Recent geodynamica items

Carbon Depletion of Ices by Diamond Precipitation in Sub-Neptune Exoplanets

Tue, 15 Sep 2026 00:00:00 +0000

Hydrocarbons are observed on the surfaces of many icy moons and planets. At high-pressure high-temperature conditions, such as occur in larger planets, they are known to dissociate to form diamond and hydrogen. Within our solar system Uranus and Neptune easily reach the requisite 10 GPa and 2000 K for this process, while icy moons do not. Densities indicative of icy compositions are commonly observed for exoplanets, many of which have radii intermediate between the local icy moons and icy planets. These so-called 'mini-neptunes' are a common class of exoplanet and, where hydrocarbons are incorporated within their ices, are candidates for diamond formation. Here we simulate model icy exoplanets to investigate the size required to induce diamond formation. Where the conditions are met, the denser diamond will sink through the ices deeper into the planet under gravity. This provides a source of internal heating, and will sequester the carbon deep within the planet....

Heat flow scaling relationships for the glass-ceiling convective regime and implications for Venus

Sun, 16 Aug 2026 00:00:00 +0000

Most rocky planets operate in a stagnant lid convective regime. They are characterized by the strongly temperature-dependent viscosity that locks the cold mantle silicates near the surface into a stiff layer, or lid, which does not participate in mantle convection. Stagnant lid planets have lower surface heat flows than mobile lid planets like Earth; however, Earth-like heat flows have been inferred from elastic lithosphere thickness estimates for Venus leading researchers to wonder how these higher heat fluxes occur. Mineral phase transitions in the upper mantle can inhibit or enhance mass exchange through the mantle transition region at pressures and temperatures relevant for larger terrestrial mantles such as Earth’s or Venus’s. For a multiphase composition of anhydrous pyrolite, small cold plume instabilities originating at the base of the stagnant lid sink to a depth of about 600 km. When a critical amount of material accumulates, the drips avalanche into the lower...

Crustal-Scale Signatures of Steady-State Thermal Inheritance: Insights from the South China Sea

Fri, 14 Aug 2026 00:00:00 +0000

Long-lived lateral variations in radiogenic heat production create persistent thermal heterogeneities that shape continental lithosphere over geological timescales. We introduce a steady-state concept of thermal inheritance, linking these variations to crustal-scale strain localization and tectonic architecture.
Using numerical models, we explore both crustal- and lithospheric-scale consequences of heterogeneous heat production. A key finding is that lateral variations in heat production leave a distinct crustal-scale tectonic signature, controlling patterns of strain localization. The South China Sea serves as a proof-of-concept: the segmented, oblique extension observed there aligns with zones of mechanically weaker crust, reflecting the underlying inherited thermal heterogeneity.
These results highlight that crustal-scale tectonic features can emerge from steady-state thermal conditions, independently of transient anomalies. They provide a quantitative framework linking...

CPO2Hill: An Efficient Parametrisation to Infer Anisotropic Viscous Behaviour Directly from Olivine Texture Parameters

Mon, 15 Jun 2026 00:00:00 +0000

Anisotropic viscosity is likely prevalent within the upper mantle, but is usually disregarded in geodynamics models. On a crystal scale, olivine’s intrinsic properties are such that dislocation creep occurs over an order of magnitude more easily along olivine’s [100] symmetry axis than along its [001] axis. However, deforming olivine aggregates generate crystallographic preferred orientations (CPO) with their own macroscopically effective anisotropic viscosities that have proven difficult to estimate from the microscopic anisotropies of individual olivine crystals. Here we present a simple method to derive anisotropic viscosity parameters directly from the CPO mean orientation tensors. To calibrate the method, we created a large database of textures likely to occur in geodynamic simulations. We tested our method within numerical simulations of simple shear with both constant and varying shear directions. Finally, we integrated our method into the geodynamic code ASPECT, where...

Lithospheric Mantle Density Anomalies Determined From Lithosphere Thickness and Dynamic Topography

Mon, 12 Jan 2026 00:00:00 +0000

Chemical buoyancy within the lithosphere may be prevalent in certain depth regions. To constrain those depths, we follow an approach similar to Wang et al. (2023) and plot the difference between residual topography—where only crustal isostatic topography has been removed—and dynamic topography—where only sub-lithospheric density anomalies are considered—against lithosphere thickness. In theory, this difference should be caused by density anomalies in the lithosphere, and the slope of the fitting line versus lithosphere thickness should hence indicate depth-dependent density anomalies in the lithosphere. When computing dynamic topography, lithosphere thickness and density anomalies outside the continental lithosphere are derived from tomography. Within the continental lithosphere, density anomalies are set to a reference value, for which we use either the global mean, or the depth-dependent mean values below mid-ocean ridges. With densities in the continental lithosphere...