CSEDI: Constraining the mechanisms of melt transport, storage, and crustal contamination from temporal geochemical variations in monogenetic vents

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Monogenetic vents are relatively small volcanoes that are active for a single eruption over a period of a few months to a few years, in contrast to more typical volcanoes that are gradually built up over many different eruptions and which are typically intermittently active for 10s of thousands of years or longer. Monogenetic vents often occur in clusters, and are a common type of volcanism in many tectonic settings. Several monogenetic vent fields occur in or near high-population-density areas, including Auckland, New Zealand and Mexico City, Mexico. Therefore, monogenetic vents represent a significant volcanic hazard. Previous studies have shown that the compositions of the ash and lava erupted from a monogenetic vent during the course of an eruption often varies systematically over time. The cause of this variability is not clear, but it most likely reflects either processes involved in melt generation and extraction from the mantle, or melt storage in the continental crust and melt/crust interaction prior to eruption. A better understanding of the cause(s) of the chemical variations observed in monogenetic vent eruptions would provide scientists with a better understanding of the plumbing system that feeds these volcanoes. This in turn will allow better prediction of the precursor signals that may signal an impending eruption.This study will combine numerical modeling of melt transport and storage processes with detailed geochemical analyses of material erupted from selected monogenetic vent eruptive sequences to better constrain the processes of melt generation, ascent, and storage that precede the eruption of monogenetic vents. Different hypothesized mechanisms for generating chemical variations in monogenetic vent sequences (e.g., reactive melt transport in the mantle or progressive draining of magma sills that are emplaced in the shallow crust prior to eruption) will produce different temporal chemical variations. We will compare model predictions with observations to constrain the likely origin of these variations, and then use the observed variations to extract information on important variables related to melt generation, transport, and storage such as the size of chemical heterogeneities in the mantle source region, the volume and geometry of magma storage chambers in the crust, and the time interval between melt injection into the crust and subsequent eruption of this stored magma. This information can be used in future studies to predict the most likely signals that may indicate an impending eruption (e.g., upward ground deformation due to magma injection) as well as the likely time lag between these signals and an actual eruption. The proposed study with therefore both improve our overall understanding of a geologically important and widespread style of continental volcanism, and improve our ability to evaluate and plan for the risks inherent in possible future monogenetic vent eruptions.