We report ³He/⁴He for 150 mid-ocean ridge basalt (MORB) glasses from the Southeast Indian
Ridge (SEIR). Between 81°E and 101°E ³He/⁴He varies from 7.5 to 10.2 R[subscript A], encompassing more than half the
MORB range away from ocean island hot spots. Abrupt transitions are present and in one case the...