A general model for intermediate-depth earthquakes and water transport into the mantle
Abstract
Recent experimental results on high-pressure dehydration of serpentine under stress have shown strong differences concerning whether a shearing instability does or does not develop. To address these differences we have conducted a series of experiments on serpentinized harzburgite that vary from 0% to essentially 100% antigorite. Our results are that both of the end members are ductile but that almost all intermediate compositions display dehydration embrittlement (see Xia et al., this meeting). Using these results and previous findings that subducting lithosphere is essentially dry below 400 km, we present a model that involves dehydration-induced earthquakes within subducting crust and mantle from which the water evolved escapes upwards, serpentinizing the mantle wedge immediately overlying the slab. The serpentine generated at the slab-wedge interface then potentially enables development of a ductile shear zone that could carry water downwards as a component of serpentine to conditions of higher P & T where antigorite is replaced by the 10Å phase and/or clinohumite that enables continuation of the hydrous shear zone. In this talk, we will explore the T, P, H2O conditions at the slab mantle interface that are consistent with this hypothesis.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMDI21C..04G
- Keywords:
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- 3613 MINERALOGY AND PETROLOGY / Subduction zone processes;
- 3653 MINERALOGY AND PETROLOGY / Fluid flow;
- 8135 TECTONOPHYSICS / Hydrothermal systems