We report a new procedure for the analysis of oxygen and hydrogen isotopes in water that is experimentally produced in high-temperature high-pressure experiments via wavelength-scanned cavity ring down spectroscopy (WS-CRDS). This work builds on a recently developed method by Affolter et al. (2014) for the analysis of fluid inclusions in cave carbonate deposits. We show that a simple modification of the setup allows extraction and analysis of experimentally produced fluids from their noble metal capsules in an online water extraction line, and analyse them without further treatment of the water molecule prior to isotope determination. We tested this method on standard water reference samples and water experimentally generated during thermal decomposition of hydrous minerals in hydrothermally altered rocks. Preliminary results indicate that fluids released from hydrothermally altered rocks at conditions of 640 °C and 100 MPa maintain isotopic compositions close to those of the meteoric water involved in their alteration. Further development and application of this method will offer great insights into the origin and evolution of water in magmatic and metamorphic systems, and be a valuable tool in the determination of experimentally derived fluid-melt and fluid-mineral isotope fractionation.
