『Abstract
　Carbonation of partially serpentinized and weathered peridotites was studied experimentally under hydrothermal conditions (T: 200℃, PCO2: 130-180 bars). Experiments were performed in a closed system using whole rock drill core samples (height: 1 cm, diameter: 1 cm) as starting material. The initial samples were composed mainly of meshwork serpentine, relics of primary olivine and an olivine weathering product (deweylite assemblage). Two types of solutions, each with a total salt content corresponding to that of average seawater (35 g/L dissolved salts), were used: (1) a Na-Ca-Cl solution (12.5 g/L CaCl2 + 22.5 g/L NaCl) and (2) a NaCl solution (35 g/L NaCl). After 15-25 days of experimental treatment, the samples were partly covered with carbonates. In addition, noticeable carbonation reactions had occurred below the sample surfaces within zones with thicknesses up to 250μm. In the Na-Ca-Cl solution, both the olivine relicts and the deweylite assemblage were partly replaced by calcite along the surrounding serpentine veins. However, the extent of calcitization was found to be considerably larger for the deweylite assemblage than for the olivine. Bulk fluid analyses show an increase in the Mg and Si concentrations with reaction time. In the NaCl solution, the deweylite assemblage was partly dissolved resulting in large voids within the reaction zone. In contrast, the olivine was replaced by magnesite. Under the conditions of our experiments, the meshwork serpentine was not reactive, but aided fluid infiltration into the rock samples. The experimentally produced microtextures closely resemble those found in natural examples. Our study elucidates the mechanisms by which carbonates form in ultramafic rocks under relatively high PCO2-T conditions and particularly in the presence of Ca-bearing aqueous solutions. The existence of a serpentine meshtexture and the presence of weathering products formed from primary Mg-silicates may have significant beneficial effects on in situ CO2 mineral sequestration in ultramafic rocks.』

1. Introduction
2. Materials and methods
　2.1. Analytical methods
　2.2. Description of the starting material
　2.3. Experimental procedures
　2.4. Aqueous speciation calculations
3. Results
　3.1. Textural characteristics of the reacted peridotite samples
　　3.1.1. After reaction with the Na-Ca-Cl solution
　　3.1.2. After reaction with the NaCl solution
　3.2. Changes in the chemistry of the aqueous solutions
4. Discussion
　4.1. Reaction mechanisms
　　4.1.1. The formation of calcite
　　4.1.2. The formation of magnesite
　4.2. Mobilization of Mg and Si
　4.3. Comparison of the experimentally produced microtextures with natural examples
　4.4. The impact of weathering and serpentinization on the carbonation of ultramafic rocks and some implications for in situ CO2 storage
5. Conclusions
Acknowledgments
References