This research addresses separate but related questions about the origin of chemical diversity within monogenetic volcanoes and the physical behaviors of magmas in the dikes and sills that comprise their shallow plumbing systems. One outcome of the research will be to test the hypothesis that flow differentiation of crystal bearing magmas can play an important role in producing larger scale compositional variations among the entire suite of lava flows and tephra at these volcanoes. The study focuses on the Sinker Butte volcano, a compositionally diverse basaltic shield-tuff cone complex in the western Snake River Plain of Idaho. This site affords an extraordinary research opportunity because the volcano has been dissected by the Snake River, exposing a complete sequence of lava flows, tephra, and radial dikes in the canyon walls. Flow directions of magma in the dikes and sheets will be estimated by determining anisotropy of magnetic susceptibility (AMS) in drilled cores. An independent estimate of flow directions will be made by statistically analyzing crystal orientations in thin sections. Chemical variations within and among dikes will be compared with phenocryst modes and movement directions to assess the effects of flow differentiation.
This study will contribute to a better understanding of the physical and chemical processes operating at short-lived, basaltic volcanoes, which are the most common type of non-marine volcano on our planet. By focusing on the physical mechanisms that operate inside volcanoes, the project builds on recent studies of the shallow plumbing systems at Mt. Etna in Italy and Kilauea volcano in Hawaii. Broader impacts of the study include research training for students at the undergraduate and graduate level, and the possibility that knowledge gained from this study will contribute information useful for assessing hazards associated with unexpected explosive eruptions at basaltic volcanoes.
This project is being supported by both the EPSCoR (EHR) and the Petrology and Geochemistry (EAR) programs.
