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Bending-related faulting and mantle serpentinization at the Middle America trench


The dehydration of subducting oceanic crust and upper mantle has been inferred both to promote the partial melting leading to arc magmatism and to induce intraslab intermediate-depth earthquakes, at depths of 50–300 km. Yet there is still no consensus about how slab hydration occurs or where and how much chemically bound water is stored within the crust and mantle of the incoming plate. Here we document that bending-related faulting of the incoming plate at the Middle America trench creates a pervasive tectonic fabric that cuts across the crust, penetrating deep into the mantle. Faulting is active across the entire ocean trench slope, promoting hydration of the cold crust and upper mantle surrounding these deep active faults. The along-strike length and depth of penetration of these faults are also similar to the dimensions of the rupture area of intermediate-depth earthquakes.

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The bathymetry data were collected during R/V Sonne cruises 76, 81, 107, 144, 150 and 163, R/V Meteor cruise 54 and R/V M. Ewing cruises 0005 (Chief Scientist K. McIntosh) and 0104 (Chief Scientist A. Fisher). The seismic reflection data were collected during BGR99 cruise aboard M/V Professor Polshkov. We thank the scientific parties for their efforts and officers and crews for their technical and logistical support. R/V Sonne cruises were funded by Deutsche BMBF, the R/V Meteor cruise by the DFG and the R/V M. Ewing cruises by the NSF-USA. This work is a contribution of ‘SFB574 Volatiles and Fluids in Subduction Zones’ from the University of Kiel.

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The authors declare that they have no competing financial interests.

Correspondence to C. R. Ranero.

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Further reading

Figure 1: Colour-coded bathymetry and elevation map along 600 km of the Middle America trench.
Figure 2: Poststack finite-difference time migration of various lines.
Figure 3: Fault offsets measured at the sea floor and top of igneous basement for faults marked on Fig. 2, plotted versus distance to the trench axis.
Figure 4: Histogram of fault density versus distance to the trench axis.


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