scispace - formally typeset

Journal ArticleDOI

Plate tectonics and mantle controls on plume dynamics

01 Oct 2020-Earth and Planetary Science Letters (Elsevier)-Vol. 547, pp 116439

Abstract: Mantle plumes provide valuable information about whole-mantle convection: they originate at the core-mantle boundary, cross Earth's mantle and interact with the lithosphere. For instance, it has been proposed that the mobility/stability of plumes depends on plume intrinsic properties, on how slabs interact with the basal boundary layer, on mantle flow, or on their proximity to mid-ocean ridges. Here, we use 3D-spherical models of mantle convection generating self-consistent plate-like behaviour to investigate the mechanisms linking tectonics and mantle convection to plume dynamics. Our models produce fully-dynamic mantle plumes that rise vertically with deflection 10 ° and present excess temperatures, rising speeds, buoyancy and heat fluxes comparable to observations. In the absence of plate tectonics, plumes are stable and their lifetime exceeds hundreds of million years. With plate tectonics, plumes are more mobile, and we identify four physical mechanisms controlling their stability. 1/ Fixed plumes are located at saddle points of basal mantle flow. 2/ Plumes moving at speeds between 0.5-1 cm yr−1 are slowly entrained by passive mantle flow. 3/ Fast plume motions between 2-5 cm yr−1 lasting several tens of million years are caused by slab push. 4/ Plumes occasionally drift at speeds >5 cm yr−1 over 25%, which suggests that fixed hotspot reference frames can be defined from carefully selected hotspot tracks.
Topics: Mantle convection (72%), Hotspot (geology) (69%), Plate tectonics (60%), Mantle plume (59%), Plume (59%)

Summary (4 min read)

1. Introduction

  • Collectively, the above-mentioned studies highlight the need to investigate the coupled behaviour of mantle plumes, plate tectonics, large-scale mantle flow and basal thermochemical structures.
  • Here the authors use time-dependent 3Dspherical numerical models of whole-mantle convection at Earth-like con-vective vigour and self-generating plate tectonics to jointly investigate the mechanisms linking plate tectonics, mantle convection and plume dynamics.
  • In these models, drifting plumes arise self-consistently and dynamically interact with surface tectonics, large-scale and small-scale convection.
  • Focusing on model plume conduits, the authors show that their number, lifetime, shape, temperature excess, rising speed, buoyancy and heat fluxes are comparable to observations.
  • This serves as a basis to investigate the role of plate tectonics, plate layout, convective vigour of the lowermost mantle and basal thermochemical structures on plume spatio-temporal dynamics.

2.1. Numerical models of mantle convection with plate-like tectonics

  • The authors track the evolution of compositional fields using the tracer-ratio method (Tackley and King, 2003) .
  • Model continents are low-density lithospheric rafts, thicker and stiffer than the oceanic lithosphere to prevent their entrainment by the convective flow (Table 1 ).
  • Their margins are recycled through time (Supplementary Movies 1-3), consistent with estimates of continental recycling at subduction zones (Coltice et al., 2019).
  • The use of pseudo-plasticity favours Earth-like surface velocities and tectonics (e.g. Coltice et al., 2017) .
  • As in Arnould et al. (2018) , the authors verify that Models 2-5 favour plate-like behaviour with Earth-like plateness (proxy for the degree of surface deformation localisation, Tackley, 2000) , surface mobility, plate velocities, heat flow and topography (Table 2 , Fig. 1 , Fig. S3 (a), Movie S1 and S2).

2.2. Automated detection of mantle plumes

  • Therefore, in their models, "net rotation" is the net rotation of the mantle with respect to a fixed surface.

3. Phenomenology of model mantle plumes

  • The authors first describe and quantify the spatio-temporal characteristics of model mantle plumes.

3.1. Number

  • The number of detected plumes is in broad agreement with other numerical models of whole-mantle convection although model parameters (including physical assumptions and surface boundary conditions) differ (e.g. Davies and Davies, 2009; Hassan et al., 2015; Li and Zhong, 2019) .
  • On Earth, the number of hotspots of lower mantle origin remains debated.

3.2. Lifetime

  • These results are compatible with the longest lived oceanic hotspot tracks for St-Helena (about 120 Myr), Tristan (about 120 Myr) and New England (about 130 Ma) plumes (Duncan, 1984; Williams et al., 2015) .
  • Shorterlived hotspot tracks (e.g. Hawaii and Louisville active at least from 87 Ma) terminate at subduction zones, but may have been active longer, the potential oldest parts of their tracks having been subducted (e.g. Portnyagin et al., 2008) .
  • Finally, geochemical analyses suggest that South Pacific Cook-Austral plumes have been active for at least 120 Ma (e.g. Konter et al., 2008) .

3.3. Shape and radius

  • Plumes originate from topographic crests (Fig. 1 ), either along the edges or on the top of the basal thermochemical heterogeneities, as in previous models that consider dense and hot basal material (Garnero and McNamara, 2008; Hassan et al., 2015; Li and Zhong, 2017, 2019) .

3.5. Buoyant rising speed

  • In Model 5 (thermochemical plumes), buoyant rising upper mantle speeds are only approximately 17 cm yr −1 because entrained denser basal material decreases the positive thermal buoyancy of plume material.

3.6. Buoyancy flux

  • With ρ m the reference mantle density, α the reference thermal expansivity, ∆T the mantle plume temperature excess, A p the cross-sectional area of mantle plume conduits and v p the buoyant rising speed.
  • This range of model plume buoyancy fluxes is comparable to estimates for present-day hotspots (Crosby and McKenzie, 2009) .

3.7. Heat flow

  • Davies (1988) and Sleep (1990) estimated the contribution of plumes to the total surface heat flow as 2.5 TW from hotspot swells.
  • The ratio of upper-mantle plume heat flow to core heat flow (about 50-60% in Models 1-5) is consistent with numerical models of incompressible and isoviscous (Labrosse, 2002) or temperature-dependent viscosity convection with different internal heating rates (Mittelstaedt and Tackley, 2006) . (2006) showed that plumes contribute to heat up sinking slabs, therefore losing some heat on their way up (Fig. S6 ).
  • Using extended-Boussinesq (Leng and Zhong, 2008; Zhong, 2006) and compressible models (Bunge, 2005) , it was also suggested that the proportion of core heat flux advected by plumes decreases towards the surface following a steep plume adiabatic gradient.

3.8. Pulses of activity

  • This temperature decrease is consistent with geological estimates of the temperature evolution of the Galapagos and Iceland plumes (Herzberg and Gazel, 2009) .
  • Changes in plume buoyancy flux tend to occur after plume merging events or after interaction with a ridge (Fig. 2d ).

3.9. Absolute motions of plumes

  • This reflects that some plumes are tilted by vigorous upper mantle convection.

3.11. Topographic swell

  • The swell extent and amplitude depend on 1/ plume buoyancy flux that decreases over time (Fig. 2 and Movies S1 and S2), 2/ the nature of the impacted lithosphere (thickness, type, plate boundary proximity) and 3/ the relative motion between the plume and the lithosphere, which can shear the conduit and result in an asymmetric shape of the plume trail (Fig. S2 , Movies S1 and S2; see also Arnould et al., 2019) .

3.12. Plume-ridge interactions

  • Finally, some plumes can cross ridge axes and contribute to the propagation of a new spreading axis (Fig. 6c ).
  • This case shares similarities with the Réunion hotspot crossing the Central Indian Ridge about 30 Myr ago and its putative link to the formation of the Rodriguez ridge (Morgan, 1978) .

4. Sources of plume drift

  • The authors used the above analysis of the characteristics of model plumes to classify the lateral plume motions into categories.

4.1. "Fixed" plumes

  • These plumes are rooted at saddle points of basal flow and therefore remain stable throughout their lifetime.
  • This stability is favoured by the absence of plate tectonics at the surface, since the number of fixed plumes decreases to between 25% (Model 5) and 50% (Model 3) when platelike behaviour occurs (Fig. 5a ).
  • In Li and Zhong (2019) , the proportion of fixed plumes is 10-20%, possibly due to the deep mantle rotation rotation induced by imposed plate velocities (Rudolph and Zhong, 2014) .

4.2. Basal mantle flow entrainment

  • IDs 18 and 18) coincides in direction and magnitude with lowermost mantle flow in their vicinity (Fig. 5a and Table 2 ).

4.3. Slab-induced drift

  • Have not yet been documented on Earth, which could be explained by the rare occurrence and short duration of such model events.

5.1. Limitations of models and analysis

  • This threshold was defined by comparing the number of plumes detected by the algorithm to the number of mantle plumes detected visually.

5.2. What controls plume dynamics?

  • Here, the authors focus on the causes of lateral motions of already developed plumes and do not investigate the controls on the position of their source, which is likely to also affect their dynamics (e.g.

5.2.1. Indirect control by plate tectonics

  • The authors show that planetary surface dynamics exerts a first-order control on plume drift: if the surface is in stagnant lid, stable or slowly moving plumes predominate.
  • The impossibility for mantle plumes to drift rapidly in the absence of plate tectonics and lithospheric thickness heterogeneities was noted by Zhong (2009) who studied the origin of Martian volcanism.
  • Plate-like behaviour promotes faster plume motion (Fig. 5 ) due to the interaction of plume conduits with slabs in the upper or the lower mantle.

5.2.2. Limited stabilisation of mantle plumes by mid-ocean ridges

  • It has been proposed that mantle plumes can be pinned to stable ridges (Tarduno et al., 2009) .
  • In their models, three plume behaviours arise depending on the type of spreading centre they interact with.
  • The possible slow motion of the Azores plume could fall in that category (Arnould et al., 2019) .
  • Finally, mantle plumes interacting with fast-migrating ridges, usually neighbouring small plates affected by fast reorganisations, tend to move laterally faster and more eratically (Fig. 6d ).

5.2.3. The role of the mantle environment on plume dynamics

  • Model mantle plumes rooted at the edges of basal thermochemical heterogeneities tend to be more mobile (Fig. 5a ) and are more likely to be deflected (Fig. 4 ) than purely thermal plumes (Davaille et al., 2002; Li and Zhong, 2019) because the entrainment of dense material by plume conduits slows their rise by a factor of two in their experiments.

5.2.4. Plume characteristics are not diagnostic of plume motions

  • Moreover, plume tilt angles do not correlate with plume drifting rates (Fig. 8b ).
  • Instead, fast-moving plumes are characterized by small tilt angles.
  • This suggests that intrinsic plume characteristics cannot be used as a diagnostic for plume drift.

5.3. Implications for absolute plate reconstructions

  • Moreover, their results show that plumes with different drifting rates can coexist within the same global convective system, depending on their location and potential interactions with slabs, plate tectonics and regional convective flow (Fig. S9 ).
  • Indeed, model plume velocities can exceed 2 cm yr −1 , consistent with geochronological and paleomagnetic observations for Hawaii (Tarduno et al., 2003; Konrad et al., 2018) and Kerguelen (Antretter et al., 2002) .
  • The authors study therefore reconciles contradictory observations of plume drift and suggests that defining a global reference frame based on hotspot tracks to reconstruct past absolute plate motions requires the careful selection of slow-moving plumes based on paleomagnetic and geochronological data.

6. Conclusion

  • The intrinsic properties of plumes observed from the surface (age, excess temperature, buoyancy flux, rising speed, tilt angle) are not diagnostic of plume motion since they do not correlate with lateral plume velocity.

Did you find this useful? Give us your feedback

Content maybe subject to copyright    Report

HAL Id: hal-03228588
Submitted on 18 May 2021
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entic research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diusion de documents
scientiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
Plate tectonics and mantle controls on plume dynamics
Maëlis Arnould, Nicolas Coltice, Nicolas Flament, Claire Mallard
To cite this version:
Maëlis Arnould, Nicolas Coltice, Nicolas Flament, Claire Mallard. Plate tectonics and mantle con-
trols on plume dynamics. Earth and Planetary Science Letters, Elsevier, 2020, 547, pp.116439.
�10.1016/j.epsl.2020.116439�. �hal-03228588�

Plate tectonics and mantle controls on plume dynamics
Ma¨elis Arnould
, Nicolas Coltice
, Nicolas Flament
, Claire Mallard
Laboratoire de eologie,
Ecole Normale Sup´erieure, CNRS UMR 8538, PSL Research
University, 24 rue Lhomond, 75005 Paris, France
Universit´e de Lyon,
Ecole Normale Sup´erieure de Lyon, Universit´e Claude Bernard,
Laboratoire de eologie de Lyon, Terre, Plan`etes, Environnement, CNRS UMR 5276, 2
rue Rapha¨el Dubois, 69622 Villeurbanne, France
EarthByte G roup, School of Geosciences, The Uni vers i ty of Sydney, NSW 2006,
Now at Centre for Earth Evolution and Dy nam ics , Department of Geosciences,
University of Oslo, 0371 Oslo, Norway
GeoQuEST Research Centre, School of Earth, Atmospheric and Life Sciences,
University of Wollongon g, Northfields Avenue, Wollongong, NSW 2522, Australia
Mantle plumes provide valuable informatio n about whole Earth convecti on :
they originate at th e core-mantle boundary, cross Earth’s ma ntle and in-
teract with the lithosphere. For i n st an ce , it has been p ro posed that the
mobility/stability of plumes depends on plum e intrinsic properties, on how
slabs interact with the basal boundary layer, on mantle flow, or on their
proximity to mid-ocean ridges.
Here, we use 3D-spherical models of mantle convection generating self-
consistent plate-like behaviour to investigate the mechanisms linking tec-
tonics and mantle convection to plume dynamics. Our models produce fully-
dynamic mantle plumes that rise vertically with deflection < 1 0
and present
excess temper a t u re s, rising speeds, buoyancy a n d heat fluxes comparable to
Corresponding author.
Email address: (Ma¨elis Arnould)
Preprint submitted to Earth and Planetary S cien ce Letters May 11, 2021

observations. In the absence of plat e tectonics, plumes are stable and their
lifetime exceeds hundreds of million years. With plate tectonics, plumes are
more mob i l e, an d we identify four physical mechanisms controlling their sta-
bility. 1/ Fixed plumes are located at saddle points of basal mantle flow. 2/
Plumes moving at speeds between 0.5-1 cm yr
are slowly e ntrained by pas-
sive mantle flow. 3/ Fast plume motions between 2-5 cm yr
lasting several
tens of million years are caused by slab push. 4/ Plumes occasionally drift
at speeds > 5 cm yr
over < 10 Myr through plume merging. We do not
observe systematic anchoring of plumes to mid-oceanic ridges. Independent
of the presence of a dense basal layer, plate-like regimes decrease the lifetim e
of plumes compared to stagnant-lid models. Plume age, temperature excess
or buoyancy flux are not diag n os ti c of plume lateral speed. The fraction
of plumes m oving by less t h a n 0.5 cm yr
is > 25%, which suggests that
fixed hotspot reference frames can be defined from carefully selected hotspot
Keywords: Mantle pl u m es, plume drift, numerica l modelling, mantle
convection, plate-like tectonics
1. Introduction1
Since Morga n (1972) linked deep mantle plumes to tectonics motio n s, the2
combination of seismology, petrology and geophysics have led to th e charac-3
terisation of hotspots an d deep mantle plumes. Recent full-waveform tomog-4
raphy suggests that Earth’s major plume conduits are vertical and broad,5
> 6 0 0 km in diameter in the lower mantle, prefer entially ti l te d in the upper6
mantle and likely anchored at th e base of the mantle (Fr ench a n d Romanow-7

icz, 2015). The composition of olivine p h e n ocrysts indicates upper mantle8
plume excess temperatures between +150 K and +300 K (e.g. Puti r ka, 2005).9
The vertical deflection of oceanic lithosphere by mantle plumes (e.g. Sleep,10
1990; Crosby and McKenzie, 2009) and the propagation velocity of plum e-11
related V-shaped ridges (Poore et al., 2009; Parnell-Turn e r et al., 2014) con-12
strain plume buoyancy fluxe s to betwee n 0.3×10
kg s
(Bowie, Sleep, 1990)13
and > 70×10
kg s
(Iceland, Parnell-Turner et al., 2014). Combining info r -14
mation on plume radius, ex cess temperature and buoyancy flux gives plume15
rising speeds between 23 cm yr
and 54 cm yr
(Poore et al., 2009 ; Turcotte16
and Schubert, 2014) and plume heat flow anomalies between 10-20 mW m
(Sleep, 1990).18
Plumes can provide valuable information about the physics of mantle19
convection since they potentially interact with the whole ma ntle, includi n g20
both the basal and top boundary layer. Several studies have focused on21
characterising the temporal stability of mantle plumes, because fixed pl u m e s22
can serve as an absolute reference for global tectonic reco n st r u ct i on s (e.g.23
Wilson, 1963). However, pal eom a g n et i c, geochronological and petrological24
studies su gg est contrasting plume stability/mobility. Early geochronologi-25
cal and paleomagnetic observations (e.g. Morgan, 1981), and studies of the26
uncertainties of plate-reconstruction circuits (e.g. Duncan, 1 98 1) su gg est ed27
negligible Indo-Atlantic plume motions during the last 100 Myr. In con-28
trast, more recent analyses of geochronological and paleomagnetic dat a set s29
suggested either a true polar wander episode (e.g. Koivisto et al., 2014), a30
change in Pacific plate moti o n (e.g. Torsvik et al . , 2017), a southward mo-31
tion of the Hawaiian plume reaching 4 cm yr
between 81 and 47 Ma (e.g.32

Tarduno et al., 2003), or a combination of plume and plate moti on (e.g. Fi n -33
layson et al., 2018; Konrad et al., 2018) to explain the bent Hawaii-Empe ro r34
hotspot track. Petr ol o g i cal data also suggest that the Azores plume has35
drifted northwards by 1-2 cm yr
along the Mid-Atlantic ridge over the last36
85 Myr (Arnould et al., 2019).37
Numerical and laboratory experiments give independent constrai nts on38
mantle plume behaviour. The viscosity contrast between plume conduits and39
the ambient mantle (e.g. Jellinek and Manga, 2004)) may influence their dy-40
namics and stability. Mantle convection has also been shown to contribute41
to plume motion. A highly viscous lower mantle (Richards, 1991) or the42
anchoring of plume conduits along the edges of dense basal thermochemi-43
cal heterogeneities (e.g. Davaille et al., 2002) representing Large Low Shear44
Velocity Provinces (LLSVPs) , is expected to stabilise plumes, while lateral45
mantle flow, sometim e s called mantle wind (Duncan and Richards, 1991;46
Richards and Griffiths, 1988), would favour highly tilted plum es (Steinberger47
and O’Conn e l l , 1998; O’Neill et al., 2005). Finally, plate tectonic s have been48
proposed to promote plu m e stability via ridge captu r e (e.g. Tarduno et al. ,49
2009). Subduction can also indirectly induce plume motions through the50
effect of supercontinent cycles on the p l a n fo rm of global convection (Zh o n g51
et al., 2007) or the lateral push of plume conduits by lower mantle slabs52
(Hassan et al., 2016).53
Collectively, the above-mentioned studies highlight the need to invest i g at e54
the coupled behaviour of mantle plumes, plate tectonics, la r ge -sca l e mantle55
flow and basal thermochemical structures. Here we u se time-dependent 3D-56
spherical numerical models of whole-mantle convection at Earth-like con-57

Figures (10)
More filters

Fabio Crameri1, Paul J. Tackley1, I. Meilick1, Taras Gerya1  +2 moreInstitutions (2)
01 Apr 2012-
Abstract: [1] Earth’s lithosphere is characterized by the relative movement of almost rigid plates as part of global mantle convection. Subduction zones on present-day Earth are strongly asymmetric features composed of an overriding plate above a subducting plate that sinks into the mantle. While global self-consistent numerical models of mantle convection have reproduced some aspects of plate tectonics, the assumptions behind these models do not allow for realistic single-sided subduction. Here we demonstrate that the asymmetry of subduction results from two major features of terrestrial plates: (1) the presence of a free deformable upper surface and (2) the presence of weak hydrated crust atop subducting slabs. We show that assuming a free surface, rather than the conventional free-slip surface, allows the dynamical behavior at convergent plate boundaries to change from double-sided to single-sided. A weak crustal layer further improves the behavior towards steady single-sided subduction by acting as lubricating layer between the sinking and the overriding plate. This is a first order finding of the causes of single-sided subduction, which by its own produces important features like the arcuate curvature of subduction trenches. Citation: Crameri, F., P. J. Tackley, I. Meilick, T. V. Gerya, and B. J. P. Kaus (2012), A free plate surface and weak oceanic crust produce single-sided subduction on Earth, Geophys. Res. Lett., 39, L03306, doi:10.1029/2011GL050046.

12 citations

Posted ContentDOI
Iris van Zelst1, Fabio Crameri2, Adina E. Pusok3, Anne Glerum  +2 moreInstitutions (5)
TL;DR: The basics of geodynamics modelling for first-time and experienced modellers, collaborators, and reviewers from diverse backgrounds to (re)gain a solid understanding of geodynamic modelling as a whole are presented.
Abstract: . Geodynamic modelling provides a powerful tool to investigate processes in the Earth's crust, mantle, and core that are not directly observable. However, numerical models are inherently subject to the assumptions and simplifications on which they are based. In order to use and review numerical modelling studies appropriately, one needs to be aware of the limitations of geodynamic modelling as well as its advantages. Here, we present a comprehensive, yet concise overview of the geodynamic modelling process applied to the solid Earth, from the choice of governing equations to numerical methods, model setup, model interpretation, and the eventual communication of the model results. We highlight best practices and discuss their implementations including code verification, model validation, internal consistency checks, and software and data management. Thus, with this perspective, we encourage high-quality modelling studies, fair external interpretation, and sensible use of published work. We provide ample examples from lithosphere and mantle dynamics and point out synergies with related fields such as seismology, tectonophysics, geology, mineral physics, and geodesy. We clarify and consolidate terminology across geodynamics and numerical modelling to set a standard for clear communication of modelling studies. All in all, this paper presents the basics of geodynamic modelling for first-time and experienced modellers, collaborators, and reviewers from diverse backgrounds to (re)gain a solid understanding of geodynamic modelling as a whole.

11 citations

Cites background from "Plate tectonics and mantle controls..."

  • ...For example, all the following studies model plate tectonics, but the geometry of the model can be complex (e.g., a 3D spherical domain like Arnould et al. (2020)) or simple (e.g., a 1D or 2D domain like Bercovici and Ricard (2014))....


Journal ArticleDOI
Abstract: Global tomography models show a large low‐velocity anomaly extending from the core‐mantle boundary (CMB) beneath South Africa to the upper mantle in East Africa. Although it is believed that this anomaly is linked to mantle upwellings that control key surface features of the African continent, its origin and evolution are still debated. Here we assemble geochemical and seismological constraints along with information from new seismic analyses and geodynamic laboratory experiments to propose that presently there are at least two different plume heads beneath Afar and Kenya that originated at the CMB. A third plume between Kenya and Afar may have caused the Ethiopia‐Yemen traps 30 Ma, now merging with the Afar plume. We infer that the Afar plume is presently detached from the CMB probably because of an interaction with the subducted Tethyan slab and that it is likely a dying plume. This may imply that rifts along the Main Ethiopian Rift would fail by the loss of thermal sources, which consequently hampers continental breakup.

10 citations

Journal ArticleDOI
Abstract: Decompression melting of the upper mantle produces magmas and volcanism at the Earth's surface. Experimental petrology demonstrates that the presence of CO2 and H2O enhances peridotite melting anywhere within the upper mantle down to approximately 200–300 km depth. The presence of mantle melts with compositions ranging from carbonate-rich to silicate-rich unavoidably affects the geophysical signals retrieved from Earth's mantle. Geochemical investigations of erupted intraplate magmas along with geophysical surveys allow for constraining the nature and volume of primary melts, and a sound formalism is required to integrate these diverse datasets into a realistic model for the upper mantle including melting processes. Here, we introduce MAGLAB, a model developed to calculate the composition and volume fraction of melts in the upper mantle, together with the corresponding electrical conductivity of partially molten mantle peridotites at realistic pressure-temperature conditions and volatile contents. We use MAGLAB to show how the compositions of intraplate magmas relate to variations in lithosphere thickness. Progressive partial melting of a homogeneous peridotitic mantle source can in theory create the diversity of compositions observed among the spectrum of intraplate magma types, with kimberlite melts beneath thick continental shields, alkaline magmas such as melilitite, nephelinite and basanite beneath thinner continents and relatively old plus thick oceanic lithospheres, and ‘regular’ basalts beneath the youngest and thinnest oceanic lithospheres as well as beneath significantly thinned continental lithospheres. MAGLAB calculations support recent experimental findings about the role of H2O in the upper mantle on producing primary kimberlitic melts in addition to CO2. We demonstrate the robustness of MAGLAB calculations by reproducing the compositions of erupted melts as well as associated mantle electrical conductivities beneath the Society hotspot in the Pacific Ocean. A comparison of our simulations with magnetotelluric surveys at various oceanic settings shows that the heterogeneities in electrical conductivity of Earth's upper mantle are related to variations in volatile content via the presence of small (generally

7 citations

Journal ArticleDOI
Abstract: The head of a mantle plume can weaken the oceanic lithosphere through the combined action of its buoyancy forces and excess temperature, which eventually induces intra-oceanic subductions. However, the dynamics of plume-induced subductions, their lifetime and their ability to propagate at the scale of an entire ocean remain unknown. Here, we combine a quantitative synthesis of the ophiolitic record of the Neotethys subduction in the Late Cretaceous with 3D spherical modeling of mantle convection self-generating plate-like tectonics to propose that the pre-Deccan plume initiated the Southern Neotethys Subduction. We suggest that this subduction retreated at 5-10 cm yr−1 until it reached the continental margins of Arabia and India. The sequential segmentation of this subduction during its retreat and the diachronous deactivation of the resulting segments drove the Late Cretaceous-Eocene series of plate reorganization events recorded in the Indian Ocean's fabric.

7 citations

More filters

Journal ArticleDOI
Abstract: Laboratory measurements of rock strength provide limiting values of lithospheric stress, provided that one effective principal stress is known. Fracture strengths are too variable to be useful; however, rocks at shallow depth are probably fractured so that frictional strength may apply. A single linear friction law, termed Byerlee's law, holds for all materials except clays, to pressures of more than 1 GPa, to temperatures of 500°C, and over a wide range of strain rates. Byerlee's law, converted to maximum or minimum stress, is a good upper or lower bound to observed in situ stresses to 5 km, for pore pressure hydrostatic or subhydrostatic. Byerlee's law combined with the quartz or olivine flow law provides a maximum stress profile to about 25 or 50 km, respectively. For a temperature gradient of 15°K/km, stress will be close to zero at the surface and at 25 km (quartz) or 50 km (olivine) and reaches a maximum of 600 MPa (quartz) or 1100 MPa (olivine) for hydrostatic pore pressure. Some new permeability studies of crystalline rocks suggest that pore pressure will be low in the absence of a thick argillaceous cover.

1,658 citations

Journal ArticleDOI
Abstract: Closely spaced satellite altimeter profiles collected during the Geosat Geodetic Mission (-6 km) and the ERS 1 Geodetic Phase (8 km) are easily converted to grids of vertical gravity gradient and gravity anomaly. The long-wavelength radial orbit error is suppressed below the noise level of the altimeter by taking the along-track derivative of each profile. Ascending and descending slope profiles are then interpolated onto separate uniform grids. These four grids are combined to form comparable grids of east and north vertical deflection using an iteration scheme that interpolates data gaps with minimum curvature. The vertical gravity gradient is calculated directly from the derivatives of the vertical deflection grids, while Fourier analysis is required to construct gravity anomalies from the two vertical deflection grids. These techniques are applied to a combination of high-density data from the dense mapping phases of Geosat and ERS 1 along with lower-density but higher-accuracy profiles from their repeat orbit phases. A comparison with shipboard gravity data shows the accuracy of the satellite- derived gravity anomaly is about 4-7 mGal for random ship tracks. The accuracy improves to 3 mGal when the ship track follows a Geosat Exact Repeat Mission track line. These data provide the first view of the ocean floor structures in many remote areas of the Earth. Some applications include inertial navigation, prediction of seafloor depth, planning shipboard surveys, plate tectonics, isostasy of volcanoes and spreading ridges, and petroleum exploration.

1,626 citations

Journal ArticleDOI
Abstract: The available data, mainly topography, geoid, and heat flow, describing hotspots worldwide are examined to constrain the mechanisms for swell uplift and to obtain fluxes and excess temperatures of mantle plumes. Swell uplift is caused mainly by excess temperatures that move with the lithosphere plate and to a lesser extent hot asthenosphere near the hotspot. The volume, heat, and buoyancy fluxes of hotspots are computed from the cross-sectional areas of swells, the shapes of noses of swells, and, for on ridge hotspots, the amount of ascending material needed to supply the length of ridge axis which has abnormally high elevation and thick crust. The buoyancy fluxes range over a factor of 20 with Hawaii, 8.7 Mg s -1, the largest. The buoyancy flux for Iceland is 1.4 Mg s -1 which is similar to the flux of Cape Verde. The excess temperature of both on-ridge and off-ridge hotspots is around the 200oC value inferred from petrology but is not tightly constrained by geophysical considerations. This observation, the similarity of the fluxes of on-ridge and offridge plumes, and the tendency for hotspots to cross the ridge indicate that similar plumes are likely to cause both types of hotspots. The buoyancy fluxes of 37 hotspots are estimated; the global buoyancy flux is 50 Mg s -1, which is equivalent to a globally averaged surface heat flow of 4 mWm -2 from core sources and would cool the core at a rate of 50 o C b.y. -1. Based on a thermal model and the assumption that the likelihood of subduction is independent of age, most of the heat from hotspots is implaced in the lower lithosphere and later subducted. I.NTRODUCWION ridge plumes using Iceland as an example. The geometry of flow implied by the assumed existence of a low viscosity Linear seamount chains, such as the Hawaiian Islands, are asthenospheric channel is illustrated by this exercise. Then the frequently attributed to mantle plumes which ascend from deep methods for obtaining the flux of plumes on a rapidly moving in the Earth, perhaps the core-mantle boundary. The excessive plate are discussed with Hawaii as an example. These methods volcanism of on-ridge hotspots, such as Iceland, is also often involve determining the flux from the plume from the crossattributed to plumes. If on-ridge and midplate hotspots are sectional area of the swell and taking advantage of the kinematreally manifestations of the same phenomenon, one would ics of the interaction of asthenospheric flow away from the expect that the temperature and flux of the upwelling material plume and asthenospheric flow induced by the drag of the would be similar under both features. In particular, the core- lithospheric plate. The methods for extending this approach to mantle boundary is expected to be nearly isothermal so that the hotspots on slowly moving plates are then discussed which Cape temperature of plumes ascending from the basal boundary layer Verde as an example. An estimate of the global mass and heat should be the same globally provided that cooling by entrain- transfer by plumes is then obtained by applying the methods to ment of nearby material and thermal conduction are minor. 34 additional hotspots. The magnitude of this total estimated Finally, the global heat loss from plumes should imply a reason- flux is compatible with the heat flux expected from cooling the

1,033 citations

Journal ArticleDOI
J. Tuzo Wilson1Institutions (1)
Abstract: It is noted that different physicists and geologists have in recent years espoused not less than four groups of theories of the physical behavior of the Earth's interior. Recent observations of sub...

953 citations

Journal ArticleDOI
Abstract: The origin of mantle hotspots is a controversial topic. Only seven (‘primary’) out of 49 hotspots meet criteria aimed at detecting a very deep origin (three in the Pacific, four in the Indo-Atlantic hemisphere). In each hemisphere these move slowly, whereas there has been up to 50 mm/a motion between the two hemispheres prior to 50 Ma ago. This correlates with latitudinal shifts in the Hawaiian and Reunion hotspots, and with a change in true polar wander. We propose that hotspots may come from distinct mantle boundary layers, and that the primary ones trace shifts in quadrupolar convection in the lower mantle.

884 citations

No. of citations received by the Paper in previous years