Seismic images of Earth's interior reveal two massive anomalous zones at the base of the mantle, above the core, where seismic waves travel slowly. The mantle materials that surround these anomalous regions are thought to be composed of cooler rocks associated with downward advection of former oceanic tectonic plates. However, the origin and composition of the anomalous provinces is uncertain. These zones have long been depicted as warmer-than-average mantle materials related to convective upwelling. Yet, they may also be chemically distinct from the surrounding mantle, and potentially partly composed of subducted or primordial material, and have therefore been termed thermochemical piles. From seismic, geochemical and mineral physics data, the emerging view is that these thermochemical piles appear denser than the surrounding mantle materials, are dynamically stable and long-lived, and are shaped by larger-scale mantle flow. Whether remnants of a primordial layer or later accumulations of more-dense materials, the composition of the piles is modified over time by stirring and by chemical reactions with material from the surrounding mantle, underlying core and potentially from volatile elements transported into the deep Earth by subducted plates. Upwelling mantle plumes may originate from the thermochemical piles, so the unusual chemical composition of the piles could be the source of distinct trace-element signatures observed in hotspot lavas.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Evidence for compositionally distinct upper mantle plumelets since the early history of the Tristan-Gough hotspot
Nature Communications Open Access 03 July 2023
Journal of High Energy Physics Open Access 17 April 2023
Communications Earth & Environment Open Access 17 March 2023
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Rent or buy this article
Prices vary by article type
Prices may be subject to local taxes which are calculated during checkout
Ritsema, J., Deuss, A., van Heijst, H. J. & Woodhouse, J. H. S40RTS: a degree-40 shear-velocity model for the mantle from new Rayleigh wave dispersion, teleseismic traveltime and normal-mode splitting function measurements. Geophys. J. Int. 184, 1223–1236 (2011).
Lekic, V., Cottaar, S., Dziewonski, A. & Romanowicz, B. Cluster analysis of global lower mantle tomography: a new class of structure and implications for chemical heterogeneity. Earth Planet. Sci. Lett. 357, 68–77 (2012).
Garnero, E. J. & McNamara, A. K. Structure and dynamics of Earth's lower mantle. Science 320, 626–628 (2008).
Koelemeijer, P., Ritsema, J., Deuss, A. & van Heijst, H. J. SP12RTS: a degree-12 model of shear- and compressional-wave velocity for Earth's mantle. Geophys. J. Int. 204, 1024–1036 (2016).
He, Y. & Wen, L. Geographic boundary of the “Pacific Anomaly” and its geometry and transitional structure in the north. J. Geophys. Res. 117, B09308 (2012).
Tanaka, S. et al. On the vertical extent of the large low shear velocity province beneath the South Pacific Superswell. Geophys. Res. Lett. 36, L07305 (2009).
Suetsugu, D. et al. South Pacific mantle plumes imaged by seismic observation on islands and seafloor. Geochem. Geophys. Geosyst. 10, Q11014 (2009).
French, S. W. & Romanowicz, B. Broad plumes rooted at the base of the Earth's mantle beneath major hotspots. Nature 525, 95–99 (2015).
Zhao, C., Garnero, E. J., McNamara, A. K., Schmerr, N. & Carlson, R. W. Seismic evidence for a chemically distinct thermochemical reservoir in Earth's deep mantle beneath Hawaii. Earth Planet. Sci. Lett. 426, 143–153 (2015).
Sun, D. & Miller, M. S. Study of the western edge of the African large low shear velocity province. Geochem. Geophys. Geosyst. 14, 3109–3125 (2013).
Frost, D. A. & Rost, S. The P-wave boundary of the large-low shear velocity province beneath the Pacific. Earth Planet. Sci. Lett. 403, 380–392 (2014).
McNamara, A. K., Garnero, E. J. & Rost, S. Tracking deep mantle reservoirs with ultra low velocity zones. Earth Planet. Sci. Lett. 299, 1–9 (2010).
Rost, S., Earle, P. S., Shearer, P. M., Frost, D. A. & Selby, N. D. in The Earth's Heterogeneous Mantle: A Geophysical, Geodynamical, and Geochemical Perspective (eds Khan, A. & Deschamps, F.) 367–390 (Springer Publishing, 2015).
Frost, D. A., Rost, S., Selby, N. D. & Stuart, G. W. Detection of a tall ridge at the core–mantle boundary from scattered PKP energy. Geophys. J. Int. 195, 558–574 (2013).
Cobden, L. & Thomas, C. The origin of D" reflections: a systematic study of seismic array data sets. Geophys. J. Int. 194, 1091–1118 (2013).
Cobden, L., Thomas, C. & Trampert, J. The Earth's Heterogeneous Mantle: A Geophysical, Geodynamical, and Geochemical Perspective (eds Khan, A. & Deschamps, F.) 391–440 (Springer Publishing, 2015).
Nakagawa, T. & Tackley, P. J. Effects of low-viscosity post-perovskite on thermo-chemical mantle convection in a 3-D spherical shell. Geophys. Res. Lett. 38, L04309 (2011).
Lay, T., Hernlund, J., Garnero, E. J. & Thorne, M. S. A post-perovskite lens and D" heat flux beneath the Central Pacific. Science 314, 1272–1276 (2006).
Li, M., McNamara, A. K. & Garnero, E. J. Chemical complexity of hotspots caused by cycling oceanic crust through mantle reservoirs. Nature Geosci. 7, 336–370 (2014).
Brandenburg, J. P. & van Keken, P. E. Deep storage of oceanic crust in a vigorously convecting mantle. J. Geophys. Res. 112, B06403 (2007).
Nakagawa, T., Tackley, P. J., Deschamps, F. & Connolly, J. A. D. The influence of MORB and harzburgite composition on thermo-chemical mantle convection in a 3-D spherical shell with self-consistently calculated mineral physics. Earth Planet. Sci. Lett. 296, 403–412 (2010).
Grocholski, B., Catalli, K., Shim, S.-H. & Prakapenka, V. B. Mineralogical effects on the detectability of the post-perovskite boundary. Proc. Natl. Acad. Sci. USA 109, 2275–2279 (2012).
Grocholski, B., Shim, S.-H. & Prakapenka, V. B. Stability, metastability, and elastic properties of a dense silica polymorph, seifertite. J. Geophys. Res. 118, B50360 (2013).
Wang, Y. & Wen, L. Complex seismic anisotropy at the border of a very low velocity province at the base of the Earth's mantle. J. Geophys. Res. 112, B09305 (2007).
Lynner, C. & Long, M. D. Lowermost mantle anisotropy and deformation along the boundary of the African LLSVP. Geophys. Res. Lett. 41, 3447–3454 (2014).
Trampert, J., Deschamps, F., Resovsky, J. & Yuen, D. A. Probabilistic tomography maps chemical heterogenities throughout the mantle. Science 306, 853–856 (2004).
Kuo, C. & Romanowicz, B. On the resolution of density anomalies in the Earth's mantle using spectral fitting of normal-mode data. Geophys. J. Int. 150, 1620179 (2002).
Masters, G. & Gubbins, D. On the resolution of density within the Earth. Phys. Earth Planet. In. 140, 159–167 (2003).
Romanowicz, B. Can we resolve 3D density heterogeneity in the lower mantle? Geophys. Res. Lett. 28, 1107–1110 (2001).
Masters, G., Laske, G., Bolton, H. & Dziewonski, A. M. in Earth's Deep Interior (eds Karato, S. et al.) 63–87 (Geophysical Monograph Series Vol. 117, American Geophysical Union, 2000).
Koelemeijer, P., Duess, A. F., Ritsema, J. & van Heijst, H. J. Normal mode insights into the long wavelength velocity and density structure of the lowermost mantle. Abstr. DI33B-02 (American Geophysical Union, Fall Meeting, 2014).
Burke, K., Steinberger, B., Torsvik, T. H. & Smethurst, M. A. Plume generation zones at the margins of large low shear velocity provinces on the core–mantle boundary. Earth Planet. Sci. Lett. 265, 49–60 (2008).
Thorne, M., Garnero, E. J. & Grand, S. P. Geographic correlation between hot spots and deep mantle lateral shear-wave velocity gradients. Phys. Earth Planet. In. 146, 47–63 (2004).
Torsvik, T. H., Burke, K., Steinberger, B., Webb, S. J. & Ashwal, L. D. Diamonds sampled by plumes from the core–mantle boundary. Nature 466, 352–355 (2010).
Davies, D. R., Goes, S. & Sambridge, M. On the relationship between volcanic hotspot locations, the reconstructed eruption sites of large igneous provinces and deep mantle seismic structure. Earth Planet. Sci. Lett. 411, 121–130 (2015).
Steinberger, B. & Torsvik, T. H. A geodynamic model of plumes from the margins of large low shear velocity provinces. Geochem. Geophys. Geosyst. 13, Q01W09 (2012).
Weis, D., Garcia, M. O., Rhodes, J. M., Jellinek, M. & Scoates, J. S. Role of the deep mantle in generating the compositional asymmetry of the Hawaiian mantle plume. Nature Geosci. 4, 831–838 (2011).
Payne, J. A., Jackson, M. G. & Hall, P. S. Parallel volcano trends and geochemical asymmetry of the Society Islands hotspot track. Geology 41, 19–22 (2013).
Farnetani, C. G., Hofmann, A. W. & Class, C. How double volcanic chains sample geochemical anomalies from the lowermost mantle. Earth Planet. Sci. Lett. 359, 240–247 (2012).
McNamara, A. K. & Zhong, S. Thermochemical piles under Africa and the Pacific. Nature 437, 1136–1139 (2005).
Bull, A. L., McNamara, A. K. & Ritsema, J. Synthetic tomography of plume clusters and thermochemical piles. Earth Planet. Sci. Lett. 278, 152–162 (2009).
Zhang, N., Zhong, S., Leng, W. & Li, Z. X. A model for the evolution of the Earth's mantle structure since the Early Paleozoic. J. Geophys. Res. 115, B06401 (2010).
Thompson, P. F. & Tackley, P. J. Generation of mega-plumes from the core–mantle boundary in a compressible mantle with temperature-dependent viscosity. Geophys. Res. Lett. 25, 1999–2002 (1998).
Schubert, G., Masters, G., Olson, P. & Tackley, P. J. Superplumes or plume clusters? Phys. Earth Planet. In. 146, 147–162 (2004).
Schuberth, B. S. A., Bunge, H.-P. & Ritsema, J. Tomographic filtering of high-resolution mantle circulation models: Can seismic heterogeneity be explained by temperature alone? Geochem. Geophys. Geosyst. 10, Q05W03 (2009).
Davies, D. R., Goes, S., Schuberth, B. S. A., Bunge, H. P. & Ritsema, J. Reconciling dynamic and seismic models of Earth's lower mantle: the dominant role of thermal heterogeneity. Earth Planet. Sci. Lett. 353, 253–269 (2012).
Tackley, P. J. in The Core–Mantle Boundary Region (eds Gurnis, M. et al.) 231–253 (Geodynamic Series, American Geophysical Union, 1998).
Nakagawa, T., Tackley, P. J., Deschamps, F. & Connolly, J. A. D. Incorporating self-consistently calculated mineral physics into thermochemical mantle convection simulations in a 3-D spherical shell and its influence on seismic anomalies in Earth's mantle. Geochem. Geophys. Geosyst. 10, Q03004 (2009).
Mulyukova, E., Steinberger, B., Dabrowski, M. & Sobolev, S. V. Survival of LLSVPs for billions of years in a vigorously convecting mantle: replenishment and destruction of chemical anomaly. J. Geophys. Res. 120, 3824–3847 (2015).
Tolstikhin, I. N., Kramers, J. D. & Hofmann, A. W. A chemical Earth model with whole mantle convection: the importance of a core–mantle boundary layer (D") and its early formation. Chem. Geol. 226, 79–99 (2006).
Labrosse, S., Hernlund, J. W. & Coltice, N. A crystallizing dense magma ocean at the base of the Earth's mantle. Nature 450, 866–869 (2007).
Lee, C. T. A. et al. Upside-down differentiation and generation of a 'primordial' lower mantle. Nature 463, 930–933 (2010).
Carlson, R. W. et al. How did early Earth become our modern world? Ann. Rev. Earth Planet. Sci. 42, 151–178 (2014).
Hirose, K., Fei, Y. W., Ma, Y. Z. & Mao, H. K. The fate of subducted basaltic crust in the Earth's lower mantle. Nature 397, 53–56 (1999).
Knittle, E. & Jeanloz, R. Simulating the core–mantle boundary: an experimental study of high-pressure reactions between silicates and liquid iron. Geophys. Res. Lett. 16, 609–612 (1989).
Dubrovinsky, L. et al. Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle. Nature 422, 58–61 (2003).
Li, M. & McNamara, A. K. The difficulty for subducted oceanic crust to accumulate in upwelling mantle plume regions. J. Geophys. Res. 118, 1–10 (2013).
Davaille, A., Girard, F. & Le Bars, M. How to anchor hotspots in a convecting mantle? Earth Planet. Sci. Lett. 203, 621–634 (2002).
Tan, E. & Gurnis, M. Compressible thermochemical convection and application to lower mantle structures. J. Geophys. Res. 112, B06304 (2007).
Lassak, T. M., McNamara, A. K., Garnero, E. J. & Zhong, S. Core–mantle boundary topography and mantle dynamics. Earth Planet. Sci. Lett. 289, 232–241 (2010).
Soldati, G., Koelemeijer, P., Boschi, L. & Deuss, A. Constraints on core–mantle boundary topography from normal mode splitting. Geochem. Geophys. Geosyst. 14, 1333–1342 (2013).
Lundin, S. et al. Effect of Fe on the equation of state of mantle silicate perovskite over 1 Mbar. Phys. Earth Planet. In. 168, 97–102 (2008).
Fei, Y. et al. Spin transition and equation of state of (Mg, Fe)O solid solution. Geophys. Res. Lett. 34, L17307 (2007).
Irifune, T. et al. Iron partitioning and density changes of pyrolite in Earth's lower mantle. Science 327, 193–195 (2010).
Nakajima, Y., Frost, D. J. & Rubie, D. C. Ferrous iron partitioning between magnesium silicate perovskite and ferropericlase and the composition of perovskite in the Earth's lower mantle. J. Geophys. Res. 117, B08201 (2012).
Jackson, J. M., Zhang, J. Z. & Bass, J. D. Sound velocities and elasticity of aluminous MgSiO3 perovskite: implications for aluminum heterogeneity in Earth's lower mantle. Geophys. Res. Lett. 31, L10614 (2004).
Kawai, K. & Tsuchiya, T. Small shear modulus of cubic CaSiO3 perovskite. Geophys. Res. Lett. 42, 2718–2726 (2015).
Nomura, R. et al. Spin crossover and iron-rich silicate melt in the Earth's deep mantle. Nature 473, 199–202 (2011).
Andrault, D. et al. Solid-liquid iron partitioning in Earth's deep mantle. Nature 487, 354–357 (2012).
Gu, C. et al. Electronic structure of iron in magnesium silicate glasses at high pressure. Geophys. Res. Lett. 39, L24304 (2012).
Kesson, S. E., Fitz Gerald, J. D. & Shelley, J. M. G. Mineral chemistry and density of subducted basaltic crust at lower-mantle pressures. Nature 372, 767–769 (1994).
Deschamps, F., Kaminski, E. & Tackley, P. J. A deep mantle origin for the primitive signature of ocean island basalt. Nature Geosci. 4, 879–882 (2011).
Deschamps, F., Cobden, L. & Tackley, P. J. The primitive nature of large low shear-wave velocity provinces. Earth Planet. Sci. Lett. 349–350, 198–208 (2012).
Holzapfel, C., Rubie, D. C., Frost, D. J. & Langenhorst, F. Fe–Mg interdiffusion in (Mg, Fe)SiO3 perovskite and lower mantle reequilibration. Science 309, 1707–1710 (2005).
Andrault, D. et al. Melting of subducted basalt at the core–mantle boundary. Science 344, 892–895 (2014).
Fiquet, G. et al. Melting of peridotite to 140 gigapascals. Science 329, 1516–1518 (2010).
Nomura, R. et al. Low core–mantle boundary temperature inferred from the solidus of pyrolite. Science 343, 522–525 (2014).
Tsuchiya, J. First principles prediction of a new high-pressure phase of dense hydrous magnesium silicates in the lower mantle. Geophys. Res. Lett. 40, 4570–4573 (2013).
Nishi, M. et al. Stability of hydrous silicate at high pressures and water transport to the deep lower mantle. Nature Geosci. 7, 224–227 (2014).
Ohira, I. et al. Stability of a hydrous δ-phase, AlOOH-MgSiO2(OH)2, and a mechanism for water transport into the base of lower mantle. Earth Planet. Sci. Lett. 401, 21–27 (2014).
Ohtani, E., Amaike, Y., Kamada, S., Sakamaki, T. & Hirao, N. Stability of hydrous phase H MgSiO4H2 under lower mantle conditions. Geophys. Res. Lett. 41, 8283–8287 (2014).
Mosca, I., Cobden, L., Deuss, A., Ritsema, J. & Trampert, J. Seismic and mineralogical structures of the lower mantle from probabilistic tomography. J. Geophys. Res. 117, B06304 (2012).
Seto, Y., Hamane, D., Nagai, T. & Fujino, K. Fate of carbonates within oceanic plates subducted to the lower mantle, and a possible mechanism of diamond formation. Phys. Chem. Miner. 35, 223–229 (2008).
Oganov., A. R., Ono, S., Ma, Y., Glass, C. W. & Garcia, A. Novel high-pressure structures of MgCO3, CaCO3, and CO2 and their role in Earth's lower mantle. Earth Planet. Sci. Lett. 273, 38–47 (2008).
Takafuji, N., Hirose, K., Mitome, M. & Bando, Y. Solubilities of O and Si in liquid iron equilibrium with (Mg, Fe)SiO3 perovskite and the light elements in the core. Geophys. Res. Lett. 32, L06313 (2005).
Ozawa, H. et al. Chemical equilibrium between ferropericlase and molten iron to 134 GPa and implications for iron content at the bottom of the mantle. Geophys. Res. Lett. 35, L05308 (2008).
Frost, D. J. et al. Partitioning of oxygen between the Earth's mantle and core. J. Geophys. Res. 115, B02202 (2010).
Badro, J., Côté, A. S. & Brodholt, J. P. A seismologically consistent compositional model of Earth's core. Proc. Natl. Acad. Sci. USA 111, 7542–7545 (2015).
Manga, M. & Jeanloz, R. Implications of a metal-bearing chemical boundary layer in D" for mantle dynamics. Geophys. Res. Lett. 23, 3091–3094 (1996).
Otsuka, K. & Karato, S.-I. Deep penetration of molten iron into the mantle caused by a morphological instability. Nature 492, 243–246 (2012).
Kanda, R. V. S. & Stevenson, D. J. Suction mechanism for iron entrainment into the lower mantle. Geophys. Res. Lett. 33, L02310 (2006).
Johnson, T. E., Brown, M., Kaus, B. J. P. & VanTongeren, J. A. Delamination and recycling of Archaean crust caused by gravitational instabilities. Nature Geosci. 7, 47–52 (2013).
Hofmann, A. W. & S. R. Hart. Assessment of local and regional isotopic equilibrium in the mantle. Earth Planet. Sci. Lett. 38, 44–62 (1978).
Mukhopadhyay, S. Early differentiation and volatile accretion recorded in deep-mantle neon and xenon. Nature 486, 101–104 (2012).
Ricolleau, A. et al. Phase relations and equation of state of a natural MORB: implications for the density profile of subducted oceanic crust in the Earth's lower mantle. J. Geophys. Res. 115, B08202 (2012).
Williams, C. D., Li, M., McNamara, A. K., Garnero, E. J. & van Soest, M. C. Episodic entrainment of deep primordial mantle material into ocean island basalts. Nature Commun. 6, 8937 (2015).
McDonough, W. F. & Sun, S.-S. The composition of the Earth. Chem. Geol. 120, 223–253 (1995).
Schilling, J.-G. et al. Petrologic and geochemical variations along the mid-Atlantic ridge from 29°N to 73°N. Am. J. Sci. 283, 510–586 (1983).
Kesson, S. E., Fitz Gerald, J. D. & Shelley, J. M. Mineralogy and dynamics of a pyrolite lower mantle. Nature 393, 252–255 (1998).
Hirose, K., Takafuji, N., Sata, N. & Ohishi, Y. Phase transition and density of subducted MORB crust in the lower mantle. Earth Planet. Sci. Lett. 237, 239–251 (2005).
The authors thank T. Torsvik for the LIP and kimberlite data set, seismic tomographers that made their models publically available, D.A. Frost and P. Koelemeijer for fruitful discussions, and J. Ritsema, F. Deschamps and A. Stracke for abundant helpful comments. M. Li provided model results and images from ref. 19 that were the basis of Supplementary Fig. S6. This research was partially supported by National Science Foundation grants EAR1401270, EAR1161038 and EAR1338810.
The authors declare no competing financial interests.
About this article
Cite this article
Garnero, E., McNamara, A. & Shim, SH. Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle. Nature Geosci 9, 481–489 (2016). https://doi.org/10.1038/ngeo2733
This article is cited by
Nature Reviews Earth & Environment (2023)
Evidence for compositionally distinct upper mantle plumelets since the early history of the Tristan-Gough hotspot
Nature Communications (2023)
Nature Geoscience (2023)
Communications Earth & Environment (2023)