<div>Long-period magnetotelluric (MT) data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP), collected as part of Geoscience Australia’s Exploring for the Future program with contributions from the Northern Territory Geological Survey and the Geological Survey of Queensland, provide important first-order information for resolving large-scale lithospheric architecture and identifying the broad footprint of mineral systems in northern Australia. Large-scale crust/mantle conductivity anomalies map pathways of palaeo-fluid migration which is an important element of several mineral systems. For example, the Carpentaria conductivity anomaly east of Mount Isa and the Croydon, Georgetown to Greenvale conductivity anomaly are highly conductive lithospheric-scale structures, and show spatial correlations with major suture zones and known mineral deposits. These results provide evidence that some mineralisation occurs at the gradient of or over highly conductive structures at lower crustal and lithospheric mantle depths, which may represent fertile source regions for mineral systems. These observations provide a powerful means of highlighting prospective greenfield areas for mineral exploration in under-explored and covered regions.</div><div><br></div><div>Higher resolution scale-reduction MT surveys refine the geometry of some conductive anomalies from AusLAMP data, and investigate whether these deep conductivity anomalies link to the near surface. These links may act as conduits for crustal/mantle scale fluid migration to the upper crust, where they could form mineral deposits. For example, data reveals a favourable crustal architecture linking the deep conductivity anomaly or fertile source regions to the upper crust in the Cloncurry region. In addition, high-frequency MT data help to characterise cover and assist with selecting targets for drilling and improve the understanding of basement geology.</div><div><br></div><div>These results demonstrate that integration of multi-scale MT surveys is an effective approach for mapping lithospheric-scale features and selecting prospective areas for mineral exploration in covered terranes with limited geological knowledge.</div><div><br></div><div>Some models in this presentation were produced on the National Computational Infrastructure, which is supported by the Australian government. Abstract presented to the Australian Institute of Geoscientists – ALS Friday Seminar Series: Geophysical and Geochemical Signatures of Queensland Mineral Deposits October 2023 (https://www.aig.org.au/events/aig-als-friday-seminar-series-geophysical-and-geochemical-signatures-of-qld-mineral-deposits/)

This animation shows how Magnetotelluric (MT) Surveys Work. It is part of a series of Field Activity Technique Engagement Animations. The target audience are the communities that are impacted by our data acquisition activities. There is no sound or voice over. The 2D animation includes a simplified view of what magnetotelluric (MT) stations and equipment looks like what the equipment measures and how the survey works.

Geoscience Australia has undertaken a series of integrated studies to identify prospective regions of mineral potential using new geological, geophysical and geochemical data from the Exploring for the Future (EFTF) program, together with legacy datasets. The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is a collaborative national survey, which aims to acquire long-period magnetotelluric (MT) data on a half-degree grid spacing (~55 km) across the entire Australian continent. The resistivity model derived from the newly-acquired AusLAMP data has mapped deep lithospheric-scale conductivity anomalies in highly endowed mineralised regions and in greenfield regions where mineralisation was not previously recognised. For example, the model reveals a conductivity anomaly extending from the Tennant Region to the Murphy Province, representing a potential fertile source region for mineral systems. This conductive feature coincides with a broadly northeast-southwest-trending corridor marked by a series of large-scale structures identified from preliminary interpretation of seismic reflection and potential field data. This under-explored region, referred to as East Tennant, is, therefore, considered to have significant mineral potential. We undertook a higher-resolution magnetotellurics survey to investigate if the deep conductivity anomaly is linked to the near surface by crustal-scale fluid pathways. Broadband MT (BBMT) and audio-MT (AMT) data were acquired at 131 stations with station spacing of ~2 km to ~15 km in an area of approximately 90 km x 100 km. The 3D resistivity model revealed two prominent conductors in the resistive host whose combined responses result in the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. The resistivity contrasts coincide with major structures preliminarily interpreted from seismic reflection and potential field data. Most importantly, the conductive structures extend from the lower crust to the near surface. This observation strongly suggests that the major faults in this region are deep-penetrating structures that potentially acted as pathways for transporting metalliferous fluids to the upper crust where they could form mineral deposits. This result indicates high mineral prospectivity for iron oxide copper–gold deposits in the vicinity of these major faults. We then used AMT data to constrain cover thickness to select targets at drillable depths for the stratigraphic drilling program which, in turn, will test the models and improve our understanding of basement geology, cover sequences and mineral potential. This study demonstrates that integration of geophysical data from multiscale surveys is an effective approach to scale reduction during mineral exploration in covered terranes with limited geological knowledge. This Abstract was submitted/presented to the 2021 Australasian Exploration Geoscience Conference 13 - 17 September https://2021.aegc.com.au/.

Magnetotellurics is one of few techniques those can provide multiple-scale datasets to understand the larger mineral system. We have used long-period data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) as first-order reconnaissance survey to resolve large-scale lithospheric architectures for mapping areas of mineral potential in northern Australia. The 3D resistivity model reveals a broad conductivity anomaly extending from the Tennant Region to the Murphy Province, representing a potential fertile source region for mineral systems. We then undertook a higher-resolution infill magnetotellurics survey to refine the geometry of major structures, and to investigate if the deep structure is connected to the near surface by crustal-scale fluid pathways. The resistivity models reveal two prominent conductors in the resistive host whose combined responses result in the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. The resistivity contrasts coincide with major structures preliminarily interpreted from seismic reflection and potential field data. Most importantly, the conductive structures extend from the lower crust to the near surface at where the major faults are located. This observation strongly suggests that these major faults are deep-penetrating structures that potentially acted as pathways for transporting metalliferous fluids to the upper crust where they could form mineral deposits. This result indicates high mineral prospectivity for iron oxide copper–gold deposits in the vicinity of these major faults. We then used high-frequency data to estimate cover thickness to assist with drill targeting for the stratigraphic drilling program which, in turn, will test the models and improve our understanding of basement geology, cover sequences and mineral potential. This study demonstrates that integration of geophysical data from multiscale surveys is an effective approach to scale reduction during mineral exploration in covered terranes. This Abstract was submitted/presented to the 2021 Australasian Exploration Geoscience Conference 13 - 17 September https://2021.aegc.com.au/.

The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) aims to collect long period magnetotelluric data on a half degree (~55 km) grid across the Australian continent. New data have recently been collected in New South Wales under a National Collaborative Framework agreement between Geoscience Australia and the Geological Survey of New South Wales. This data release contains a preferred resistivity model and associated inversion files for southeast Australia using data from AusLAMP Victoria (Duan & Kyi, 2018), far west NSW (Robertson et al. 2016) and from the rest of New South Wales up to August 2019 (Kyi et al 2020). The original work behind this model can be cited through the following paper which contains discussion on model development and its significance for tectonic evolution and metallogenic potential: Kirkby, A., Musgrave, R.J., Czarnota, K., Doublier, M.P., Duan, J., Cayley, R.A., Kyi, D., 2020. Lithospheric architecture of a Phanerozoic orogen from magnetotellurics: AusLAMP in the Tasmanides, southeast Australia. Tectonophysics, v. 793, 228560.

<div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div>We present a 3-D resistivity model derived from magnetotelluric data collected by two recent surveys in the Curnamona and Delamerian Region: the Curnamona Cube survey led by the University of Adelaide and funded by AuScope and the Curnamona Cube Extension survey (https://doi.org/10.26186/147904) by Geoscience Australia as part of Exploring for the Future Program. In total, data from 231 sites were used to produce 3-D models using the ModEM code. Details of data inversion are provided in the Readme.pdf file. The resistivity model can be used to enhance the understanding of the geodynamics and mineral potential in the Curnamona Province and Delamerian Orogen.</div><div><br></div><div>We greatly appreciate that Prof. Graham Heinson from the University of Adelaide has made the Curnamona Cube survey data available for this work. The modelling work was undertaken with the assistance of resources from the National Computational Infrastructure (NCI Australia).</div><div><br></div><div>This release package contains the preferred 3-D resistivity model in SGrid format and geo-referenced depth slices in .tif format.</div><div><br></div>

The magnetotelluric (MT) method is increasingly being applied to mineral exploration under cover with several case studies showing that mineral systems can be imaged from the lower crust to the near surface. Driven by this success, the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is delivering long-period data on a 0.5° grid across Australia, and derived continental scale resistivity models that are helping to drive investment in mineral exploration in frontier areas. Part of this investment includes higher-resolution broadband MT surveys to enhance resolution of features of interest and improve targeting. To help gain best value for this investment it is important to have an understanding of the ability and limitations of MT to resolve features on different scales. Here we present synthetic modelling of conductive, narrow, near-vertical faults 500 m to 1500 m wide, and show that a station spacing of around 14 km across strike is sufficient to resolve these into the upper crust. However, the vertical extent of these features is not well constrained, with near-vertical planar features commonly resolved as two separate features. This highlights the need for careful interpretation of anomalies in MT inversion. In particular, in an exploration scenario, it is important to consider that a lack of interconnectivity between a lower crustal/upper mantle conductor and conductors higher up in the crust and the surface might be apparent only, and may not reflect reduced mineral prospectivity. Appeared in Exploration Geophysics Journal 05 Dec 2022

The footprint of a mineral system is potentially detectable at a range of scales and lithospheric depths, reflecting the size and distribution of its components. Magnetotellurics is one of a few techniques that can provide multiscale datasets to understand mineral systems. The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is a collaborative national survey that acquires long-period magnetotelluric data on a half-degree grid spacing (about 55 km) across Australia. This project aims to map the electrical conductivity/resistivity structure in the crust and mantle beneath the Australian continent. We have used AusLAMP as a first-order reconnaissance survey to resolve large-scale lithospheric architecture for mapping areas of mineral potential in Australia. AusLAMP results show a remarkable connection between conductive anomalies and giant mineral deposits in known highly endowed mineral provinces. Similar conductive features are mapped in greenfield areas where mineralisation has not been previously recognised. In these areas we can then undertake higher-resolution infill magnetotelluric surveys to refine the geometry of major structures, and to investigate if deep conductive structures are connected to the near surface by crustal-scale fluid-flow pathways. This presentation summarises the results from a 3D resistivity model derived from AusLAMP data in Northern Australia (Figure 1). This model reveals a broad conductivity anomaly in the lower crust and upper mantle that extends beneath an undercover exploration frontier between the producing Tennant Creek region and the prospective Murphy Province to the northeast. This anomaly potentially represents a fertile source region for mineral systems. A subsequent higher-resolution infill magnetotelluric survey revealed two prominent conductors within the crust (Figure 2) whose combined responses produced the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. Integration of the conductivity structure with deep seismic reflection data revealed a favourable crustal architecture linking the lower, fertile source regions with potential depositional sites in the upper crust. Integration with other geophysical and geochronological datasets suggests high prospectivity for major mineral deposits in the vicinity of major faults. In addition to these insights, interpretation of high-frequency magnetotelluric data helps to characterise cover and assist with selecting targets for stratigraphic drilling. This study demonstrates that the integration of geophysical data from multiscale surveys is an effective approach to scale reduction during mineral exploration in covered terranes. The success of this data integration and scale reduction approach is demonstrated by the uptake of over 11,000 square kilometres of new exploration tenements in the previously under-explored East Tennant region of northern Australia. This abstract was submitted to and presented at the 26th World Mining Congress (WMC) 2023 (https://wmc2023.org/)

Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government. As part of Exploring for the Future (EFTF) program with contributions from the Geological Survey of Queensland, long-period magnetotelluric (MT) data for the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) were collected using Geoscience Australia's LEMI-424 instruments on a half-degree grid across Queensland from April 2021 to November 2022. This survey aims to map the electrical resistivity structures in the region. These results provide additional information about the lithospheric architecture and geodynamic processes, as well as valuable precompetitive data for resource exploration in this region. This data release package includes processed MT data, a preferred 3D resistivity model projected to GDA94 MGA Zone 54 and associated information for this project. The processed MT data were stored in EDI format, which is the industry standard format defined by the Society of Exploration Geophysicists. The preferred 3D resistivity model was derived from previous EFTF AusLAMP data acquired from 2016-2019 and recently acquired AusLAMP data in Queensland. The model is in SGrid format and geo-referenced TIFF format.

<div>The Geoscience Australia magnetotellurics (MT) program collaborates with state and territory geological surveys, universities, and AuScope to acquire audio- (AMT), broadband- (BBMT), and long-period-MT (LPMT) data to help understand the electrical conductivity structure of the Australian continent.</div><div><br></div><div>This report collates the time-series and processed data, electrical conductivity models, and publications released for projects for which Geoscience Australia was the lead organisation, a collaborator, or an in-kind or financial supporter. For the most part, this report does not reference MT data, models or publications released by other parties for projects in which Geoscience Australia had no involvement. Please see Geoscience Australia’s AusLAMP, Exploring for the Future AusLAMP, and Regional Magnetotellurics webpages for more information.</div>