The classification of chemical weathering of basic igneous rocks with respect to mineralogical composition and pedogeochemical conditions

摘要

The chemical composition of superficially weathered layers in mafic rocks (MR) is studied. Proceeding from the chemical effect of MR weathering, three types of weathering are distinguished, which arise from the chemico-mineralogical composition of rocks: (1) timaferric weathering, typical of cenotypal (unchanged) rocks, with Ti, Mn, Fe, and Mg accumulating residually in weathering products; (2) balanced chemical weathering, typical for the paleotypal (hypogenically alter, and containing rock-forming phyllosilicates) rocks, with chemical composition of weathered and fresh rocks almost equivalent; (3) amorphous fersialitic weathering, typical noncrystalline MR, nonsilicate forms of Al, Fe, and Si being relatively accumulated. As shown here, soil weathering is qualitatively similar in genetically different soils, geochemically different horizons, and different bioclimatic provinces of the boreal zone. The chemical results of weathering essentially differ only in the stable reduction conditions of weathering.