IGI onboard the M-162 scientific expedition in the NE Atlantic

Marianne Nuzzo from IGI will participate on the M-162 scientific expedition onboard the German Research Vessel “Meteor” in the NE Atlantic along the Azores-Gibraltar Transform Fault Zone (AGTFZ; Fig. 1). The M-162 expedition will start in São Miguel in the Azores Islands on the 6^th March 2020 and terminate in Las Palmas, Canary Islands, on the 5^th April 2020.

Figure 1: Location of the Azores-Gibraltar Transform Fault Zone in the NE Atlantic and seismicity along the fault zone (Omira et al., 2019)

The aim of the expedition is to lead a geochemical and geophysical survey of indications for micro-seepage of fluids along the AGTFZ in the abyssal plain. These would provide significant geochemical evidence for fluid-rock interactions in the lower crust, with the seismic activity in the fault zone driving fluid flow to the lower crust (Hensen et al., 2019; Fig. 2).

Figure 2: Schematic representation of the mechanism for seismic pumping of fluids to the deep crust/upper mantle and their release during seismic rupture (Hensen et al., 2019)

The emission of methane, which is formed as a by-product of the serpentinization of the lower crust/mantle, is an important parameter in identifying fluid-rock interactions. Amongst other measurements, methane sensors mounted on Automated Underwater Vehicles (AUVs) will be used to measure methane concentrations in the water column for the identification of potential gas plumes. Marianne will work with the geochemistry team on the measurement of methane in-situ in the water column and other inorganic water chemistry measurements.

The scientific team onboard the RV-Meteor, including Marianne, has been involved with multidisciplinary work on fluid seepage and seismicity in the Gulf of Cadiz, in the eastern part of the AGTFZ, for over a decade.  They first identified geochemical signals for the seepage of fluids having interacted with the lower crust in the accretionary wedge of the Gulf of Cadiz (Hensen et al., 2007; Nuzzo et al., 2009) and then further west out of the sedimented wedge area (Hensen et al., 2015; Nuzzo et al., 2019). Based on these previous investigations, this mission aims at identifying tenuous signs of the release of methane and other chemical species along the extensive AGTFZ. Despite the expectedly low emission rates, the large area of this and other fault zones implies that they could have an important and yet un-characterised impact on the global budgets of methane and other inorganic elements.

 In particular, understanding and quantifying the background emissions of the potent methane greenhouse gas in the oceans is an important parameter to devise strategies for the transition to carbon-free energies and mitigation of global warming effects in the next decades.

References

Hensen, C., et al. and Nuzzo, M. 2019. Marine transform faults and fracture zones: a new perspective integrating seismicity, fluid flow and life. Frontiers in Earth Science, Review Article 438241, www.frontiersin.org.

Hensen C., Nuzzo M., Hornibrook E. R. C., Pinheiro L. M., Bock B., Magalhães V. H., and Brückmann W. (2007) “Sources of mud volcano fluids in the Gulf of Cadiz - Indications for hydrothermal imprint”.  Geochimica et Cosmochimica Acta 71, 1232-1248.

Nuzzo, M., Tomonaga, Y., Schmidt, M., Valadares, V., Faber, E.,Piñero, E., Reitz, A., Haeckel, M., Tyroller, L., Godinho, E., Kipfer, R., Terrinha, P. and Hensen, C., 2019. Formation and migration of hydrocarbons in deeply buried sediments of the Gulf of Cadiz convergent plate boundary – Insights from the hydrocarbon and helium isotope geochemistry of mud volcano fluids. Marine Geology 410, 56-69.

Nuzzo M., Hornibrook E. R. C., Gill F., Hensen C., Pancost R., Haeckel M., Reitz A., Scholz F., Magalhães V. H., Bruckmann W., and Pinheiro L. M. (2009) Origin of light volatile hydrocarbon gases in mud volcano fluids, Gulf of Cadiz - Evidence for multiple sources and transport mechanisms in active sedimentary wedges. Chemical Geology 266, 359-372.

Omira R., Neres M., and Batista, L. (2019). The Gloria Transform Fault-NE Atlantic: Seismogenic and Tsunamigenic Potential. In Transform Plate Boundaries and Fracture Zones, J. C. Duarte editor, 157-167 (https://doi.org/10.1016/B978-0-12-812064-4.00008-6).