Abstract
Recent geophysical surveys indicate that hydration (serpentinization) of oceanic mantle is related to outer-rise faulting prior to subduction. The serpentinization of oceanic mantle influences the generation of intermediate-depth earthquakes and subduction water flux, thereby promoting arc volcanism. Since the chemical reactions that produce serpentinite are geologically rapid at low temperatures, the flux of water delivery to the reaction front appears to control the lateral extent of serpentinization. In this study, we measured the permeability of low-temperature serpentinites composed of lizardite and chrysotile, and calculated the lateral extent of serpentinization along an outer-rise fault based on Darcy’s law. The experimental results indicate that serpentinization extends to a region several hundred meters wide in the direction normal to the outer-rise fault in the uppermost oceanic mantle. We calculated the global water flux carried by serpentinized oceanic mantle ranging from 1.7 × 1011 to 2.4 × 1012 kg/year, which is comparable or even higher than the water flux of hydrated oceanic crust.
Highlights
It has been observed that hydration of oceanic plate occurs in outer-rise regions through bending-related faulting prior to subduction
Intermediate-depth earthquakes occur in the lower plane of the double seismic zones, located within the subducting oceanic mantle, and these events might be triggered by serpentine dehydration reactions through dehydration embrittlement[12]
There is still no consensus regarding the hydration processes that affect oceanic mantle, water could penetrate along outer-rise faults that cut through the oceanic crust, thereby reaching the oceanic mantle and promoting serpentinization[13,14]
Summary
It has been observed that hydration of oceanic plate occurs in outer-rise regions through bending-related faulting prior to subduction. Serpentinite that forms by the hydration of oceanic mantle carries 13 wt% water to the deep mantle, and can remain stable down to 200 km depth in cold subduction zones[10]. There is still no consensus regarding the hydration processes that affect oceanic mantle, water could penetrate along outer-rise faults that cut through the oceanic crust, thereby reaching the oceanic mantle and promoting serpentinization[13,14]. The permeability of serpentinite seems to play an important role in controlling the extent of hydration of the oceanic mantle along outer-rise faults. We discuss the lateral extent of serpentinization and the subduction water flux transported into the Earth’s interior
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
