Clay minerals in recent sediments of the World Ocean and their relation to types of lithogenesis

Abstract

Problem of the distribution of clay minerals in water areas of the World Ocean and their relation to different (humid, arid, and volcanosedimentary) types of lithogenesis is considered. It is shown that layer silicates can be used as index minerals for distinguishing types of lithogenesis under conditions of marine sedimentation. Humid marine lithogenesis is represented by sediments of the White, Baltic, Black, and Mediterranean seas. Genetic link of marine clay formation with soil-climatic zones is clearly manifested in recent sediments of the World Ocean. Accumulation of statistic data on the mineral composition of clays allowed us to distinguish two modes of spatial-latitudinal distribution of clay minerals: maximal concentrations of illites and chlorites are confined to high latitudes, whereas kaolinite and smectite accumulate in the equatorial zone. In the arid lithogenesis, the dependence of clay formation on drainage areas is practically absent. The whole process is realized in surficial sediments and bottom waters: under conditions of intense evaporation, especially in closed water basins, the concentration of elements in the medium is enough for the synthesis of layer silicates, such as palygorskite and sepiolite. The processes were studied based on the Paleogene Fergana Bay and bottom sediments of the Sea of Aral, as well as DSDP core materials from the Atlantic (near the western coast of Africa) and Indian (the Arabian Peninsula area) oceans. The investigation of processes of volcanosedimentary lithogenesis was carried out within the East Pacific Rise (on the basis of core materials obtained during cruises of R/V Dmitry Mendeleev and Akademik Kurchatov). The results obtained made it possible to establish authigenic (primarily celadonite) K-Fe mineralization in the most active geothermal zones. The formation of clay minerals has specific features in each of the studied (humid, arid, and volcanosedimentary) types of lithogenesis. This should be taken into consideration during the lithological investigations and the study of clay mineralogy of past geological epochs. Clay minerals (particularly, unstable mixed-layered phases) are actively used as index minerals for paleogeographic and climatologic reconstructions.