Thermochemical structure of Gondwana terrains from multi-observable
probabilistic inversion
Abstract
The supercontinent Gondwana broke up 200 Myrs ago in smaller continents
known today as South America, Africa, India, Australia, Antarctica. In
the last twenty years, extensive petrological, geochemical, and
geophysical studies were done in Australia and South Africa. Still,
models of the post-Gondwana lithospheric mantle evolution are
constrained by sparse geochemical analysis and/or numerical modelling.
Access to different scale geophysical datasets allow applying joint
inversion framework to better constrain the present-day physical state
of cratonic lithosphere. Here we use a 3D multi-observable inversion
method based on a probabilistic (Bayesian) formalism. This approach
constrains the present-day thermochemical structure (temperature and
major element composition) of the mantle using the sensitivity of
multi-geophysical datasets within a thermodynamically consistent
Bayesian framework, solved with state-of-the-art Markov Chain Monte
Carlo algorithms. This presentation will show recent thermochemical
tomography of central-southern Africa, Antarctica, South America, and
Australia at a resolution of 1°x1°. We will show new thermal
lithospheric thickness and the average chemical composition of the
lithospheric mantle maps beneath these Gondwana terranes. We will
discuss the evolution of cratonic lithosphere derived from our modelling
and previously suggested by comparing it with external observables
(xenolith/xenocrysts thermo-barometry analysis, hotspot tracks
reconstruction, volcanism). This contribution will address the following
questions: 1. How thick, cold and depleted is the cratonic lithosphere
beneath Gondwana terranes? 2. How did mantle plumes affect the
thermochemical structure in the last 200 Myrs? 3. What can geophysical
data and paleo reconstruction tell us about the evolution of the
cratonic lithosphere?