Intellectual Merit. Continental magmatic arcs are the site of massive additions of mantle derived magmas which serve to drive melting, thickening, and reorganization of the crust. Much of what we know about Cretaceous and older continental magmatic arcs results from studies of the physics and chemistry of plutonic rocks, and the derivative data strongly influence models of crustal growth and evolution. In contrast to modern arcs where single eruptive units may be analyzed, plutons record a much richer, albeit complex, history and represent a much greater percentage of the total magmatic flux than volcanic rocks alone. Critical questions concern how and at what rate intermediate composition magmas move through the crustal column, and how the crust accommodates these potentially large fluxes? Key to answering these questions is to understand how large masses of crystallized magmas or plutons and batholiths are constructed. To address these questions, collaborative research is proposed to better understand sub-arc magmatic plumbing systems. This project focuses on the roots of a continental magmatic arc in the North Cascades that comprises three well-exposed intrusive bodies emplaced at different depths in the crust. Integrated field mapping, structural analysis, mineral geochemistry, high-precision geochronology and coupled isotopic studies will be employed to [1] determine the degree to which plutons represent single magma batches or complex mixtures of partially crystallized magmas of different origins, [2] estimate magma flux rates and timescales for melt generation, transport, and eruption of intermediate composition magmas, and [3] evaluate potential linkages between regional tectonic strain and magma formation. This multidisciplinary collaborative research is expected to contribute significantly to understanding of magma plumbing systems and the formation of plutons in continental magmatic arcs.
Broader Impacts. This research will support Ph.D. students at MIT and USC, and at least 2 M.S. students at SJSU, and multiple undergraduate student assistants at all 4 institutions. Bpth SJSU PIs have supervised 2 B.S. research projects supported by their most recent grants, and Paterson teaches a formal research class at USC that has involved >20 undergraduates in NSF-supported research. Graduate students from SJSU and USC will visit Kent's lab at OSU to conduct their own analyses, and the MIT graduate student will visit SJSU and assist in SHRIMP analyses. Four M.S. students at SJSU have gone to MIT to carry out U-Pb dating under the tutelage of PI Bowring and his students, and this type of interaction is expected to continue. All of the PIs routinely incorporate their research in class lectures and use research samples in lab courses. Most importantly, The PI's are demonstrating to a large cross section of new students the power of strongly interdisciplinary and collaborative work.
