Geochemistry and Geochronology of the First Submarine Intraplate Lavas Recovered from the Arctic Ocean -- Bearing on the Plate Tectonic Evolution of the Amerasian Basin.

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The tectonic development of the Amerasian Basin (the western Arctic Ocean) is largely unknown, but is key to understanding formation of the vast apron of continental shelves that ring the Arctic Ocean. This region is increasingly becoming important because of the receding ice cover due to global warming, national security considerations as we look to the future of new Arctic shipping lanes, and the maneuvering by the seven Arctic nations (including the United States) to expand their continental-shelf jurisdiction in accordance with Article 76 of the United Nations Convention on the Law of the Sea. This project will test competing hypotheses for formation of the Alpha and Mendeleev Ridges through geochemical analysis of the first suite of volcanic rocks that have been dredged from the western Arctic. This three-year research project will involve several key analytical areas: 1) isotopic dating of selected dredged samples to establish a chronologic framework for follow-up geochemical work, and for tectonic interpretations; 2) petrographic and microprobe analysis of thin sections to identify samples best suited for major and trace element modeling to determine the degrees and depth of melting while also being mindful of any fractional crystallization effects; 3) identify a subset of samples for measurements by Fourier transform infrared (FTIR) spectroscopy, and secondary ionization mass spectrometry (SIMS) of the primary melt volatile concentrations in olivine-hosted melt inclusions; 4) measurement of major elements by electron microprobe and trace elements by laser ablation ICP-MS on the same melt inclusions as those characterized for volatiles to identify the compositions of the most primitive magmas preserved in any form within the submarine lavas, and 5) measurement of a complete set of isotopic compositions for 40 samples. The project will support one graduate student and one undergraduate.