Volatiles cycle

The exchange of volatiles (water -as hydrogen-, carbon, nitrogen, noble gases, halogens and sulphur) between the Earth’s surface and its interior controls on the long-term the composition of the atmosphere and hydrosphere, thus affecting climate and the biosphere. Degassing of the mantle occurs principally at divergent plate boundaries and at volcanic centres via magmatic processes, while extensive recycling of volatiles in the mantle occurs via subduction of metasomatized, volatiles-rich oceanic plates. The distribution of volatiles within the Earth’s mantle – the largest volatiles reservoir – has profound implications on the dynamics and the evolution of our planet, as small quantities of volatiles strongly affect the physical properties of rocks (viscosity, density, seismic wave velocities, electrical conductivity). Water -as hydrogen- is the most abundant volatiles species (~75%), which explain why much attention has been focused on its long-term deep cycle.

In this direction, I have mainly investigated processes related to water in subducting oceanic plates that lead ultimately to mantle regassing, such as the mechanism of slab hydration during bending-related normal faulting, its subsequent dehydration at intermediate depths and the potential role of hydrated normal faults acting as seismic anisotropy source in the forearc.

Slab hydration (red) during bending-related deformation

(from Faccenda et al., 2009, Nat. Geo.)

Publications:

1. Faccenda M. Water in the slab: a trilogy. Tectonophys. 614, 1-30 (2014).
2. Eberarth-Phillips D.,Reyners M., Faccenda M., Naliboff J. Along-strike variationin subducting plate seismicity and mantle wedge attenuation related to fluid release beneath the North Island, New Zealand. Phys. Earth Planet. Int. 225, 12-27 (2013).
3. Faccenda M., T. V. Gerya, N.S. Mancktelow, and L. Moresi. Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling. Geochem. Geophys. Geosyst. 13, Q01010, doi:10.1029/2011GC003860 (2012).
4. Faccenda M. and Mancktelow, N. S. Fluid flow during unbending: implications for slab hydration, intermediate-depth earthquakes and deep fluid subduction. Tectonophys. 494, 149-154 (2010).
5. Faccenda M., Gerya T.V., Burlini L. Deep slab hydration induced by bending-related variation of the tectonic pressure. Nat.Geosci. 2, 790-793 (2009).
6. Faccenda M., Burlini L., Gerya T.V., Mainprice D. Fault-induced seismic anisotropy by hydration in subducting oceanic plates. Nature 455, 1097-1100 (2008).