This is a two-part project to continue investigation of the sources and petrogenesis of Cretaceous flood basalts in Madagascar and the Deccan Traps of India. It is proposed to complete study of Madagascan lavas and dikes, conducted in collaboration with A. Saunders and M. Storey (U. Leicester, U.K.). Specifically the plan is: (a) to continue Nd, Pb, and Sr isotopic analysis of a subset of 300 well-documented samples; (b) for Mahoney to contribute to a planned 1991 field trip to the major remaining exposures in northern Madagascar; and (c) to conduct isotopic work on selected samples therefrom. The second focus of the proposed work is an isotopic (Pb, Nd, Sr) study of a unique collection of near-primary picritic lavas and associated basalts in the northern Deccan Traps. These samples are markedly enriched in highly incompatible elements compared to the Western Ghats formations. However, their incompatible element patterns suggest that some are likely to be affected little by continental material. Also, because they may represent some of the earliest eruptions in the Deccan, the plan is to obtain high-quality 40Ar-39Ar dates (from R. Duncan, OSU).
