Integrated magnetotelluric and petrological analysis of felsic magma reservoirs: Insights from Ethiopian rift volcanoes

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Authors

Friedemann Samrock , Alexander V. Grayver , Olivier Bachmann , Özge Karakas , Martin O Saar 

Abstract

Geophysical and petrological probes are key to understanding the structure and the thermochemical state of active magmatic systems. Recent advances in laboratory analyses, field investigations and numerical methods have allowed increasingly complex data-constraint models with new insights into magma plumbing systems and melt evolution. However, there is still a need for methods to quantitatively link geophysical and petrological observables for a more consistent description of magmatic processes at both micro- and macro-scales. Whilst modern geophysical studies provide detailed 3-D subsurface images that help to characterize magma reservoirs by relating state variables with physical material properties, constraints from on-site petrological analyses and thermodynamic modelling of melt evolution are at best incorporated qualitatively.
Here, we combine modelling of phase equilibria in cooling magma and laboratory measurements of electrical properties of melt to derive the evolution of electrical conductivity in a crystallizing silicic magmatic system. We apply this framework to 3-D electrical conductivity images from magnetotelluric studies of two volcanoes in the Ethiopian Rift. The presented approach enables us to constrain key variables such as melt content, temperature and magmatic volatile abundance at depth. Our study shows that accounting for magmatic volatiles as an independent phase is crucial for understanding electrical conductivity structures in magma reservoirs at an advanced state of crystallization.
Furthermore, our results deepen the understanding of the mechanisms behind volcanic unrest and help assess the long-term potential of hydrothermal reservoirs for geothermal energy production.

DOI

https://doi.org/10.31223/X5Q600

Subjects

Earth Sciences, Geochemistry, Geophysics and Seismology, Volcanology

Keywords

geochemistry, petrology, magnetotelluric imaging, melt evolution, magmatic volatiles

Dates

Published: 2021-01-16 17:01

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
In this paper we present a method to link existing geophysical and petrological observations and models through thermodynamic modelling of melt evolution. The geophysical models, petrological data, thermodynamic modelling tools and techniques used in the quantitative interpretation are presented in this manuscript or are available from the cited publications.

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