Analysis of the lunar Bouguer gravity field under major basins reveals how gravity varies with spherical harmonic degree L and, potentially, with depth (to relate the two we use a relationship based on point masses).  We have studied 19 lunar basins based upon a GRAIL 1200 degree and order gravity model (GRGM1200B).  The vertical component of Bouguer gravity shows how the gravity is distributed in spherical harmonic degree between the lowest degree, 2, and the highest degree, 1200. Under each basin, this gravity spectrum of accelerations per individual spherical harmonic degree shows a benign region for L from 800 to 100, a range of approximately 20 km immediately below the surface, consistent with the observation that the upper crust is largely homogenous (Zuber et al., 2013). A region of more varied gravity signal occurs down to L~20, approximately 60 km deeper. The basin gravity signal merges with the deep interior at L~10, approximately 150 km below the surface. A set of profiles over latitude or longitude through an individual basin anomaly shows how the magnitude of the gravity signal changes with depth as it passes from the annular moat to the central high of the anomaly; all of which takes place between L~100-20, a depth range estimated to be ~20-80 km.  However, all basins are different to some extent. Outside of the basin anomaly the gravity spectra are relatively benign from just below the surface to L~40, a depth of approximately 45 km and consistent with the approximate average thickness of the lunar crust.  An exception to the general characteristics of the spectra of basins is South Pole-Aitken (SPA) which indicates a structure with few variations that is very similar to the regions that have near zero Bouguer gravity at the surface with no large anomalies in the top 100 km. We interpret this result for SP-A as a result of its largely compensated state.

How to cite: Smith, D. E., Goossens, S., and Zuber, M. T.: Implications of Bouguer Gravity Structure Under Major Lunar Basins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3530, https://doi.org/10.5194/egusphere-egu23-3530, 2023.

The Moon is the most well-known extraterrestrial planetary body thanks to observations from ground-based, space-borne instruments and lunar surface missions. Data from Lunar Laser Ranging (LLR), magnetic, gravity, surface observations and seismic Apollo ground stations help us to quantify the deformation undergone by the Moon due to body tides. These observations provide one of the most significant constraints that can be employed to unravel the deep interior. The Moon deforms in response to tidal forcing exerted by, to first order, the Earth, the Sun and, to a lesser extent, by other planetary bodies. We use the degree-2 tidal Love number as a tool for studying the inner structure of our satellite. Based on measurements of the tidal Love numbers k2 and h2 and quality factors from the GRAIL mission, LLR and Laser Altimetry on board the LRO spacecraft, we perform a random walk Monte Carlo samplings for combinations of thicknesses and viscosities for models of Moon with and without inner core. By comparing predicted and observed parameters of the lunar tidal deformations, we infer constraints on the outer core viscosity, for a Moon with a thin outer core and a thick inner core, and a Moon with a thicker outer core but a denser and thinner inner core. In addition, by deducing the temperature and assuming the chemical composition of the low-viscosity zone, we obtain stringent constraints on its radius, viscosity and density. 

How to cite: Briaud, A., Ganino, C., Fienga, A., Rambaux, N., Mémin, A., Hussmann, H., Stark, A., and Hu, X.: Exploration of the lunar deep interior through global deformation modeling., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14366, https://doi.org/10.5194/egusphere-egu23-14366, 2023.

The compositional diversity of volcanic rocks revealed by NASA’s MESSENGER at the surface of Mercury has been interpreted to result from partial melting of a heterogenous sulfur-rich Mercurian mantle. However, melting relations and the composition of partial melts for iron-free and sodium-rich mantle, together with the effect of sulfur as a key volatile, have not yet been studied in detail. In this study we present results from high-pressure and high-temperature experiments on the mineralogical and geochemical evolution of the mantle residue and melting products of primitive deep Mercury’s mantle with two starting compositions differing by their Mg/Si ratios. Both compositions have sulfur added as FeS. Experiments were conducted using a multi-anvil press under reduced conditions (by controlling the Si/SiO₂ ratio of the starting composition) at pressures of 3 and 5 GPa.

The residual mantle of Mercury with the lower Mg/Si ratio of 1.02 contains olivine + orthopyroxene above ~15 wt% melting at 3 and 5 GPa, and olivine disappears at melting over ~30 wt.% at 5 GPa. The Mercurian mantle with the Mg/Si of 1.35 contains olivine + orthopyroxene in the residue above ~15 wt% melting at 3 and 5 GPa, and olivine only when the melting degree is over ~50 wt.%. Our experiments also show that the majority of chemical composition of the High-Magnesium region (HMR) can result from ~25±15 wt.% melting of a deep primitive mantle. Further work will enable us to evaluate the compositional diversity of the mantle that is needed to explain the broad range of surface lavas. We also aim at understanding the role of the highly refractory residual mantle as a controlling factor for the end of major volcanic activity on Mercury at 3.5 Ga.

How to cite: Wu, P., Xu, Y., Lin, Y., and Charlier, B.: Melting relations for putative mantles of Mercury and the compositional diversity of the crust, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6480, https://doi.org/10.5194/egusphere-egu23-6480, 2023.

It has been proposed that a basal magma ocean (BMO) may have existed, or even still exists, at the base of the Martian mantle [1]. One formation scenario for such a BMO involves a mantle-scale overturn just after the crystallization of the main magma ocean. In this case, the BMO would be enriched in iron and heat-producing elements (HPE), and hence gravitationally stable at the base of the mantle, with potential effects on the efficiency of mantle convection. The Insight mission has allowed geophysical investigation of the Martian interior and has indeed provided seismic evidence of a basal liquid silicate layer just above the core-mantle boundary. It is thus crucial to understand the effect of such a layer on the long-term evolution of the interior of Mars.

Here, we model thermochemical mantle convection and crust production for a Mars-sized planet in a 2D spherical annulus geometry using code StagYY.  Assuming that the top of the BMO is at ~1800 km radius, we parameterize the basal magma ocean as a ‘primordial layer’ with a low viscosity and a high effective thermal conductivity to account for the enhanced effective heat flux in a liquid layer due to turbulent flow. HPE are preferentially partitioned into the silicate liquid layer following a mass balance equation assuming an interstitial porosity.  We systematically vary BMO thickness and interstitial porosity in order to study the outcome of the different HPE distributions.  The liquid density, which is attributed by the different degrees of iron enrichment, is also examined to explore the mechanical stability and entrainment of the BMO.

We present results of our models, comparing our present-day temperature profiles with areotherms deduced from seismic observation [2,3].  We find that the interstitial porosity is an important factor that determines the thermal structure of the mantle throughout Martian evolution. A value of ~50% provides the best fit with crustal production history, crustal thickness, HPE enrichment in the crust, as well as the seismically-constrained present-day areotherm. This result suggests that the initial HPE partitioning has not been controlled by end-member fractional crystallization of the main magma ocean (for which interstitial porosity would be close to 0%), and/or that some re-equilibration occurred during subsequent overturn. Meanwhile, the BMO thickness, within the uncertainties from seismic inversion, does not strongly influence Mars thermal evolution.

[1] Samuel et al. (2021) doi:10.1029/2020JE006613

[2] Khan et al. (2021) doi: 10.1126/science.abf2966

[3] Duran et al. (2022) doi: 10.1016/j.pepi.2022.106851

How to cite: Cheng, K. W., Ballmer, M., and Tackley, P.: Long-term effect of a basal magma ocean on Martian mantle convection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11648, https://doi.org/10.5194/egusphere-egu23-11648, 2023.

Zircon is an important silicate mineral to help understand the evolution of geochemistry and genesis of magma in early planets. The composition of evolved magma can be deduced from the concentrations of elements in zircon and their partition coefficients between zircon and silicate melt. Although the phosphorus (P) contents range from ~100 to ~100000 ppm in extraterrestrial zircon, the effects of P on REE partition coefficients between zircon and silicate melt are still debated. Here we have studied the effect of P contents on the partition coefficients of elements between zircon and silicate melt using high-temperature experiment. With the increase of phosphorus content, the partition coefficients of alkaline elements and Al between zircon and silicate melt show a negative and positive trend, respectively, and there is no effect on itself and Ti. It is worth mentioning that phosphorus content has a negligible effect on REE partitioning, indicating that the REE partition coefficients in this study can be applied to extraterrestrial zircon even with varying P concentrations. After filtering out altered zircon and combining the experimentally updated partition coefficients of REE, the characteristic of evolved melt equilibrated with early protogenetic zircon can thus be yielded and then help to understand early magmatism on the planets. 

How to cite: Shang, S. and Lin, Y.: Experimentally revisiting the REE partition coefficients between zircon and silicate melt, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3076, https://doi.org/10.5194/egusphere-egu23-3076, 2023.

In this work, we test the hypothesis of surface-erosion controlled plate tectonics preceded by plume-induced retreating subduction tectonic regime on Earth proposed by Sobolev and Brown (2019) using 2D global compressible convection models. To simulate the effect of increased sediment supply as a result of surface erosion after the emergence of continents in the late Archean and after the Neoproterozoic "snowball Earth" glaciation, we decrease the effective frictional strength of the oceanic lithosphere in models spanning the age of the Earth. These StagYY models self-consistently generate oceanic and continental crust while considering both plutonic and volcanic magmatism (Jain et al., 2019). Pressure-, temperature-, and composition-dependent water solubility maps calculated with Perplex (Connolly, 2009) are also utilised, which control the ingassing and outgassing of water between the mantle and surface (Jain et al., 2022). The core cools with time and different initial mantle potential temperature values are tested within the range of 1750-1900 K (Herzberg et al., 2010; Aulbach and Arndt, 2019).

Models that consider a more realistic upper mantle rheology (diffusion creep and dislocation creep proxy) show higher recycling of denser basaltic-eclogitic (oceanic) crust, efficient cooling of the planet, and higher mobilities (ratio of surface to mantle rms velocities) (Tackley (2000); Lourenço et al. (2020)). These models exhibit intermittent episodes of long-lasting mobile-lid regime and short-lived plutonic-squishy-lid regime in the Hadean and the early Archean accompanied by extensive subduction leading to rapid production and recycling of the continental crust. Models that consider adaptive frictional strength (to mimic sedimentation post glaciation and continental emergence) predict the transition to continuous plate tectonics in the late Archean, reproduce features of supercontinent cycles, and appear to be consistent with cooling history of the Earth inferred from petrological observations (Herzberg et al., 2010). 

The thermo-compositional evolution can vary between models due to the inherent randomness arising from the initial thermal perturbations and the initial positions of the tracers/particles. Accordingly, we intend to run multiple instances of every model considered in our parameter space to present statistically robust results. We also aim to test more realistic models where the lithospheric frictional strength adapts with the surface topography.

How to cite: Jain, C. and Sobolev, S.: Exploring the interplay between continent formation, surface erosion, and the evolution of plate tectonics on Earth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4755, https://doi.org/10.5194/egusphere-egu23-4755, 2023.

The short-lived isotope systems, including ¹⁴⁶Sm-¹⁴²Nd (half-life = 103 Ma) and ¹⁸²Hf-¹⁸²W (half-life = 8.9 Ma), provide evidence for mantle differentiation events in early Earth, as both the daughter nuclides are more incompatible than the parent nuclides. For the ¹⁴⁶Sm-¹⁴²Nd system, both positive and negative μ¹⁴²Nd measurements are observed in Hadean-Archean mantle-derived rocks, which possibly indicates a major differentiation event of the silicate Earth before the extinction of ¹⁴⁶Sm (e.g., Boyet and Carlson, 2005, Science). The diminishing trend of μ¹⁴²Nd between Hadean and Archean, on the other hand, suggests continuous mantle mixing during this period. However, for the ¹⁸²Hf-¹⁸²W system, Hadean-Archean mantle-derived rocks often show positive μ¹⁸²W anomalies followed by a decline in at 2.5~3.0 Ga ago without a mixing trend (e.g., Carlson et al., 2019, Chem. Geol.). Also, μ¹⁴²Nd and μ¹⁸²W often show no or negative correlation in Hadean-Archean mantle derived rocks (e.g., Rizo et al. 2016, Geochim. Cosmochim. Acta), which requires a mechanism to decouple these two isotopic systems.

In this study, we implement both ¹⁸²Hf-¹⁸²W and ¹⁴⁶Sm-¹⁴²Nd system in a global thermochemical geodynamic model, StagYY (Tackley, 2008, PEPI), to track the evolution of these isotope systems through Earth’s mantle evolution. Based on the particle-in-cell method, the geodynamic model incorporates melting and magmatic crust production that allow us to track both fractionation (by melting and crustal production) and mixing (through mantle convection) of trace elements through time. We discuss in detail how (1) the ‘basalt barrier’ at the base of the mantle transition zone (Davies, 2008 EPSL), (2) crustal delamination from intrusive magmatism, or plutonic-squishy-lid tectonics (Lourenco et al., Nat. Geo. 2018; GCubed 2020), and (3) late accretion could affect the tectonics of early Earth, and the preservation of geochemical heterogeneities and decoupling of two isotopic systems in the mantle through time.

How to cite: Tian, J. and Tackley, P.: Long-term preservation of geochemical heterogeneities in early Earth: tracking short-lived isotopes in geodynamic models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8965, https://doi.org/10.5194/egusphere-egu23-8965, 2023.

Our understanding of the compositional structure of Earth's mantle is still incomplete. Heterogeneity in the lower mantle, documented by both geochemical and geophysical observations, has not yet been explained within a definitive geodynamic framework. Moreover, the origin, geometry and interaction of such heterogeneities remain controversial. In the “marble cake” mantle hypothesis, slabs of basaltic Recycled Oceanic Crust (ROC) are subducted and deformed but never fully homogenized in the convecting mantle. Conversely, MgSiO₃-rich primordial material may resist convective entrainment due to its intrinsic strength, leading to a “plum pudding” mantle. While previous geodynamic studies have successfully reproduced these regimes of mantle convection in numerical models, the effects of the physical properties of ROC on mantle dynamics have not yet been fully explored. Furthermore, predictions from numerical models need to be tested against geophysical observations. However, current imaging techniques may be unable to discriminate between these two end members, due to limited resolution in the lower mantle.

Here, we model mantle convection in a 2D spherical-annulus geometry with the finite-volume code StagYY. We investigate the style of heterogeneity preservation as a function of the intrinsic density and strength (viscosity) of basalt at lower-mantle conditions. Additionally, we use the thermodynamic code Perple_X and the spectral-element code AxiSEM to compute, respectively, seismic velocities and synthetic seismograms from the predictions of our models.

Our results fall between two end-member regimes of mantle convection: low-density basalt leads to a well-mixed, "marble cake"-like mantle, while dense basalt aids the preservation of primordial blobs at mid-mantle depths as in a "plum pudding". Intrinsically viscous basalt also promotes the preservation of primordial material. These trends are well explained by lower convective vigour of the mantle as intrinsically dense (and viscous) piles of basalt shield the core. In order to test these results, we translate the predicted compositional, temperature and pressure fields to seismic velocities for two opposite end-member cases. These two synthetic velocity maps are first analysed and compared in terms of their respective radial correlation matrices and spherical harmonic spectra. Then, we use AxiSEM to simulate wave propagation through the two velocity models. Finally, we discriminate between the two end-members by comparing statistical properties of the corresponding ensembles of synthetic seismograms. Our results highlight how the interplay between primordial and recycled heterogeneities shape the evolution of the thermal and compositional structure of the lower mantle. Furthermore, they provide a framework for relating the style of heterogeneity preservation in the Earth's lower mantle with specific features of the seismic waveforms.

How to cite: Desiderio, M., Gülcher, A. J. P., and Ballmer, M. D.: The Heterogeneous Earth Mantle: Numerical Models of Mantle Convection and their Synthetic Seismic Signature, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10101, https://doi.org/10.5194/egusphere-egu23-10101, 2023.

The rigid surface of the Earth is divided into a jigsaw puzzle of about 50 tectonic plates separated by boundaries. Nowadays, three-dimensional spherical mantle modelling manages to produce self-consistently a stiff surface fragmented into several rigid caps that exhibit a plate-like behaviour. It thus becomes possible to analyse the dynamics of these models through the prism of plate tectonics theory and compare it to plate reconstruction models for the Earth. Such an analysis requires a robust method to automatically detect plates and their boundaries from continuous geophysical fields. The method should further recognize diffuse plate boundaries, as observed on Earth and reproduced in mantle convection models. We propose here a method to automatically detect and track plates through time, based on a trans-disciplinary approach combining a geodynamical and kinematic analysis with applied mathematics and computer sciences. This analysis is performed using the free and open-source software Paraview and the open-source software platform TTK (Topology ToolKit) designed for an efficient topological analysis of scalar fields. We apply our method to a three-dimensional spherical mantle convection model generating Earth-like plate tectonics at its surface. Our results show that, as for the Earth, the motion of modelled plates is stable over million-years-long periods separated by abrupt reorganizations occurring in less than 5 Myrs. The full plate-motion analysis over 262 Myrs in the model allows us to discuss the spatial extent of kinematic changes and shows that a plate reorganization can have regional to global effects on the plate network.

How to cite: Janin, A., Coltice, N., Tierny, J., and Chamot-Rooke, N.: The automatic detection of tectonic plates in 3D mantle convection models and plate motion changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12628, https://doi.org/10.5194/egusphere-egu23-12628, 2023.

The absence of seismic anisotropy in most regions of the lower mantle suggests that diffusion creep may be the dominant mechanism in the lower mantle. Because the diffusion-creep rate is inversely proportional to the 2~3 power of grain size, knowledge of the grain-growth kinetics is crucial for studying lower-mantle dynamics. For these reasons, this study determined the grain-growth kinetics of bridgmanite at a pressure of 27 GPa using advanced multi-anvil techniques.

We first measured the grain sizes of bridgmanite in an olivine bulk composition with various annealing durations at 2200 K. The results were fitted to an equation dⁿ – d₀ⁿ = kt, where d and d₀ are the final and initial grain sizes, respectively, n is the grain-size exponent, t is the annealing duration, and k is the growth-rate constant. This fitting yielded n = 5.2 ± 0.3, which is much smaller than given by a previous study [Yamazaki et al., 1996], n = 10.6 ± 1.1. This discrepancy may be because Yamazaki et al.’s [1996] olivine starting material may have contained adhesive water, which enhanced grain growth at the beginning of annealing. We then conducted runs at various temperatures, yielding the activation energy of 260 ± 20 kJ/mol. These results suggest that the bridgmanite grain sizes over 0.1 – 1 Gyr should have grain sizes of 150-230 μm, which is one order of magnitude larger than Yamazaki et al.’s [2006] estimation. Consequently, the lower mantle should be much harder than previously considered.

Furthermore, we measured the grain-growth kinetics as a function of the fraction of coexisting ferropericlase. Although the grain-growth kinetics is almost independent of the ferropericlase fraction down to 20 vol.%, it rapidly increases with decreasing ferropericlase fraction at lower fractions. Over 0.1~4.5 Gyr, the bridgmanite grain sizes in pure-bridgmanite rock should be 2 ~ 3 orders of magnitude larger than those coexisting with 20 vol.% of ferropericlase. These results suggest that pure-bridgmanite rock has 4 ~ 9 orders of magnitude lower flow rates than pyrolite if the diffusion creep is dominant. Since the diffusion creep rate in pure-bridgmanite rock is so low, the dislocation creep should dominate in pure-bridgmanite rock. We estimated that the pure-bridgmanite rock should have 1 ~ 2.5 orders of magnitude more viscous than pyrolite if the stress condition is 0.1~0.5 MPa in the lower mantle. This variation may interpret the viscosity variation in the lower mantle inferred from the geoid analysis [Rudolph et al., 2015], subduction speed [van der Meer et al., 2018], and plume morphology [French & Romaniwicz, 2016].

How to cite: Fei, H., Faul, U., Ballmer, M., Walte, N., and Katsura, T.: Grain growth kinetics of bridgmanite under topmost lower-mantle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7732, https://doi.org/10.5194/egusphere-egu23-7732, 2023.

A tectonic regime is the surface expression of interior dynamics in a planet. With the help of numerical models, different tectonic regimes have been proposed. Some of these are: (1) plate tectonics or mobile lid, (2) stagnant lid, (3) episodic lid, (4) plutonic-squishy lid, (5) and heat pipe (e.g., Lourenço et al., G3 2020). Over time, a tectonic regime shapes the surface of a planet, including its surface topography. Using the numerical models, we can compute the topographies associated with different tectonic regimes including spatial and temporal measures of variations. In this study, we compute statistics for the topography formed by different tectonic regimes in numerical models and compare with the statistics of observed topography of different terrestrial planets, with the aim of linking a planet to a tectonic regime at the present-day. Venus’ topography is better matched by topography distributions obtained for plutonic-squishy lid models than those for stagnant- or episodic-lid models, while Earth’s oceanic topography is best matched by mobile-lid models.

How to cite: Louro Lourenço, D., Manga, M., and Tackley, P.: Topographic signatures and statistics of different tectonic regimes and application to terrestrial planets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3622, https://doi.org/10.5194/egusphere-egu23-3622, 2023.

Terrestrial exoplanets, ranging in size up to approximately twice Earth-size (10 Earth masses), may have a range of characteristics that are not found in solar system planets, including but not limited to: larger size, different bulk composition (possibly resulting in being core-less), being tidally-locked to their host star, and being covered by water layers. Larger size has been proposed to result in sluggish deep-mantle convection and also (for stagnant-lid exoplanets) lower magmatism and outgassing, but internal differentiation is still expected to take place. Different bulk composition may lead to different viscosity (among other physical properties), modified melting behaviour and different core size (including the possibility of having no core). Tidally-locked exoplanets likely have hemispherical tectonics and internal structures, but the asymmetry would be reduced if they are continuously reorienting due to true polar wander. We are pursuing a range of studies investigating most of these different aspects using thermo-chemical convection models that include self-consistent lithospheric dynamics, partial melting and crustal production, using the code StagYY. Some of these studies are presented elsewhere at this meeting; this presentation will focus on additional interesting results.

How to cite: Tackley, P.: Studies of terrestrial exoplanet thermo-chemical-magmatic mantle and lithosphere dynamics and evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16119, https://doi.org/10.5194/egusphere-egu23-16119, 2023.

     Constraining thermo-chemical evolution for the interior of terrestrial planets is substantial to understanding their evolutionary path. Thermo-chemical processes is controlled by stages of large-scale melting, or magma oceans (MO), due to the energy released during accretion, differentiation, radioactive decay of heat-producing elements and crystallization of the melt. Previous work shows that one of the product of considering fractional crystallization (FC) for  MO is a FeO-enriched molten layer or basal magma ocean (BMO) which is stabilized at the core-mantle boundary for a few billion years. The BMO is expected to freeze by FC because it cools very slowly. FC always yield a highly iron-enriched BMO and last stage cumulates. Other crystallization mode could be dominated and has not yet been systemically explored – at least for the Earth-like planets.

To explore the fate of the BMO cumulates in the convecting mantle, we explore 2D geodynamic models with a moving-boundary approach. Flow in the mantle is explicitly solved, but the thermal evolution and related crystallization of the BMO are parameterized. The composition of the crystallizing cumulates is self-consistently calculated  in the FeO-MgO-SiO₂ ternary system according to Boukaré et al. (2015). In some cases, we also consider the effects of Al₂O₃ on the cumulate density profile. We then investigate the  entrainment and mixing of BMO cumulates by solid-state mantle convection over billions of years as a function of BMO initial composition and volume, BMO crystallization timescales, distribution of internal heat sources, and mantle rheological parameters (Ra# and activation energy), . We varied the initial composition of BMO by manipulating the molar fraction of FeO, MgO, and SiO₂  -based on published experiments- to model different BMO-compositions: Pyrolitic composition, After 50% crystallization of Pyrolitic composition Boukaré et al. (2015), After 50% crystallization of Pyrolitic composition Caracas et al. (2019), and Archean Basalt.

For all our model cases, we find that most of the cumulates (first ~90% by mass) are efficiently entrained and mixed through the mantle. However, the final ~9% of the cumulates are too dense to be entrained by solid-state mantle convection, and rather remain at the base of the mantle as a strongly FeO-enriched solid layer. We conclude that this inevitable outcome of BMO FC – at least for Earth - leads to inconsistent evolutionary path comparing to recent geophysical constraints. FC substantially change the compositional, thermal, and geometrical properties for the lower mantle structures.  An alternative mode of crystallization may be driven by an efficient reaction between a highly-enriched last-stage BMO with the overlying mantle due to chemical disequilibrium. 

How to cite: Ismail, M. and Ballmer, M.: The Consequences of Fractional Crystallization for Basal Magma Ocean on the Long-term Planetary Evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-723, https://doi.org/10.5194/egusphere-egu23-723, 2023.