Spontaneous Oxygen Isotope Exchange between Carbon Dioxide and Oxygen-Containing Minerals: Do the Minerals 'Breathe' CO2?

摘要

The spontaneous isotopic exchange of oxygen atoms between dry powdered (TiO2)-O-16-containing minerals and gaseous (CO2)-O-18 was studied using gas-phase high-resolution Fourier transform infrared absorption spectroscopy (FTIR) of carbon dioxide isotopologues. The absorption rovibrational spectra of all measured carbon dioxide isotopologues were assigned and then used for quantification of the time-dependent isotope exchange of oxygen atoms (O-16) from the surface crystalline lattice of the solid mineral samples with (O-18) oxygen atoms from gaseous (CO2)-O-18. Similar to our previous studies devoted to the isotopic exchange activity of titanium dioxide, we determined that rutile, montmorillonite, siderite, calcite, and basaltic minerals also exhibit unexpectedly significant oxygen mobilities between solid and gas phases. The rate of formation of gaseous (CO2)-O-16 is found to be highly dependent on the nature of the mineral sample. Our previous studies together with the results presented here suggest that such crystal-surface oxygen isotope mobilities can be explained by two mechanisms: the cluster-like structure of finely powdered materials or the existence of oxygen-deficiency sites in the structure of the surface crystal lattice.