International Research Fellowship Program: The Origin and Evolution of Mid-Ocean Ridge Segmentation at Normal and Hotspot Affected Ridges

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0757920MittelstaedtThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Eric L. Mittelstaedt to work with Dr. Anne Davaille at Institut de Physique du Globe de Paris (IPGP) in France.Segmentation of the global mid-ocean ridge system is continually changing with old segments dying and new segments being created. The largest ridge discontinuities are manifest to 1st order as transform faults and to 2nd order as either overlapping spreading centers (OSCs) or non-transform offsets with little or no overlap (NTOs). Observations along the East Pacific Rise, the Mid-Atlantic Ridge, the Juan de Fuca Ridge and the Galapagos Spreading Center indicate that ridge axis segmentation patterns vary with spreading rate and proximity to a hotspot. Fast-spreading and magmatically-robust ridges generally display rapid segment migration and numerous OSCs. In contrast, slow-spreading and magmatically-poor ridges typically have long lived ridge segmentation with very slow migration rates and favor NTOs and small transform faults to OSCs. This research focuses primarily on understanding the processes which control these differing styles of ridge segmentation. Previous separate numerical, laboratory, and theoretical studies have attempted to understand the formation of ridge segmentation as a function of lithospheric deformation or mantle flow patterns. However, an overall theory of ridge segmentation is lacking. We use a joint laboratory and 3-D numerical approach to study the mechanics of ridge segmentation. The laboratory experiments involve imposing extension on a fluid mixture with brittle-ductile behavior, heated from below and cooled on the surface. The numerical models use the finite-element code Citcom with our recent implementation of pseudo-plastic rheology and simplified melting and melt transport. The results of these experiments and simulations will be compared to existing geophysical and geochemical data to provide a better understanding of the creation and evolution of ridge segmentation.