The basal mantle layer, situated just above the Earth’s core, constitutes a complex boundary zone bridging the molten outer core and the rocky mantle above. It is characterized by heterogeneous structures that have eluded definitive explanation despite decades of seismic and geodynamic observations. One of the persistent puzzles in geoscience has been deciphering how these heterogeneities originate and persist over geological timescales. Peng et al.’s study pioneers a sophisticated model that couples mantle convection simulations with the tectonic cycles of supercontinent formation, demonstrating a feedback mechanism that regenerates distinct basal mantle structures.

At the heart of their approach lies the integration of plate tectonic histories with mantle convection dynamics. Supercontinents, massive landmasses composed of nearly all continental crust, periodically aggregate and disperse every several hundred million years. This cyclical behavior is known to rearrange tectonic plates and alter mantle flow patterns, yet its effect on deep mantle strata has been challenging to quantify until now. By employing state-of-the-art numerical modeling techniques, the authors reveal that the assembly of supercontinents leads to the concentration and accumulation of chemically distinct material in the basal mantle, sculpting the structure we detect with seismic imaging.

Their simulations indicate that the repeated formation of supercontinents drives downwelling of subducted lithosphere to the mantle’s base, where it accumulates and interacts with the preexisting basal structures. This buildup of material, coupled with subsequent mantle fluids’ dynamic convection, continuously reshapes the basal mantle environment. The phenomenon results in long-lived heterogeneities that mirror the tectonic supercontinent cycle, implying a tight link between surface plate motions and deep mantle chemical reservoirs.

A striking aspect of the newly unveiled model is its ability to reproduce seismic velocity anomalies seen in the ultra-low velocity zones (ULVZs) at the mantle-core boundary. These zones have long baffled geoscientists due to their unexpected seismic signatures, suggesting compositional differences or partial melting. Peng and colleagues demonstrate that the supercontinent-driven regeneration of the basal mantle leads to compositional layering and thermal variations that can explain these ULVZ observations. This connection between tectonic cycles and the basal mantle offers a cohesive framework for Earth’s deep mantle heterogeneity.

The implications of this work extend beyond an improved understanding of mantle dynamics. Since the basal mantle region influences mantle plume formation and, in turn, surface volcanism and climate systems, the tectonic modulation of its structure could have driven significant episodes in Earth’s geological and environmental history. For instance, pulse events of supercontinent cycling might have triggered mantle plume upwellings, linking the deep Earth’s internal rhythms to surface evolutionary milestones.

Further exploration within the study reveals how the model accounts for chemical and thermal complexity beneath different regions of Earth over time. It underscores that supercontinent cycles not only redistribute heat in the mantle but also generate compositional anomalies that can persist for hundreds of millions of years. This persistent memory of plate tectonics captured in the basal mantle reframes how geologists interpret seismic tomography and geochemical signatures from mantle-derived rocks.

Moreover, the authors bridge the insights from geophysical observations with petrological evidence, contributing to resolving long-standing debates about the origin of deep mantle heterogeneities. Their model suggests that recycled oceanic crust and lithospheric material create distinct basal layers when dragged down by subduction, modulated by the cyclical formation of supercontinents. This synthesis offers a robust explanation for variations observed in mantle xenoliths and deep-Earth geochemistry.

The technical rigor of the model is noteworthy. It incorporates not only the mechanical convection of mantle materials but also complex chemical differentiation processes and thermal conductivity variations. Such an integrative approach allowed the researchers to simulate the long-term evolution of the mantle for durations exceeding a billion years, capturing the essential dynamics that link tectonics and deep mantle architecture.

Significantly, the study contributes predictive elements for future seismic investigations. By mapping how basal mantle structures evolve and regenerate, it provides testable hypotheses about where distinct compositional anomalies might be found today, guiding targeted geophysical campaigns globally. These advances promise to refine interpretative models for seismic tomography and improve our understanding of Earth’s internal processes.

A notable conceptual leap presented by Peng et al. is framing the basal mantle as a dynamic, regenerating system rather than a static repository of ancient materials. This paradigm shift impacts broader geodynamic theories, implying that the mantle’s deep structure has been continuously sculpted by surface tectonics, producing a complex and temporally evolving landscape to be deciphered.

The study also resonates with planetary sciences by offering analogies that might apply to other terrestrial planets exhibiting tectonic activity. Understanding Earth’s basal mantle regeneration can inspire comparative planetology inquiries into the deep interiors of Venus or Mars, potentially revealing universal principles of planetary evolution under tectonic regimes.

In addition to delivering scientific revelations, this work exemplifies the power of interdisciplinary research combining geodynamics, seismology, geochemistry, and computational modeling. It emphasizes the necessity of integrating diverse datasets and theoretical approaches to unravel Earth’s deep mysteries. Future advancements will likely build on this framework, incorporating even finer scales of mantle flow and chemical interactions.

With the increasing resolution of seismic networks and improvements in geodynamic modeling, the authors’ methodology sets a benchmark. As observational data become more detailed, this research framework can be potentially refined and extended, offering even more nuanced insights into the interaction between Earth’s surface and its profound interior.

In conclusion, the finding that the basal mantle is continually regenerated through supercontinent cycles fundamentally enriches our conception of Earth’s internal dynamics. It highlights the deep-time interconnectedness of surface tectonics and mantle processes and invites a reevaluation of how we decode signals from Earth’s interior. This landmark study paves the way for transformative progress in understanding planetary evolution and the energetic interplay within our planet’s depths.

Subject of Research: The dynamic regeneration of Earth’s basal mantle structure through supercontinent cycles and its implications for mantle heterogeneity and geodynamics.

Article Title: Basal mantle structure regenerated through supercontinents.

Article References:
Peng, P., Mitchell, R.N., Zhang, N. et al. Basal mantle structure regenerated through supercontinents. Nat Commun 16, 9666 (2025). https://doi.org/10.1038/s41467-025-64657-8

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41467-025-64657-8

The preparation of starting materials was a critical first step in this investigation. Researchers synthesized glasses representing diverse compositions, carefully controlling the ratios of calcium, magnesium, iron, aluminum, silicon, and oxygen. Melting powders of MgO, SiO₂, CaO, and Fe₂O₃ at temperatures exceeding 1900 K in a high-temperature furnace, they rapidly quenched the melts in cold water, producing homogenous glassy substances. These glasses were rigorously characterized using energy-dispersive X-ray spectroscopy integrated within scanning electron microscopy, ensuring precise compositional verification and uniformity essential for subsequent high-pressure experiments.

Following synthesis, the materials were subjected to ultrahigh-pressure multi-anvil press experiments to simulate the forbidding conditions of the lower mantle, where pressures reach up to 50 gigapascals and temperatures soar beyond 2700 kelvin. These experiments utilized state-of-the-art assemblies and heating systems tailored to maintain precise control over pressure and temperature profiles. Intricate sample assemblies involved platinum or rhenium capsules encased within aluminum oxide sleeves and LaCrO₃ heaters, demonstrating a sophisticated approach to balancing thermal insulation and mechanical stability. Remarkably, strategies such as embedding trace amounts of magnesium hydroxide promoted grain growth through the release of water vapor, optimizing the quality of mineral grains for chemical analysis.

Temperature monitoring employed type-D thermocouples strategically positioned between rhenium capsules, enabling highly accurate real-time measurement during the ramp-up and annealing stages. Annealing at target conditions for extended durations, typically 24 hours, ensured equilibrium attainment within samples. This rigorous control of temperature, pressure, and time allowed for the faithful reproduction of the natural processes governing mineral formation and transformation in Earth’s deep mantle, ultimately facilitating the detection of subtle phase equilibria essential for understanding mineral stability fields.

Post-experiment analyses leveraged advanced microscopy and spectroscopy to unravel the mineralogical evolution of the samples. The polished cross-sections underwent scanning electron microscopy to assess grain size distributions and morphologies. Ultrathin lamellae prepared via focused ion beam techniques allowed for high-resolution chemical mapping using scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. Such detailed compositional mappings revealed the distribution of constituent elements at nanometric spatial scales, with corrections applied to account for complex effects such as atomic number (Z) and X-ray absorption for more accurate quantification.

Beyond elemental analysis, electron energy-loss spectroscopy provided discerning insight into the iron oxidation states within the synthesized minerals. By analyzing the Fe-L₂,₃ edges, researchers quantified Fe³⁺/ΣFe ratios, shedding light on redox conditions that influence mineral stability and phase relations. Such measurements are essential because the valence state of iron profoundly affects the structural properties and seismic signatures of mantle phases, thereby linking laboratory experiments directly to geophysical observations.

Complementary microprobe analyses validated the compositions of recovered phases, employing standards precise for magnesium, silicon, calcium, and iron to ensure analytical fidelity. Meanwhile, phase identification utilized micro-focused X-ray diffraction with Co–Kα radiation and cutting-edge two-dimensional detectors, offering definitive confirmation of crystallographic structures formed under extreme conditions. Extended exposure times and focused beam sizes optimized diffraction patterns, facilitating the detection of even minor phases critical to the mineralogical assemblage.

Central to interpreting these experimental results was the development of an empirical model linking the mole fraction of calcium silicate (χ_Ca) in bridgmanite (Bdm) to pressure and temperature. This relationship was expressed as an exponential function incorporating fitted parameters to capture the thermal and baric dependencies observed. Drawing from thermodynamic principles, these parameters corresponded directly to changes in enthalpy, entropy, and volume associated with the equilibration reaction between calcium silicate in davemaoite (Dvm) and bridgmanite. Such an approach enabled researchers to extrapolate mineral stability fields beyond accessible experimental ranges reliably.

The fitted model predicted that davemaoite coexists with bridgmanite across a broad spectrum of lower-mantle conditions, persisting even at pyrolitic solidus temperatures. Calculations revealed mole fractions of CaSiO₃ in bridgmanite remain below pyrolitic levels across pressures extending to 120 GPa, signifying the continuous presence of davemaoite within the mantle’s complex mineralogy. This challenges earlier conceptions that davemaoite would break down or be significantly depleted under such extreme conditions, emphasizing its role as a stable and integral phase within Earth’s deep interior.

Seismic modeling further underscored the implications of these mineralogical findings. Using the BurnMan software, researchers simulated shear-wave velocities for regions enriched in davemaoite relative to those dominated by bridgmanite alone. They incorporated compositional variations involving magnesium, iron, and aluminum contents within bridgmanite to reflect realistic mantle compositions. By varying temperature and phase proportions, the models elucidated how the presence of davemaoite-enriched domains could contribute to observed seismic anomalies, thereby connecting mineral physics directly to geophysical phenomena.

The study’s meticulous experimental design, combined with comprehensive analytical precision, represents a transformative step in understanding Earth’s deep mantle. By establishing the persistence of davemaoite under lower-mantle conditions, it enriches our comprehension of the mineralogical diversity influencing mantle dynamics, chemical heterogeneity, and seismic wave propagation. These insights open new avenues for interpreting data from seismology, mineral physics, and geochemistry, fostering integrated models that reconcile observations from laboratory to planetary scales.

Moreover, the implications of persistent davemaoite affect geochemical cycling and mantle evolution. As a calcium-bearing phase stable in deep mantle assemblages, it influences element partitioning, melt generation, and the overall mineralogical framework governing mantle convection. Understanding its stability enhances predictive models of mantle composition and behavior, thereby refining interpretations of geodynamic processes shaping Earth’s interior through deep time.

The experimental approach, employing cutting-edge multi-anvil presses capable of replicating the ultrahigh pressures of the deep mantle, exemplifies the forefront of high-pressure mineralogy. The integration of multiple analytical methodologies, including synchrotron-based diffraction, transmission electron microscopy, and electron energy-loss spectroscopy, provides a holistic view of mineral structures, compositions, and valence states. Such technological synergy is essential for unraveling the profound complexities of Earth’s inaccessible depths.

Equally significant is the temperature control strategy, wherein samples were annealed for prolonged periods under tightly regulated thermal regimes, ensuring that equilibrium was established. This detail is crucial because kinetic barriers often hinder phase transformations at lower temperatures or shorter timescales, and the careful annealing protocols adopted here allow a more accurate reflection of natural mantle conditions.

The study also illuminates subtle effects such as selective magnesium diffusion caused by electron beam irradiation during transmission electron microscopy analysis, a factor that researchers accounted for in compositional quantifications. Recognizing and correcting for such intricacies enhances confidence in the precision of mineral composition data, fostering robust interpretations of the physicochemical behavior of deep mantle phases.

In sum, this comprehensive research not only confirms the persistence of davemaoite as a stable calcium silicate phase in Earth’s lower mantle but also bridges the realms of experimental petrology, mineral physics, and geophysics. It reinforces the complex mineralogical landscape within which mantle processes operate and underscores the indispensable role of interdisciplinary approaches in Earth sciences. As seismic and geochemical probing of our planet’s interior advances, such fundamental knowledge forms the backbone of our understanding of the dynamic Earth beneath our feet.

Subject of Research: Persistence and stability of davemaoite (CaSiO₃) under lower mantle pressure and temperature conditions.

Article Title: Persistence of davemaoite at lower-mantle conditions.

Article References:
Wang, L., Miyajima, N., Wang, F. et al. Persistence of davemaoite at lower-mantle conditions. Nat. Geosci. 18, 365–369 (2025). https://doi.org/10.1038/s41561-025-01657-9

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41561-025-01657-9