Colloquium: Olivier Rouxel

Olivier Rouxel, Research Scientist, Laboratoire Géochimie et Métallogénie, Institut français de recherche pour l'exploitation de la mer (IFREMER)

Abstract:  Seafloor hydrothermal systems exert tremendous influence over the chemistry, biology, and geology of their surrounding environments. This influence extends to the unique ecosystems they host, the economically important mineral deposits they generate, and to the composition of seawater itself on both local and global scale. While it is widely recognized that Fe acts as a limiting nutrient for marine phytoplankton in large regions of world’s ocean, the farfield consequences of hydrothermal Fe input is just starting to be recognized. Over geological times, oceanic Fe cycling is controlled by the complex interplay between oceanic, geological and biological processes, leading to a paradigm shift in biological and Earth system co-evolution.

Guided by recent advances in Fe isotope geochemistry, I will discuss the impact of seafloor hydrothermal venting on Fe oceanic cycles over the course of geological time. First,  I will evaluate whether the iron fluxes in the ocean derived from benthic diagenesis and seafloor hydrothermal systems have characteristic isotope signatures that are distinct from riverine and atmospheric iron sources. Secondly, using Precambrian banded iron formations and black shales as proxies for oceanic metal cycling in the deep past, we will investigate the link between hydrothermal input of metals to seawater, biological evolution, and changes in the redox state of Earth’s ocean-atmosphere system.