This project will involve a detailed petrologic, geochemical, and isotopic (O,S,H & C) investigation of the alteration materials in Site 786 core (Izu-Bonin arc), which is the deepest core in an arc basement with the best recovery. The goal is to quantify the nature of the altered material that is being subducted, compare with ophiolite complexes, and obtain constraints on the origin of hydrothermal sulphide ore deposits associated with arc type materials.