This project will conduct spatial, thermal, and compositional analyses of fluid inclusions in plutonic samples from Ocean Drilling Project core 735B and a suite of metaplutonic and diabase samples recovered from the Atlantis II fracture zone. Microthermometric results of fracture-bound fluids in these ductily-deformed and hydrothermally altered rocks will be used to develop a model for fracture-fluid evolution in the high- temperature root zones of submarine hydrothermal systems associated with slow spreading environments.