Alteration and very-low grade metamorphism are common processes in volcanic rocks. The large volume of fluid involved leads to drastic changes in porosity and deposition of important economic deposits. In addition, altered volcanics transport large quantities of water to great depths in the Earth by subduction processes and are thus a major factor in the evolution of fundamental geodynamic processes. For these reasons, we propose a symposium aimed at a better understanding of the alteration and very-low grade metamorphism of volcanic rocks including quantification of corresponding processes. The proposed interdisciplinary symposium should bring together petrologists, economic geologists and other geoscientists to address processes in recent as well as fossil systems all over the world. The symposium will involve various aspects of alteration and metamorphism ranging from field studies to thermodynamic modelling.