In a groundbreaking advancement in geodynamics, researchers have unveiled intricate simulations that reshape our understanding of the Earth’s mantle and lithosphere interactions during continental rifting. Leveraging the sophisticated finite element code ASPECT, this study delves deep into the dynamic evolution of the continental lithosphere and the asthenosphere over a 100 million-year timespan, providing fresh insights into mantle convection and lithospheric deformation with unprecedented detail. By solving fundamental conservation equations for energy, mass, and momentum under conditions of viscoplastic deformation, the team offers an illuminating portrait of how rifts migrate and how deep mantle processes sculpt the Earth’s surface on geological timescales.
This investigation centers on how mechanical and thermal properties govern the behavior of Earth materials that undergo complex flow laws related to temperature, pressure, and strain rate. Remarkably, the simulations integrate strain weakening mechanisms that enable researchers to capture the gradual failure and subsequent reconfiguration of lithospheric plates as they stretch and break apart. Imposed boundary velocity conditions create a kinematically driven environment where rifts develop and migrate laterally, delaying the eventual tearing apart of the continental lithosphere. Beneath the rift, pressure gradients provoke vigorous rotational flow patterns within the asthenosphere, catalyzing instabilities that propagate inward beneath ancient cratonic regions.
The model is designed with a horizontal extent of 2,000 kilometers and a depth of 300 kilometers, discretized into 800 horizontal and 120 vertical finite elements. Four uniform geological layers constitute the initial model set-up: a 20-kilometer-thick upper crust, a 15-kilometer lower crust, a 125-kilometer mantle lithosphere, and a 140-kilometer asthenosphere layer. Intriguingly, the model initiates rifting within a predefined central zone where the crust thickens by 5 kilometers and the mantle lithosphere thins by 25 kilometers, replicating mobile belt conditions observed where intracontinental rifts typically develop. These asymmetries induce a localized thermomechanical weakness, fostering the onset of rifting. The transition from altered to ambient lithosphere occurs smoothly over 200 kilometers to mirror natural geological gradations.
Central to this study is the incorporation of a 30-kilometer-thick asthenospheric layer beneath parts of the lithosphere. This layer models a metasomatized, mechanically weaker lithospheric keel—a crucial feature influencing mantle dynamics. Empirical data from xenoliths and geothermometry constrain this thermal boundary layer thickness to approximately 30 to 35 kilometers, confirming the physical realism embedded within the model. The overall thermal lithosphere-asthenosphere boundary is posited at 160 kilometers depth, aligning closely with seismic interpretations beneath kimberlite emplacement sites over hundreds of millions of years.
The rheological behavior in each geological layer is meticulously parameterized using experimentally derived flow laws: wet quartzite for the upper crust, wet anorthite for the lower crust, dry olivine for the mantle lithosphere, and wet olivine for the asthenosphere. By conducting sensitivity analyses, the team establishes that the viscosity variations within realistic bounds for the thermal boundary layer and asthenosphere minimally affect key parameters such as the spacing and propagation velocity of Rayleigh-Taylor instabilities — critical to convective peeling and transport of lithospheric material. The dominant driver of these instabilities remains the density contrast, emphasizing buoyancy forces as the primary agent in instability formation.
A novel aspect of the modeling involves strain-dependent weakening affecting both frictional and viscous behavior. Friction coefficients reduce progressively up to 75% within a brittle strain range from zero to one, beyond which they stabilize. Similarly, the viscous viscosity undergoes linear weakening over a defined strain window, simulating mechanical softening during deformation. These mechanisms are critical to realistically reproducing the progressive lithospheric failure and eventual detachment processes driving lithospheric removal and mantle entrainment in rifting contexts.
In the asthenosphere, attention to activation energy in olivine creep deformation reveals its sensitivity to instability kinetics. The chosen activation energy of 480 kJ/mol sits within experimentally validated values, confirming the robustness of adopted rheology. Additional simulations varying activation energies within experimental uncertainty bounds reveal a strong dependence of viscosity—and thus convective instability formation—on this parameter. Lower activation energies reduce viscosity, accelerating the lateral pace of mantle dripping below cratonic keels, while higher energies impede instability genesis altogether, underscoring a threshold viscosity regime for convective erosion to occur.
Kinematic boundary conditions impose extension at a rate of 10 millimeters per year at lateral boundaries, with complementary free-slip conditions to avoid artificial flow restrictions. Material influx from the lower boundary ensures mass balance despite outflow at one lateral side, while the free surface boundary atop enables unrestricted lithospheric deformation. Thermal boundary conditions maintain a cold surface at zero degrees Celsius and a hot mantle base at 1,420 degrees Celsius, fostering realistic geotherms. Initial temperature profiles equilibrate for 30 million years before extension to smooth thermal gradients, producing a credible starting thermal state consistent with lithospheric and asthenospheric mantle temperatures derived from geological observations.
Crucially, the models abstract away complex chemical feedbacks such as melt generation and magma transport, focusing instead on mechanical and physical thermodynamics. Although the omission of melting dynamics represents a limitation, the authors argue that this simplification likely biases the results conservatively. Partial melting would tend to reduce viscosity further, potentially enhancing lithospheric peeling and transport rather than diminishing it, indicating that observed dynamics represent a fundamental mechanical process underpinning continental root erosion.
Another simplifying assumption excludes influences from mantle plumes, along-strike lithospheric heterogeneity, or large-scale mantle circulation patterns. The study purposefully narrows its scope to deep continental lithospheric removal and lateral transport within the upper mantle, avoiding complications from whole-mantle convection and plume-related melting. Extended domain tests confirm that Rayleigh-Taylor instability scale and spacing remain stable even when model depth increases, validating the modeled convection cells’ focus and justifying the truncated vertical extent used in simulations.
The constant initial lithosphere-asthenosphere boundary depth also represents a simplifying condition, with supplementary models incorporating sloping interfaces confirming that the fundamental behavior of dripping instabilities remains intact. This finding reduces concern that regional lithospheric thickness variations undermine the generality of conclusions. Various perturbations to extension velocity—ranging from symmetric velocity boundaries to time-variable strain rates—retain the core instability dynamics, although with slight variations in migration velocities consistent with natural tectonic variability.
To zero in on the controls over lithospheric keel removal, the researchers executed 28 simulations systematically varying the density and viscosity (via activation energy) of the metasomatized keel, spanning ±1.5% density contrasts relative to the asthenosphere. This parametric study revealed three distinct behavioral regimes governing stability and timing of delamination, confirming that convective removal and suboceanic mantle entrainment occur across all scenarios but at differing geological tempos. The simulation outputs quantitatively tracked the flux of decoupled keel material into the asthenosphere, applying refined integrals of vertical flow velocity weighted by tracer fractions to visualize material throughput relative to key positions along the rift.
Remarkably, time series analyses of this material flux demonstrate statistically significant periodic pulses spaced roughly every 5 to 6 million years—signals linked to episodic gravitational ‘dripping’ driven by stark lithosphere-asthenosphere temperature gradients and related viscosity contrasts. These episodic peelings, resembling convective mantle drips, result in discrete lithospheric keel shedding events rather than continuous removal, providing a powerful explanation for observed pulsed volcanic signatures in continental margin settings.
Complementing the geodynamic simulations, an extensive geochemical data compilation from the eastern Indian Ocean Seamount Province links these mantle dynamics to real-world volcanic isotope signatures. The region exhibits strong enriched mantle (EM1) geochemical fingerprints absent influences from mantle plumes, reinforcing the connection between continental root erosion and mantle enrichment in adjacent oceanic volcanism. Rigorous statistical bootstrapping methods correct for potential sampling biases, while plate reconstruction software charts the paleo-distribution of analyzed volcanic centers, painting a coherent spatial-temporal picture tying lithospheric removal to enriched mantle input.
Time series analyses of isotopic ratios extracted from oceanic volcanoes along the Broken Ridge, Ninety East Ridge, and Kerguelen Plateau further corroborate model predictions, revealing step changes and trends in isotopic compositions synchronous with phases of continental break-up and lithospheric delamination. Additional scrutiny of kimberlite volcanism in southern Africa and India synchronizes with modeled lithospheric keeling processes, cementing the link between mantle instabilities, lithospheric erosion, and surface magmatism.
Perhaps most compelling is the observed lag between the lithospheric removal events and subsequent mantle-derived volcanism at oceanic ridges, estimated via Monte Carlo simulations combining convection cell length scales and mantle flow velocities. Lag times on the order of 5 to 14.5 million years, with medians around 8 million years, align naturally with geological observations of volcanic sequences following continental rifting. This temporal correlation provides a concrete mechanism bridging deep mantle dynamics with surface geological phenomena, offering a predictive framework for interpreting mantle-enriched volcanism adjacent to rifted continents.
Taken together, this comprehensive approach combining advanced thermomechanical simulations, rigorous sensitivity analyses, and rich geochemical datasets establishes a compelling paradigm in which persistent convective erosion of continental roots generates enriched mantle domains detectable through distinct volcanic signatures. These findings advance fundamental knowledge of mantle-lithosphere coupling, continental breakup dynamics, and mantle geochemical heterogeneity. They beckon new avenues of research into how deep Earth processes shape surface tectonics and magmatism on multimillion-year timescales, with profound implications for reconstructing Earth’s dynamic evolution and assessing mantle melt generation in rifted margins.
Subject of Research:
Geodynamic processes governing the thermomechanical evolution of continental lithosphere and asthenosphere interaction during rifting and break-up.
Article Title:
Enriched mantle generated through persistent convective erosion of continental roots.
Article References:
Gernon, T.M., Brune, S., Hincks, T.K. et al. Enriched mantle generated through persistent convective erosion of continental roots. Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01843-9
Image Credits:
AI Generated
DOI:
https://doi.org/10.1038/s41561-025-01843-9
Keywords:
Geodynamics, Mantle Convection, Continental Rifting, Lithospheric Delamination, Rayleigh-Taylor Instabilities, Viscoplastic Deformation, Metasomatized Lithosphere, Mantle Enrichment, Thermomechanical Modeling, ASPECT code
