Bend-faulting, serpentinization, and double seismic zones - new insights from reaction-transport modeling.

Iyer, Karthik, Rüpke, Lars and Grevemeyer, Ingo (2010) Bend-faulting, serpentinization, and double seismic zones - new insights from reaction-transport modeling. [Talk] In: SFB 574 Subduction Workshop. , 04.-07.11.2010, Pucon, Chile .

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Abstract

Double Benioff zones (DBZs) are globally observed parallel bands of seismicity corresponding to planes of internal deformation that occur in subducting plates irrespective of plate age, subduction rate, or stress orientation. One of the more favored methods that trigger lower regions of seismic activity is the dehydration of antigorite/chlorite.
We explore the likely degree of hydration of subducting lithosphere and its consequences for intermediate depth seismicity and formation of DBZs. We have developed a reaction transport model that resolves for the circulation of seawater as well as serpentinization of cold oceanic lithospheric mantle. We find that bend-faults forming during plate bending at the outer rise are likely to be highly serpentinized. Background serpentinization away from faults is most intense around the 270°C isotherm where the rate of serpentinization is at its maximum.
In a series of along- and across-trench numerical experiments, we demonstrate that the degree of hydration increases with plate age. The across trench simulations show a band of high serpentine contents around the 270°C
isotherm. The depth of the 270°C is plate age dependent as plate cooling models show. As a consequence, the depth at which maximum serpentinisation is favored, i.e. the 270°C isotherm increases with plate age. Strikingly the location of this band of high serpentine content correlates reasonably well with the observed dominant spacing of DBZs observed worldwide for different plate ages. Deviations from this correlation can be related to 3D effects during serpentinization, which have been explored in a series of along trench numerical experiments.

Document Type: Conference or Workshop Item (Talk)
Keywords: Geodynamics; subduction
Research affiliation: OceanRep > SFB 574 > C5
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-JRG-B3 Seabed Resources
OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Date Deposited: 10 Dec 2010 12:21
Last Modified: 23 Feb 2012 06:22
URI: http://oceanrep.geomar.de/id/eprint/10418

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