Elastic properties of hydrogrossular garnet and implications for water in the upper mantle

B. O'Neill, J. D. Bass, G. R. Rossman

Research output: Contribution to journalArticlepeer-review


The single-crystal elastic properties of a hydrous silicate garnet, hibschite, were measured using Brillouin spectroscopic techniques. The adiabatic bulk modulus of hibschite, Ks = 99.8 ± 1.0 GPa, and the shear modulus, μ = 64.3 ± 0.5 GPa, are 40% lower than the bulk and shear moduli for anhydrous grossular garnet. Density considerations indicate that hydrogarnet is likely to be stable relative to an assemblage with H2O as a separate phase throughout the upper mantle and probably the transition zone. Assuming garnet to be the sole repository for mantle water, the seismic wave velocities of a "wet' eclogitic layer are 6-8% lower than those of dry eclogite. A hydrated eclogitic layer several times thicker than the oceanic crust would probably be required for a water-rich region of the mantle to be seismologically detectable. -from Authors

Original languageEnglish (US)
Pages (from-to)20,031-20,037
JournalJournal of Geophysical Research
Issue numberB11
StatePublished - 1993
Externally publishedYes

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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