『Abstract
To understand the initial reactions of granite in a CO2-saturated
hydrothermal system, experiments were conducted using a batch-type
autoclave over a temperature range of 100-350℃ at up to 250 bar
and numerical computations of phase equilibria based on the experimental
results were carried out. The experiments showed that the dissolution
of granite and the deposition of secondary minerals were encouraged
by the addition of CO2. Solution chemistry
and examination of the granite's surface texture suggested that
its initial dissolution is characterized by the release of Na
and Ca (from the dissolution of plagioclase) and that initial
precipitation occurs by deposition of some secondary minerals
on to plagioclase and/or biotite in the CO2-saturated
system. However, the effect of CO2 was small
at 350℃ owing to the low activity of H2CO3. According to EDX analysis and numerical phase
equilibrium calculations, the secondary minerals formed might
be kaolinite, muscovite, smectite and calcite. That is, the granite
as a whole might have the potential to take-up dissolved CO2. The results suggest that the alteration of
granite under CO2-saturated hydrothermal
conditions has the potential to capture CO2
when it is injected at moderate temperatures (150-250℃) into granite-hosted
rock masses.』
1. Introduction
2. Experimental
3. Results
3.1. Estimation of experimental pressure and amount of CO2 in the system
3.2. Initial pH
3.3. Solution chemistry
Si and Al
Na and K
Ca and Mg
Total iron; Fe
3.4. SEM observations of the granite surface
3.4.1. Quartz surface
3.4.2. Plagioclase surface
3.4.3. K-feldspar surface
3.4.4. Biotite surface
4. Discussion
4.1. Phase equilibrium in granite/water/CO2
system
4.2. Alteration of granite in a CO2-saturated
hydrothermal system
5. Conclusions
Acknowledgements
References