Geochemical Characterization of Lavas from the 2005-06 EPR Eruption at 9º 50' N: Implications for Magma Genesis, Evolution, and Transport along a Fast Spreading Mid-Ocean Ridge

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ABSTRACTOCE-0819469Intellectual Merit: Since its designation as a RIDGE 2000 Integrated Study Site (ISS) in 2001, the 8°-11° N segment of the East Pacific Rise (EPR) has become one of the best characterized regions of the global mid-ocean ridge (MOR) system. However, even here our understanding of ocean-ridge volcanism has been significantly limited by the lack of geologic, chemical and petrologic data on individual on- and off-axis Fundamental questions remain regarding the spatial and, in particular, the temporal chemical evolution of fast spreading centers. In 2005-06, a submarine eruption occurred within the EPR ISS (9º 47?-54? N) at exactly the same location as the well-documented 1991-1992 EPR. This cyclic eruption provides a unique opportunity for the proposed multidisciplinary study in that it is the first time ridge geologists will be able to evaluate variations in MOR lava geochemistry at one place over a controlled time period (~15 years). Moreover, pre-eruption seismic data, high-resolution mapping and high-precision 210Po-Pb dating of the lavas from the 2005-06 eruption have resulted in its emergence as the best spatially and temporally-constrained MOR eruption in the world. Together with the dense lava sampling completed since 2006, these data provide an unprecedented opportunity to examine the petrologic and geochemical aspects of the eruption as well as the temporal and spatial changes that accompanied this magmatic event.The investigators will search for systematic variations in lava chemistry over space and time, as well as differences in fractional crystallization and mixing between lavas erupted in 2005-06 and those erupted in 1991-92. Melt-hosted xenoliths will be studied to reveal details of the magmatic conditions in the source melt lens, as well as for possible signatures of contamination, degassing and water-magma interactions within the sub-seafloor. The project involves laboratory analysis of existing samples, including isotopic, petrologic and studies of volatiles, halogens and high-precision Pb isotopes.Broader Impacts: This project will provide new quantitative information on the petrologic, geochemical, and thermal evolution of the EPR magma plumbing system, of immediate and significant consequence to achieving Ridge2000 Program goals to integrate and synthesize results across data sets at the East Pacific Rise Integrated Study Site. The project will bring two young scientists into the marine geologic and geochemical field. The principal investigator has been extensively involved in outreach activities over the past decade, and will continue with to co-Principal Investigator to support and develop University of Florida and RIDGE 2000 education and outreach programs both locally and nationally.