Mechanisms of Mg-phyllosilicate formation in a hydrothermal system at a sedimented ridge (Middle Valley, Juan de Fuca)

The results of a detailed mineralogical and geochemical study of the progressive hydrothermal venting at the sedimented, axial rift valley of Middle Valley in the northern Juan de Fuca ridge are offered. The results show a characterization of newly formed phyllosilicates and provide constraints on the mechanisms of clay formation and controls of mineral reactions on the chemical and isotopic compositions of hydrothermal fluids.