Читать книгу Isotopic Constraints on Earth System Processes - Группа авторов - Страница 29

It is well known that sustained temperature differences in gases and liquids can measurably fractionate elements and isotopes. The existence of this phenomenon in gases was described theoretically by Enskog (1911) and later confirmed by the experiments of Chapman and Dootson (1917). In the case of liquids, thermal diffusion was first demonstrated experimentally by Soret (1879) who found that ionic salts dissolved in water became measurably enriched at the cold end of an imposed temperature gradient. There have also been studies involving silicate liquids (see, for example, Lesher & Walker, 1986), in which Soret diffusion caused some components (e.g., CaO, MgO, FeO) to become enriched in the colder end of a temperature gradient, while other components (e.g., SiO₂ and alkali oxides) became enriched in the hot end. The earliest evidence of thermal isotope fractionation in a silicate liquid appears to be the study by Kyser et al. (1998), who reported oxygen isotope fractionation in some of the diffusion couples from the Lesher and Walker (1986) experiments.