EXCESS HE-3 AND HE-4 IN GALAPAGOS SUBMARINE HYDROTHERMAL WATERS

SINCE the discovery of excess 3He in Pacific deep waters 1, it has been argued that the source of this anomaly is the mid-depth injection of primordial helium from seafloor spreading centres 1,2. This hypothesis is consistent with the spatial distribution of excess 3He in the deep waters3-5, its presence in the glassy (rapidly quenched) margins of extruded ocean basalts6,7, and the detection of a large 3He excess in a 'thermal plume' (thermal anomaly ∼0.1 °C, sampled using a deep-tow sled) over the Galapagos Spreading Centre8-10. In this report, we summarise 37 measurements of excess helium in hydrothermal waters sampled using the Alvin deep submersible at the Galapagos Spreading Centre during February and March of 1977. © 1978 Nature Publishing Group.