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Project name: Olympic Domain Magnetotellurics
Project leader: Stephan Thiel
Project group: Tom Wise
Ian Hopton
Lyn Broadbridge
Ursula Michael
Jonathan Irvine
Tristan Kemp (Geoscience Australia)
Program: Next Generation Copper Discovery Program

Synopsis

Map of South Australia showing location of the Olympic Domain Magnetotellurics projectRecent results from the Australian Lithosphere Architecture Magnetotelluric Project (AusLAMP) across the Gawler Craton, have revealed zones of enhanced crustal conductivity along the eastern margin of the craton. These zones coincide with the highly prospective iron oxide copper gold (IOCG) belt that connects to a mantle plumbing system.  

The Olympic Domain Magnetotellurics survey will investigate a zone of such increased conductivity by acquiring over 320 new broadband and audio magnetotelluric (MT) sites with variable site spacing between 1.5 km and 10 km across an area of approximately 100 km x 100 km. The acquisition of this new data will cover an area of the eastern Gawler Craton that extends west of Lake Torrens and covers mineral prospects such as Carrapateena, Fremantle Doctor, Red Lake, Punt Hill, Emmie Bluff and Mount Gunson.

This new, detailed dataset will greatly value add to other geophysical and geological data, in particular the new magnetic data collected as part of the Gawler Craton Airborne Survey as well as the Olympic Domain airborne electromagnetic survey.  It will greatly enhance our understanding of the deformation zones and fluid pathways through the entire crust up to the sedimentary cover of the Olympic Domain.

The outcome will be a novel geophysical data layer that will reduce risk for exploration across the Olympic Domain and provide an improved understanding of the primary lithospheric architecture controlling the location of deposits across the Olympic Domain.

Background/Aims

The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is a collaborative national magnetotelluric (MT) project focused on acquiring long-period MT data at approximately 2800 sites across Australia over half degree grid spacing (approximately 50 km). The resultant AusLAMP data will be used to map the electrical conductivity of the entire continent in three dimensions. The project aims to provide significant additional information about Australia’s geodynamic framework as well as valuable precompetitive data for resource exploration.

The recent observations in the Gawler Craton AusLAMP data linking zones of enhanced crustal conductivity with the IOCG belt indicate a broad connection to a mantle plumbing system. These broad zones are well constrained in the mid crust and deeper through the regional AusLAMP grid and suggest that the eastern margin of the Gawler Craton has experienced significant crustal deformation accompanied with a fluid and magmatic overprint.

The Olympic Domain MT survey across the IOCG belt and the location of the deep crustal conductor is designed to reduce scale and enhance resolution of the resistivity model across the prospective area. The shift from long-period (10 – 10,000 s periodicity) data, spaced every ~50 km, of the AusLAMP grid to broadband and audio magnetotelluric data (10-5 – 2000 s periodicity) combined with a reduction in site spacing by almost a factor of ten will greatly enhance our understanding of the deformation zones and fluid pathways through the entire crust up to the sedimentary cover.

This survey builds on the promising 2D MT profiles collected across Olympic Dam by the University of Adelaide, and applies this concept on a broader grid to achieve a high resolution 3D resistivity image of the Olympic Domain. This new image will also be integrated into the more regional AusLAMP results.

This project is being undertaken in partnership with Geoscience Australia (a Division of the Commonwealth Department of Innovation and Science) under the National Collaboration Framework promoting State–Federal precompetitive geoscientific collaborative programs.

Key outcomes

  • ~320 new broadband MT sites across a variable 100 km x 100 km array covering the Olympic Domain around Carrapateena, Fremantle Doctor, Red Lake, Punt Hill, Emmie Bluff and Mount Gunson (site spacing between 10 km and 1.5 km)
  • Three-dimensional resistivity model of the crust beneath the survey area
  • Joint interpretation with existing lithospheric AusLAMP MT models and near-surface AEM models
  • Joint interpretation with gravity and magnetic data

Schedule for information and product delivery

DeliverableTime frame

Completion of Olympic Domain MT data acquisition

Q2 2017 (pending land access)
New 3D crustal resistivity model of the Olympic DomainQ3 2017
Data available on SARIGQ3 2017
Resistivity models available on SARIGQ4 2017
Report on survey results. Journal article in MESA journal and peer-reviewed international journal articleQ4 2017 – Q1 2018