How Much Serpentine is Necessary for Dehydration Embrittlement?
Abstract
Double seismic zones, which consist of two subparallel planes of seismicity separated by 15-40 km are a global feature of subduction zones in the 50-250 km depth range. While the physical mechanism of lower plane seismicity is still controversial, the leading hypotheses currently are associated with dehydration of serpentine within the subducting lithospheric plate. We are conducting high-pressure (1-3 GPa), high-temperature (993-1023K), deformation experiments on variably serpentinized harzburgite in a 5 GPa Griggs apparatus. Using interlayered thin disc samples of a natural antigorite and a synthetic harzburgite, we find that dehydration embrittlement occurs down to ~30 vol % serpentine content. For smaller fractions of serpentine, we fabricate specimens with a homogeneous distribution of antigorite in harzburgite; with these specimens, dehydration embrittlement is still observed with as little as 10 wt % antigorite. These results suggest that dehydration embrittlement of serpentine may be possible with very limited hydrous alteration of the subducting upper mantle.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T13A2352X
- Keywords:
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- 3613 MINERALOGY AND PETROLOGY / Subduction zone processes;
- 5112 PHYSICAL PROPERTIES OF ROCKS / Microstructure;
- 8045 STRUCTURAL GEOLOGY / Role of fluids;
- 8162 TECTONOPHYSICS / Rheology: mantle