Reconstruction of Sources in River Sediments in the Lower Part of the Bureya River Based on Geochemical Indices

摘要

The results of studies of the macro- and microelement composition of the riverbed sediments of the Bureya River are presented. Analysis of the changes in the distribution of microelements (rare-earth elements), as well as in the values of geochemical indices (WIP, STI, R, CIA, CIW, PIA, and V), shows that the sediments in different parts of the river were formed by various sources. Thus, the values of the mentioned indices, as well as their trends, allow one to assume that the primary matter sources in the upper (mountain) reaches of the Bureya River are granitoids occurring within the bounds of the river valley. This part of the river shows downstream a regular increase in the fraction of more weathered matter in the erosion area. The indices of chemical weathering in the riverbed deposits of the lower reaches of the Bureya River (the river reaching the submountain plain) do not follow the trend appearing in the upper reaches. The riverbed sediments as such in the lower reaches of the Bureya River are similar in chemical composition to the sediments of the Amur River. The author assumes in view of these facts that the riverbed sediments of the lower reaches of the Bureya River are mainly constituted by the substance supplied by the Amur River.