Collaborative Research: The role of oxygen fugacity in calc-alkaline differentiation and the creation of continental crust at the Aleutian arc

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This proposal seeks to examine the role of oxygen variations in the origin of the calc-alkaline magmas that erupt at subduction-related volcanoes (arc volcanoes). In particular, the PIs seek to determine how oxygen varies during differentiation and degassing, and see how it varies along strike of the Aleutian arc as a function of material derived from the subducted slab. The work will also include an experimental study of the relationship and interplay between H2O and fO2 during magma formation, a critical question with implications for the formation of continental crust. The PIs note that the Aleutian arc features local and regional variations in numerous geochemical features, but lacks the complexities introduced when magmas move through continental crust. The proposed work includes novel (micro XANES analysis of the ferrous/ferric ratio in glasses (a proxy for oxygen content), especially glass inclusions in mineral. Water, CO2 and major and trace elements (including Cl and S) will also be analyzed. The PIs also propose an experimental program in which fO2 is varied at constant water content. The experimental glasses will be analyzed using the same techniques as described for the natural glasses. Broader impacts include a new interactive exhibit at the Smithsonian that will include an on-line component. Material from the exhibits will be incorporated into undergraduate curricula. There will be undergraduate mentoring through REU and/or senior thesis, as well as mentoring of grad students and a post-doc.