SGER: Dating Volcanic Rocks Using Syngenetic Non-Silicate Minerals

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In this Small Grant for Exploratory Research (SGER), it is proposed to test a new geochronological technique based on U-series disequilibrium of cogenetic non-silicate minerals to date young lava flows. Previous attempts to dating lavas with U-series isotopic techniques have been problematic due to the fact that silicate crystals have variable magma residence times and, in many cases, do not have the requisite U concentration and U/Th ratios. The proposed analytical plan will be focused on the mineral gypsum. Gypsum is a common cogenetic mineral in basalts often found in lava tubes. They have the required high U and low Th concentrations. Preliminary data on gypsum crystals give encouraging but mixed results. The ultimate purpose of this SGER will be to develop a set of criteria to distinguish datable materials from those that are not by using strontium, sulfur and in some cases radium isotopic data in a suitable field area. These will be used eventually to document and establish the likelihood that this new technique is feasible for a number of different rock types. If successful, results from this project will have broad applicability in the Earth Sciences.