Our understanding of the core-mantle boundary (CMB) region has improved significantly over the past several years due, in part, to the discovery of the postperovskite phase. Sesimic data suggest that the CMB region is highly heterogeneous, possibly reflecting chemical and physical interaction between outer core material and the lowermost mantle. In this contribution we present the results of a new mechanism of mass transfer across the CMB and comment on possible repercussions that include the initiation of deep, siderophile-enriched mantle plumes. We view the nature of core-mantle interaction, and the geodynamic and geochemical ramifications, as multiscale processes, both spatially and temporally. Three lengthscales are defined. On the microscale (1-50 km), we describe the effect of loading and subsequent shearing of the CMB region and show how this may drive local flow of outer core fluid upwards into D″. We propose that larger scale processes operating on a mesoscale (50-300 km) and macroscale regimes (> 300 km) are linked to the microscale, and suggest ways in which these processes may impact on global mantle dynamics.
|Original language||English (US)|
|Title of host publication||Post-Perovskite|
|Subtitle of host publication||The Last Mantle Phase Transition, 2007|
|Publisher||Blackwell Publishing Ltd|
|Number of pages||17|
|State||Published - Jan 1 2007|
|Name||Geophysical Monograph Series|
Bibliographical noteFunding Information:
This work was partly supported by a Grant in Aid for Fundamental Scientific Research from the Ministry of Education of Japan. Special thanks are due to Dr. T. Okada for observation of ACF samples with a high resolution transmission electron microscopy.
© 2007 by the American Geophysical Union. All rights reserved.