Two dimensional cross-gradient joint inversion of gravity and magnetic data sets constrained by airborne electromagnetic resistivity in the Capricorn Orogen, Western Australia

Abstract

In many geological scenarios, the interpretation of multiple geophysical datasets through the use of joint inversion has become a common practice provided all data share compatible spatial resolution. Unfortunately, this requirement has also limited the application of airborne electromagnetic (AEM) data in joint inversion. For instance, we commonly assume that airborne gravity and magnetic datasets largely originate at a depth of a few kilometres, whereas co-located AEM signals can only penetrate a few hundred metres, thus rendering spatially incompatible datasets. We believe, however, that a fraction of these datasets originate from the same structures and provide a common ground for structural joint inversion strategies. We aim to explore the viability of jointly inverting such datasets using potential and AEM field data acquired in Western Australia with three comparative experiments. First, we generate conventional 2D separated models for each dataset to gauge their individual resolution capability. We then perform the 2D cross-gradient joint inversion of gravity and magnetic datasets. Finally, we adapt the structural joint inversion to include the AEM resistivity model as a constraint. We show that there is an area commonly sensed by the three datasets and that the coupled resolution influences both shallow and deep structures of the joint models. This yields a coherent integrated interpretation of shallow and deep structures of the studied section, which is validated when compared to a nearby seismic traverse section.

Airborne collection of electromagnetic and potential field data is a common strategy for extensive resource exploration and reconnaissance. Since these datasets contain information about different properties at different depths, they are normally considered complementary and are interpreted separately. Using airborne data acquired in Western Australia, we explore the viability of their joint inversion and show the advantages of their combined analysis and interpretation.

• airborne electromagnetics
• Australia
• gravity
• inversion
• magnetics

Acknowledgements

We wish to thank the GADDS for the availability of the gravity and magnetic data used in this work. We acknowledge the Geological Survey of Western Australia (GSWA) for the availability of the geological maps. We thank the CONACyT for the PhD scholarship granted to Adrián Misael León-Sánchez. Parts of the work presented here was supported by the Discovery theme within CSIRO’s Minerals Recourses Flagship, the Science and Industry Endowment Fund and other industry funding sponsors, which we would also like to thank. This document was largely improved by the insightful work of two anonymous reviewers and the associate editor, which is greatly appreciated.