Isotopic Abundance Ratio of Oxygen in Refractory Siliceous Stone

Abstract

Isotopic abundance ratio of oxygen in refractory siliceous stone in Japan was investigated. Several methods for separation of oxygen in silicates were criticized, and two of them were investigated experimentally. The first reaction wasSiO2+2Mg=Si+2MgO Cl2/300-310°C→SiCl4↑+2MgO HCl/400-500°C→2MgCl2+2H2O-↓O2electrolyticdecompositionThe yield of this reaction was about 40%. The second reaction wasSiO2+2KHF2 230-300°C/→K2SiF6+2KF+2H2OThe yield of this reaction was about 95%. The second reaction was used for our research.Two thirds of the distilled water was electrloytically decomposed, and the obtained oxygen was recombined with the hydrogen stored in a bomb. The same proportion of the standard water (tap water of Osaka city) was also electrolytically deccmposed and recombined with the hydrogen of the samebomb. Density difference between the both water was determined with a froat. Deviation of the abundance ratio (δ) of oxygen was calculated, and the results were compared with that of P. Baertschi and Sol R. Silverman.Deviation of silica stone and diatomite was +1.2-+13.5, and that of igneous minerals was -3.5--5.7 (gneissic granite, South Dakota=±0.0). According to P. Baertschi, deviation of sedimentary rocks was +2-+22, and that of igneous rocks was 0--4.5. Therefore, Mikawa quartz schist, Tamba recrystallized chert, Kuroda chert, Tamba vein quartz, and Wakasa vein quartz is of sedimentary origin. It is noteworthy that the vein quartz in the Tamba siliceous stone (compound rock) has the value as high as the recrystallized chert in the same rock. Accordingly, this vein quartz it presumed not being of igneons origin but being a segregation product.