Tectonic significance of serpentinites

Stéphane Guillot (1) , Stéphane Schwartz (1) , Bruno Reynard (2) , Philippe Agard (3) , Cécile Prigent (1)

1 ISTerre - Institut des Sciences de la Terre
2 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
3 iSTeP - Institut des Sciences de la Terre de Paris

At plate boundaries, where deformation is localized along centimetre- to kilometre-scale shear zones, the influence of serpentinite on tectonic processes is linked to its unique rheological properties. In this paper wereview the physical properties of serpentinites and their role in tectonic processes. At the ocean –continent transition, serpentinization weakens the upper mantle layer, promoting strain localization and allowing the normal faults in the distal margin to root at low angle. Similarly, at slow to ultra-slow spreading ridges, serpentinite is potentially very abundant at the sea floor and locally associated with domal structures. Extensional deformation is localized in a ~100 m thick shear zone at the footwall of detachment zones dominated by serpentine derived minerals. Within subduction zone, the depth of decoupling between the mantle wedge and the subducting slab corresponds to the stability depth of serp entine weak mineral. Dehydration of serpentine has also been hypothesized to play an important role in the origin of double seismic zones, however the exact mechanism through which dehydration promotes seismicity remains a matter of debate. During exhumation of high-pressure or ultrahigh-pressure rocks, the opposite trajectories of exhumation and subduction require a decoupling zone within the subducting slab. A serpentinized layer has the potential to become a decoupling zone between the oceanic crust and underlying lithosphere. The buoyancy of serpentinite also likely contributes to eclogite exhumation.Finally,along majorstrike-slip faults, serpentiniteshave been associated with faultcreep, as well as low fault strength. The presence of serpentinite blocks along creeping segments of active faults worldwide is therefore likely to originate from fluids deriving from the progressive dehydration of the mantle wedge that move such bodies upward

Domaines: Sciences de la Terre

Stéphane Guillot, Stéphane Schwartz, Bruno Reynard, Philippe Agard, Cécile Prigent. Tectonic significance of serpentinites . Tectonophysics, 2015, 646, pp.1-19. ⟨10.1016/j.tecto.2015.01.020⟩. ⟨hal-01406783⟩