Subduction zone thermal structure and mineralogy and their relationship to seismic wave reflections and conversions at the slab/mantle interface

G. R. Helffrich, S. Stein, B. J. Wood

Research output: Contribution to journalArticlepeer-review

89 Scopus citations

Abstract

Seismological studies of the interface between downgoing slabs of subducted lithosphere and the overriding mantle provide constraints against which models of mantle and slab temperature and bulk composition can be tested. These studies, employing waves reflected and converted at the slab/mantle interface, suggest that a velocity contrast of 5-10% occurs over a distance of 10-20 km to depths of at least 350 km. We have investigated whether such sharp contrasts can result from thermal structure, compositional differences, phase changes, or other effects such as preferred mineral orientation. Results indicate that temperature and bulk compositional differences between mantle and slab are inadequate to cause the observed velocity contrasts. We propose that phase transformations in mantle and slab mineralogies, notably elevation of the olivine-spinel phase change normally occurring at 400 km depth, are important factors in these sharp contrasts. Other contributing effects may include preferential mineral orientation near the slab surface and, at shallower depths, the presence of partial melt or hydrous fluid evolved from dehydration reactions along the interface. -from Authors

Original languageEnglish (US)
Pages (from-to)753-763
Number of pages11
JournalJournal of Geophysical Research
Volume94
Issue numberB1
DOIs
StatePublished - Jan 1 1989

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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