PICO
This session aims to provide a holistic view of the dynamics, tectonics, structure, composition and evolution of Earth and rocky planetary bodies (including exoplanets) on temporal scales ranging from the present day to billions of years, and on spatial scales ranging from microscopic to global, by bringing together constraints from geodynamics, seismology, mineral physics, geochemistry, petrology, volcanology, planetary science and astronomy.
The solubility of various volatiles in magma oceans plays a significant role in the formation and evolution of planetary atmospheres. Using ab initio molecular dynamics simulations, we investigate the dissolution of various volatiles in a magma ocean with bulk silicate Earth composition under conditions relevant to both early Earth and exoplanetary systems.
We find that hydrogen is highly soluble in silicate magma oceans, and its solubility increases dramatically with pressure and temperature. In particular for exoplanets, like sub-Neptunes, this solubility influences the structure and functioning of the entire planet. It significantly alters the redox state of the system and causes a massive outflux of oxygen. The results are large-scale formation of water vapor and the release of other complex chemical species. This process profoundly impacts the thermal and chemical evolution of exoplanets, particularly sub-Neptunes, whose atmospheres may show observable spectral signatures linked to magma ocean interactions. At conditions characteristic to the beginning of the Hadean, the Earth’s magma ocean could have easily dissolved large amounts of hydrogen. As a result, the amount of water present in the early atmosphere was determined by a fine balance between water degassing and hydrogen solubility. Changes in the redox state of the magma at shallow conditions would further influence this balance.
With regard to noble gases and CO/CO2, our simulations show that they are profoundly incompatible in silicate melts. They easily degas under lower pressure conditions, particularly when they are present jointly in the melt. The partial pressures of either of these gases need to reach at least a couple GPa to prevent degassing. These results suggest that the magma ocean contributed to the CO2-reach atmosphere of the Hadean, by both limited ingassing in the aftermath of the giant impact, and by massive outgassing, once the magma ocean was put in place.
How to cite: Caracas, R.: Outgassing of the Hadean magma ocean: a computational perspective , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12545, https://doi.org/10.5194/egusphere-egu26-12545, 2026.
Degassing of the magma ocean shaped the Earth’s early atmosphere and volatile budget. Despite its fundamental importance, the oxidation conditions of the magma ocean and the associated degassing processes remain poorly constrained. Sulfur, an abundant volatile element with multiple valence states, provides a sensitive tracer of redox-dependent degassing, making it an ideal probe for these processes.
Here, we present the first systematic investigation of sulfur degassing under realistic magma ocean conditions typical of the beginning of the Haden, using ab initio molecular dynamics simulations. Our results reveal that sulfur volatility and its speciation in the gas phase are strongly controlled by redox conditions: oxidizing conditions make sulfur highly volatile as sulfur oxides, reducing conditions keep it bound to the silicate melt. In view of our results, the observations of sulfur depletion in the Earth today, can be explained if degassing of the early magmas from planetesimals during accretion occurred under relatively reducing conditions. Sulfur degassing at the magma ocean stage of the early Earth brought reducing species to the early atmosphere, with the sulfur vapor phases being favorable for the prebiotic synthesis of amino acids. Our sulfur degassing results establish a direct link between the depletion of volatile elements, the redox state of the magma ocean, and the composition of the early atmosphere, providing new insights into the evolution of early Earth.
How to cite: Wang, D., Wang, W., Wu, Z., and Caracas, R.: Redox Controls on Sulfur Degassing in the Magma Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5569, https://doi.org/10.5194/egusphere-egu26-5569, 2026.
Rocky planets such as the Earth or Venus likely experienced at least one magma ocean (MO) episode, during which the silicate mantle was molten in part or in full due to the heat generated by accretion and radioactive heating. During this MO stage, volatile elements present in the magma degassed to form the secondary atmosphere. Better understanding this degassing process can help us constrain the duration of the MO stage, the volatile enrichment of the subsequent mantle and the conditions for habitability.
The degassing process is typically assumed to be efficient, in equilibrium with the atmosphere: instant degassing of oversaturated fluid parcels in a well-mixed magma ocean. However, MO parcels may experience considerable delay in reaching the shallow pressures where bubbles can form and degas into the atmosphere.
We take into account this out-of-equilibrium degassing in a 1D interior model coupled to a radiative-convective CO2/H2O atmosphere. The model is parameterized using scaling laws derived from joint laboratory and numerical experiments. We explore a broad range of planet sizes, stellar radiation and CO2 and H2O initial concentrations, and examine the impact of rapid rotation akin to that of the early Earth.
Using this coupled model, we explore the impact of out-of-equilibrium degassing on atmospheric composition and habitability, the cooling time of the MO, and the volatiles trapped in the mantle.
How to cite: de Larminat, A., Samuel, H., and Limare, A.: Impact of out-of-equilibrium degassing of magma oceans on volatile trapping, solidification time and habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22000, https://doi.org/10.5194/egusphere-egu26-22000, 2026.
The formation and earliest evolution of a secondary atmosphere is tightly linked to its underlying magma ocean. Our current understanding of this coupled evolution is mainly built on thermal evolution coupled to chemical equilibrium models, which inherently assumes instant chemical exchange between the atmosphere and magma ocean. However, some recent numerical models [1,2] have challenged this assumption. In this work, we address the issue both theoretically and numerically.
Volatile transport within the bulk of the magma ocean can, to a certain extent, be approximated as a passive particle diffusion process. Even when the buoyancy of volatiles is neglected, we demonstrate through two complementary approaches that the bulk transport is rapid. First, we extend a theoretical model for turbulent diffusion whose predictions align well with numerical simulations, which enables to replace empirical constants with more fundamental parameters. When extrapolated to magma ocean conditions, the characteristic diffusion timescale is found to be significantly shorter than the expected lifetime of the magma ocean. Second, we perform numerical experiments by initializing a passive scalar field at mid-depth in a statistically steady-state turbulent convection simulation. The evolution of its distribution, governed by an advection-diffusion equation, shows that the initial central peak flattens within just a few free-fall time units, which is a direct indicator of vigorous turbulent mixing.
The seemingly inefficient transport observed in some recent studies may be attributed to the behavior of a compositional boundary layer, which forms in conjunction with a laminar velocity boundary layer near the top surface. We analytically derive the composition flux across a no-slip boundary layer, which is supposed to scale with the chemical diffusivity and the square root of a characteristic Reynolds number. Numerical simulations show good agreement with this prediction. Nonetheless, this boundary-layer bottleneck is unlikely to significantly limit vertical volatile transport under realistic magma ocean conditions, for several reasons:
- Volatile parcels could grow in size as they approach the boundary layer, when buoyancy becomes significant and the "passive particles" assumption no longer holds
- Even a no-slip boundary layer can be turbulent at the relevant extremely high Rayleigh number, where vertical transport is much more efficient than in a low-Ra laminar boundary layer
- The atmosphere-magma ocean interface is a free-surface, instead of a no-slip or free-slip wall
Building on recent findings that rotation significantly alters magma ocean dynamics (e.g., [3]), our future research will incorporate rotational effects to develop a more comprehensive understanding of volatile transport efficiency.
References:
[1] Salvador, A. & Samuel, H. Icarus 390, 115265 (2023).
[2] Walbecq, A., Samuel, H. & Limare, A. Icarus 434, 116513 (2025).
[3] Maas, C. & Hansen, U. EPSL 513, 81–94 (2019).
How to cite: Yang, X., Gillmann, C., and Tackley, P.: Efficient volatile exchange between atmosphere and magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7098, https://doi.org/10.5194/egusphere-egu26-7098, 2026.
In their hot initial phase, rocky planetary bodies undergo a magma ocean (MO) stage. Crystallisation of this magma ocean sets the initial structure of planetary mantles, and thus determines the early stages, and long term evolution, of solid-state mantle convection, thus regulating the litrhospheric tectonic, core convection and associated magnetic field. This major planetary differentiation process also controls the outgassing of the primary atmosphere, and therefore the long-term surface evolution and habitability. While several studies have addressed this crystallisation process from a mass-balance or a dynamical point of view, few have studied remelting of the convecting solid mantle while a magma ocean was still present. We here present spherical annulus numerical calculations of mantle convection and melting under a magma ocean to address the role of heterogeneity and dynamic recrystallisation on remelting and differentiation. Results indicate that the parameters that typically impact mantle convection (viscosity, density anomaly, etc) also impact the differentiation of the magma ocean. In particular, dynamic topography has a great influence on the composition of the magma ocean and its differentiation, as it conditions both, excess melting above upwellings (e.g. Figure 1) and excess crystallisation above downwellings. These topography effects are greater the closest the system is to a magma ocean overturn. Our findings can help to understand the differences between solar system bodies, such as the presence or absence of basal magma oceans in terrestrial bodies, or to predict the convective evolution of rocky exoplanets.
Figure 1: Effects of different MO density on mantle upwellings, the greater topography due to higher density of the MO causes increased excess melting.
How to cite: Manjón-Cabeza Córdoba, A., Ballmer, M. D., and Shorttle, O.: Planetary controls on magma ocean crystallisation, re-melting and overturn, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18147, https://doi.org/10.5194/egusphere-egu26-18147, 2026.
Calcium silicate perovskite (CaPv) is the host for many large ion lithophile elements including the heat-producing elements in the lower mantle. Whether, when, and where it forms during the solidification of the magma ocean is fundamental to understanding the geochemical and geodynamical evolution of the early Earth and the trace element distribution in the lower mantle. In this study, we performed first-principles molecular dynamics simulations to investigate the partitioning behavior of Ca (alongside other alkali-earth elements, Sr and Ba) between bridgmanite and molten pyrolite. Our results show that the bridgmanite-melt partition coefficient of Ca remains smaller than 1 along the liquidus across the lower mantle, and decreases further between the magma ocean liquidus and solidus, indicating that Ca is incompatible in bridgmanite at all relevant crystallization conditions in the lower mantle. This results in a progressive enrichment of Ca in the magma ocean as it solidifies, leading unavoidably to the crystallization of CaPv during the final stages of solidification in the deep mantle. Laser-heated diamond anvil cell experiments performed to replicate the crystallization of pyrolitic melt in the same conditions as our simulations confirm the crystallization of CaPv in the last stages of solidification. From Ca to Sr to Ba, the bridgmanite-melt partition coefficients decrease by orders of magnitude, indicating a significant enrichment of these large ion lithophile trace elements in the residual melt. Combined with previous experimental studies at lower P-T conditions, our findings infer that both large ion lithophile elements and their host, CaPv, will be concentrated in the deep mantle at the end of magma ocean solidification.
How to cite: Wang, T., Badro, J., Caracas, R., Gendre, H., and Hébert, C.: Formation of calcium silicate perovskite above the core-mantle boundary during solidification of Earth’s magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5529, https://doi.org/10.5194/egusphere-egu26-5529, 2026.
The Thermal Lattice Boltzmann Method (TLBM) models finite Prandtl number thermal convection and multiphase flow at high Rayleigh numbers in the turbulent regime. As such, it offers a powerful means to study early earth which was shaped by magma oceans (MOs) where turbulent convection governed the transport of heat, silicates and volatiles. Ab-initio molecular dynamics shows that pressure and temperature dependent viscosity of silicates can vary by many orders of magnitude resulting in stratified Prandtl numbers ranging from much lower to much higher than unity spanning up to 3 – 5 orders of magnitude. We incorporated such P-T dependent viscosity into the Thermal LBM to explore the impact of stratified Pr on the convective dynamics of turbulent magma oceans. We find that the Pr stratification has a dramatic influence on turbulent flow, with strong vorticity only occurring at shallower depths above 1000 km for colder adiabats which implies greater chemical equilibration. We also combined the TLBM and multiphase LBM to model iron-silicate segregation due to large iron-rich impactors in a 3000 km thick magma ocean with a Prandtl number of unity. These studies indicate that thermal convection exerts only a modest influence on the spatial distribution of iron in MOs. Our results reveal that the time for iron droplets to fully settle lies in the range 15 – 30 days, and that vigorous thermal convection tends to confine fragments of smaller impactors to deeper regions of the MO, whereas, fragments of larger impactors disperse throughout all depths of the MO.
How to cite: Mora, P., Morra, G., Honarbakh, L., Jackson, C., and Karki, B.: Research progress with Thermal Lattice Boltzmann Method to study early Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2345, https://doi.org/10.5194/egusphere-egu26-2345, 2026.
Terrestrial planets—Mercury, Venus, Earth and Mars—formed by the accretion of smaller objects, each planet with their own timescale. The Earth was probably the latest terrestrial planet to form and reached about 99% of its final mass within about 60–100 Myr after condensation of the first solids in the Solar System. This contribution examines the disproportionate role of the last approximately 1% of Earth’s growth, or late accretion, in controlling its long-term interior evolution, and in particular metal-silicate mixing and bulk volatile budget.
The coupling of impact and geodynamical simulations reveals underappreciated consequences of Earth’s late accretion with implications for a correct interpretation of the geochemical and geodynamical properties of the present Earth’s mantle. Similar implications are expected for Venus and Mars, and are also likely to occur and modulate the interior evolution of rocky exoplanets.
How to cite: Marchi, S. and Korenaga, J.: The shaping of the terrestrial planet’s interiors by late accretions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5902, https://doi.org/10.5194/egusphere-egu26-5902, 2026.
The existence and eruptibility of mantle plumes in the Hadean-early Archean mantle are fundamental to interpreting the scarcity and timing of komatiites and other ultramafic magmas. Existing approaches often rely on parameterized thermal evolution or idealized forced-plume setups, so they rarely test plume eruptibility in fully convecting, high-Rayleigh whole-mantle dynamics. We use a thermal lattice-Boltzmann mantle convection approach with a multiphase formulation to test whether thermochemical plumes in a hot, vigorous, post-magma-ocean mantle can dynamically reach the surface, and under which conditions they are expected to erupt rather than stall and pond.
We simulate whole-mantle convection in annular geometry, solving Boussinesq Stokes flow coupled to heat advection-diffusion, and explore Hadean-like thermal structures at high Rayleigh numbers. Deformation is governed by nonlinear, visco-plastic rheology with Reynolds temperature-dependent viscosity, allowing transitions between weak- and strong-lid regimes via depth-dependent yield stress. Thermochemical plumes are represented by introducing a dense (e.g., eclogite-rich) component in the deep mantle that can be entrained into rising hot material, enabling us to quantify how compositional loading modifies plume ascent, head-tail structure, and interaction with the lithosphere. Melting is implemented within the simulations: melt generation, extraction, and retention are explicitly coupled so that density and viscosity evolve continuously as function of temperature, melt fraction, and composition.
Across the parameter suite, we track plume head trajectories, maximum ascent depth, and the spatiotemporal distribution of melt production/extraction to map an “eruption window” in Rayleigh-rheology-composition space. We compare this dynamical window with the observed timing and abundance of komatiites, and infer how thermochemical structure near the core-mantle boundary may have regulated the longevity and eruptibility of early Earth plumes.
How to cite: Pilia, S., Bargees, A., Mora, P., and Morra, G.: Can Hadean thermochemical plumes erupt? Insights from a high-Rayleigh number thermal lattice-Boltzmann mantle convection model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4360, https://doi.org/10.5194/egusphere-egu26-4360, 2026.
How the very early Earth lost its internal heat remains a subject of debate. Early Earth may have been characterized by extensive magmatism due to a hot mantle, which then acted as the primary heat loss mechanism, or been more volcanically quiescent, where heat conduction through the lithosphere served as the primary heat loss mechanism. The primary mode of early Earth heat loss would then strongly influence tectonics and crust formation, the long-term thermal evolution of the interior, and surface environments where life could originate in the Hadean or Eoarchean.
Our recent crustal evolution model suggests that mantle melt production and mafic extrusive volcanism must have been limited prior to 3.6 Ga to remain consistent with Hf isotope data. We hypothesized that these geochemical constraints require a 'quiescent Earth' with a low melt production rate (<0.6 mm/yr). However, the actual magma supply is governed by complex geodynamic factors: specifically, the mechanics of melt generation, ascent, and accumulation at the mantle-crust boundary. Understanding these physical mechanisms is critical, particularly when evaluating high-flux regimes such as heat-pipe tectonics, which may be incompatible with the low rates inferred from the geochemical record.
A critical phenomenon affecting this supply is the formation of a decompaction layer beneath the mantle-crust interface (Sparks and Parmentier, 1991). Since the crust acts as a rigid thermal boundary, temperatures drop rapidly near this interface. Consequently, ascending melt encounters a freezing horizon that acts as a permeability barrier, causing it to accumulate. Within this zone, the decompaction layer and accumulated magma generate significant melt overpressure relative to the solid matrix, driving magma into the plumbing system and initiating ascent. Therefore, characterizing the dynamics of the decompaction layer is crucial for understanding the physical controls on melt supply.
Recent numerical modeling of Io, an active heat-pipe body (OReilly and Davies, 1981), demonstrates that crustal thermal structure is controlled by the physics of two-phase melt transport (Spencer et al., 2020). This model suggests that magma transport is driven by mantle overpressure at the decompaction layer but limited by solidification within the plumbing system. Applying this physical framework to the Hadean, we tested which mantle dynamics and temperature ranges are compatible with the restricted melt fluxes required by the geochemical record. Preliminary results demonstrate the existence of a decompaction layer, where both effective pressure and extraction rates increase significantly with porosity. By systematically exploring the parameter space, we identify the specific mantle geodynamic conditions required to align plateau melting tectonics with the Hf isotope constraints.
How to cite: Kubota, Y., Rudge, J., and Foley, B.: The role of the mantle decompaction layer in Hadean volcanism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7793, https://doi.org/10.5194/egusphere-egu26-7793, 2026.
Sagduction, the downward movement of dense crustal material into the underlying mantle, is considered one of the plausible tectonic mechanisms operating during the Archean time, when the lithosphere was hotter and weaker than today (Bedard, 2006; Johnson et al., 2014; Sizova et al., 2015; Sizova et al., 2018; Piccolo et al., 2019). Understanding the physical conditions that enable sagduction is key to deciphering the early evolution of Earth’s crust and mantle lithosphere.
In this study, we employ a suite of 2D numerical models using ASPECT code, to systematically investigate the dynamics of sagduction under varying rheological and thermal conditions. We vary the viscosity structure and the depth at which lower crustal metamorphism initiates, to test how mantle’s viscosity and metamorphic density changes influence the style and efficiency of sagduction. Our results reveal how the interplay between viscosity layering and metamorphic phase transitions controls the timing and extent of downward crustal recycling.
We further examine how these parameters influence the long-term evolution of the lower crust and the mantle lithosphere beneath it. Our findings provide new insight into the dynamics of Archean lithosphere and the mechanisms that may have governed early continental differentiation.
References
Bedard, J.H., 2006. A catalytic delamination-driven model for coupled genesis of Archaean crust and sub-continental lithospheric mantle. Geochim. Cosmochim. Acta 70, 1188–1214. https://doi.org/10.1016/j.gca.2005.11.008.
Johnson, T., Brown, M., Kaus, B., van Tongeren, J., 2014. Delamination and recycling of Archaean crust caused by gravitational instabilities. Nat. Geosci. 7, 47–52. https:// doi.org/10.1038/ngeo2019.
Sizova, E., Gerya, T., Stüwea, K., Brown, M., 2015. Generation of felsic crust in the Archean: A geodynamic modeling perspective. Precambr. Res. 271, 198–224. https://doi.org/10.1016/j.precamres.2015.10.005.
Sizova, E., Gerya, T., Brown, M., Stüwea, K., 2018. What drives metamorphism in early Archean greenstone belts? Insights from numerical modeling, Tectonophysics 746, 587–601. https://doi.org/10.1016/j.tecto.2017.07.020.
Piccolo, A., Palin, R., & B.J.P. Kaus, R.W. (2019), Generation of Earth’s Early Continents From a Relatively Cool Archean Mantle, Geochemistry, Geophysics, Geosystems, 20, 1679–1697, doi:https://doi.org/10.1029/2018GC008079.
How to cite: Roy, P., van Hunen, J., and Pons, M.: Sagduction: Could This Explain Early Earth Tectonics? A Modeling Perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-83, https://doi.org/10.5194/egusphere-egu26-83, 2026.
The formation and stabilization of continental crust during the Archean remains a fundamental problem in Earth sciences, requiring numerical models that can self-consistently capture multiphase flow, melt segregation, and thermochemical buoyancy within a convecting mantle. Here, we employ a thermal Lattice Boltzmann Method (TLBM) based on the Rothman–Keller multiphase formulation to investigate continent formation in a dynamically evolving Archean mantle. The model resolves two interacting lithological components representing basaltic crust and peridotitic mantle, coupled to a thermal field through the Boussinesq approximation. Melt generation, extraction, and retention are explicitly incorporated, allowing density and viscosity to evolve continuously as functions of temperature, melt fraction, and composition. Melt extracted from basalt is treated as an immiscible, low-density phase representing Tonalite–Trondhjemite–Granodiorite (TTG) crust. Unlike traditional marker-based or fixed-density approaches, this framework enables self-consistent tracking of compositional evolution without prescribing rigid phase boundaries. Simulations are conducted in annular geometry to approximate spherical curvature while retaining computational efficiency, with spatial resolution ranging from ∼15 km near the surface to ∼8 km at the core–mantle boundary (CMB). Results show that thermally driven melt production and compositional differentiation naturally generate buoyant, long-lived TTG crust that thickens and stabilizes against recycling. Residual basalt forms a denser layer beneath the TTG crust, contributing to lithospheric stabilization while remaining susceptible to recycling under cold, dense conditions.
How to cite: Bargees, A., Pilia, S., Mora, P., Morra, G., Kuang, J., and Honarbakh, L.: Thermal Lattice Boltzmann Modeling of Archean Continent Formation Using a Rothman–Keller Multiphase Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2842, https://doi.org/10.5194/egusphere-egu26-2842, 2026.
Do the various continental crustal growth curves formulated from disparate geochemical models robustly inform us as to why the Hadean (pre-4 Ga) rock record is basically non-existent? Is its absence due to extrinsic effects (bombardment)? Or, could it be that little or no continental crust existed at first? On the other hand, was this record essentially lost over time by recycling processes? For instance, the biggest problem with searching for any information about the history of plate tectonics is that the process erases evidence of its own existence. The age of oceanic crust averages about 70 Ma and is not older than 200 Ma because plate tectonics keeps recycling it (except for some old ophiolites). Most of the crust by surface area is oceanic, whereas most crust by volume is continental. The mean age of continental crust (ca. 2 Ga) is 36× greater than that of oceanic crust because its buoyancy prevents it from subducting except for loss to subduction via erosion. The overall decline in preserved continental crust based simply on the detrital zircon record shows a roughly 1.4 Gyr e-folding time. The residence time of the lithosphere is the average length of time that it will remain as a geochemical entity; this is estimated to be about 500-750 Myr. The value is about half of the observed e-folding time for the pre-Phanerozoic (>542 Ma) continental crust, but is close to the average mixing timescale since the Archean of about 420-440 Myr for primitive mantle, recycled continental crust and mantle residue. Assuming the residence time of 750 Myr is a good estimate for the half-life of continental crust, then the e-folding time is in broad agreement with both the zircon record and model calculations of crustal reworking. The zircon record is strongly biased to continental crust, because zircon is most commonly found in granites and granitoids, which constitute the major rock fraction of the continents. The trends in the detrital zircon data can be interpreted to represent decreasing preservation rather than increasing production, of continental crust.
How to cite: Mojzsis, S. J.: Whence the Missing Hadean Rock Record?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4906, https://doi.org/10.5194/egusphere-egu26-4906, 2026.
Early planetary accretion and giant impacts likely generated a global magma ocean on the proto-Earth, enabling extensive dissolution of primordial volatiles from the solar nebula into silicate melts. During subsequent core-mantle differentiation, the partitioning of noble gases between pyrolitic silicate melts and iron-sulfur (Fe-S) melts would have controlled their redistribution and long-term preservation in Earth’s deep interior. The contrasting noble gas signatures observed in mid-ocean ridge basalts and mantle plume sources, particularly in He/Ne ratios, motivated the existence of a deep primitive reservoir potentially linked to early core-mantle differentiation. Here, we use ab initio molecular dynamics simulations combined with thermodynamic integration to quantify the partition coefficients of He, Ne, Ar, Kr, and Xe between pyrolitic silicate melts and Fe-S melts. We further assess the effects of melt composition by comparing pyrolite with MgSiO3 melts and Fe-S with metallic iron melts. Our results reveal systematic variations in noble gas partitioning with atomic size and melt chemistry. Based on these partitioning coefficients, we estimate the potential noble gas inventories preserved in the mantle and core. These results provide new quantitative constraints on the fate of primordial noble gases and the origin of deep-mantle volatile reservoirs.
How to cite: Zhao, Y., Wang, T., Caracas, R., Wang, W., and Wu, Z.: Fate of primordial noble gases during core-mantle differentiation from ab initio simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7052, https://doi.org/10.5194/egusphere-egu26-7052, 2026.
Evolution of deep mantle reservoirs after the magma ocean: the influence of melt extraction
Laura Lark, ChEd Boukaré, James Badro, Henri Samuel
Earth’s magma ocean stage and aftermath likely produced a reservoir of iron and trace element enriched silicate melt at the base of the mantle, termed a “basal magma ocean” (BMO) (Boukaré et al., 2025; Labrosse et al., 2007). As the BMO crystallized, its cumulates would likely be buoyant both because iron would behave somewhat incompatibly and because melt under extreme pressure is compressed to similar (or even higher) density than crystal of the same composition (Caracas et al., 2019). Consequentially, BMO crystallization would have been self-limiting, in that heat loss is necessary for crystallization to progress, but crystallization forms a layer of cumulates which insulate the BMO, reducing heat loss. Therefore, the evolution of the cumulates of the BMO interacting with convection in the overlying mantle is extremely important for the thermal evolution of the deep planet, with implications for BMO longevity and core dynamo generation.
We investigate the co-evolution of the BMO, its cumulates, and the overlying mantle with the fluid dynamics code Bambari (Boukaré, 2025) which incorporates melting, melt-crystal fractionation, and melt migration into a mantle convection model with coupled core (0-D heat reservoir). We are exploring the evolution of cumulates from the freezing BMO and how this affects BMO heat loss. For example, we vary the initial concentration of heat-producing elements in the BMO vs. solid mantle (γ) and observe that piles form preferentially in models with a more strongly heated basal magma ocean. At the base of piles, melting and drainage of iron-rich melts results in overall depletion of iron from piles. The lower density reinforces piling behavior, which strengthens melting and iron drainage (Figure 1). We are continuing to evaluate regimes of piling and implications for heat loss and interaction with the overlying mantle.
Figure 1. Snapshots of model mantle composition, cropped to show deep mantle only. Piles in convecting mantle overlie freezing basal magma ocean (white above melt fraction of 0.9). Model with more strongly heated BMO (higher ) shows more depleted upwellings within piles (yellow arrows).
References
Boukaré, C.-É., Badro, J., & Samuel, H. (2025). Solidification of Earth’s mantle led inevitably to a basal magma ocean. Nature, 640(8057), 114–119. https://doi.org/10.1038/s41586-025-08701-z
Caracas, R., Hirose, K., Nomura, R., & Ballmer, M. D. (2019). Melt–crystal density crossover in a deep magma ocean. Earth and Planetary Science Letters, 516, 202–211. https://doi.org/10.1016/j.epsl.2019.03.031
Labrosse, S., Hernlund, J. W., & Coltice, N. (2007). A crystallizing dense magma ocean at the base of the Earth’s mantle. Nature, 450(7171), 866–869. https://doi.org/10.1038/nature06355
How to cite: Lark, L., Boukaré, C.-E., Badro, J., and Samuel, H.: Evolution of deep mantle reservoirs after the magma ocean: the influence of melt extraction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7578, https://doi.org/10.5194/egusphere-egu26-7578, 2026.
The thermal history of the Earth, it’s chemical differentiation and also the reaction of the interior with the
atmosphere is largely determined by convective processes within the Earth’s mantle. A simple physical model,
resembling the situation,shortly after core formation, consists of a compositionally stable stratified mantle, as
resulting from fractional crystallization of the magma ocean. The early mantle is subject to heating from below
by the Earth’s core and cooling from the top through the atmosphere. Additionally internal heat sources will
serve to power the mantle dynamics. Under such circumstances double diffusive convection will eventually lead
to self organized layer formation, even without the preexisting jumps is material properties. We have conducted
2D and 3D numerical experiments in Cartesian and spherical geometry, taking into account mantle realistic
values, especially a strong temperature dependent viscosity and a pressure dependent thermal expansivity . The
experiments show that in a wide parameter range. distinct convective layers evolve in this scenario. The layering
strongly controls the heat loss from the core and decouples the dynamics in the lower mantle from the upper
part. With time, individual layers grow on the expense of others and merging of layers does occur. We observe
several events of intermittent breakdown of individual layers. Altogether an evolution emerges, characterized by
continuous but also spontaneous changes in the mantle structure, ranging from multiple to single layer flow. Such
an evolutionary path of mantle convection allows to interpret phenomena ranging from stagnation of slabs at
various depth to variations in the chemical signature of mantle upwellings in a new framework
How to cite: Hansen, U. and Dude, S.: Dynamical layering in planetary mantles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4522, https://doi.org/10.5194/egusphere-egu26-4522, 2026.
As the origin of the stable large low shear velocity provinces (LLSVPs) beneath Africa and the Pacific is still unclear, we numerically consider two possible scenarios. Structures can form either from a primordial layer or a growing layer above the core-mantle boundary (CMB). The primordial layer is considered as a remnant of the early magma ocean phase, while the growing layer results from core-mantle interaction. In our 2D Cartesian study we analyze a diffusive influx of iron-rich core material.
We investigate the temporal and spatial stability of thermochemical piles under the influence of rheological parameters. Our model rheology is given by a viscosity depending on temperature, stress, depth and composition. Furthermore, we also investigate the effect of a depth-dependent thermal expansion coefficient. As all these parameters affect the strength of convection, they ultimately also have an impact on the stability of piles. Increasing the ratio between the top and bottom viscosity or expansivity leads to longer pile lifetimes and more stable piles. Therefore, piles can have formed in the Archean mantle but will have broadened and stabilized in time with the cooling of the mantle.
Typically, we find that these piles anchor thermochemical plumes, so that long-lived plumes exist in the center of piles. Less stable plumes occur at the edges of piles for a few million years as piles move and merge. The movement of piles results is a consequence of slabs pushing them around or of thermal plumes attracting dense piles.
How to cite: Stein, C., Sitte, H. W., Weber, C., and Hansen, U.: Stability of thermochemical piles of different origins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2708, https://doi.org/10.5194/egusphere-egu26-2708, 2026.
The mantle’s redox properties play a pivotal role in regulating the exchange of redox budget between Earth’s deep interior and surface, ultimately influencing the accumulation of atmospheric oxygen and the evolution of life. However, how mantle redox state developed, particularly the mantle source associated with mid-ocean ridge-like settings, remains a subject of ongoing debate. Here, we employed thermodynamic-thermomechanical numerical simulations to explore the redox properties of melts formed under mid-ocean ridge-like settings in both Archean and modern conditions. The results of these simulations were systematically compared with an extensive database of mid-ocean ridge-like rocks, dating back as far as 3.8 Ga, to reconstruct the mantle’s redox evolution since the early Archean. This reconstruction utilized a novel and reliable redox proxy, the whole-rock Fe3+/ΣFe ratio, by integrating forward numerical modeling with thermodynamic inversion based on natural observations. This ratio is defined as the primary proxy for redox budget variations under mantle reference conditions, especially when the influence of other minor redox-sensitive elements (e.g., carbon, sulfur) is negligible. Our findings demonstrate that the mantle’s average Fe3+/ΣFe ratio has approximately doubled since the early Archean. Moreover, our calculations suggest that the ancient ultra-low-oxygen-fugacity mantle found in modern oceanic lithosphere results from an initially reduced origin, rather than deep and hot partial melting. By linking the non-monotonic evolution to geological evidence of tectonic activity, we suggest that the mantle’s redox history may reflect significant tectonic reorganization events. Our findings highlight the intrinsic coupling between Earth’s oxygen-rich environment and tectono-magmatic processes.
How to cite: Duan, W., Zhu, X., Gerya, T., Zhou, X., and Tian, J.: The Mantle Fe3+/ΣFe Ratio Has Doubled Since the Early Archean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2595, https://doi.org/10.5194/egusphere-egu26-2595, 2026.
Accretion and early differentiation processes have left Earth's mantle in a chemically heterogeneous state at the end of the Hadean. Since then, these primordial heterogeneities have been progressively erased by mantle convection stirring. This is well-illustrated by short lived isotopic systems such as 146Sm-142Nd: mantle-derived rocks 2.7 to 4.0 Gy old have been found with measurable anomalies in 142Nd/144Nd, while younger rocks show no detectable deviations from the mantle average. This indicates that convective stirring within the mantle has reduced the level of heterogeneities below the instrumental detection limit in ~1.8 Gy since Earth's formation. These observations have the potential of giving constraints on the mantle stirring rate in the Archean, and therefore on the mantle's dynamical state. However, the survival time of an heterogeneity depends not only on the mixing rate, but also on the initial level of heterogeneity and instrumental detection limit. For these reasons, and also because of the relative scarcity of available data, the observed survival time cannot be simply translated into a mantle stirring time. A quantitative interpretation of the geochemical data in terms of stirring rate requires comparison with a model that can predict the evolution of the probability density function (PDF) of the abundance of a geochemical tracer (or, equivalently, histograms of concentration), as a function of the convective regime and characteristics of the initial heterogeneity. We present here an analytical model for the time evolution of the PDF of a chemical tracer that is initially heterogeneously distributed. The model predictions compare very well with results from numerical simulations. This provides a solid physical basis for interpreting 142Nd/144Nd variations in terms of mantle dynamical state.
How to cite: Deguen, R.: Mixing of a passive heterogeneity by mantle convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14260, https://doi.org/10.5194/egusphere-egu26-14260, 2026.
Thermo-chemical mantle convection models featuring heterogeneous thermal conductivity indicate that heat-producing element (HPE) enrichment in large low shear velocity provinces (LLSVPs) significantly impacts the long-term stability of these regions. Because the rate of internal heating was more significant in the past, thermal conductivity's influence on thermal buoyancy (and bulk erosion) must have also been more substantial. Consequently, their initial volume may have been significantly larger than their present-day volume. Energy balance calculations suggest that a smaller initial mantle volume fraction of LLSVPs material supports more HPE enrichment than a larger mantle volume fraction to maintain the mantle's internal heat budget. For example, an initial layer thickness of 160km (~3% mantle volume) implies present-day HPE enrichment factors greater than ~45 times the ambient mantle heating rate (compared with more conservative factors of 10 to 20 for similar initial conditions employed in previous studies of thermo-chemical pile stability). Thus, HPE enrichment may have been significantly underestimated in earlier models of LLSVPs evolution. Conversely, and assuming that LLSVPs formed from a much larger reservoir, HPE enrichment may be overestimated based on the present-day LLSVPs volume. Our study considers LLSVPs with a primordial geochemical reservoir composition (consistent with an undegassed 4He/3He signature and HPE enrichment). We present thermo-chemical mantle convection models that feature time-dependent internal heating rates and HPE enrichment (implied by initial mantle volume fraction). In this new context, we re-examine, in particular, the impact of a fully heterogeneous thermal conductivity, including a radiative conductivity, on the stability of LLSVPs. We then calculate synthetic seismic shear-wave velocity anomalies from the final distributions in temperature and composition tomographic of our simulations, filter these anomalies with a tomographic filter built from tomographic model HMSL-SPP06, and examine their distribution together with the heat-flux patterns at the core-mantle boundary. Using LLSVPs' present-day volume and core-mantle boundary coverage as a constraint, we finally discuss potential initial conditions, heating scenarios, and thermal conductivity for an Earth-like model.
How to cite: Guerrero, J., Deschamps, F., Hsieh, W.-P., and Tackley, P.: Assessing the effects of heat-producing element enrichment and mantle thermal conductivity on the stability of primordial reservoirs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8865, https://doi.org/10.5194/egusphere-egu26-8865, 2026.
Large low shear-wave velocity provinces (LLSVPs) are degree-2, antipodal structures in Earth’s lowermost mantle that may play a key role in mantle convection and plate tectonics. However, the origin and timing of their degree-2 configuration remain poorly understood due to the lack of geological constraints (McNamara, 2019). Tidal evolution models predict that Earth’s length of day (L.O.D) increased from ~6 h to 24 h over geological time (Farhat et al., 2022), suggesting that centrifugal force could have significantly influenced early LLSVPs evolution. Here, we investigate this mechanism using 3D self-consistent thermochemical mantle convection models that incorporate centrifugal force, implemented with the code StagYY. In our models, L.O.D increases linearly from 6 h to 24 h over the full 4.56 Gyrs model time. We assume that LLSVPs originate from a uniform basal dense layer that are results of either magma ocean crystallization (Labrosse et al., 2007) or the Moon-forming giant impact (Yuan et al., 2023). We find that centrifugal force substantially accelerates the formation of degree-2 basal mantle structures. A subduction girdle centered at the equator and two basal mantle structures centered at the poles are observed in our models. These degree-2 structures emerge consistently across experiments with varying yield stresses and corresponding plate tectonic configurations. Thus, our simulations demonstrate that centrifugal force drives the formation of antipodal LLSVPs, further suggesting that the polar LLSVPs may subsequently migrate through true polar wander.
References:
Farhat, M., Auclair-Desrotour, P., Boué, G., Laskar, J., 2022. The resonant tidal evolution of the Earth-Moon distance. Astronomy & Astrophysics 665.
Labrosse, S., Hernlund, J.W., Coltice, N., 2007. A crystallizing dense magma ocean at the base of the Earth’s mantle. Nature 450, 866-869.
McNamara, A.K., 2019. A review of large low shear velocity provinces and ultra low velocity zones. Tectonophysics 760, 199-220.
Yuan, Q., Li, M., Desch, S.J., Ko, B., Deng, H., Garnero, E.J., Gabriel, T.S.J., Kegerreis, J.A., Miyazaki, Y., Eke, V., Asimow, P.D., 2023. Moon-forming impactor as a source of Earth’s basal mantle anomalies. Nature 623, 95-99.
How to cite: Shi, Z., Li, Y., and Zhu, R.: Centrifugal force drives the formation of the antipodal basal mantle structures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12628, https://doi.org/10.5194/egusphere-egu26-12628, 2026.
Radiogenic heating plays a crucial role in shaping a planet’s evolution and dynamics. On Earth, ~50% of surface heat loss originates from the decay of three long-lived, heat-producing elements (HPEs): potassium, thorium, and uranium. These elements are strongly lithophile and preferentially concentrate in the silicate mantle of planets. However, a recent study by Luo et al. (Science Advances, 2024) suggests that under the high-pressure, high-temperature conditions of core formation in large rocky planets (so-called super-Earths), these HPEs may become siderophile, partitioning preferentially into the iron core. The presence of HPEs in the mantles of super-Earths plays a crucial role in their internal dynamics. A feedback loop between internal heating, temperature, and viscosity regulates mantle temperature, adjusting viscosity to the value needed to facilitate convective loss of the radiogenic heat (Tackley et al., Icarus 2013). However, if these sources of radiogenic heat partition into the core, mantle convection in super-Earths becomes dominated by heat flowing from the core rather than by a mix of internal heating and cooling from above (as in Earth). Using 1D, parameterized mantle evolution models, Luo et al. (Science Advances, 2024) show that this shift leads to a sharp rise in core-mantle boundary (CMB) temperatures and an increase in total CMB heat flow, with significant implications for volcanism and magnetic field generation.
In this study, we perform mantle convection simulations using the StagYY code (Tackley, PEPI 2008), extending the models of Tackley et al. (Icarus, 2013) to include HPEs in the core, as suggested by Luo et al. (Science Advances, 2024). Our models are run in a 2D spherical annulus geometry and allow for melting at all mantle depths. We test different planetary masses, from 1 to 10 Earth masses, as well as different post-perovskite rheologies, (upper- and lower-bound, following Tackley et al. 2013, and interstitial rheology following Karato 2011), two tectonic regimes (stagnant and mobile-lid), and three mantle-to-core partitioning ratios of HPEs (0.1, 1, and 10). This work contributes to the growing understanding of the interior dynamics of super-Earths, and their implications on surface and atmospheric conditions, the presence of a magnetic field, and habitability potential.
How to cite: Lourenço, D. and Tackley, P.: Impact of Heat-Producing Elements in the Core on Super-Earth Evolution and Dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20916, https://doi.org/10.5194/egusphere-egu26-20916, 2026.
Through Gibbs free energy solvers combined with published experimental data, we assess the structurally bound water capacity (sH2O) of nominally anhydrous minerals, together with low and high pressure hydrous phases. These maps are implemented into a global mantle convection model to investigate the long-term evolution of the mantle water content (cH2O). A parameter study spanning a range of yield stresses is performed, with particular emphasis on the role of surface mobility in controlling volatile exchange fluxes between the mantle and the atmosphere. Across multiple simulation ensembles, surface mobility emerges as the primary control on the intensity of ingassing between the two reservoirs. Time-series autocorrelation analysis of reservoir H2O mass indicates that the mantle transition zone (MTZ) behaves as a transient, high-sH2O layer that is unable to sustain long-lived hydrated states in the absence of frequent water-rich slabs penetrating beyond 410 km depth. Principal component analysis reveals divergence in simulation evolution as a function of surface yield stress, leading to distinct H2O partitioning regimes between the MTZ and the lower mantle, with coupled increase in upper mantle cH2O dominance. This highlights the tendency of episodic or stagnant-lid regimes to sequester water at greater mantle depths relative to tectonically active planets. Bottom-up integration of our model profiles suggests a total stored mantle H2O in the order of 1–1.5 ocean masses, an amount significantly lower than previous estimates, resulting from the rapid decrease of sH2O beyond 660 km depth and subsequent ease of outgassing. Because supercriticality-enhanced extraction processes are not included and a depth-dependent background permeability restricts vertical transport, this estimate should be regarded as an upper bound. We further find that the sH2O associated with the perovskite phase is of first-order importance in determining total mantle water storage. Low convective velocities maintain relative water enrichment within the perovskite-dominated region, implying that deviations from the commonly assumed dry-perovskite composition may increase estimated storage by non-negligible amounts.
In addition, recent advances in high-pressure thermodynamic databases enable the assessment of oxygen fugacity profiles down to core–mantle boundary depths. Building on this framework, a separate suite of simulations explores a new carbon-tracking scheme that accounts for solid and molten reservoirs, redox-dependent melting interactions, and enhanced shallow magmatism, with the ultimate objective of coupling the deep carbon and water cycles.
How to cite: Moccetti Bardi, N. and Tackley, P.: Effects of Surface Mobility on Relevant Mantle H2O - C Fluxes and Distribution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8347, https://doi.org/10.5194/egusphere-egu26-8347, 2026.
Large Igneous Province (LIP) volcanism is a major driver of past global change via degassing of large volumes of climate-altering and poisonous gases (such as H₂O, CO₂, CH₄, SO2). These volatile species can produce contrasting effects on the atmosphere, from long-term global warming to short-lived volcanic winters. We know from historical cases (e.g., the 1783–84 Laki fires, the 1991 Pinatubo eruption) that sulfur-rich eruptions can produce global cooling with societal consequences. In deep time, repeated volcanic winters occurring during LIP emplacement, superimposed on long-term warming, could have stressed ecosystems and contributed to mass extinction, but their short duration makes them difficult to detect in the stratigraphic record (Callegaro et al., 2020; 2023; Kent et al., 2024). Sedimentary proxies of short-term cooling such as glendonite crystallization are being explored, but their signals remain ambiguous (Vickers et al., 2020). We propose a complementary, “within-magma” approach for tracing sulfur-rich magmatic pulses capable of generating volcanic winters. Using synchrotron X-ray microfluorescence, we measure sulfur concentrations in clinopyroxene from LIP magmas, and calculate equilibrium melt concentrations with established partition coefficients. Since clinopyroxene is an early and almost ubiquitous phase in LIPs magmas, this method allows the detection of variations in sulfur budgets throughout the stratigraphy of a lava pile, identifying intervals of sulfur-rich lavas as potential drivers of volcanic winters. We discuss future developments of the method, and results obtained for magmas of the Deccan Traps (Western Ghats lava pile, India), and Franklin large igneous province.
Callegaro, S., Geraki, K., Marzoli, A., De Min, A., Maneta, V. & Baker, D. R., 2020. The quintet completed: The partitioning of sulfur between nominally volatile-free minerals and silicate melts. American Mineralogist 105, 697–707.
Callegaro, S., Baker, D. R., Renne, P. R., Melluso, L., Geraki, K., Whitehouse, M. J., De Min, A. & Marzoli, A., 2023. Recurring volcanic winters during the latest Cretaceous : Sulfur and fluorine budgets of Deccan Traps lavas. Science Advances 9, 1–12.
Kent D.V., Olsen, P.E., Wang, H., Schaller, M.F., Et-Touhami, M. 2024. Correlation of sub-centennial-scale pulses of initial Central Atlantic Magmatic Province lavas and the end-Triassic extinctions. Proceedings of the National Academy of Sciences U.S.A. 121, e2415486121.
Vickers M.L., Lengger, S.K., Bernasconi, S.M., et al., 2020. Cold spells in the Nordic Seas during the early Eocene Greenhouse. Nature Communications, 11, 4713.
How to cite: Callegaro, S., Baker, D. R., Geraki, K., De Min, A., Melluso, L., Marzoli, A., Capriolo, M., Deegan, F. M., Caraffini, F., Bédard, J., Davies, J. H. F. L., Boscaini, A., and Renne, P. R.: Sulfur-in-clinopyroxene: tracing potential volcanic winters in deep time from a within-magma perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11141, https://doi.org/10.5194/egusphere-egu26-11141, 2026.
Rock-deformation laboratory experiments have shown that upper mantle flows with a combination of different creep mechanisms making its rheology composite (Karato & Wu, 1993; Hirth & Kohlstedt, 2003). At low stress levels in the cold and deep upper mantle, deformation occurs by diffusion creep where diffusive mass transport happens between grain boundaries. Whereas at relatively high stress levels in the hot regions of the uppermost mantle, deformation occurs by dislocation creep where crystalline dislocations move between grains. Although composite rheology has been considered in some recent global-scale geodynamical studies of rocky planets (e.g., Dannberg et al., 2017; Schierjott et al., 2020; Tian et al., 2023; Arnould et al., 2023), its influence on the thermo-compositional evolution and tectonic regime of early Earth remains unexplored.
In this study, the code StagYY (Tackley, 2008) is used to model the thermochemical evolution of solid Earth with three different rheological setups. In the first rheological setup, viscous deformation includes only diffusion creep. In the second setup, deformation is accommodated by a combination of diffusion creep and stress-dependent dislocation creep. In the third setup, a proxy for dislocation creep viscosity is used, which resembles temperature- and pressure-dependent Newtonian flow viscosity, where activation energy and activation volume relate to laboratory-estimated dislocation activation parameters divided by the stress exponent, representing dislocation creep with a constant strain rate. Such an approximation has been demonstrated to be a reasonable proxy of power-law viscosity in the classical modelling work by U. Christensen (1983, 1984).
These models self-consistently generate oceanic and continental crust, consider both plutonic and volcanic magmatism and incorporate pressure-, temperature-, and composition-dependent water solubility maps. Irrespective of the rheology considered, models exhibit mobile-lid regime with high mobility (ratio of rms surface velocity to rms velocity of mantle) with plume-induced lithospheric subduction for the initial 200-300 Myr. Afterwards, they transition to episodic-lid or ridge-only regime and are characterised by global resurfacing events. When compared to models with only diffusion creep rheology, models with composite rheology (either as stress dependent dislocation creep or dislocation creep proxy) have higher surface mobilities, experience resurfacings more frequently, produce more continental crust, and are more efficient at planetary cooling. These trends stay similar even in models that do not consider melting. In terms of code performance, computations with composite rheology take longer than just with diffusion creep. However, dislocation creep proxy models are faster than stress-dependent dislocation creep models by a factor of ~1.6x. In summary, a combination of diffusion and dislocation creep proxy is a viable formulation to realistically model long-term thermochemical planetary evolution with relatively low additional computational expense.
How to cite: Jain, C. and Sobolev, S.: Influence of composite rheology on planetary dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9998, https://doi.org/10.5194/egusphere-egu26-9998, 2026.
Plate tectonics is a characteristic feature of Earth, but its initiation and early evolution remain debated. Geological and geochemical evidence suggests that plate tectonics was initiated from a stagnant-lid regime in the Archaean, however mechanisms associated with this transition are unclear. Previous geodynamic models, which typically assume fixed lithospheric strength, require a low effective yield-stress rheology to obtain plate-like behaviour, inconsistent with laboratory measurements. Here, we apply a global-scale mantle convection model that incorporates a temperature-dependent friction coefficient, representing thermodynamic weakening on fault planes during rapid slip (Brantut & Platt, 2017), to study the tectonic evolution of Earth-like planets. As the timescales of geodynamic models and fault motion differ by several orders of magnitude, a simplified step-function approach is adopted, where reduced friction coefficients of 0.01~0.1 are applied below the temperature threshold to mimic unstable fault motion (Karato & Barbot, 2018). Our results show that temperature-dependent weakening does not systematically promote stagnant-to-mobile lid transitions. Instead, plume-induced subduction serves as the dominant process to transition from an initial stagnant phase to plate-like lithospheric behaviour (mobile lid). We find that temperature-dependent friction coefficients can act as an additional weakening mechanism to promote subduction even at high lithospheric strengths. Unlike earlier models, which produced mobile-lid behaviour only under lithospheric strengths much lower than laboratory estimates, these findings demonstrate that more realistic rheological parameters can sustain mobile-lid behaviour when dynamic weakening is considered. We also find that subduction-zone locations are stabilised over time in cases with temperature-dependent friction coefficients. This behaviour is associated with localised lithospheric weakening in cold downwellings, and consistent with the stability of trench locations in plate reconstructions (Müller et al., 2019) as well as of seismically-observed lower-mantle structures (Torsvik et al., 2010). Our results provide a possible explanation for why plume-induced subduction on Venus, where high surface temperatures inhibit dynamic weakening, remains short-lived and localised, preventing plate tectonics.
References
Brantut, N., & Platt, J. D. (2017). https://doi.org/10.1002/9781119156895.ch9
Karato, S., & Barbot, S. (2018). https://doi.org/10.1038/s41598-018-30174-6
Müller, R. D., Zahirovic, S., Williams, S. E., Cannon, J., Seton, M., Bower, D. J., Tetley, M. G., Heine, C., Le Breton, E., Liu, S., Russell, S. H. J., Yang, T., Leonard, J., & Gurnis, M. (2019). https://doi.org/10.1029/2018TC005462
Torsvik, T. H., Burke, K., Steinberger, B., Webb, S. J., & Ashwal, L. D. (2010). https://doi.org/10.1038/nature09216
How to cite: Lam, P. W., Ballmer, M., and Zarebski, A.: The Effect of Temperature-dependent Strength of Lithosphere on the Earth's Tectonic Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14754, https://doi.org/10.5194/egusphere-egu26-14754, 2026.
The geological record indicates that Earth has experienced rapid and drastic tectonic reorganizations, such as the breakup of Pangea and the global event at ∼50 Ma marked by the Hawaiian–Emperor bend and synchronous kinematic shifts across all major plates (Whittaker et al., 2007). The mantle lithosphere system is a complex nonlinear dynamical system (Coltice, 2023) that can produce such tectonic transitions (Janin et al., 2025; Guerrero et al., 2025). By analogy with the climate system, which alternates between icehouse and hothouse states, a fundamental question arises: can plate tectonics exhibit multistability, and if so, does the whole mantle-lithosphere system as well?
Here we investigate dynamical transitions in mantle convection with self-consistent plate tectonics using tools from dynamical systems theory. We analyze outputs from 3D spherical mantle convection model of Coltice et al. (2019), which reproduces major tectonic features of Earth. From a 850 Myr long simulation, we construct a database of tectonic and physical variables, including plate-boundary lengths, number of plates, proportion of deforming lithosphere, global and surface root-mean-square velocities, surface and core–mantle boundary heat fluxes, mean mantle temperature, number of mantle plumes, and lithospheric net rotation rate.
We apply two complementary methods to detect dynamical transitions: (1) sample-based tests using Maximum Mean Discrepancy (MMD; Gretton et al., 2012), which identify statistical discontinuities in multidimensional distributions, and (2) Recurrence Quantification Analysis (RQA; Eckmann et al., 1987), which characterizes changes in recurrence patterns within the system’s phase space. We perform analyses separately on surface variables, mantle variables, and the combined dataset.
We identify four statistically significant transitions. Some coincide with major tectonic reorganizations, such as supercontinent assembly and breakup or global kinematic shifts, while others reflect intrinsic changes in convective or tectonic regimes. Certain transitions affect both mantle and surface dynamics synchronously, whereas others are confined to either the lithosphere or mantle flow. To interpret these transitions, we combine Principal Component Analysis (PCA) with spectral analyses of mantle thermal heterogeneity. In this framework, detected transitions correspond to shifts in one or more principal components representing distinct tectonic, thermal, and kinematic states of the system, providing quantitative evidence for multistability in mantle-plate dynamics.
How to cite: Jaah, I., Coltice, N., Janin, A., and Flament, N.: Tectonic Reorganizations and Multistability of the Mantle-Plate System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9605, https://doi.org/10.5194/egusphere-egu26-9605, 2026.
Earth’s interior plays a fundamental role in the long-term evolution of the surface, climate, and biosphere. However, Earth's mantle evolution remains largely ambiguous, as imaging techniques are limited to present-day observations and geochemical or geological constraints apply to a non-global scale. Plate tectonic reconstructions coupled with convection models could provide constraints on the evolution of mantle structure. In this study, we employ both fully self-consistent and kinematically constrained mantle convection models[1]. The mantle rheology is temperature-, pressure-, phase-, and stress-dependent, with the latter represented through pseudo-plasticity. The novelty of this work lies in employing a composite rheology with “realistic” rheological parameters[2] in a fully three-dimensional geometry. By using both fully self-consistent models and plate-driven models, we aim to address the discrepancies in terms of long-term convective and tectonic behaviour that arise when forcing plate velocities onto the surface. The latter is done by imposing time-dependent surface velocity boundary conditions provided by a plate tectonic reconstruction[3].
To evaluate the extent to which the models reproduce plate-like tectonics, we explore several independent constraints. In particular, we compute slab sinking rates and compare them to estimates inferred from seismic tomography[4]. Slab sinking rates in self-consistent models provide insight into the mantle’s rheology. For example, sinking rates that are lower than those based on tomographic and geological data may indicate an overly viscous mantle. Our results show that the slab sinking rate is generally higher in models with imposed plate velocities compared to fully self-consistent models. Furthermore, a tessellation algorithm[5] will be applied to the surface of the models to detect plates in the self-consistent models with plate-like behaviour. Based on these results, a plate-size frequency distribution can be calculated and compared to present-day Earth[6]. Results show that low yield stresses generate too many small plates, and too few large plates [Fig. 1]. In order to generate Earth-like plate tectonics, yield stress needs to be sufficiently high to reproduce the plate-size frequency distribution of present-day Earth, but also sufficiently low to facilitate a long-term mobile lid regime.
[1] Tackley, P. J. (2008). Phys. Earth Planet. Inter. 171, 1–4.
[2] Tackley, P. J., Ammann, M., Brodholt, J. P., Dobson, D. P., & Valencia, D. (2013). Icarus 225, 50–61.
[3] Merdith, A. S., Williams, S. E., Collins, A. S., et al. (2021). Earth-Sci. Rev. 214, 103477.
[4] Van der Meer, D. G., van Hinsbergen, D. J. J., & Spakman, W. (2018). Tectonophysics 723, 309–448.
[5] Janin, A., Coltice, N., Chamot-Rooke, N., & Tierny, J. (2025). Nat. Geosci. 18, 1041–1047.
[6] Bird, P. (2003). Geochem. Geophys. Geosyst. 4, 2001GC000252.
How to cite: Metternich, M., Tackley, P., Arnould, M., and Janin, A.: Rheological Controls on the Plate-Mantle System: Self-Consistent vs. Kinematically Constrained Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18572, https://doi.org/10.5194/egusphere-egu26-18572, 2026.
Mantle plumes are hot upwellings that transport heat from the core to the base of the lithosphere, and sample lowermost-mantle chemical structure. Plume buoyancy flux QB measures the vigor of upwellings, which relates to the mass and heat fluxes that mantle plumes convey to sub-lithospheric depths. Hotspot swells are broad regions of anomalous topography generated by the interaction between mantle plumes and the overlying lithosphere, yet the links between plume properties and swell morphology remain poorly understood.
Traditional approaches to measure QB are based on two assumptions: (1) the asthenosphere moves at the same speed as the overriding plate; (2) hotspot swells are fully isostatically compensated, in other words, the seafloor is uplifted due to the isostatic effect of replacing ”normal” asthenosphere with hot plume material. However, at least some plumes (e.g., Iceland) can spread laterally faster at the base of the lithosphere than the corresponding plate motion. Also, hotspot swells are partly dynamically compensated. With increasingly accurate observational constraints on dynamic seafloor topography, it is the time to update plume buoyancy fluxes globally and build a scaling law between the surface dynamic topography and plume buoyancy flux.
Here, we conduct thermomechanical models to study plume-lithosphere interaction and hotspot swell support. We use the finite-element code ASPECT in a high-resolution, regional, 3D Cartesian framework. We consider composite diffusion-dislocation creep rheology, and a free-surface boundary at the top. We systematically investigate the effects of plume excess temperature (∆T), plume radius (rp), plate velocity (vp), plate age, and mantle rheological parameters. From these results, we develop a scaling law that relates swell geometry to plume parameters. We find that swell height and cross-sectional area (Aswell) have a robust power-law relationship with QB. Aswell shows an almost linear dependence and provides the most reliable geometric indicator of QB. Empirical fitting further reveals that rp has a dominantly positive correlation with swell height, width, and Aswell, while ∆T contributes secondarily. On the contrary, vp has a relatively small (and mostly negative) effect on swell parameters. Higher viscosities in the asthenosphere lead to wider swells, higher Aswell andQswell. Applying these empirical fits to Hawaii indicates a minimum QB of ~3,860 kg/s.
Figure 1. Results of example cases at 300 Myr. Each row represents the cases A2, A7, and C7. The left column displays the potential temperature isosurface (contours at 1500K and 1700K), while the right column presents the dynamic topography.
We demonstrate that previous swell-geometry-based estimates underestimate the true buoyancy fluxes of the underlying upwelling, partly because plumes spread faster than plate motion for high QB and low vp. The empirical fits developed here highlight the need for future models to incorporate melting, compositional effects, and variable lithospheric structure.
As a final step, we invert these predictive fittings and apply them to intraplate hotspot swells in all ocean basins to quantify the heat and material fluxes carried by plumes on Earth. This effort will help to inform the Core-Mantle Boundary heat flux.
How to cite: Ma, Z., Ballmer, M., and Manjón-Cabeza Córdoba, A.: New Scaling between Plume Buoyancy Fluxes and Dynamic Topography from Numerical Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-720, https://doi.org/10.5194/egusphere-egu26-720, 2026.
Cooling of the core provides a substantial part of the mantle heat budget, while mantle convection determines the heat flux across the core-mantle boundary, hence the existence or not of a planetary dynamo. Thus, the thermal evolutions of core and mantle should be treated in a coupled manner. To accomplish this, the core has normally been coupled into mantle convection simulations assuming that it has an adiabatic temperature profile and can thus be characterized by single temperature (e.g. the CMB temperature) (e.g. Nakagawa & Tackley, 2014 GCubed), allowing a simple 0-dimensional parameterization such as a uniform "heat bath" or one including inner core growth (e.g. Buffett et al, 1996 JGR).
However, when the CMB heat flux FCMB becomes lower than adiabatic, core convection no longer occurs (as evidenced by no magnetic field on Venus and Mars) and thus the core temperature profile is not adiabatic. FCMB can even become negative in models with a layer of dense heat-producing-element (HPE)-enriched material above the CMB: assuming this heats the entire core uniformly is unrealistic as heating from above is a very inefficient way of heating a layer. Another end-member approximation is to decouple the core and mantle temperatures in the latter case (Cheng et al, 2025 JGR).
To treat cases where FCMB is sub-adiabatic or negative, a 1-D conductive core model is presented. When the temperature profile is adiabatic to super-adiabatic, an eddy diffusivity acting on the super-adiabatic temperature parameterizes heat transport by turbulent convection and keeps the temperature profile very close to adiabatic (see Abe, 1997 PEPI). When the temperature profile is sub-adiabatic, normal thermal diffusion is the dominant heat transport process. Compressibility, crystallization of an inner core and the presence of light elements are included.
A MATLAB implementation is presented. Then, results from coupling this 1-D core model to 2-D thermo-chemical mantle evolution models using StagYY (Tackley, 2008 PEPI) are presented. When FCMB is always super-adiabatic, similar results are obtained for 1-D and 0-D models, but:
(i) Results for a post-giant-impact core superadiabatic temperature profile with the outermost core extremely hot were presented by Tackley (2025 AGU Meeting; https://agu.confex.com/agu/agu25/meetingapp.cgi/Paper/1909859). A thin, convecting layer forms at the top of the core and rapidly thickens until the whole core becomes adiabatic again.
(ii) For an HPE-enriched dense layer above the core-mantle boundary the layer and CMB temperatures to rise quickly if the core is decoupled from the mantle, slowly for a 0-D coupled core model, and at an intermediate rate with this 1-D core model. The layer temperature has implications for the formation of plumes, as well as other thermal evolution characteristics.
In conclusion, the new 1-D core model facilitates more realistic core-mantle coupled evolution simulations in the case that CMB heat flux is lower than that conducted down the core adiabat or even into the core.
How to cite: Tackley, P. J.: A one-dimensional core model for coupling to mantle convection simulations: Equations and results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5829, https://doi.org/10.5194/egusphere-egu26-5829, 2026.
Geodynamic models require constraints from phase equilibria to infer how changes in phase abundance and composition affect physical properties. When applying such models on a planetary scale, performance becomes especially crucial. Therefore, computationally costly methods, such as Gibbs free energy minimisation, are no longer a viable option for predicting phase equilibria directly. We present a machine learning (ML) surrogate that can approximate phase equilibrium predictions for silicate mantles of rocky planets. ML surrogates have proven to be useful tools for approximating complex physics-based simulations in various fields, as they are computationally efficient, highly scalable, and fully compliant with GPU-based computation in high-performance computing clusters and automatic differentiation.
We calibrated a neural network surrogate on a large synthetic dataset (n = 2.0×106) generated using MAGEMin (Riel et al., 2022) and the thermodynamic dataset from Stixrude and Lithgow-Bertelloni (2022). The training dataset ranges over typical upper to transition-zone mantle conditions in terms of pressure, temperature, and bulk rock composition. The model architecture and calibration strategy presented can accurately predict the molar proportions and molar oxide composition of multicomponent solid solutions from pressure, temperature, and bulk rock composition. Constraints on mass balance and closure of compositional variables are actively enforced during calibration through additional physics-informed misfits, in addition to the data-driven convergence. Evaluation of the model indicates uncertainties of less than ±0.02 molmol-1 for the prediction of phase fractions and less than ±0.005 molmol-1 for most compositional variables within solid solutions for the phases considered. The performance assessment shows a systematic increase in computational speed of two orders of magnitude when comparing the prediction between the ML surrogate and MAGEMin. Moving the computation to a GPU can improve performance by up to 5 orders of magnitude, <100ns per point, for large data sets of 10⁵ points, compared to the Gibbs free energy minimiser.
In this presentation, the ML surrogate will be used to map the stability of wadsleyite, ringwoodite and akimotoite within the Martian mantle. This ultra-fast prediction method enables the incorporation of poorly constrained minor components (e.g. Na₂O) using a Monte Carlo approach. Our results demonstrate the significant influence of these minor components on phase stability. This, in turn, determines seismic velocities and can be associated with water storage in nominally anhydrous minerals.
[1] Riel, N., Kaus, B. J. P., Green, E. C. R., & Berlie, N. (2022). MAGEMin, an efficient Gibbs energy minimizer: Application to igneous systems. Geochemistry, Geophysics, Geosystems, 23.
[2] Stixrude, L. & Lithgow-Bertelloni, C. (2022), Thermal expansivity, heat capacity and bulk modulus of the mantle, Geophysical Journal International, 228 (2), 1119–1149.
How to cite: Hartmeier, P. and Lanari, P.: Machine learning is all you need: A surrogate model for phase equilibrium prediction for planetary-scale models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7087, https://doi.org/10.5194/egusphere-egu26-7087, 2026.
During the past 2 decades, data coverage and methodological developments have considerably improved the resolution of seismic tomography maps, refining our mapping of the deep Earth’s mantle structure. Nevertheless, the uneven distributions in sources (the earthquakes) and receptors (the seismic stations) leads to non-uniqueness of the solution and requires the prescription of a priori information (mostly damping and smoothing), the effect of which is to smear out seismic images and degrade their effective resolution. Alternatively, statistical quantities have been used to investigate the nature, purely thermal or thermo-chemical, of the structures observed by seismic tomography. In particular, it has long been recognized that the statistical distribution of shear-velocity anomalies (dlnVS) in the lowermost mantle shows some degree of asymmetry in the form of a slow velocity tail, and that this slow tail is associated with the large low shear-wave velocity provinces (LLSVPs), the prominent feature on lowermost mantle tomographic maps. This bimodal distribution appears from around 2200 km and persists towards the deeper mantle. Yet, the phase transition to post-perovskite (PPv) at depth ~2700 km, if not happens globally, implies a trimodal distribution for dlnVS. Here, we bring new insights on these questions. First, we investigate the effect of the seismic tomography ‘operator’ on seismic velocity anomalies triggered by different possible lowermost mantle thermo-chemical structures. For this, we first run simulations of thermal and thermo-chemical convection including or not the post-perovskite phase, and we calculate synthetic velocity anomalies predicted by these simulations. We then apply to these synthetic velocity anomalies a tomographic filter built for the tomographic model HMSL-SP06. We show that seismic signatures corresponding to different materials (regular mantle, thermo-chemical piles and PPv) are clearly distinct on statistical distribution of unfiltered shear-and compressional velocity anomalies, dlnVS and dlnVP, but get mixed or partially mixed after applying the filter. Interestingly, for synthetic velocity anomalies built from thermo-chemical simulations, a low velocity tail clearly appears on dlnVS histograms, but not on dlnVP histograms, similar to what is observed in real seismic tomography maps. For synthetic velocity anomalies built from purely thermal simulations, dlnVS histograms do not feature any low velocity tail, and distribution histograms for both dlnVS and dlnVP are fairly Gaussian. Overall, our results therefore support the hypothesis that the LLSVPs observed at the bottom of the mantle are composed of hot, chemically differentiated material. They further show that the mixing of seismic signatures due to tomographic filter, implying the statistical distribution of dlnVS and dlnVP may be richer and more complex than it appears to be from seismic tomography models. Acknowledging the mixing of seismic signatures inherent to tomography models, we then apply cluster analysis with trimodal distribution to four recent tomographic models: GLAD-M35, REVEAL, SPiRaL-1.4, and TX2019slab. We identify three velocity clusters, slow, neutral, and fast, which we associate with thermo-chemical piles, regular mantle, and PPv. Based on this analysis, we provide a probability map of the three clusters, which may be used to better understand the lowermost mantle structure and facilitate future geodynamic studies.
How to cite: Shih, S.-A., Deschamps, F., and Su, J.: Seismic signatures: mixing with a tomographic filter and identifying with cluster analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2256, https://doi.org/10.5194/egusphere-egu26-2256, 2026.
The Lunar crustal dichotomy, expressed in farside-nearside differences in crustal thickness, volcanism and surface composition, does not yet have a well-established origin. Multiple mechanisms proposed in the literature can explain some aspects of the dichotomy; however no single model is able to fully explain the entirety of its observed features. We hypothesize that all aspects of the dichotomy are related and originate from the solidification of the Lunar Magma Ocean (LMO). Given that the dichotomy is aligned in reference to Earth, we investigate if Earth’s tidal influence on the LMO, when the Moon was in proximity to the Roche limit, can explain this dichotomy.
We investigate this hypothesis with numerical models of lunar evolution, using a modified version of StagYY (Tackley, 2008) that includes three-dimensional gravity accounting for tidal effects. We model the LMO solidification starting from a fully molten Moon, followed by the onset of solid-state mantle convection.
Our models show that an asymmetric degree-two convection pattern can emerge during the early stages of the LMO solidification. This tide-driven magma ocean convection is characterized by two large plumes on the nearside and farside, with downwelling in the perpendicular plane at the poles. The nearside plume upwells faster than the farside plume given the asymmetries in the tidal forces between each side of the Moon. This convection pattern inhibits both the solidification of the LMO, and the compaction of the solid fraction, resulting in a convecting mush. Melt segregates towards the sides of the plume heads, where velocities are lowest, forming a low crystallinity magma ocean that is continuously replenished by decompression melting of the mostly solidified mantle that rises through the plumes. The LMO solidifies near the surface as material travels towards the perpendicular plane and subducts, creating a barrier that isolates the two hemispheres. Differences in the timing of melt segregation and the rate of decompressive melting eventually create significant hemispheric chemical contrasts, which ultimately can lead to all observed aspects of the crustal dichotomy of the Moon.
Reference
Tackley, P. J. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Physics of the Earth and Planetary Interiors, 171(1-4), 7-18.
How to cite: Astudillo, D., Tackley, P., and Lourenço, D.: Tide-Driven Magma Ocean Convection as the Origin of the Lunar Crustal Dichotomy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7700, https://doi.org/10.5194/egusphere-egu26-7700, 2026.
Near the equator of Mars, between the branched valleys of Noctis Labyrinthus and Valles Marineris, a large rift system, lies a heavily fractured and eroded region, whose tectonic history is poorly constrained. In this region, an eroded shield volcano, named ‘Noctis Mons’, was recently identified through satellite imaging (Lee & Shubham, 2024). Its complex topography makes it difficult to provide a clear chronology of events that led to its formation and erosion. Processes such as plume uplift, fracturing and interaction with the Valles Marineris rift system, gravitational collapse, and the contact of hot volcanic materials with shallow subsurface ice likely played an important role for shaping this volcanic construct.
In this work, we test the hypothesis that an ascending mantle plume is responsible for the unique features of Noctis Mons. We first model a rising plume using the geodynamic code GAIA (Hüttig et al., 2013). The Tharsis province represents a large-scale and thick regional crustal thickness anomaly that we incorporate into our plume model by adding a step-like function to evaluate the influence of varying crustal thickness on an ascending plume. We further test several parameters that control the plume dynamics and morphology, including the distribution of heat sources between the mantle and crust, the thermal conductivity of the crust and mantle, the depth-dependence of the viscosity, as well as the consideration of partial melting and melt extraction. Once the plume reaches the base of the lithosphere, we use the GAIA-generated plume temperature distribution to compute crustal deformation. We evaluate flexural uplift and strains in response to this plume to identify regions of extension using a methodology similar to (Broquet & Andrews-Hanna, 2023). The density variations of the plume generated by our geodynamical models is used to solve a system of flexure equations for dynamic uplift, accounting for horizontal and vertical loading as well as self-gravity effects. We iterate both the plume characteristics produced by the geodynamical model and its induced crustal deformation until we find an optimal scenario that reproduces Noctis Mons’ topography and predicts extensional features similar to Noctis-related graben systems seen in satellite images and topography. We also analyze present-day gravity and topography to characterize the rigidity of the lithosphere and the density of the materials composing Noctis Mons.
With our computational framework we aim to constrain the magmatic behavior as well as thermophysical and rheological parameters for the crust and mantle that led to the complexity of tectonic features observed at Noctis Mons, informing our understanding of the formation and evolution of volcanic constructs on Mars.
Studying plume ascent near Noctis Mons further informs our understanding of volcanism on Mars in its early history. Recent seismic recordings from the InSight lander reported activity in Elysium Planitia, indicating a potential upturn in tectonic activity. We will apply our ascending mantle plume model to Elysium Planitia, a region near Mars’ equator, that potentially hosts a giant and presently active mantle plume (Broquet & Andrews-Hanna, 2023).
How to cite: North, A., Broquet, A., and Plesa, A.-C.: Flexure Modeling of Plume Ascension on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-416, https://doi.org/10.5194/egusphere-egu26-416, 2026.
Recent analyses of seismic data recorded on Mars suggests a heterogeneous mantle where a global molten silicate layer lies above the core, followed by a partially crystallized layer (Samuel et al., 2023). The formation of such mantle structure is inherently link to the planet's early evolution when a global magma ocean was present and its crystallization process. Previous studies have shown that mantle overturn events during/after crystallization can produce a silicate layer enriched in iron and heat-producing elements that resides above the core-mantle boundary (CMB) (e.g., Tosi et al., 2013; Plesa et al., 2014; Samuel et al., 2021). However, processes such as melt transport, phase change, and chemical fractionation are not accounted for which are important in the describing the mantle's long-term evolution. By accounting for the aforementioned processes (Boukaré et al., 2025), we show that for the first time, a stratified melt layer can be formed and preserved over geological timescales in a self-consistent model. We observe that during the early stages of solidification, iron-rich silicates produced by chemical fractionation at the shallow mantle are delivered to the CMB. The presence of iron-rich materials at the CMB not only reduces the melting temperature of the silicates, but also produces a stably stratified melt structure at the bottom of the mantle that is resistant to chemical and thermal erosion over long timescales.
How to cite: Lim, K. W., Boukaré, C.-É., Samuel, H., and Badro, J.: The Formation of Mars' Basal Melt Layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7328, https://doi.org/10.5194/egusphere-egu26-7328, 2026.
