ROW: Petrologic Studies of Migrating Ridge-Mantle Heterogeneity Interactions at the Heckle Seamounts, N.E. Pacific

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This study will test the hypothesis that some seamounts form as a result of preferential, off-axis melting within small, low melting temperature heterogeneities embedded within the mantle upwelling beneath spreading centers that migrate in the absolute reference frame. The hypothesis predicts that a systematic variation will be exhibited along the chain which reflects the temporally varying interaction between the seamount and ridge axis sources. The data will be obtained on rock samples dredged during a fourteen day field program on the Heckle seamount and adjacent abyssal hills. Laboratory analysis of the samples for major, trace, rare earth element concentrations and Sr, Nd and Pb isotope ratios. Ar-Ar age dating of selected samples will help constrain the chronology of compositional variations in seamount lavas. %%% Geometry and dimensions of the melt segregation zone beneath spreading centers is a fundamental scientific problem. Direct observation is difficult, but inferences can be made by examining interactions between small seamounts forming near spreading centers and the adjacent ridge axis. The study of one such interaction is being carried out in this project.