Geochronological Evaluation of Circa 600 Ma Events in Northwest Svalbard, Arctic Caledonides

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This award supports a US contribution to a collaborative project with Swedish geologists to evaluate the geochronology of the Richarddalen Group of northwestern Svalbard. These rocks have recently yielded "Pan African" aged zircons (620-660 million years old) that are enigmatic because there is little other evidence in the Arctic or Scandinavian Caledonides to rock-forming or metamorphic/deformational events of this age. Detailed geochronologic studies based on field and micro-structural study, and high-precision U-Pb methods will be used to directly date metamorphic and deformational fabrics. Lead-207/Lead-206 ages will be measured by direct evaporation of single zircon grains to test for the presence of older (inherited) components, thereby further constraining the interpretation of existing zircon ages. These new data will permit a direct assessment of whether the isotopic ages reflect protolith, metamorphic or deformational, or mixed ages, and the significance of these rocks to global tectonic reconstructions in the Neoproterozoic.