花崗岩中のカリ長石および黒雲母の微生物風化

概要

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Microorganisms are influential in environmental earth materials. Elemental circulation, environmental changes and the Earth evolution have been associated with microorganisms. In this study, biomineralization of clay minerals and biodegradation of K-feldspar and biotite in granite were identified by XRD, optical microscope, SEM-EDX, TEM and atomic absorption. Bioweathering experiments were carried out using thin section of granite in freshwater with iron bacteria (Toxothrix and Gallioonella) at Omma Formation, Ishikawa Pref., Japan. Microbial mats were formed on the surface of the thin section after 3 and 10 days. Cavities and chaps with bacilli and filamentous bacteria were observed on the surface of feldspars and biotite. Si content was reduced at flake materials (Si:Al=3:2) with bacillio on the surface of K-feldspar. K and Si release was recognized in the solution of both K-feldspar and biotite immersed in the freshwater after a 2 months aging. TEM observation and electron diffraction analyses revealed that kaolinite formed on the surface of K-feldspar immersed in the freshwater after 2 months, suggesting K and Si were released from K-feldspar by bacteria to form kaolinite. The results suggest that the weathering of granite were accelerated by microorganisms to offer the nutrients such as K-ion.
1998-12-28