Accomplishment Based Renewal: Magmatic Processes at Mid-Ocean Ridges

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ABSTRACT (0524922) Sinton Intellectual Merit: This project investigates processes that control the chemical composition and mineralogy of mid-ocean ridge volcanic rocks. It specifically addresses how variations in melting of upwelling mantle affect the composition of primary magmas and how these magmas are changed in chemistry and mineralogy by cooling and crystallization at different depths in the crust and mantle. This research combines theoretical models, geophysical constraints on the thickness of the crust, and chemical and petrographic analyses of natural samples from the Galapagos Spreading Center and Icelandic Western Volcanic Zone mid-ocean ridges. These contrasting sample sets will allow evaluation how variations in spreading rate, mantle source composition, mantle temperature, crustal thickness and variations in eruptive style create physical and chemical variations in mid-ocean ridge lavas at specific locations along spreading ridges. The work involves determining the relative proportions of individual minerals (olivine, feldspar, pyroxene and oxide) in selected samples and analyzing for the chemical compositions of these minerals as well as of whole-rock samples. Specific sample sets include: (1) unusual submarine lavas from the Galapagos area with very high aluminum contents; (2) at least two other sample sets from the Galapagos area that represent samples with varying distance from the mantle anomaly that is responsible for the Galapagos archipelago; and (3) Two eruptive units close in age and location from the subaerial mid-ocean ridge exposed in Iceland. The Icelandic work will investigate samples erupted at different times during single eruption episodes, which will allow us to address eruptive processes in ways not possible in the Galapagos area. It also permits investigation of variations in mantle sources, melting conditions and magma evolution processes over short spatial (~20 km) and temporal (~400 years) scales.Broader Impacts: This work supports a faculty member and graduate student at the University of Hawaii. Student training will include a wide range of analytical and petrological techniques and theory, as well as an introduction to Icelandic geology. Undergraduate students will be involved in the preparation of rock samples for chemical and petrographic analysis. Results of this research will be incorporated into classroom teaching and community presentations and published in widely accessible peer-reviewed journal articles.