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Oxidized Biotite in the Weathering Profile of Andong Cranite  

정기영 (안동대학교 지구환경과학과)
김혜빈 (안동대학교 지구환경과학과)
Publication Information
Journal of the Mineralogical Society of Korea / v.15, no.3, 2002 , pp. 183-194 More about this Journal
Abstract
Biotite and its weathering Products in the weathering Profile of Andong granite were examined using X-ray diffraction, chemical analysis, and electron microscopy. Major weathering product of biotite was oxidized biotite, which is decomposed into kaolinite in the upper part. Discrete vermiculite or hydrobiotite was not detected although minor vermiculite (5%) was randomly interstratified with oxidized biotite. Excess positive charge induced by iron oxidation was balanced by release of Fe (16%) and Mg (12%) from octahedral site and K (13%) from interlayer site. After slight chemical and structural modification induced by iron oxidation, oxidized biotite persists through the weathering profiles with partial decomposition in the upper part of the profile. Formation environments and dissolution experiments of oxidized biotite highly resistant to weathering are required to understand the elemental behavior in the surface environments on the biotite-bearing bedrocks.
Keywords
biotite; weathering; granite; oxidation;
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