Saccocia 9313980 The PIs will study oxygen-siotopic and D/H fractionation in serpentine, talc, and brucite from mid ocean ridge environments, ophiolites and alpine peridotites. The results will provide much needed foundation of experimental data to apply stable isotopes in interpreting alteration history of ultramafic rocks. The new data will also lead to an understanding of the mineral-mineral and mineral-water geothermometers. It would also lead to an understanding of the depth of circulation of hydrothermal fluids and impact of serpentinization on tectonic evolution of mid-ocean ridges.