Diagenesis and burial of hydrothermal iron in the deep sea

Iron (Fe) is an essential micronutrient for marine phytoplankton that take up CO2 during photosynthesis. Therefore, Fe bioavailability and the pathways of supply to and removal from the ocean are of great scientific interest. Iron supply by hydrothermal vents is a potentially important but poorly constrained source of Fe to the deep sea. In order to understand the role of hydrothermal vents in the global marine iron (Fe) cycle, we need to determine the mechanisms of Fe precipitation, settling and burial around hydrothermal vents. We will apply Fe K-edge EXAFS to nanoscale Fe-rich aggregates in the water column and sedimentary Fe around a mid-Atlantic hydrothermal vent field ('Rainbow') and thus track the precipitation and diagenesis of hydrothermal Fe. XAS results from this unique dataset will provide, for the first time, insight into the long-term fate of hydrothermal nanoparticulate Fe aggregates beyond what have so far obtained from microscopic and chemical analyses.