TY - JOUR
T1 - Core-mantle boundary topography as a possible constraint on lower mantle chemistry and dynamics
AU - Lassak, Teresa Mae
AU - McNamara, Allen K.
AU - Garnero, Edward
AU - Zhong, Shijie
N1 - Funding Information:
National Science Foundation grants EAR-0456356 , EAR-0510383 , EAR-0711366 , and EAR-0838565 provided funds for this research. We thank Frank Timmes and the ASU HPC for allowing us to use their resources for our calculations. We also extend our gratitude to Thorsten Becker, Amanda Clark, Matt Fouch, Jim Tyburczy, and Abigail Bull for fruitful discussions. Reviews and comments from Yanick Ricard, Masaki Yoshida, and an anonymous reviewer enhanced the manuscript greatly.
PY - 2010/1/15
Y1 - 2010/1/15
N2 - The origin of large low shear-wave velocity provinces (LLSVPs) in the lowermost mantle beneath the central Pacific and Africa is not well constrained. We explore numerical convection calculations for two proposed hypotheses for these anomalies, namely, thermal upwellings (e.g., plume clusters) and large intrinsically dense piles of mantle material (e.g., thermochemical piles), each of which uniquely affects the topography on Earth's core-mantle boundary (CMB). The thermochemical pile models predict a relatively flat but elevated CMB beneath piles (presumed LLSVPs), with strong upwarping along LLSVP margins. The plume cluster models predict CMB upwarping beneath upwellings that are less geographically organized. Both models display CMB depressions beneath subduction related downwelling. While each of the two models produces a unique, characteristic style of CMB topography, we find that seismic models will require shorter length scales than are currently being employed in order to distinguish between the end-member dynamic models presented here.
AB - The origin of large low shear-wave velocity provinces (LLSVPs) in the lowermost mantle beneath the central Pacific and Africa is not well constrained. We explore numerical convection calculations for two proposed hypotheses for these anomalies, namely, thermal upwellings (e.g., plume clusters) and large intrinsically dense piles of mantle material (e.g., thermochemical piles), each of which uniquely affects the topography on Earth's core-mantle boundary (CMB). The thermochemical pile models predict a relatively flat but elevated CMB beneath piles (presumed LLSVPs), with strong upwarping along LLSVP margins. The plume cluster models predict CMB upwarping beneath upwellings that are less geographically organized. Both models display CMB depressions beneath subduction related downwelling. While each of the two models produces a unique, characteristic style of CMB topography, we find that seismic models will require shorter length scales than are currently being employed in order to distinguish between the end-member dynamic models presented here.
KW - CMB topography
KW - core-mantle boundary
KW - mantle convection
KW - plume clusters
KW - thermochemical piles
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U2 - 10.1016/j.epsl.2009.11.012
DO - 10.1016/j.epsl.2009.11.012
M3 - Article
AN - SCOPUS:72949120806
SN - 0012-821X
VL - 289
SP - 232
EP - 241
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 1-2
ER -