Serpentinization and Life: Insights through ocean drilling
  • Devonport Lecture Theatre, Portland Square Building

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The University of Plymouth, in association with ECORD (European Consortium for Ocean Research Drilling) and IODP (International Ocean Discovery Program) are delighted to welcome ECORD Distinguised Lecturer 2016/17 Gretchen Früh-Green (ETH Zürich) to give this public lecture entitled 'Serpentinization and Life: Insights through ocean drilling'.

Abstract (source: ECORD website)

Ultramafic and lower crustal rocks are exposed on the seafloor in many tectonic settings and have been the target of a number of expeditions throughout the history of ocean drilling. Progressive interaction of seawater with mantle-dominated lithosphere during serpentinization is a fundamental process that controls rheology and geophysical properties of the oceanic lithosphere and has major consequences for heat flux, geochemical cycles and microbial activity in a wide variety of environments. At slow spreading ridge environments, serpentinization occurs along detachment faults (major, large-scale offset normal faults), as mantle rocks are uplifted to the seafloor and are incorporated in dome-shaped massifs known as oceanic core complexes. The processes controlling fluid flow and a deep biosphere are intimately linked, however, the spatial scale of lithological variability, the implications for geochemical cycles and the consequences for subsurface ecosystems supported by these systems remain poorly constrained.

This presentation will provide an overview of mid-ocean ridge processes and will highlight recent results of drilling the Atlantis Massif on the western flank of the Mid-Atlantic Ridge at 30°N. The Atlantis Massif is one of the best-studied oceanic core complexes and hosts the unique Lost City hydrothermal field on its southern wall.

Serpentinization reactions in the underlying mantle rocks produce high pH fluids that form large carbonate-brucite structures upon venting on the seafloor. The fluids have negligible dissolved carbonate and metals, but have high concentrations of hydrogen, methane and formate that support novel microbial communities dominated by methane-cycling archaea in the hydrothermal carbonate deposits. Understanding the links between serpentinization processes and microbial activity in the shallow subsurface of the Atlantis Massif was the focus of IODP Expedition 357, which used seabed rock drilling technology for the first time in the history of the ocean drilling programs to recover ultramafic and mafic rock sequences along a detachment fault zone. The expedition also successfully applied new technologies that provide insight into active serpentinizing systems. A sensor package and water sampling system on the seabed drills monitored real-time variations in dissolved oxygen and methane, pH, oxidation-reduction potential, temperature and conductivity during drilling and allowed sampling of bottom water after drilling. A borehole plug system for sealing the boreholes was installed at two sites to allow access for future sampling; and chemical tracers for contamination testing were delivered into the drilling fluids with the seabed drills. Thus, results of drilling the Atlantis Massif will provide important insights for future studies of serpentinization processes and microbial activity at slow-spreading ridges.

All are welcome to attend. A wine reception at 18:00 will be held before the talk which starts at 18:30.

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