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Publication Detail
Weakening of calcium iridate during its transformation from perovskite to post-perovskite
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Article
  • Authors:
    Hunt SA, Weidner DJ, Li L, Wang LP, Walte NP, Brodholt JP, Dobson DP
  • Publisher:
    NATURE PUBLISHING GROUP
  • Publication date:
    11/2009
  • Pagination:
    794, 797
  • Journal:
    NAT GEOSCI
  • Volume:
    2
  • Issue:
    11
  • Print ISSN:
    1752-0894
  • Language:
    EN
  • Keywords:
    EARTHS D''-LAYER, PHASE-TRANSITION, LOWERMOST-MANTLE, MGSIO3, BOUNDARY, CAIRO3
  • Addresses:
    Hunt, SA
    UCL
    Dept Earth Sci
    London
    WC1E 6BT
    England
Abstract
The lowermost part of the Earth's mantle-the similar to 200-km-thick D" layer-shows anomalous seismic properties(1,2), and is rheologically distinct from the rest of the lower mantle(3,4). The difference is thought to result from a phase transition from silicate perovskite to silicate post-perovskite(3,4). However, the rheology of the latter phase remains to be documented owing to experimental difficulties in reproducing pressures equivalent to those in the lowermost mantle. Here we address this problem by conducting laboratory experiments that use calcium iridate, which has been shown to be an appropriate low-pressure analogue(5,6). We find that the post-perovskite phase of this analogue is approximately five times weaker than its perovskite phase, and that it further weakens by a factor of two during the phase transformation; these are minimum estimates. If, as is likely, a similar weakening occurs in lower-mantle magnesium-silicate compositions, this could provide an explanation for the behaviour of the lowermost mantle as inferred from geophysical data.
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Dept of Earth Sciences
Dept of Earth Sciences
Dept of Earth Sciences
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