Compositional mantle layering revealed by slab stagnation at ~1000-km depth

The stagnation of ~1000-km deep slabs indicates that dense basalt may be more abundant in the lower mantle than in the upper mantle. Improved constraints on lower-mantle composition are fundamental to understand the accretion, differentiation, and thermochemical evolution of our planet. Cosmochemical arguments indicate that lower-mantle rocks may be enriched in Si relative to upper-mantle pyrolite, whereas seismic tomography images suggest whole-mantle convection and hence appear to imply efficient mantle mixing. This study reconciles cosmochemical and geophysical constraints using the stagnation of some slab segments at ~1000-km depth as the key observation. Through numerical modeling of subduction, we show that lower-mantle enrichment in intrinsically dense basaltic lithologies can render slabs neutrally buoyant in the uppermost lower mantle. Slab stagnation (at depths of ~660 and ~1000 km) and unimpeded slab sinking to great depths can coexist if the basalt fraction is ~8% higher in the lower mantle than in the upper mantle, equivalent to a lower-mantle Mg/Si of ~1.18. Global-scale geodynamic models demonstrate that such a moderate compositional gradient across the mantle can persist can in the presence of whole-mantle convection.

[1]  L. Miyagi,et al.  Slab stagnation in the shallow lower mantle linked to an increase in mantle viscosity , 2015 .

[2]  D. Rubie,et al.  Why cold slabs stagnate in the transition zone , 2015 .

[3]  M. Ballmer,et al.  Asymmetric Dynamical Behavior of Thermochemical Plumes and Implications for Hawaiian Lava Composition , 2015 .

[4]  R. Allen,et al.  Seismic Constraints on a Double‐Layered Asymmetric Whole‐Mantle Plume Beneath Hawai‘i , 2015 .

[5]  M. Ballmer,et al.  Intraplate volcanism due to convective instability of stagnant slabs in the mantle transition zone , 2015 .

[6]  J. Hunen,et al.  The effect of metastable pyroxene on the slab dynamics , 2014 .

[7]  F. Niu.  Distinct compositional thin layers at mid-mantle depths beneath northeast China revealed by the USArray , 2014 .

[8]  P. Tackley,et al.  Spontaneous development of arcuate single‐sided subduction in global 3‐D mantle convection models with a free surface , 2014 .

[9]  E. Garnero,et al.  Chemical complexity of hotspots caused by cycling oceanic crust through mantle reservoirs , 2014 .

[10]  P. Tackley,et al.  Influence of combined primordial layering and recycled MORB on the coupled thermal evolution of Earth's mantle and core , 2014 .

[11]  D. Yuen,et al.  Mid-mantle heterogeneities associated with Izanagi plate: Implications for regional mantle viscosity , 2014 .

[12]  Timo Heister,et al.  BurnMan: A lower mantle mineral physics toolkit , 2013 .

[13]  S. Solomon,et al.  Double layering of a thermochemical plume in the upper mantle beneath Hawaii , 2013 .

[14]  A. Deuss,et al.  Reconciling PP and P′P′ precursor observations of a complex 660 km seismic discontinuity , 2013 .

[15]  S. Ghosh,et al.  Effect of water in depleted mantle on post-spinel transition and implication for 660 km seismic discontinuity , 2013 .

[16]  N. Tosi,et al.  Mantle dynamics with pressure- and temperature-dependent thermal expansivity and conductivity , 2013 .

[17]  É. Kaminski,et al.  A two-stage scenario for the formation of the Earth's mantle and core , 2013 .

[18]  Y. Fukao,et al.  Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity , 2012 .

[19]  P. Tackley,et al.  The primitive nature of large low shear-wave velocity provinces , 2012 .

[20]  Y. Ohishi,et al.  A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data , 2012, Nature.

[21]  P. Tackley.  Dynamics and evolution of the deep mantle resulting from thermal, chemical, phase and melting effects , 2012 .

[22]  S. King,et al.  Dynamic buckling of subducting slabs reconciles geological and geophysical observations , 2011 .

[23]  John H. Woodhouse,et al.  S40RTS: A degree-40 shear-velocity model for the mantle from new Rayleigh wave dispersion, teleseismic traveltime and normal-mode splitting function measurements , 2011 .

[24]  D. Giardini,et al.  Signatures of downgoing plate-buoyancy driven subduction in Cenozoic plate motions , 2011 .

[25]  S. Speziale,et al.  Mid‐mantle layering from SKS receiver functions , 2010 .

[26]  M. Billen.  Slab dynamics in the transition zone , 2010 .

[27]  P. Koumoutsakos,et al.  The fate of the slabs interacting with a density/viscosity hill in the mid-mantle , 2010 .

[28]  Maisha Amaru,et al.  Towards absolute plate motions constrained by lower-mantle slab remnants , 2010 .

[29]  Louis Moresi,et al.  Upper plate controls on deep subduction, trench migrations and deformations at convergent margins , 2010 .

[30]  N. Ribe.  Bending mechanics and mode selection in free subduction: a thin-sheet analysis , 2010 .

[31]  P. Koumoutsakos,et al.  he fate of the slabs interacting with a density / viscosity hill in the mid-mantle , 2010 .

[32]  Kerry Gallagher,et al.  Thermochemical interpretation of 1-D seismic data for the lower mantle: The significance of nonadiabatic thermal gradients and compositional heterogeneity , 2009 .

[33]  B. Romanowicz,et al.  Inferring the thermochemical structure of the upper mantle from seismic data , 2009 .

[34]  A. Deuss,et al.  Global Observations of Mantle Discontinuities Using SS and PP Precursors , 2009 .

[35]  P. Tackley,et al.  Intraplate volcanism with complex age‐distance patterns: A case for small‐scale sublithospheric convection , 2009 .

[36]  G. Morard,et al.  Density profile of pyrolite under the lower mantle conditions , 2009 .

[37]  Paul J. Tackley,et al.  Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid , 2008 .

[38]  P. Tackley,et al.  Modeling mantle convection in the spherical annulus , 2008 .

[39]  Wenbo Xu,et al.  The effect of bulk composition and temperature on mantle seismic structure , 2008 .

[40]  S. Taylor,et al.  Inversion of seismic and geodetic data for the major element chemistry and temperature of the Earth's mantle , 2008 .

[41]  L. Elkins‐Tanton.  Linked magma ocean solidification and atmospheric growth for Earth and Mars , 2008 .

[42]  Jennifer Andrews,et al.  Detailed nature of the 660 km region of the mantle from global receiver function data , 2008 .

[43]  E. Garnero,et al.  Structure and Dynamics of Earth's Lower Mantle , 2008, Science.

[44]  D. Stegman,et al.  Global trench migration velocities and slab migration induced upper mantle volume fluxes: Constraints to find an Earth reference frame based on minimizing viscous dissipation , 2008 .

[45]  G. Morra,et al.  Evidence of lower-mantle slab penetration phases in plate motions , 2008, Nature.

[46]  G. Morra,et al.  Dynamic models of downgoing plate-buoyancy driven subduction: subduction motions and energy dissipation , 2007 .

[47]  M. Sacchi,et al.  Imaging mantle discontinuities using least squares Radon transform , 2007 .

[48]  J. Bass,et al.  On the bulk composition of the lower mantle: Predictions and limitations from generalized inversion of radial seismic profiles , 2007 .

[49]  Eh Tan,et al.  Compressible thermochemical convection and application to lower mantle structures , 2007 .

[50]  Insights into the nature of the transition zone from physically constrained inversion of long-period seismic data , 2007, Proceedings of the National Academy of Sciences.

[51]  R. Hilst,et al.  Buckling instabilities of subducted lithosphere beneath the transition zone , 2007 .

[52]  F. Niu,et al.  Observations of the mid‐mantle discontinuity beneath Indonesia from S to P converted waveforms , 2006 .

[53]  Shijie Zhong,et al.  Thermochemical structures beneath Africa and the Pacific Ocean , 2005, Nature.

[54]  J. Bass,et al.  Lower mantle composition and temperature from mineral physics and thermodynamic modelling , 2005 .

[55]  S. Hart,et al.  Major and trace element composition of the depleted MORB mantle (DMM) , 2005 .

[56]  D. Giardini,et al.  Seismic discontinuities in the Mediterranean mantle , 2005 .

[57]  B. Buffett,et al.  Mass transport mechanism between the upper and lower mantle in numerical simulations of thermochemical mantle convection with multicomponent phase changes , 2005 .

[58]  W. Schellart.  Kinematics of subduction and subduction-induced flow in the upper mantle , 2004 .

[59]  N. Bellahsen,et al.  Dynamics of Subduction and Plate Motion in Laboratory Experiments. , 2004 .

[60]  David A. Yuen,et al.  Characteristics-based marker-in-cell method with conservative finite-differences schemes for modeling geological flows with strongly variable transport properties , 2003 .

[61]  Y. Fukao,et al.  Seismic evidence for a chemical heterogeneity in the midmantle: A strong and slightly dipping seismic reflector beneath the Mariana subduction zone , 2003 .

[62]  Paul J. Tackley,et al.  Testing the tracer ratio method for modeling active compositional fields in mantle convection simulations , 2003 .

[63]  S. Solomon,et al.  Seismological evidence for a mid-mantle discontinuity beneath Hawaii , 2003 .

[64]  J. Woodhouse,et al.  A systematic search for mantle discontinuities using SS‐precursors , 2002 .

[65]  G. Hirth.  Laboratory Constraints on the Rheology of the Upper Mantle , 2002 .

[66]  D. Yuen,et al.  Rheological structure and deformation of subducted slabs in the mantle transition zone: implications for mantle circulation and deep earthquakes , 2001 .

[67]  H. Kawakatsu,et al.  Search for seismic discontinuities in the lower mantle , 2001 .

[68]  Masayuki Obayashi,et al.  Stagnant slabs in the upper and lower mantle transition region , 2001 .

[69]  A. Davaille,et al.  Simultaneous generation of hotspots and superswells by convection in a heterogeneous planetary mantle , 1999, Nature.

[70]  Shijie Zhong,et al.  Mixing in a 3D spherical model of present-day mantle convection , 1999 .

[71]  T. Becker,et al.  THERMAL CONSTRAINTS ON THE SURVIVAL OF PRIMITIVE BLOBS IN THE LOWER MANTLE , 1999 .

[72]  W. J. Morgan,et al.  Two-stage melting and the geochemical evolution of the mantle: a recipe for mantle plum-pudding , 1999 .

[73]  K. Creager,et al.  A steeply dipping discontinuity in the lower mantle beneath Izu‐Bonin , 1999 .

[74]  R. Hilst,et al.  Compositional stratification in the deep mantle , 1999, Science.

[75]  G. Helffrich,et al.  Dipping low-velocity layer in the mid-lower mantle: evidence for geochemical heterogeneity , 1999, Science.

[76]  H. Mao,et al.  The fate of subducted basaltic crust in the Earth's lower mantle , 1999, Nature.

[77]  F. Niu,et al.  Broadband converted phases from midmantle discontinuities , 1998 .

[78]  G. Helffrich,et al.  Detection of lower mantle scatterers northeast of the Marianna subduction zone using short-period array data , 1998 .

[79]  Sri Widiyantoro,et al.  Global seismic tomography: A snapshot of convection in the Earth: GSA Today , 1997 .

[80]  Marie-Pierre Doin,et al.  A comparison of methods for the modeling of thermochemical convection , 1997 .

[81]  McSween Hy,et al.  Evidence for Life in a Martian Meteorite , 1997 .

[82]  E. R. Engdahl,et al.  Evidence for deep mantle circulation from global tomography , 1997, Nature.

[83]  R. Hilst,et al.  High resolution global tomography : a snapshot of convection in the Earth , 1997 .

[84]  F. Niu,et al.  Depth variation of the mid‐mantle seismic discontinuity , 1997 .

[85]  A. Hofmann,et al.  Mantle geochemistry: the message from oceanic volcanism , 1997, Nature.

[86]  Louis Moresi,et al.  The accuracy of finite element solutions of Stokes's flow with strongly varying viscosity , 1996 .

[87]  B. Romanowicz,et al.  P′P′ Precursors Under Africa: Evidence for Mid-Mantle Reflectors , 1995, Science.

[88]  Albrecht W. Hofmann,et al.  The chemical composition of the Earth , 1995 .

[89]  M. Javoy.  The integral enstatite chondrite model of the earth , 1995 .

[90]  W. McDonough,et al.  The composition of the Earth , 1995 .

[91]  F. Niu,et al.  Seismic evidence for a 920-km discontinuity in the mantle , 1994, Nature.

[92]  Patrick Wu,et al.  Rheology of the Upper Mantle: A Synthesis , 1993, Science.

[93]  David J. Stevenson,et al.  Effects of an endothermic phase transition at 670 km depth in a spherical model of convection in the Earth's mantle , 1993, Nature.

[94]  Albrecht W. Hofmann,et al.  Chemical differentiation of the Earth: the relationship between mantle, continental crust, and oceanic crust , 1988 .

[95]  D. L. Anderson,et al.  Transition region of the Earth's upper mantle , 1986, Nature.

[96]  D. Yuen,et al.  Layered convection induced by phase transitions , 1985 .

[97]  D. Yuen,et al.  The interaction of a subducting lithospheric slab with a chemical or phase boundary , 1984 .

[98]  Ulrich R. Christensen,et al.  Convection with pressure- and temperature-dependent non-Newtonian rheology , 1984 .

[99]  William S. Curran,et al.  A/I: a synthesis , 1982, ACM-SE 20.

[100]  Alfred Edward Ringwood,et al.  Origin of the Earth and Moon , 1979 .

[101]  B. Mason.  Composition of the Earth , 1966, Nature.