Lithospheric structure and melting processes in southeast Australia: new constraints from joint probabilistic inversions of 3D magnetotelluric and seismic data

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2023JB028257. This is version 3 of this Preprint.

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Authors

Maria Constanza Manassero, Sinan Özaydin, Juan Carlos Afonso, Joshua Shea, Stephan Thiel, Alison Kirkby, Ilya Fomin, Karol Czarnota

Abstract

The thermochemical structure of the lithosphere exerts control on melting mechanisms in the mantle as well as the location of volcanism and ore deposits. Imaging the complex interactions between the lithosphere and asthenospheric mantle requires the joint inversion of multiple data sets and their uncertainties.
In particular, the combination of seismic velocity and electrical conductivity with data proxies for bulk composition and elusive minor phases is a crucial step towards fully understanding large-scale lithospheric structure and melting.
We apply a novel probabilistic approach for joint inversions of 3D magnetotelluric and seismic data to image the lithosphere beneath southeast Australia. Results show a highly heterogeneous lithospheric structure with deep conductivity anomalies that correlate with the location of Cenozoic volcanism. In regions where the conductivities have been at odds with sub-lithospheric temperatures and seismic velocities, we observe that the joint inversion provides conductivity values consistent with other observations. The results reveal a strong relationship between metasomatized regions in the mantle and i) the limits of geological provinces in the crust, which elucidates the subduction-accretion process in the region; ii) distribution of leucitite and basaltic magmatism; iii) independent geochemical data, and iv) a series of lithospheric steps which constitute areas prone to generating small-scale instabilities in the asthenosphere. This scenario suggests that shear-driven upwelling and edge-driven convection are the dominant melting mechanisms in eastern Australia rather than mantle plume activity, as conventionally conceived. Our study offers an integrated lithospheric model for southeastern Australia and provides insights into the feedback mechanism driving surface processes.

DOI

https://doi.org/10.31223/X53S9P

Subjects

Geochemistry, Geophysics and Seismology, Volcanology

Keywords

Magnetotellurics, seismic, joint inversion, probabilistic Inversion, metasomatism, volcanism, southeast Australia

Dates

Published: 2022-11-19 03:11

Last Updated: 2023-01-25 10:43

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License

CC-By Attribution-NonCommercial-NoDerivatives 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
Data upon request