South Australian scientists look deep for minerals in a world leading, national geophysics project

Looking deep into the Earth’s crust, side on: geophysicists use specialist equipment that is supported by AuScope to scan down to tens or hundreds of kilometres into the Earth to reveal the geological complexity of the subsurface, and shine a light on potential new mineral deposits. Image: via    Australian Academy of Science   .

Looking deep into the Earth’s crust, side on: geophysicists use specialist equipment that is supported by AuScope to scan down to tens or hundreds of kilometres into the Earth to reveal the geological complexity of the subsurface, and shine a light on potential new mineral deposits. Image: via Australian Academy of Science.


Since 2013, geophysicists have worked across all states and territories to undertake a comprehensive geophysical survey of the Australian crust and mantle, the Australian Lithospheric Architecture Magnetotellurics Project (AusLAMP).  

Recently, the project team comprising the Geological Survey of South Australia, the University of Adelaide, Geoscience Australia and AuScope celebrated the completion of the South Australian portion of the AusLAMP project, shining a light on potential ore deposits ‘hiding’ at depth.


On 5th December 2018, The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) team in South Australia celebrated a major milestone: releasing data from 406 long-period magnetotelluric (MT) stations across the state to the public via the South Australian Resources Information Gateway (SARIG).

To mark the occasion, the Geological Survey of South Australia (GSSA) team and Geoscience Australia hosted a national MT workshop at the South Australia Drill Core Reference Library. Over 85 registered participants attended a day of talks on lithospheric architecture, the AusLAMP project around Australia,
and scale reduction and integration of MT data for mineral exploration.

Government, academia and industry coming together at the AusLAMP Workshop in February 2019. Pictured (clockwise from top left): presenters Dr. Stephan Thiel, Dr. Kate Robertson, Dr. Bruce Goleby, and Macquarie University PHD candidate Maria Manassero. Images:    Dr Kate Robertson    and    Dr Kate Selway   .

Government, academia and industry coming together at the AusLAMP Workshop in February 2019. Pictured (clockwise from top left): presenters Dr. Stephan Thiel, Dr. Kate Robertson, Dr. Bruce Goleby, and Macquarie University PHD candidate Maria Manassero. Images: Dr Kate Robertson and Dr Kate Selway.

Project Leader, Dr Stephan Thiel reflects on the AusLAMP project milestone:

“The completion of the AusLAMP South Australia as part of the nation-wide endeavour to map the Australian continent is a major achievement for the Geological Survey of South Australia in collaboration with the University of Adelaide and Geoscience Australia.

It is a scientific success, and has sparked great interest with the mineral exploration industry through our new understanding of how mineral systems form. The 5 year project has also resulted in lasting land holder engagements and interactions, which goes well beyond what we have dreamed of achieving when the project set out.”

Roger Williams from Oak Valley with magnetotelluric installation on Maralinga Tjarutja Lands, South Australia with Dr Bruce Goleby from The University of Adelaide. Image: Tim Anderson, Helifarm.

Roger Williams from Oak Valley with magnetotelluric installation on Maralinga Tjarutja Lands, South Australia with Dr Bruce Goleby from The University of Adelaide. Image: Tim Anderson, Helifarm.

AusLAMP collaborator and AuScope project leader, Prof Graham Heinson, University of Adelaide, stressed the importance of MT in the national UNCOVER initiative:

“Only in the last 10-15 years, do we see MT being applied to mapping the entire mineral system rather than a single deposit [...] driven by the philosophy of UNCOVER mapping the entire Lithospheric Architecture.”

As a result, the GSSA team, Dr Kate Robertson and Dr Stephan Thiel, explain one of the greatest findings with the data to date:

“A revelation of the AusLAMP data set and its widespread coverage was the remarkable insight that major IOCG ore deposits are predominantly aligned with zones of enhanced electrical conductivity in the deeper crust. We now have a novel tool to map mineral systems hidden beneath hundreds of metres of barren cover.”

A telling map: South Australia’s known copper occurrences (red and cyan dots) layered over the electrical resistivity map of the state. Spatial coexistence of the two shows that the minerals we are looking for near the surface can be traced deep into the crust and beyond. Image:    Dr Stephan Thiel   .

A telling map: South Australia’s known copper occurrences (red and cyan dots) layered over the electrical resistivity map of the state. Spatial coexistence of the two shows that the minerals we are looking for near the surface can be traced deep into the crust and beyond. Image: Dr Stephan Thiel.

One of the workshop participants, Dr Kate Selway, ARC Future Fellow at Macquarie University explains the excitement of discovery when working with MT data:

“...almost everywhere we look with MT we see something unexpected. It’s exciting because it is telling us something new about the Earth. The national MT workshop was a great opportunity for the community to work together to understand these new insights.”

The AusLAMP project in South Australia has further stimulated the exploration industry, with Havilah Resources Ltd, Ausmex Mining Group, and Investigator Resources Ltd exploring prospective MT anomalies that were identified from visualised AusLAMP data on their respective tenements between 2017 — 2018. Furthermore, major exploration companies such as BHP are now using MT as an exploration tool.

The AusLAMP team would like to acknowledge that data acquisition was enabled due to the national MT instrument pool at the University of Adelaide maintained by technician Goran Boren. It is established and maintained through funding from AuScope. The National Computational Infrastructure (NCI) is pivotal in hosting 3D inversion codes to model the national AusLAMP MT data.

 

 
 

AUTHORS

This article has been produced by Jo Condon of AuScope, Dr Stephan Thiel and Dr Kate Robertson from the Geological Survey of South Australia, Prof Graham Heinson from the University of Adelaide, and Dr Kate Selway from Macquarie University.