The effect of the carbon dissolution on the crystal structure of a-quartz

Abstract:

Silicon is one of the major and important element that constitutes the Earth’s crust and mantle. An enormous amount of carbon is also contained in the Earth’s interior, which suggests that silicate could be closely interacted with carbon under high-pressure and high-temperature (Sen et al. 2013, PNAS). It is suggested that carbon dioxide is dissolved in cristobalite and the average composition of CO₂-SiO₂ solid solution is C_0.6(1)Si_0.4(1)O₂ High-pressure experiment (Santoro et al. 2014, Nat. Commun.). Furthermore, the first-principles calculations suggested the possibility of successive CO₂ dissolution in cristobalite at ambient pressure (Aravindh et al. 2007, Solid State Commun.). However, CO₂-SiO₂ solid solution at ambient pressure has not confirmed in laboratory experiment. In this study, we mixed amorphous silica and amorphous carbon and synthesized CO₂-SiO₂ solid solution at high-temperature under ambient pressure. Powder amorphous silica and graphite was mixed together in the agate mill in order to be homogenized mixture. They were heated for 1300 ˚C, 3 days under ambient pressure. Then, the samples were quenched at room temperature. The samples of CO₂-SiO₂ solid solution were carefully examined by powder XRD, EPMA measurement, and so on. From the result of the powder XRD, the products were a-quartz. In this lecture, we report the quantity of carbon dissolved in a-quartz and its effect for the crystal structure of a-quartz in detail.