1D and 2.5D electromagnetic data Inversion



Bryah Basin, northern Western Australia

Description of the project

The Bryah Basin is part of the Capricorn Orogen, northern Western Australia. It contains a succession of mafic and ultramafics overlain by clastic sediments. The Basin is host to significant mineralisation, including the DeGrussa and Horseshoe Cu-Au VMS deposits. This case study is based upon a SPECTREM AEM reconnaissance survey, Munday et. al., 2013. The survey was peformed to stimulate mineral exploration by mapping the very conductive carbonaceous / graphitic / BIF / iron rich sediments which are present under the regolith or at depth in this area.

Intrepid Geophysics present this case study to highlight GeoModeller's inbuilt 2.5D airborne electromagnetic inversion module, directly interacting with 3D geological modelling - a huge advantage over more commonly used CDI transforms or simple 1D inversions. We also demonstrate a substantially rewritten version of ArjunAir (Wilson et al., 2006; CSIRO/Amira) in our new GSVD solver - designed with adaptive regularisation also incorporating a misfit to the reference model and a model smoothness function.

Authors: Jovan Silic, Rod Paterson, Des FutzGerald & Tim Archer 2015

download paper: "Comparing 1D and 2.5D AEM inversions in 3D geological mapping using a new adaptive solver" 

Both 1D and 2.5D inversions were conducted for the study area. The dramatic improvement from 1D to 2.5D in being able to indicate geological trends, at depth, for conductors with complex geometries, is starkly evident in the figure above.