Identifying Crustal and Mantle Processes in the Central Trans-Mexican Volcanic Belt

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Intellectual Merit: Subduction zones are the sites of much of the Earth's active explosivevolcanism and associated hazards, and also important sites of mass exchange between the crust and mantle, and fundamental agents in the growth of the continental crust and evolution of the crust-mantle system through time. Much attention has been focused on explosive silicicstratovolcanoes, yet less studied mafic monogenetic cones are very common and can be highly destructive. In addition, their mafic composition makes them ideal for study of mantle processes in subduction settings. We propose to do a detailed multi-isotopic study of the historic Jorullo and Parícutin monogenetic volcanic centers in the central Trans-Mexican Volcanic Belt. Jorullo and Parícutin volcanoes are ideal for a paired case study because: they both produced well documented historic eruptions; detailed field studies have been done so samples selected for geochemical analysis can be placed in stratigraphic context; they both exhibit a temporal compositional trend of increasing SiO2 with time that is common in mafic monogenetic eruptions but the origin of which is poorly understood; they represent possible endmembers in inferred extents of crustal interaction, with lesser contamination of Jorullo lavas and very extensive contamination of Parícutin lavas; existing local upper and lower crustal xenoliths will allow rigorous investigation of the role of lithospheric assimilation; and their close geographic proximity enables a comparison of potential variability of mantle and crustal processes in different volcanic centers in a relatively fixed tectonic/geologic setting. Sr-Nd-Pb-Hf-Os isotopic compositions will be measured on whole-rock lavas, tephra, and crustal xenoliths, O and Os isotopes on olivine-oxide-matrix separates, and Sr isotopes in single melt-inclusion-bearing olivines. These data should uniquely constrain the relative roles of lower and upper crustal assimilation and the potential addition of slab-derived components to the mantle wedge including hydrous slab-fluid and sediment-melt. This study will have important implications regarding the establishment of magma reservoirs in mafic monogenetic volcanic systems and the cause of temporal-compositional variations in eruptive products, and will provide insights into the nature and heterogeneities of slab-derived fluids/melts over small spatial scales within a mantle wedge.Broader Impacts: Student Training & Education: Students involved in this project will gain extensive experience in several state-of-the-art analytical techniques, and at least one student will participate in fieldwork, receiving training in field volcanology. It is anticipated that the field work will be done in conjunction with a volcanology field workshop, providing the opportunity for additional students to benefit. Results from this research will also be incorporated into the classroom in lecture material and related hands-on, inquiry-based learning activities. Mentoring Women in Science: Widom serves as a role model/mentor for women in science, and currently has a research group with 4 female Ph.D. students. Widom and her students have worked closely with undergraduates in the past, and it is anticipated that the female-dominated research group will help attract participation of female undergraduate students. Outreach Activities: This project will be closely linked to the recent von Humboldt Foundation grant to Siebe and Schmincke, in which results of field mapping and volcanological studies, and our new geochemical data, will be integrated with the establishment of Jorullo as a new UNESCO GeoPark. In addition, Widom and her students will be involved in outreach programs through Miami U, including serving as consultants with Miami's Limper Geology Museum and providing research-based educational experiences to the community through the museum's K-12 programs as well as lab tours/demonstrations to local retirees and community college students. Volcanic Hazard Assessment: The results of this project will help constrain pre-eruptive processes in two historic volcanoes in a highly active volcanic region in which any future eruption will have a major impact on the local population and major urban centers including Morelia and likely Mexico City. International Collaboration: This project will foster ongoing international collaborations with Mexican geologists Siebe and Schaaf, as well as German volcanologist Schmincke.This award is co-funded by the Office of International Science and Engineering (OISE).