Pyrohydrolysis-IRMS determination of silicate chlorine stable isotope compositions. Application to oceanic crust and meteorite samples

The method was further applied to ten silicate rocks of various mineralogy and chemistry (meteorite, fresh MORB glasses, altered basalts and serpentinized peridotites) chosen for their large range of Cl contents (70-2156 ppm) and their geological significance. δ37Cl values range between − 2.33 and − 0.50‰. These strictly negative values contrast with the large range and mainly positive values previously reported for comparable silicate samples and shown here to be affected by analytical problems. Thus we propose a preliminary, revised terrestrial Cl cycle, mainly dominated by negative and zero δ37Cl values.