As and Sb behaviour in fluids from various deep-sea hydrothermal systems

As and Sb elements were analyzed in deep-sea hydrothermal fluids collected from the Mid-Atlantic Ridge (MAR), the East Pacific Rise (EPR) and the Lau and Manus Back-Are Basins (BAB) in the South-West Pacific. The results clea rly show that As concentrations in fluids are mostly controlled by phase se paration process. This behaviour of As is in agreement with As speciation d ominated by H3AsO3(aq0) volatile species. Sb seems less affected by phase s eparation process. As and Sb contents in fluids from Vai Lili (Lau Basin) a nd PacManus (Manus Basin) were 10 to 100-fold higher than the values measur ed in Mid-Oceanic Ridge fluids and result from the seawater-acidic rock int eraction. ((C) Academie des sciences/Elsevier, Paris.)