Multi-observable Thermochemical Tomography: new advances and
applications to the Superior and North Australian cratons
Abstract
Imaging the Earth’s thermochemical structure is crucial for
understanding its dynamics and evolution. Moreover, the increased demand
for critical minerals and geothermal energy driven by the energy
transition has intensified the need for reliable subsurface models.
Multi-Observable Thermochemical Tomography (MTT) is a simulation-based,
probabilistic inversion platform designed to harness the combined
sensitivities of multiple geophysical datasets and thermodynamic
modelling. It produces internally-consistent estimates of the Earth’s
interior as probability distributions, offering a powerful means for
uncertainty quantification. Here, we present an updated MTT formalism
and assess its benefits and limitations to image the thermochemical
structure of the lithosphere-asthenosphere system. Individual and
combined sensitivities of different observables to parameters of
interest (e.g. temperature, composition, crustal architecture) are
explored using challenging synthetic models. Our findings demonstrate
that a judicious combination of observables can retrieve complex
thermochemical structures relevant to greenfields exploration. We then
apply MTT to study two cratonic regions of geological and economic
significance. In the Superior Craton, we jointly invert receiver
functions, gravity anomalies, gravity gradients, geoid anomalies,
Rayleigh-wave dispersion curves, absolute elevation and surface heat
flow. In the North Australian Craton, we incorporate new data from the
Ausarray and add teleseismic P- and S-phase travel times to the
datasets. The imaged lithospheric architectures provide new insights
into the tectonic evolution of these two regions and the physical
meaning of geophysical signatures. Additionally, these models offer
unique proxies to guide exploration efforts for clean energy and
critical minerals and serve as reference models for future
high-resolution studies.