Boron Isotope Fractionation between Liquid and Gas at Saturated Water Vapor Line

The first experimental data were obtained on the distribution of boron isotopes between gas and liquid at 100–350°С and the pressure of saturated water vapor, and the effect of pH on this distribution at 100°С was studied. The results showed that the value of δ11Bgas–δ11Bliquid was 5.9, 3.7, 1.1, 0.8, and –1.3 ‰ at 100, 200, 250, 300, and 350°С. In an alkaline solution, the boron distribution coefficient between gas and liquid decreases, and the isotopic shift increases; at 100°C and pH 9.1 it is 17.0. The isotopic composition of the boron of thermal waters of the Mutnovsky geothermal system (Kamchatka Peninsula, Russia) was investigated. In thermal springs, a large spread of δ11B values from 2.8 to 18‰ was determined. A wide range of isotopic compositions can be explained by the fractionation of boron between gas and liquid.