粘土圏 : 地質圏と生物圏を結ぶプロセスの場的実体(<特集>地球サブシステムとしての粘土圏の役割 : 環境親和物質としての粘土)

概要

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Once claysphere is formed by weathering of SiO_2/Al_2O_3 rich crust of the Earth, it serves as the reservoir of biologically important cations such as Fe, Ca and Mg. Biological weathering by land invading plants accelerates clay (smectite) formation and thus cation storage. Consequently, the Mg rich carbonate (dolomite) may decrease in the marine sediments. During burial, smectite to illite transformation occurs with the release of Mg. Biospheric processes such as photosynthesis and energetic metabolisms are activated by Mg ; therefore biological availability of Mg may link to biospheric fluctuations. Smectite to illite transformation also releases (interlayer) H_2O by smectite dehydration. This smectite-derived fluid may influence microbial activities in the deep subsurface biosphere. Although geothermal clay cones harbors abundant microbial life, compacted clays such as bentonite barriers for waste disposal may not necessarily attract microbial growth. The pores and surfaces of clays and clay minerals well protect organic materials from degradation. Clay constituents such as smectite bound Fe (III) are utilized for microbial anaerobic respiration. Fe (hydr) oxides may be precipitated via microbial nucleation, however, microbial involvement in clay formation has not been well proven.
日本粘土学会の論文
2003-03-28