The mid-ocean ridge in the Atlantic that separates North American and South America from Europe and Africa is one of the major tectonic plate boundaries on the planet. Only recently has it become obvious that this ridge consists of segments of alternating symmetric and asymmetric spreading, both of which are characterized by different styles of seismicity. A first order question in marine geology is: what causes these differences and do they primarily relate to differences in the mechanical or chemical properties of the crust and underlying mantle. This research sheds new light on this question. It involves an intensive field campaign to sample six adjacent mid-ocean ridge segments that alternate between symmetric and asymmetric spreading. During the campaign, deep submergence tools to identify the presence of previously undiscovered hydrothermal vents will be deployed. Samples of rock and glass dredged from the seafloor will be examined petrographically for mineral associations and to select samples for geochemical analysis. Selected samples will be analyzed for major and trace elements, volatiles, and Sr, Nd, and Pb isotopes. Melt inclusions will also be examined. These data will be used to determine whether magmatic differences that can be related to deeper mantle composition or behavior are the cause of the different types of spreading. Broader impacts of the work include strong integration of research and education. It will result in the development of a course on mid-ocean ridge science for undergraduates that includes analytical laboratory and seagoing field components, with course materials being posted on the web for dissemination. It will also directly train over 10 undergraduates, two graduate students, and two early career researchers. Samples and data collected will be made immediately available to the public and resulting geochemical analyses will be posted on a publicly accessible website. The project also involves a strong component of collaboration with French scientists.

National Science Foundation (NSF)
Division of Ocean Sciences (OCE)
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Barbara L. Ransom
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Harvard University
United States
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