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Published Online April 12, 2007
Science DOI: 10.1126/science.1138074

Research Articles

Submitted on November 28, 2006
Accepted on March 27, 2007

Pervasive Seismic Wave Reflectivity and Metasomatism of the Tonga Mantle Wedge

Yingcai Zheng 1, Thorne Lay 1*, Megan P. Flanagan 1, Quentin Williams 1

1 Earth and Planetary Sciences Department, University of California, Santa Cruz, CA 95064, USA.

* To whom correspondence should be addressed.
Thorne Lay , E-mail: thorne{at}pmc.ucsc.edu

Subduction zones play critical roles in recycling of oceanic lithosphere and generation of continental crust. Seismic imaging can reveal structures associated with key dynamic processes occurring in the upper mantle wedge above the sinking oceanic slab. Three-dimensional images of reflecting interfaces throughout the upper mantle wedge above the subducting Tonga slab were obtained by migration of teleseismic recordings of underside P- and S-wave reflections. Laterally continuous weak reflectors with tens of kilometers of topography were detected at depths near 90, 125, 200, 250, 300, 330, 390, 410 and 450 km. P- and S-wave impedances decrease at the 330-km and 450-km reflectors, and S-wave impedance decreases near 200 km in the vicinity of the slab and near 390 km just above the global 410 km increase. The pervasive seismic reflectivity results from phase transitions and compositional zonation associated with extensive metasomatism involving slab-derived fluids rising through the wedge.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Upper Mantle Discontinuity Topography from Thermal and Chemical Heterogeneity.
N. Schmerr and E. J. Garnero (2007)
Science 318, 623-626
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Science. ISSN 0036-8075 (print), 1095-9203 (online)