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The wet Nicaraguan slab
Author(s) -
Abers Geoffrey A.,
Plank Terry,
Hacker Bradley R.
Publication year - 2003
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl015649
Subject(s) - slab , geology , subduction , slab window , seismology , crust , mantle (geology) , oceanic crust , mafic , geophysics , plate tectonics , convergent boundary , petrology , tectonics
Nicaraguan volcanoes show globally high concentrations of geochemical tracers from dehydration of subducting crust, which may reflect a slab with unusually high amounts of H 2 O. To test this possibility, we measure seismic velocities at the top of the subducted plate and compare them with predictions for hydrated mafic rocks. Regional seismic P waves for intraslab events at 100–150 km depth show a high‐frequency late arrival, apparently trapped in a low‐velocity waveguide 2.5–6 km thick at the top of the downgoing plate, 14.5 ± 2.2% slower than surrounding mantle. The velocities can be explained by ≥5 wt % H 2 O in the subducted crust, 2–3 times the hydration inferred for other slabs by similar methods. This interpretation implies extensive hydration of the Cocos Plate off Nicaragua, perhaps enhanced by up‐dip fluid flow within the slab at >100 km depth.