초록

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Abstract ▼ AI-Helper

The weathering of the Namsan granite was studied in terms of sorption process. The Namsan granite consists mainly of quartz, alkali feldspar, plagioclase (${Ab_{85}An_{15}}-Ab_{100}$ and biotite with small amounts of sericite, magnetite and ilmenite. The kinetic factors for altering the g...

The weathering of the Namsan granite was studied in terms of sorption process. The Namsan granite consists mainly of quartz, alkali feldspar, plagioclase (${Ab_{85}An_{15}}-Ab_{100}$ and biotite with small amounts of sericite, magnetite and ilmenite. The kinetic factors for altering the granite body are the proton and hydroxyl ions derived from the reaction of water and mineral. There are two different types of pH variation curves for rocks of different mineral assemblages. when powdered granite was dispersed in distilled water under ambient condition. The sorption-process proceeds by three steps for fresh granite; (1) the initial rapid pH-rise to 10 by the uptake of proton by negatively charged mineral surfaces, (2) the gradual pH-down, and (3) the stable pH tail between 7.1-7.5. For somewhat weathered granites, the sorption proceeds; (1) the initial rapid pH-down to 4.8, (2) the slight pH-rise and slow ph-down, and (3) the stable pH tail between 5.0-5.3. The reaction rate is controlled by the density of adsorbable sites, the solubility of the mineral, pH of the system and formation of amorphous gel and gibbsite. Amorphous gel floates on the surface of the solution while stirring the powdered granite and then is transformed into gibbsite in an hour or so. The pH saturation values for -325 mesh fresh granite from 5 m depth is about pH 10 when rock/water ratio is over 10g/200 ml.