To aid in geological exploration.

To aid in geological exploration.

Ultra-wide band magnetotelluric data were collected at a nominal spacing of ~3 km along two profiles across the Delamerian and Lachlan orogen. The data was acquired and processed by Zonge Engineering Ltd. The author of this data package inverted...

Ultra-wide band magnetotelluric data were collected at a nominal spacing of ~3 km along two profiles across the Delamerian and Lachlan orogen. The data was acquired and processed by Zonge Engineering Ltd. The author of this data package inverted the data using 2D and 3D inversions using the CGG Geotools package. Data coverage was augmented where legacy data was available, including AusLAMP data (Thiel et al., 2018, Kirkby et al., 2020, Robertson et al., 2016) and broadband data along the Eucla MT profile (e.g. Wise and Thiel, 2020).


Northern profile DelN

Masking was applied to remove spurious data prior to inversion; error floors of 3% were applied to the impedance tensor components and 0.02 to the tipper. The data were then interpolated on five periods per decade, evenly spaced in logarithmic scale for a total of 32 periods from 0.0015 s to 2500 s. The inversion process includes a solver for distortion correction. The normalised RMS misfit between the model response and these data is 2.61 for the delivered 3D inverse model.

The site coordinates and the model were projected to WGS84 MGA Zone 54. 

The DelN 3D MT model has a horizontal cell size of 1.35 km x 2 km and a vertical cell size of 10 m at the surface, which increases with depth. Fourteen padding cells were added to each horizontal boundary, taking the total model extent to 297x63x136 cells in the X, Y and Z directions. Topography was included in the model. The delivered model is a cropped version of the original grid. 


Southern profile DelS

Masking was applied to remove spurious data prior to inversion; error floors of 2% were applied to the impedance tensor components and 0.02 to the tipper. The data were then interpolated on five periods per decade, evenly spaced in logarithmic scale for a total of 32 periods from 0.0015 s to 2500 s. The inversion process includes a solver for distortion correction. The normalised RMS misfit between the model response and these data is 2.54 for the delivered 3D inverse model.

The site coordinates and the model were projected to WGS84 MGA Zone 54. 

The DelS 3D MT model has a horizontal cell size of 1.25 km x 2 km and a vertical cell size of 3 m at the surface, which increases with depth. Fourteen padding cells were added to each horizontal boundary, taking the total model extent to 277x63x117 cells in the X, Y and Z directions. Topography was included in the model. The delivered model is a cropped version of the original grid. 


A starting model of 70 ohm-m was used. In general, features between depths of ~0.1 km and 50 km are the most robust.


Data

The 3D model for the northenr and southern profile included in this package are delivered in a variety of formats, including the native CGG Geotools format (*.out), UBC format (*.mod, *.mesh), ascii format (*.xyzv). 

Additionally, each depth slice of the 3D models are also available as separate files, in ascii format (subfolder xylog10z_utm), shapefiles (subfolder xylog10z_utm_esri_shp), and rasters (subfolder xylog10z_utm_rasters). 

Acknowledgements

The Delamerian MT data were funded by initiatives of the South Australia Department for Energy and Mining, the Geological Survey of South Australia and the Geological Survey of Victoria. MinEx CRC supplied project management to the project. Data collection was undertaken by Zonge Engineering and Research Organisation.  South Australian AusLAMP data used in the modelling were funded by initiatives of the Department of Energy and Mining using AuScope/Australian National Sounding and Imaging Research Infrastructure (ANSIR) instruments. The AusLAMP Victoria data in this model were collected under a collaborative project between the Geological Survey of Victoria (GSV) and GA using ANSIR and GA instruments. We thank AuScope and NCI for computational resources on the NCI. The authors acknowledge the support provided by individuals and communities to access the country, especially in remote and rural Australia.

Created by Stephan Thiel, CSIRO, Mineral Resources, 2023.

© Government of South Australia (Geological Survey of South Australia), and Government of Victoria (Geological Survey of Victoria), and CSIRO (Commonwealth Scientific and Industrial Research Organsiation), 2023. 
With the exception of the Commonwealth Coat of Arms and where otherwise noted, this product is provided under a Creative Commons Attribution 4.0 international licence.
http://creativecommons.org/licenses/by/4.0/legalcode

This data set is published with the permission of the Director of the Geological Survey of South Australia and the Director Geological Survey of Victoria..

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