Известия Томского политехнического университета: Инжиниринг георесурсов (Aug 2018)
Transformation of mineral composition of river sediments from sources to mouth of rivers
Abstract
Relevance. The efficiency of mineral exploration is determined by the depth of understanding a matter accumulation and scattering. The study of these processes involves an analysis of mineral and chemical composition of bedrock, the products of their processing in the zone of hypergenesis and their redeposition by water streams. The aim of the research is to reveal the trends of change in mineral and chemical composition of river sediments along the length of rivers. Methods: landscape-geochemical and statistical methods, methods of definition of chemical and mineral composition of river bottom sediments, mathematical modelling. Results and conclusions. The authors have generalized the data on mineral composition of river sediments in basins of the Ob river (in the Russian Federation: the Tom, Aktru, Pravaya Sarala, Kirgizka, Omutnaya rivers) and the Red river (Viet Nam: the Ban Thi, Che Ngu, Day, Namdu, Pho Day rivers), received in 2000-2017. It is shown that the main regularities of changes in the mineral composition of bottom sediments are associated with an increase in the share of quartz from the sources to the mouths of rivers with a length of more than 11-20 km, while reducing the contribution of minerals to the hypergenic resistance index (logarithm of factum of density and hardness) less than 1,26-1,27. It is established that the sites with a characteristic mineral composition of bottom sediments are located downstream from the sites with a conditionally uniform (or slightly variable in long-time period) chemical composition of river water (displacement of the boundaries to 100 km). A conclusion is drawn on the role of composition of bedrocks and the nature of hypergenic geochemical processes in formation of mineral composition of bottom sediments, which determine the conditions for destruction of particles and accumulation of products of interaction in the water-rock system resistant to chemical and physical weathering.
