches to study the transformation and accumulation of various solid-phase products of soil functioning. Mineralogical analysis of fractions records the distribution of mineral phases in different dimensions. Thus, quartz and feldspar are predominant in the fraction of course and medium silt, smectite is fixed in the fraction of fine silt and the content of mica increases. The clay fraction is dominated by smectite; kaolinite, illite, and quartz are also present. In contrast to the parent rock in soil horizon, there decrease in the degree of crystallization of the smectite was observed, the formation of mixed layers is not observed. In addition, in clay fraction of soil horizon Fe hydroxide (lepidocrocite) was determined in trace amounts. A detailed analysis of the state of iron compounds and the distribution of iron oxides in granulometric fractions was carried out, the contribution of granulometric fractions to the totalspecific magnetic susceptibility was determined as well. The change in geochemical indices by granulometric fractions is analyzed. Such approach is aimed to developing a system of mineralogical and geochemical indicators of soil formation in order to achieve maximum reliability of possible paleo reconstructions based on solid-phase memory of soils.