We report the discovery of a hydrothermal helium-3 plume north of the Indian Triple Junction, on the Central Indian Ridge at 19¿29'S. Water column Δ3He anomalies show a spike of 33.8% at 2460 meter depth, i.e. the highest Δ3He anomaly recorded so far in the Indian ocean.

The helium-3 data are correlated with manganese, giving a Mn/3He ratio of 700 mol/cm3 (3.8¿104 g/cm3 STP). The CH4/3He ratio deduced from available CH4/Mn data in the same area is around 7¿106. These values are close to what is observed on water column plumes on the East Pacific Rise.

On a regional scale, the 3He distribution over the Indian Triple Junction exhibits a strong Δ3He increase at the ridge crest, which appears to spread eastwards through the deep Indian ocean. ¿ American Geophysical Union 1992