Development of anisotropic structure in the Earth's lower mantle by solid-state convection

Nature
Allen K McNamaraS Karato

Abstract

Seismological observations reveal highly anisotropic patches at the bottom of the Earth's lower mantle, whereas the bulk of the mantle has been observed to be largely isotropic. These patches have been interpreted to correspond to areas where subduction has taken place in the past or to areas where mantle plumes are upwelling, but the underlying cause for the anisotropy is unknown-both shape-preferred orientation of elastically heterogeneous materials and lattice-preferred orientation of a homogeneous material have been proposed. Both of these mechanisms imply that large-strain deformation occurs within the anisotropic regions, but the geodynamic implications of the mechanisms differ. Shape-preferred orientation would imply the presence of large elastic (and hence chemical) heterogeneity whereas lattice-preferred orientation requires deformation at high stresses. Here we show, on the basis of numerical modelling incorporating mineral physics of elasticity and development of lattice-preferred orientation, that slab deformation in the deep lower mantle can account for the presence of strong anisotropy in the circum-Pacific region. In this model-where development of the mineral fabric (the alignment of mineral grains) is caused so...Continue Reading

Citations

Jun 26, 2007·Science·Sébastien MerkelHans-Rudolf Wenk
Apr 11, 2009·Science·Hauke MarquardtEdward J Garnero
Jan 13, 2006·Proceedings of the National Academy of Sciences of the United States of America·Renata M WentzcovitchJun Tsuchiya
Apr 19, 2017·Nature Communications·Xiang WuVitali B Prakapenka
Apr 23, 2004·Nature·Sébastien Merkel
Dec 13, 2019·Proceedings of the National Academy of Sciences of the United States of America·David P DobsonJohn Wheeler
Jul 24, 2018·Journal of Geophysical Research. Solid Earth·Laura ParisiJeroen Ritsema
Apr 12, 2019·Reports on Progress in Physics·Ernian Pan
Aug 11, 2005·Physical Review Letters·S OdunugaR S Averback
Jan 17, 2004·Science·Mark Panning, Barbara Romanowicz
Oct 9, 2004·Science·Edward J GarneroMatthew J Fouch
Feb 4, 2006·Science·Sébastien MerkelHans-Rudolf Wenk

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