A Detailed Chemical and Isotopic Investigation of Mesozoic Atlantic MORB

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A DETAILED CHEMICAL AND ISOTOPIC INVESTIGATION OF MESOZOIC ATLANTIC MORB (NSF OCE96-17676) This is a proposal to conduct a detailed chemical and Sr, Nd and Pb isotopic investigation of Mesozoic MORB from the central and North Atlantic. Basalts from most of these drill sites have not been investigated in detail before, and samples from only two drill sites have any isotopic data. The objective of the project is to expand our current investigation of the effects of global mid-Cretaceous plume magmatism on the composition of the oceanic upper mantle. Data for Mesozoic Pacific MORB suggest that the Pacific upper mantle underwent rapid and widespread enrichment in highly incompatible elements and radiogenic Sr soon after the initiation of effusive plateau- and seamount-building volcanism in the mid-Cretaceous around 120 Ma. We wish to constrain the magnitude and geographic extent of this upper mantle enrichment "pulse", as it will provide critical information on the nature of the widespread Cretaceous intraplate volcanism, and will allow us to test models relating the origin of the volcanic event to interactions at the core-lower mantle or lower mantle-upper mantle boundaries.