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Seismic evidence for widespread serpentinized forearc upper mantle along the Cascadia margin

Geology

By:
, , , ,
DOI: 10.1130/0091-7613(2003)031<0267:SEFWSF>2.0.CO;2

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Abstract

Petrologic models suggest that dehydration and metamorphism of subducting slabs release water that serpentinizes the overlying forearc mantle. To test these models, we use the results of controlled-source seismic surveys and earthquake tomography to map the upper mantle along the Cascadia margin forearc. We find anomalously low upper-mantle velocities and/or weak wide-angle reflections from the top of the upper mantle in a narrow region along the margin, compatible with recent teleseismic studies and indicative of a serpentinized upper mantle. The existence of a hydrated forearc upper-mantle wedge in Cascadia has important geological and geophysical implications. For example, shearing within the upper mantle, inferred from seismic reflectivity and consistent with its serpentinite rheology, may occur during aseismic slow slip events on the megathrust. In addition, progressive dehydration of the hydrated mantle wedge south of the Mendocino triple junction may enhance the effects of a slap gap during the evolution of the California margin.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Seismic evidence for widespread serpentinized forearc upper mantle along the Cascadia margin
Series title:
Geology
DOI:
10.1130/0091-7613(2003)031<0267:SEFWSF>2.0.CO;2
Volume
31
Issue:
3
Year Published:
2003
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
267
Last page:
270
Number of Pages:
4