Thermal and Compositional Architecture of the Antarctic Lithosphere Revealed by Integrated Gravity–Seismic Imaging

Understanding the thermal and compositional structure of the Antarctic lithosphere is fundamental for assessing its tectonic stability, geodynamic evolution, and mantle processes beneath East and West Antarctica. However, interpretations based on single geophysical observables remain highly non-unique due to the coupled effects of temperature and composition on seismic velocity and density. Here we present a multi-physics framework that integrates gravity, seismic velocity, heat flow, and thermodynamic modeling to derive high-resolution density, temperature, and compositional models of the Antarctic lithosphere and lithospheric mantle.

 

We first perform a three-dimensional parallel gravity inversion constrained by seismic shear-wave velocity structure, using a structurally coupled objective function that combines data misfit, model regularization, and Gramian-based structural consistency. Structural similarity between density and velocity is enforced in the mantle, where seismic constraints are strongest, while thermally corrected density relationships are incorporated within the crust. The inversion is accelerated through a matrix-free implementation with CUDA-enabled forward and adjoint modeling and MPI–GPU parallelization, enabling continental-scale imaging at a resolution of 5 km × 5 km.

 

The resulting absolute density model reproduces observed Bouguer gravity anomalies with low residuals and reveals pronounced lateral heterogeneity across Antarctica. Building on these results, we further decouple temperature (T) and composition (Mg#) in the upper mantle through joint simulation of seismic velocity and density. Forward models are constructed using Gibbs free energy minimization with Perple_X, incorporating phase equilibria, anelastic attenuation, and rheological effects. A probabilistic grid-search approach with Monte Carlo uncertainty analysis enables robust estimation of T and Mg# and identification of regions where standard solid-state physics fails to explain observations.

 

Our results indicate a cold, thick, and chemically depleted lithospheric root beneath East Antarctica, consistent with a stable cratonic mantle, while West Antarctica is characterized by elevated temperatures, fertile compositions, and widespread regions exceeding solid-state limits, suggesting active asthenospheric upwelling and possible decompression melting beneath the West Antarctic Rift System. This study demonstrates the power of integrated geophysical–thermodynamic approaches for resolving the thermo-compositional state of continental lithosphere.