"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."
Intellectual Merit: Diatreme-dike centers in the Oligocene Navajo volcanic field (NVF) are an important part of the geologic history and evolution of the Colorado Plateau. Although previous studies have focused on the generation and evolution of magmas associated with the NVF, some fundamental issues are poorly understood. The most in-depth hypothesis (Nowell, 1993; Carlson and Nowell, 2001) on mantle-magma genesis and evolution for NVF rocks argues that silica-undersaturated magmas were created by 0.5% to 1% melting of a carbonate-rich phlogopite-garnet peridotite whereas more "silica-saturated" magmas (source of minette) were generated by higher degrees of melting of hydrous-lithospheric mantle. This model is founded on the idea that asthenospheric melts were injected into the lithospheric mantle creating proximal CO2 and distal H2O metasomatism. Insight into the composition and genesis of primary mantle magmas, and an understanding of the volatile species involved, currently are not adequately constrained to fully test this model. Chemical and volatile signatures of primary silicate-melt inclusions and mineral phases in NVF rocks can contribute to an understanding of compositions and formation conditions of parent mantle melts. In this proposed research, petrologic and geochemical data on bulk-rock samples combined with information gained from micro-analytical techniques (electron and ion microprobe, and laser-ablation ICP-MS) on primary silicate-melt inclusions and mineral phases will be employed to reconstruct parental source compositions and gain insight into magmatic-volatile processes. Major and trace element data from melt inclusions and early-formed olivine (± pyroxene) will serve to assess variations in primary melt compositions. Constraints on the concentration and variation of volatile species (C, H, Cl, F) in melt inclusions and zoned-mineral phases (e.g., phlogopite and apatite) will allow insight into the involvement and evolution of volatiles in magmatic processes (e.g., metasomatism, degassing). The combined data from this research will permit a robust test of existing hypotheses on NVF magmatism, and dissemination of the results into the broader geologic community will give greater knowledge of magmatic processes. This is important in understanding regional Cenozoic magmatic events on the Colorado Plateau, and perhaps the connection of this magmatic pulse with other contemporaneous regional geologic events.
Broader Impacts: Igneous petrology at the undergraduate level has historically played an important role in the education of geology students, serving as a bridge to other key courses, and offering students opportunities to develop important skills in inquiry, observation, and analysis. A prime impact of this project beyond the basic research is to support the education and successful scientific careers of undergraduate students at Fort Lewis College by teaching them basic knowledge and skills in context of a petrologic-based research project. This will promote scientific habits of mind by engaging students as "active agents" in discovery, and the creative development and testing of ideas. It will also give students a sense of ownership in the scientific process and knowledge construction. The PI and students from Fort Lewis College will acquire new skills and knowledge in collaboration with several well-established research scientists at Arizona and the U.S. Geological Survey. An effort will be made by the PI to recruit under-represented groups (ethnic minorities and women). The PI will also gain professional advancement and insight that will be integrated into undergraduate research and curriculum at Fort Lewis College.
