Arsenic and Molybdenum in Marine Carbonates: Redistribution, Binding Forms and Isotope Systematics

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Trace elements in sedimentary sequences can be both a blessing and a curse. They are a blessing because (1) their concentration patterns can be used as proxies for the reconstruction of environmental conditions at the time of deposition, (2) they can provide information about diagenetic processes, and (3) they can be mined to meet strategic mineral needs. At the same time, they can be a curse because due to water-rock interaction, they can be transferred into groundwater, where they are detrimental to operational and health aspects of this critical resource. We know surprisingly little about the two trace elements As and Mo in carbonate sediments. This seems surprising since carbonates are among the most abundant sedimentary rock types and As and Mo are elements of considerable ecological and scientific interest. To advance our understanding, the proposed study's overarching objective will be to unravel the diagenetic history and the concomitant redistribution of As and Mo in the Floridan Aquifer System's carbonate matrix. Combining that information with detailed mineralogical observations will improve reactive transport models and help identify areas, regions, and ages of potential contamination, which will aid exploration for safe drinking water. Understanding the processes responsible for the redistribution of Mo and its isotopes should provide a tool for reconstructing paleo conditions in marine environments other than euxinic basins.