Geochemical evidence for a widespread mantle re-enrichment 3.2 billion years ago: implications for global-scale plate tectonics

Abstract Space probes in our solar system have examined all bodies larger than about 400 km in diameter and shown that Earth is the only silicate planet with extant plate tectonics sensu stricto. Venus and Earth are about the same size at 12 000 km diameter, and close in density at 5 200 and 5 500 kg.m-3 respectively. Venus and Mars are stagnant lid planets; Mars may have had plate tectonics and Venus may have had alternating ca. 0.5 Ga periods of stagnant lid punctuated by short periods of plate turnover. In this paper, we contend that Earth has seen five, distinct, tectonic periods characterized by mainly different rock associations and patterns with rapid transitions between them; the Hadean to ca. 4.0 Ga, the Eo- and Palaeoarchaean to ca. 3.1 Ga, the Neoarchaean to ca. 2.5 Ga, the Proterozoic to ca. 0.8 Ga, and the Neoproterozoic and Phanerozoic. Plate tectonics sensu stricto, as we know it for present-day Earth, was operating during the Neoproterozoic and Phanerozoic, as witnessed by features such as obducted supra-subduction zone ophiolites, blueschists, jadeite, ruby, continental thin sediment sheets, continental shelf, edge, and rise assemblages, collisional sutures, and long strike-slip faults with large displacements. From rock associations and structures, nothing resembling plate tectonics operated prior to ca. 2.5 Ga. Archaean geology is almost wholly dissimilar from Proterozoic-Phanerozoic geology. Most of the Proterozoic operated in a plate tectonic milieu but, during the Archaean, Earth behaved in a non-plate tectonic way and was probably characterised by a stagnant lid with heat-loss by pluming and volcanism, together with diapiric inversion of tonalite-trondjemite-granodiorite (TTG) basement diapirs through sinking keels of greenstone supracrustals, and very minor mobilism. The Palaeoarchaean differed from the Neoarchaean in having a more blobby appearance whereas a crude linearity is typical of the Neoarchaean. The Hadean was probably a dry stagnant lid Earth with the bulk of its water delivered during the late heavy bombardment, when that thin mafic lithosphere was fragmented to sink into the asthenosphere and generate the copious TTG Ancient Grey Gneisses (AGG). During the Archaean, a stagnant unsegmented, lithospheric lid characterised Earth, although a case can be made for some form of mobilism with “block jostling”, rifting, compression and strike-slip faulting on a small scale. We conclude, following Burke and Dewey (1973), that there is no evidence for subduction on a global scale before about 2.5 Ga, although there is geochemical evidence for some form of local recycling of crustal material into the mantle during that period. After 2.5 Ga, linear/curvilinear deformation belts were developed, which “weld” cratons together and palaeomagnetism indicates that large, lateral, relative motions among continents had begun by at least 1.88 Ga. The “boring billion”, from about 1.8 to 0.8 Ga, was a period of two super-continents (Nuna, also known as Columbia, and Rodinia) characterised by substantial magmatism of intraplate type leading to the hypothesis that Earth had reverted to a single plate planet over this period; however, orogens with marginal accretionary tectonics and related magmatism and ore genesis indicate that plate tectonics was still taking place at and beyond the bounds of these supercontinents. The break-up of Rodinia heralded modern plate tectonics from about 0.8 Ga. Our conclusions are based, almost wholly, upon geological data sets, including petrology, ore geology and geochemistry, with minor input from modelling and theory.

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Venus’ light slab hinders its development of planetary-scale subduction and habitability

10.21203/rs.3.rs-1104964/v1 ◽

2022 ◽

Author(s):

Junxing Chen ◽

Hehe Jiang ◽

Ming Tang ◽

Jihua Hao ◽

Meng Tian ◽

...

Keyword(s):

Plate Tectonics ◽

Carbon Sink ◽

Global Scale ◽

Climate Feedback ◽

Early Earth ◽

Crustal Rocks ◽

Planetary Scale ◽

Habitable Planet ◽

Missing Carbon Sink

Abstract Terrestrial planets Venus and Earth have similar sizes, masses, and bulk compositions, but only Earth developed planetary-scale plate tectonics. Plate tectonics generates weatherable fresh rocks and transfers surface carbon back to Earth’s interior, which provides a long-term climate feedback, serving as a thermostat to keep Earth a habitable planet. Yet Venus shares a few common features with early Earth, such as stagnant-lid tectonics and the possible early development of a liquid ocean. Given all these similarities with early Earth, why would Venus fail to develop global-scale plate tectonics? In this study, we explore solutions to this problem by examining Venus’ slab densities under hypothesized subduction-zone conditions. Our petrologic simulations show that eclogite facies may be reached at greater depths on Venus than on Earth, and Venus’ slab densities are consistently lower than Earth’s. We suggest that the lack of sufficient density contrast between the high-pressure metamorphosed slab and mantle rocks may have impeded self-sustaining subduction. Although plume-induced crustal downwelling exists on Venus, the dipping of Venus’ crustal rocks to mantle depth fails to transition into subduction tectonics. As a consequence, the supply of fresh silicate rocks to the surface has been limited. This missing carbon sink eventually diverged the evolution of Venus’ surface environment from that of Earth.

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Effect of grid resolution on tectonic regimes in global-scale convection models

10.5194/egusphere-egu2020-4483 ◽

2020 ◽

Author(s):

Enrico Marzotto ◽

Marcel Thielmann ◽

Gregor Golabek

Keyword(s):

Plate Tectonics ◽

Numerical Models ◽

Global Scale ◽

Grid Resolution ◽

Physical Parameters ◽

Plate Boundaries ◽

Temperature Dependent ◽

Tectonic Regime ◽

Radiogenic Heating ◽

Spherical Annulus

A key ingredient to reproduce plate-tectonics in numerical models is a viscoplastic rheology. Strongly temperature-dependent rheology generates a rigid lid at the surface, whereas plastic rheology allows for the formation of plate boundaries. The yield stress limiter &#160;controls the strength of the lithosphere.Depending on the value used for &#160;different tectonics regimes can be observed: (i) dripping behaviour (low , (ii) plate-like behaviour (intermediate-low ), (iii) Episodic behaviour (intermediate-high ) and (iv) Stagnant lid behaviour (high ).Each lid behaviour can be distinguished by comparing the evolution profile of several parameters: temperature, viscosity, surface Nusselt number and mobility (Tackley, 2000a.).Despite the great importance of physical parameters, the outcome of geodynamical models is also affected by the grid resolution as it has been shown that the critical that separates each lid behavior is resolution dependent (Tosi et al., 2015).Here we use the code StagYY (Tackley, 2008) in a 2D spherical annulus geometry (Hernlund & Tackley, 2008) to determine the resolution-dependent tectonic regime in a global-scale convection setting. We tested 12 grid resolutions (ranging from 128x32 to 1024x128 nodal points) and 9 different &#160;(ranging from 10 to 90 MPa), keeping all the remaining physical parameters unchanged.For these simplified models we assume isothermal free slip boundaries, constant radiogenic heating, no melting, endothermic (410) and exothermic (660) phase transitions. Each simulation was run for 15 Gyrs with a Rayleigh number of &#8776;8*10^7 to make sure that steady-state conditions were reached.Our resolution tests show that the observed tectonic regime is affected by grid resolution as this parameter controls how well the lithosphere is resolved. Low radial resolutions favour weak lid regimes (dripping and plate-like) as the lithosphere is defined by few thick cells, that propagate basal stress to shallower depths. On the other hand low azimuthal resolutions favour strong lid regimes (episodic and stagnant) since plate boundaries remain unresolved. In conclusion, only at high grid resolutions (512x128 and higher) the numerical influence on the observed tectonic regime is low.

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Igneous Geochemical Evidence for Continuous Plate Tectonics Since ~3.5 Ga

10.46427/gold2020.795 ◽

2020 ◽

Author(s):

Joshua Garber ◽

Robert Holder ◽

Andrew Smye ◽

Jesse Reimink

Keyword(s):

Plate Tectonics ◽

Geochemical Evidence ◽

Continuous Plate

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A non-extensive statistical physics view in Earth Physics: Geodynamic properties in terms of Complexity theory .

10.5194/egusphere-egu2020-3749 ◽

2020 ◽

Author(s):

Filippos Vallianatos

Keyword(s):

Statistical Mechanics ◽

Gaussian Distribution ◽

Plate Tectonics ◽

Statistical Physics ◽

Extreme Values ◽

Global Scale ◽

Coda Wave ◽

Research And Innovation ◽

Classical Thermodynamics ◽

Earth Dynamics

Boltzmann-Gibbs (BG) statistical physics is one of the cornerstones of contemporary physics. It establishes a remarkably useful bridge between the mechanical microscopic laws and macroscopic description using classical thermodynamics. If long-range interactions, non-markovian microscopic memory, multifractal boundary conditions and multifractal structures are present then another type of statistical mechanics, than BG, seems appropriate to describe nature (Tsallis, 2001).To overcome at least some of these anomalies that seem to violate BG statistical mechanics, non-extensive statistical physics (NESP) was proposed by Tsallis&#160; (Tsallis, 1988) that recovers the extensive BG as a particular case. The associated generalized entropic form controlled by the entropic index &#160;q that represents a measure of non-additivity of a system. Sq recovers SBG in the limit q&#8594;1. For a variable X with a probability distribution p(X), as that of seismic moment , inter-event times&#160; or distances between the successive earthquakes or the length of faults in a given region, using terms of NESP, we obtain the physical probability which expressed by a q-exponential function as defined in Tsallis, (2009). &#160;Another type of distributions that are deeply connected to statistical physics is that of the squared variable X2. In BG statistical physics, the distribution of X2 corresponds to the well-known Gaussian distribution. If we optimize Sq for X2, we obtain a generalization of the normal Gaussian that is known as q-Gaussian distribution (Tsallis, 2009). In the limit q&#8594;1, the normal Gaussian distribution, recovered. For q> 1, the q-Gaussian distribution has power-law tails with slope -2/(q-1), thus enhancing the probability of the extreme values.In the present work we review a collection of Earth physics problems such as a) NESP pathways in earthquake size distribution, b) The effect of mega-earthquakes, c) Spatiotemporal description of Seismicity, d) the plate tectonics as a case of non-extensive thermodynamics e) laboratory seismology and fracture, f) the non-extensive nature of earth&#8217;s ambient noise, and g) evidence of non-extensivity in eartquakes&#8217; coda wave. The aforementioned cases cover the most of the problems in Earth Physics indicated that non extensive statistical physics could be the underline interpretation tool to understand earth's evolution and dynamics.We can state that the study of the non-extensive statistical physics of earth dynamics remains wide-open with many significant discoveries to be made. The results of the analysis in the cases described previously indicate that the ideas of NESP can be used to express the non-linear dynamics that control the evolution of the earth dynamics at different scales. The key scientific challenge is to understand in a unified way, using NESP principles, the physical mechanisms that drive the evolution of fractures ensembles in laboratory and global scale and how we can use measures of evolution that will forecast the extreme fracture event rigorously and with consistency.&#160;Acknowledgments.&#160;We acknowledge support by the project &#8220;HELPOS &#8211; Hellenic System for Lithosphere Monitoring&#8221; (MIS 5002697) which is implemented under the Action &#8220;Reinforcement of the Research and Innovation Infrastructure&#8221;, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece & European Union (ERDF).&#160;

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Pedogenic processes and the drying of Mars

10.31223/x5ng9j ◽

2021 ◽

Author(s):

Adrian Broz ◽

Lucas Silva

Keyword(s):

Liquid Water ◽

Plate Tectonics ◽

Soil Formation ◽

Global Scale ◽

Recycle Water ◽

Definition Of ◽

Pedogenic Processes ◽

Biological Component ◽

Critical Process

New insights from Mars suggest crustal hydration contributed to the long-term drying of the planet. Three to four billion years ago, hydration of the Martian crust could have resulted from precipitation-driven surface weathering of mafic sediments, which on Earth leads to pedogenesis, i.e., the formation of soil. Although soil has been traditionally defined by its biological component, growing evidence of global scale soil formation on a presumably lifeless Mars suggests abiotic pedogenesis was a critical process early in the planet’s history. Using a recently updated definition of soil as leverage, we argue that pedogenic processes could have consumed large amounts of Mars’ exchangeable liquid water. Since there is no evidence of plate tectonics to liberate and recycle water from hydrated pedogenic minerals on Mars, the global formation of soil billions of years ago could have contributed to the irreversible desiccation of the planet.

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Abundance of water oceans on high-density exoplanets from coupled interior-atmosphere modeling

10.5194/epsc2021-270 ◽

2021 ◽

Author(s):

Philipp Baumeister ◽

Nicola Tosi ◽

Jasmine MacKenzie ◽

John Lee Grenfell

Keyword(s):

Liquid Water ◽

Plate Tectonics ◽

Water Cycle ◽

Global Scale ◽

High Density ◽

Atmospheric Composition ◽

Terrestrial Planets ◽

Parameter Study ◽

Model Combining ◽

Wide Range

Liquid water is generally assumed to be the most important factor for the emergence of life, and so a major goal in exoplanet science is the search for planets with water oceans. On terrestrial planets, the silicate mantle is a large source of water, which can be outgassed into the atmosphere via volcanism. Outgassing is subject to a series of feedback processes between atmosphere and interior, which continually shape both atmospheric composition, pressure, and temperature, as well as interior dynamics. For example, water has a high solubility in surface lava, which can strongly limit its outgassing into the atmosphere even at low atmospheric pressures. In contrast, CO2 can be easily outgassed. This drives up the surface pressure and temperature, potentially preventing further water outgassing [1]. We present the results of an extensive parameter study, where we use a newly developed 1D numerical model to simulate the coupled evolution of the atmosphere and interior of terrestrial exoplanets up to 5 Earth masses around Sun-like stars, with internal structures ranging from Moon- to Mercury-like. The model accounts for the main mechanisms controlling the global-scale, long-term evolution of stagnant-lid rocky planets (i.e. bodies without plate tectonics), and it includes a large number of atmosphere-interior feedback processes, such as a CO2 weathering cycle, volcanic outgassing based on the pressure-dependent solubility of volatiles in surface lava, a water cycle between ocean and atmosphere, greenhouse heating, as well as the influence of a primordial H2 atmosphere, which can be lost through escape processes. While many atmosphere-interior feedback processes have been studied before in detail (e.g. [2, 3]), we present here a comprehensive model combining the important planetary processes across a wide range of terrestrial planets. We find that a significant majority of high-density exoplanets (i.e. Mercury-like planets with large cores) are able to outgas and sustain water on their surface. In contrast, most planets with intermediate, Earth-like densities either transition into a runaway greenhouse regime due to strong CO2 outgassing, or retain part of their primordial atmosphere, which prevents water from being outgassed. This suggests that high-density planets could be the most promising targets when searching for suitable candidates for hosting liquid water. Furthermore, the degeneracy of the interior structures of high-density planets is limited compared to that of planets with Earth-like density, which further facilitates the characterization of these bodies, and our results predict largely uniform atmospheric compositions across the range of high-density planets, which could be verified by future spectroscopic measurements. &#160; References: [1] Tosi, N. et al. The habitability of a stagnant-lid earth. A&A 605, A71 (2017). [2] Noack, L., Rivoldini, A. & Van Hoolst, T. Volcanism and outgassing of stagnant-lid planets: Implications for the habitable zone. Physics of the Earth and Planetary Interiors 269, 40&#8211;57 (2017). [3] Foley, B. J. & Smye, A. J. Carbon Cycling and Habitability of Earth-Sized Stagnant Lid Planets. Astrobiology 18, 873&#8211;896 (2018).

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Obliquity favours propagation pulses during continental break-up

10.5194/egusphere-egu2020-9586 ◽

2020 ◽

Author(s):

Anthony Jourdon ◽

Laetitia Le Pourhiet ◽

Frédéric Mouthereau ◽

Dave A. May

Keyword(s):

Plate Tectonics ◽

Dynamic Models ◽

Major Change ◽

Global Scale ◽

Rift Propagation ◽

Deformation Regime ◽

Break Up ◽

Set Up ◽

Lithospheric Dynamics ◽

Made In

V-shaped propagators are ubiquist and the seafloor age map is often sufficient to unravel the first order features of the timing of continental break-up at regional or more global scale. Some propagators show&#160; pulses in the rate of continental break-up propagation highlighted by the geometry of magnetic anomalies. These pulses, which were first introduced by Courtillot (1982) in the Gulf of Aden, represent a major element of plate tectonics. Despite the well documented geological record of these changes of rate, and their implications for plate kinematic reconstructions or the thermal regime of oblique margins, the dynamics of ridge and rift propagation at long/geodynamic timescale remains poorly studied nor understood. To date, despite the large progress made in understanding lithospheric dynamics and continental break-up, no lithospheric scale dynamic models has been able to produce self consistently pulse of ridgepropagation followed by a phase of stagnation. One obvious reason for this lack of dynamic ground stands from the fact that this problem mandates 3D thermo-mechanically coupled simulation approach that is just starting to emerge. In this work we chose to adopt a numerical modelling set-up after Le Pourhiet et al. (2018) to produce V-shaped propagators. Simulations investigate the influence of both kinematic and rheology of the lithosphere on the propagation trend and rate. The tectonic evolution of these margins shows 3 different modes of continental break-up propagation and a major change of deformation regime between phases of propagations and phases of stagnation.

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Subduction in early Proterozoic mantle: Implications from nitrogen in carbonatites

10.5194/egusphere-egu21-15953 ◽

2021 ◽

Author(s):

Sudeshna Basu ◽

Adrian Jones

Keyword(s):

Isotopic Composition ◽

Plate Tectonics ◽

Global Scale ◽

Reduced Form ◽

Earth Planet ◽

Wide Range ◽

Different Temperatures ◽

History Of ◽

Host Rocks ◽

Nitrogen Contents

Nitrogen in the mantle exists in various speciation depending on oxidation conditions. Based on thermodynamic calculations, it predominantly occurs as N2 under relatively oxidized conditions and as NH4+ when conditions are reducing (Mikhail and Sverjensky, 2014). The speciation has an effect on its compatibility behaviour, being more soluble in melts when in reduced form, while the reverse is true for fluids (Mysen, 2019). &#160;Carbonatites are very important to constrain the nitrogen composition of the mantle with important implications for the subduction history of the Earth. Carbonatites entrain components from different reservoirs including the deep Earth near the core-mantle boundary and, temporally encompass a wide range in age (Dauphas and Marty., 1999; Basu and Murty, 2015).&#160; Studies from some young carbonatites in India from Sung Valley (107 Ma) and Ambadongar (65 Ma) indicate that the nitrogen is present as more than one component in the source, unhomogenised and hence identifiable, that can be related to their occurrence in more than one chemical form (Basu and Murty, 2015).The emergence of efficient and long-lived plate tectonics is thought to be as early as Late Archean, based on nitrogen isotopic composition of placer diamonds from Witwatersand from the Kapvaal craton (Smart et al., 2016). While this may represent a global occurrence, we have undertaken a more robust study with carbonatites ranging in age from 2500 to 770 Myrs, with the goal of identification of the initiation of subduction in a global scale and investigation of any change in the nitrogen stored in the mantle with time. The carbonatites studied are from Khambamettu (2.5 Ga), Hogenakal (2.4 Ga), and Sevattur (770 Ma), located in the southern part of India. Calcites and apatites separated from the host rocks were analysed by vacuum crushing. The apatites were also analysed by stepwise pyrolysis to release and decouple different components at different temperatures. In the carbonates, the nitrogen contents vary from 140 to 1507 ppb with accompanying &#948;15N ranging from 4.7&#177;0.4 to 11.7&#177;1.3 &#8240;. The nitrogen in the apatites from Hogenakal and Khambamettu show depleted signatures with &#948;15N as low as ~ -22 &#8240;, accompanied by low nitrogen content of ~ 60 to 140 ppb. The apatite from the younger Sevattur complex is comparable to the carbonates in terms of both concentration and isotopic composition. This can be related to increase in nitrogen input via subduction with time during Earth&#8217;s history since the Proterozoic, transported to the deep mantle, consequently overprinting any primordial signatures inherited from precursor building material such as the echondrites.ReferencesBasu, S. and Murty, S.V.S. Journal of Asian Earth Sciences 107: 53-61 (2015). https://doi.org/10.1016/j.jseaes.2015.03.044Dauphas, N. and Marty, B. Science 286(5449): 2488-2490 (1999). https://doi.org/10.1126/science.286.5449.2488Mikhail, S. and Sverjensky, D.A. Nature Geoscience 7(11): 816-819 (2014). https://doi.org/10.1038/ngeo2271Mysen, B. Prog Earth Planet Sci&#160;6,&#160;38 (2019). https://doi.org/10.1186/s40645-019-0286-xSmart, K.A., Tappe, S., Stern, R.A., Webb, S.J. and Ashwal, L.D. &#160;Nature Geoscience 9(3): 255-259 (2016). https://doi.org/ 10.1038/NGEO2628

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Long-lived low Th/U Pacific-type isotopic mantle domain

10.5194/egusphere-egu21-10496 ◽

2021 ◽

Author(s):

Xijun Liu ◽

Zhiguo Zhang ◽

Pengde Liu ◽

Yujia Song ◽

Yao Xiao

Keyword(s):

Upper Mantle ◽

Plate Tectonics ◽

Large Scale ◽

Mafic Rock ◽

Global Scale ◽

Data Set ◽

Provenance Data ◽

The Pacific ◽

Long Time ◽

Material Circulation

&#160; &#160; The presence of Pacific-type and Indian-type mid-ocean ridge (MORB) isotopic source domains in the upper mantle is a clear manifestation of global-scale mantle compositional heterogeneities. The Indian-type mantle domain is a long-lived feature that can be traced back to, at least, the Palaeozoic Tethyan mantle domain. Little temporal constraints currently exist, however, regarding the longevity of Pacific-type mantle domain. The extinct Paleo-Asia Ocean (PAO), a subsidiary ocean of the Panthalassic Ocean that formed during the breakup of the Rodinia Supercontinent in Mesoproterozoic to Neoproterozoic, can provide a solution to this dilemma. Here, we report the first complete geochemical and Sr, Nd and high-precision Pb isotopic data set for representative mafic rock samples from ophiolites representing remnants of the PAO basement ranging in age from 275 to 624Ma to constrain the composition of their mantle provenance. Data suggest that the sub-PAO mantle has a similar long time-integrated, high Sm/Nd ratio as the global depleted upper mantle, but also shows typical Pacific MORB-like Pb isotopic compositions with lower 207Pb/204Pb(t) and 208Pb/204Pb(t) for given 206Pb/204Pb(t) ratios, and low radiogenic 208Pb*/206Pb*, indicating a long time-integrated, low Th/U ratios. Thus, the Pacific-type mantle domain, like the Indian-type mantle domain, is a long-lived secular mantle domain that can be traced back to early Paleozoic or even to the Neoproterozoic. Data further indicate that the Nd and Pb isotopic distinction between such two large-scale and long-term mantle domains is due to the different evolutionary and tectonic histories of the circum-Pacific (PAO, Paleo- and modern Pacific) and sub-Tethys-Indian oceanic mantle realms. The Panthalassic-Pacific ocean realm had remarkable permanency existing as a big ocean at lease throughout the Phanerozoic, that implies that continental materials were limit to recycle into underlying mantle, thus the underlying mantle was relative free of the continental material contamination and then produce the low time-integrated Th/U Pacific-type mantle domain. In contrast, the break-up of the Gondwana supercontinent makes the Tethys realms to experience repeated opening and closures, which transferred large volume of continental materials into the underlying mantle and then produce the high Th/U Indian-type mantle domain. Our results indicate that the high Sm/Nd and low Th/U ratio of Pacific-type mantle domain most likely are an inherited, long-standing intrinsic feature of the depleted upper mantle derived from the Earth's primordial mantle with less contamination of continental materials. In contrast, the large-scale and long-lived Indian-type mantle heterogeneity is produced by plate tectonic-driven continental material circulation in the upper mantle. Such a genetic link between plate tectonics and mantle chemical geodynamics is crucial to our understanding of how the Earth system works.&#160; &#160; This study was financially supported by the National Natural Science Foundation of China (92055208&#65292;41772059) and the CAS &#8220;Light of West China&#8221; Program (2018-XBYJRC-003).

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