Excess ³He and ⁴He in Galapagos submarine hydrothermal waters

Abstract

SINCE the discovery of excess ³He in Pacific deep waters¹, 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 waters^3–5, its presence in the glassy (rapidly quenched) margins of extruded ocean basalts^6,7, 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 Centre^8–10. 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.