Geochemical features of genetic types of Quaternary deposits as a basis for geoecological research (on the example of the Syamozero model site, Republic of Karelia)

Abstract

Introduction: The most important basis for ecological and geological studies of various territories is the investigation of the geochemistry of Quaternary deposits. They provide information about the geochemical background and may indicate the natural genesis of elevated concentrations of elements. The aim of this study was the investigation of the geochemical composition of the Quaternary deposits of glacial formations in the south-eastern part of the Fennoscandian shield. Methods: The object of study is located in the southern part of the Fennoscandian shield and acts as a natural background for the located nearby technogenically transformed territories. As part of the study, sampling with the subsequent determination of the complex of the main petrogenic elements and microelements was carried out. The main petrochemical modules and indices have been calculated. Data processing was carried out using multivariate statistics methods: factorial and discriminant analyses. Results and discussion: It was revealed that the genetic types of Quaternary deposits are characterized by a difference in chemical compositions. The greatest dispersion for almost all elements was observed for glaciolimnic deposits. The high dispersion of element contents in glaciolimnic deposits was associated with the long-range transport of fine fractions containing various petrogenetic information. The analysis of petrochemical modules revealed the relative homogeneity of source area, elevated contents of quartz, feldspar, and a low proportion of clay minerals. Discriminant analysis for the main elements showed a relatively weak separation by genetic types. At the same time, silica was the main element separating glacial deposits from glaciofluvial deposits and glaciolimnic deposits. Glaciolimnic deposits were characterized by high content of Fe2O3, MnO, Ti2O. Factor analysis revealed 4 factors that determine the accumulation of trace elements in the Quaternary stratum. The main association of elements was related to the composition of the source rocks. Comparison of trace element composition with clarkes according to K. H. Wedepol revealed the accumulation of V, Cr, Ni, Cu, Bi in all genetic types. Discriminant analysis based on trace elements showed a fairly good separation into genetic types, with elements in the complex becoming the most important predictors. Conclusions: The revealed regularities in the chemical composition of the genetic types of Quaternary deposits allowed to substantiate the separate use of the geochemical background according to the types of deposits in ecological and geological studies. Median values of element contents in Quaternary deposits were proposed as a geochemical background.