We present an updated resistivity model from inversion of the 09GA-GA1 deep magnetotelluric survey, also known as the Georgina-Arunta survey. The data were originally collected in 2009 under Geoscience Australia’s Onshore Energy Security Program, together with deep seismic reflection data along the same line. The magnetotelluric data comprise broadband and long-period data. The broadband data were originally processed to a bandwidth of 0.04 s to 100 s, but have been reprocessed yielding an extended bandwidth of 0.04 s to 1000 s, which improves the resolution of deeper (>20 km depth) structures. Inversions have been carried out using the ModEM 3D inversion code given that the data indicate the presence of 3D geoelectric structure. The updated resistivity model reveals that the Casey Inlier and Irindina Province are associated with high resistivities (>2000 Dm). In contrast, the Aileron Province, which underlies and surrounds the Irindina Province, is predominantly conductive (resistivities <50 Dm). The Georgina Basin is associated with low resistivities, as would be expected for a sedimentary basin, while the Amadeus Basin is associated with low resistivities in the southern part of the line (where it overlies the Casey Inlier), and higher resistivities further north. Abstract for Australian Exploration Geoscience Conference (AEGC) 18-21 February 2018, Sydney NSW (https://www.aig.org.au/events/first-australian-exploration-geoscience-conference/)

<p>This dataset contains magnetotelluric data and a 3D inversion model from the 09GA-GA1 deep magnetotelluric transect, collected in Central Australia in 2009. The transect is 350 km long, with data acquired from 18 stations with both broadband and long period instrumentation, and 21 stations with broadband instrumentation only (a total of 39 sites). The resulting station spacing is 10km for the broadband stations, and 20km for stations with both broadband and long period instrumentation. We have reprocessed the broadband data using the Bounded Influence, Remote Reference Processing software (BIRRP), yielding an extended bandwidth of 0.003 to 1300 s and merged these data with the long period data. We have inverted the data using the ModEM 3D inversion code. <p>More details on the data processing, analysis, modelling, and interpretation can be found in the following paper: Kirkby, A. and Duan, J., 2019. Crustal Structure of the Eastern Arunta Region, Central Australia, From Magnetotelluric, Seismic, and Magnetic Data. Journal of Geophysical Research: Solid Earth, 124. <a href="https://doi.org/10.1029/2018JB016223">https://doi.org/10.1029/2018JB016223</a>

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/)

The magnetotelluric (MT) method is becoming more widely used in the geoscience community as it becomes increasingly recognised as a useful exploration tool. However, while the analysis and inversion tools available to the MT community have increased over recent years, the software available to work with these tools is still somewhat limited and often costly in comparison to some of the more mature techniques like gravity, magnetics and seismic. The MTpy python library is open source software that aims to assist MT practitioners in carrying out the processing and analysis steps that need to be carried out with MT data and in working with the various inversion codes that are available. However, MTpy still contains coding issues, bugs and gaps in functionality, which have limited its use to date. We are currently developing MTpy to rectify these problems and expand the functionality, and thus facilitate the use of MT as an exploration technique. Key improvements include adding new functions and modules, refactoring the code to give better quality and consistency, fixing bugs and adding new Graphic User Interfaces. Abstract prepared for the Australian Exploration Geoscience Conference (AEGC) 18 -21 February 2018, Sydney, NSW. (https://www.aig.org.au/events/first-australian-exploration-geoscience-conference/)

Long-period magnetotelluric (MT) data allow geoscientists to investigate the link between mineralisation and lithospheric-scale features and processes. In particular, the highly conductive structures imaged by MT data appear to map the pathways of large-scale palaeo-fluid migration, the identification of which is an important element of several mineral system models. Given the importance of these data, governments and academia have united under the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) to collect long-period MT data across the continent on a ~55 km-spaced grid. Here, we use AusLAMP data to demonstrate the MT method as a regional-scale tool to identify and select prospective areas for mineral exploration undercover. We focus on the region between Tennant Creek in the Northern Territory and east of Mount Isa in Queensland. Our results image major conductive structures up to 150 km deep in the lithosphere, such as the Carpentaria Conductivity Anomaly east of Mount Isa. This anomaly is a significant lithospheric-scale conductivity structure that shows spatial correlations with a major suture zone and known iron oxide–copper–gold deposits. Our results also identify similar features in several under-explored areas that are now considered to be prospective for mineral discovery. These observations provide a powerful means of selecting frontier regions for mineral exploration undercover.. <b>Citation:</b> Duan, J., Kyi, D., Jiang, W. and Costelloe, M., 2020. AusLAMP: imaging the Australian lithosphere for resource potential, an example from northern Australia. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

We present a resistivity model of the southern Tasmanides of southeastern Australia using Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) data. Modelled lower crustal conductivity anomalies resemble concentric geometries revealed in the upper crust by potential field and passive seismic data. These geometries are a key part of the crustal architecture predicted by the Lachlan Orocline model for the evolution of the southern Tasmanides, in which the Proterozoic Selwyn Block drives oroclinal rotation against the eastern Gondwana margin during the Silurian period. For the first time, we image these structures in three dimensions (3D) and show they persist below the Moho. These include a lower crustal conductor largely following the northern Selwyn Block margin. Spatial association between lower crustal conductors and both Paleozoic to Cenozoic mafic to intermediate alkaline volcanism and gold deposits suggests a genetic association i.e. fluid flow into the lower crust resulting in the deposition of conductive phases such as hydrogen, iron, sulphides and/or graphite. The 3D model resolves a different pattern of conductors in the lithospheric mantle, including northeast trending anomalies in the northern part of the model. Three of these conductors correspond to Cenozoic leucitite volcanoes along the Cosgrove mantle hotspot track which likely map the metasomatised mantle source region of these volcanoes. The northeasterly alignment of the conductors correlates with variations in the lithosphere-asthenosphere boundary (LAB) and the direction of Australian plate movement, and may be related to movement of an irregular LAB topography over the asthenosphere. By revealing the tectonic architecture of a Phanerozoic orogen and the overprint of more recent tectono-magmatic events, our resistivity model enhances our understanding of the lithospheric architecture and geodynamic processes in southeast Australia, demonstrating the ability of magnetotelluric data to image geological processes over time.

Geoscience Australia’s geomagnetic observatory network covers one-eighth of the Earth. The first Australian geomagnetic observatory was established in Hobart in 1840. This almost continuous 180-year period of magnetic-field monitoring provides an invaluable dataset for scientific research. Geomagnetic storms induce electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and sometimes blackouts in electricity transmission systems. Power outages to business, financial and industrial centres cause major disruption and potentially billions of dollars of economic losses. The intensity of geomagnetically induced currents is closely associated with geological structure. We modelled peak geoelectric field values induced by the 1989 Québec storm for south-eastern Australian states using a scenario analysis. Modelling shows the 3D subsurface geology had a significant impact on the magnitude of induced geoelectric fields, with more than three orders of magnitude difference across conductive basins to resistive cratonic regions in south-eastern Australia. We also estimated geoelectrically induced voltages in the Australian high-voltage power transmission lines by using the scenario analysis results. The geoelectrically induced voltages may exhibit local maxima in the transmission lines at differing times during the course of a magnetic storm depending on the line’s spatial orientation and length with respect to the time-varying inducing field. Real-time forecasting of geomagnetic hazards using Geoscience Australia’s geomagnetic observatory network and magnetotelluric data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) helps develop national strategies and risk assessment procedures to mitigate space weather hazard. This Abstract was submitted/presented to the 2023 Australian Exploration Geoscience Conference 13-18 Mar (https://2023.aegc.com.au/)

Broadband and audio magnetotelluric (BBMT and AMT) data at 476 sites on a 2 Km grid were acquired in the Cloncurry region between July and November 2016. The survey covered an area of appriximatly 40 km x 60 km on the eastern margin of the Mount Isa Province. The Cloncurry magnetotelluric (MT) project was funded by the Geological Survey of Queensland and is a collaborative project between the Geological Survey of Queensland and Geoscience Australia. Geoscience Australia managed the project and peformed data QA/QC, data analysis, and produced two-dimensional (2D) and three dimensional (3D) inverse models for both the BBMT and AMT data. This report details the field acquisition program and the methodologies used for processing, analysing, modelling and inverting the data.

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.

<p>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 datasets have been collected in Northern Australia, as part of Geoscience Australia’s Exploring for the Future (EFTF) program with in-kind contributions from the Northern Territory Geological Survey and the Queensland Geological Survey. <p>This release includes preliminary AusLAMP models in an under-explored region between Tennant Creek in the Northern Territory and Cloncurry in Queensland. Long period magnetotelluric data from 155 sites were used in this model. Magnetotelluric data acquisition in this region continues. The preliminary model results provide new insights to the lithospheric architecture and mineralisation in the region. There is a connection between conductive anomalies, large-scale lithospheric boundaries and the distribution of mineral deposits.