This project will study the helium isotope geochemistry of basalts erupted at Reunion and Heard islands and dredged samples from the Southwest Indian ridge, the Southeast Indian ridge, the Central Indian ridge, the Carlsberg ridge, and the Rodrigues triple junction. The project will document (1) the degree of He isotope variation along the ridge, (2) the temporal variation of He4/He3 on a one to one million year time scale for the subaerial history of Reunion island and (3) the He isotope signature associated with the Heard island-Kerguelen hotspot. The results will provide insight into the dynamics of hotspot-upper mantle-lithosphere interaction beneath the Reunion and Heard island hot-spot, and constraints on the chemical geodynamics of the mantle beneath the large-scale Dupal isotope anomaly. The major questions to be addressed are: (1) Is there a distinctive He isotope signature associated with the Indian Ocean? If so, how does it compare to anomalies in the Atlantic and Pacific Ocean? (2) What are the He isotope signature associated with the Reunion and Kerguelen-Heard hotspot systems? (3) Did He4/He3 vary temporally at the island of Reunion? (4) Is the Reunion hotspot signature present in the He isotope compositions of MORB erupted along the Central Indian Ridge?
