Nanoparticles and Nanostructures of Hydrothermal Clay Soils, South of Kamchatka Peninsula

Abstract

Nanomaterials are widely found in nature. Clay soils contain nanoparticles of clay and non-clay minerals, iron oxides, organic substance with sizes less than 100 nm, and they are typical representatives of natural nanomaterials. Samples of hydrothermal clays were derived from East Pauzhetsky and Lower Koshelevsky thermal fields of South Kamchatka. The composition and structure of the samples were studied with x-ray diffraction analysis and scanning electron microscope with energy dispersive spectrometer. We found that hydrothermal clays contained areas composed of mineral nanostructures. The granulometric composition of the samples contained from 5-8 to 28-30% of nanoparticles. The mineral composition of nanofraction consisted mainly of kaolinite, illite, smectites and mixed-layer minerals kaolinite-smectite, opal, iron oxides. Increase in fine particles in the clay leads to a sharp increase in the number of contacts between mineral particles, and as a result high level of porosity and increase in the specific surface area. The sorption capacity and hydrophilicity of newly formed clay soils improves, their plasticity increases. Moreover, the higher the degree of hydrothermal change of rocks and the higher the content of nanoparticles of clay minerals, the lower their permeability. All this determines the hydrothermal clays of thermal fields as the upper impermeable horizon and heat shield in the structure of geothermal deposits. The obtained data can explain the high physicochemical activity of such clays, as well as the concentration of the main ore, alkaline and rare-earth elements in them. This work was supported by the Russian Foundation for Basic Research (Project No. 17-05-01045). This work was supported by M.V.Lomonosov Moscow State University Program of Development.