Fractionation of Boron Isotopes in Icelandic Hydrothermal Systems

Abstract

Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland, Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibitmore positive values than the meteoric water recharged geothermal systems. ratios can be assessedfromboron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive than the high temperature systems, indicating fractionation of boron due to adsorption of the lighter isotope onto secondary minerals. Fractionation of boron in carbonate depositsmay indicate the level of equilibrium attained within the systems.