MCA: Destroying continental plates - unraveling the role of magmatism

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A fundamental idea of plate tectonics is that most of the ‘action’ (earthquakes, volcanoes, faulting) happens at plate boundaries and that the interiors of tectonic plates are stable and undeforming. While this is mostly true for the interiors of continents (such as North America), geologic evidence shows that under the right circumstances previously stable continental tectonic plates can deform, mobilize and possibly rift apart—with accompanying plate-interior earthquake and volcanic activity. This project will investigate one of the key processes that may lead to this destabilization: the infiltration of buoyant, hot, molten rock (magma) into the base of a continental tectonic plate. This project will explore how magma interacts with the continental mantle rocks as it infiltrates and how such melt-rock interaction may profoundly alter tectonic plates. This award will provide research and career enhancement to a female mid-career scientist who has faced barriers to research, allowing her to return to cutting-edge research. Additionally, the project will train two female graduate students (one of whom has a documented disability) in critical thinking, data analysis, numerical modeling, and machine learning, preparing them to contribute to a diverse, globally competitive STEM workforce. Overall, the project will enhance the participation of women, persons with disabilities, and underrepresented minorities in STEM. This project will combine data analysis, numerical modeling, and machine learning to develop a process-oriented understanding of the consequences of thermal and chemical disequilibrium during magma-infiltration into the continental mantle lithosphere. The team will exploit recent insights from the geochemistry of Cenozoic volcanic rocks in southwestern North America to determine how magma-infiltration aided in a progressive transformation of the physical and chemical state of the lithosphere: from earlier (60 Ma) subduction-related deformation and magmatism to the current (post 20 Ma) state of extension/transtension and associated magmatism. The research will test the idea that the Cenozoic transition in the physical and chemical state of southwestern North America is reflected in a regionally-consistent compositional transition in volcanic rocks, specifically in Ta/Th values. Using this transition as a starting point, a statistical methodology will be developed for uncovering other patterns in volcanic rock compositions in order to identify different styles of magma-lithosphere interaction. In analogy with supervised learning, the team will “train” its statistical methods on canonical volcanic rock chemical and isotopic patterns in North America, and then will apply these methods to “test” data from the Tibetan Plateau, another region of abundant Cenozoic continental volcanism and lithosphere degradation. The geochemical interpretations will inform numerical models of thermal and chemical disequilibrium between infiltrating magma and the surrounding lithospheric mantle. This integrative approach will yield a process-oriented understanding of magma-lithosphere interaction and its role in modifying and potentially degrading previously stable continental lithosphere.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.