A Lu-Hf Isotopic Investigation of the Origin and Evolution of the Indian Ocean Mantle Domain

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Under this award, the PI will attempt to constrain the evolution and origin of the unusual Indian Ocean mantle domain by determining the initial hafnium isotope compositions and Lu and Hf concentrations of old oceanic crustal basalts from 21 DSDP/ODP drill sites and two Tethyan ophiolite complexes already studied for Sr, Nd and Pb isotopes. Establishing the Hf isotopic composition of old Indian Ocean and Tethyan crust will help to determine when and where this isotopic signature first appeared in the Indian Ocean mantle domain, and if it was present in the composition of Tethyan crust produced before the opening of the Indian Ocean basin. It will also help to determine whether the distinct composition of the Indian Ocean mantle domain is primarily derived from subducted, deeply recycled components that have undergone extensive mixing and homogenization in the mantle, or whether it more likely derives from shallow contamination via the foundering of local Gondwanan continental lithosphere, which has evolved in isolation from the convecting mantle for billions of years.