The magnetotelluric (MT) data were acquired along a total of 690 km of the Youanmi deep seismic reflection traverses 10GA-YU1, 10GA-YU2 and 10GA-YU3-in Western Australia. This was a collaborative project between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA), which provided the funding. The aim of the MT survey was to produce information of the electrical conductivity structure of the crust and upper mantle. This information is complementary to that obtained from deep seismic reflection, gravity, magnetic and geological data, which together provide new knowledge of the crustal architecture, rock properties and geodynamics of the region, important for helping to determine the potential for both mineral and energy resources. Data are supplied as EDI files with support information.

Geoscience Australia is the custodian of the most comprehensive publicly available Australian airborne magnetic, gamma-ray, seismic, electromagnetic and gravity data sets. The airborne geophysics data set contains approximately 34 million line kilometres of data, which, at current prices, would cost approximately $197 million to acquire. The gravity data set contains more than 1.57 million reliable onshore stations gathered during more than 1800 surveys. The collection also includes a large number of seismic surveys from Australia's offshore basins. The onshore component of this data set was previously approved for RDSI for 8 TB. This proposal extends the collection to 150TB. The data types and access methods for the Offshore and Onshore data are identical Certain holdings are additionally hosted at the NCI (see downloads)

The MTPy Python library is open source software that aims to facilitate processing, analysis, modelling, and inversion of magnetotelluric (MT) data. Until recently, MTpy has contained bugs and gaps in both functionality and documentation, which have limited its use to date. We are developing MTPy to rectify these problems and expand functionality. Key improvements include adding new functions and classes to the modules that handle ModEM inputs and outputs, improving data and model visualization tools, refactoring the code to improve maintainability, quality, and consistency, and developing documentation.

<div><strong>Output Type: </strong>Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short Abstract: </strong>The Australian Lithospheric Architecture Magnetotelluric project (AusLAMP) is a collaborative, national survey that aims to acquire long period magnetotelluric (MT) data at 0.5° spacing (~55 km) across the Australian continent. AusLAMP started in 2013 and is ~51% complete to date. Over the last decade, regional-scale conductivity/resistivity AusLAMP models have been produced following data acquisition campaigns, but a levelled national model has not emerged. Here we present the largest AusLAMP conductivity model incorporating 85% of data acquired to date. The model images the conductivity structure of the Australian lithosphere across most parts of central and eastern Australia, including Tasmania. The resolved resistivity structures broadly conform with identified major geological domains and crustal boundaries but also reveal significant variations within geological provinces, orogens and cratons. There are strong spatial associations between crustal/mantle conductors and copper and gold deposits and carbonatites, which provide further evidence that major lithospheric conductors control the distributions of a range of mineral systems. This new model is a powerful bottom-up approach to inform exploration, particularly in covered and under-explored regions.</div><div><br></div><div><strong>Citation: </strong>Duan J. & Huston D., 2024. AusLAMP - mapping lithospheric architecture and reducing exploration search space in central and eastern Australia. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra. https://doi.org/10.26186/149675</div>

Several narrow, linear, highly electrically conductive zones in the crust have been detected across Australia by geomagnetic deep sounding and magnetotelluric measurements made during the previous 50 years. Three major such conductivity anomalies collectively span Australia from north to south; the Carpentaria anomaly in Queensland and the Flinders and Eyre Peninsula anomalies in South Australia. They do not appear to be electrically connected at present; whether they are related in origin is a subject of further research. Recently, new magnetotelluric data have been acquired across or near to all three zones along deep seismic reflection transects which were designed to investigate crustal architecture and mineral and energy potential. Results from the seismic and MT surveys across the Carpentaria Anomaly suggest that the data are imaging a west-dipping suture forming the eastern margin of the Mount Isa province. The suture is interpreted to be the consequence of subduction and accretion prior to 1850 Ma. The Flinders Anomaly extends in an arcuate belt to the east of Lake Frome in the Curnamona Province to transect the Willyama Supergroup and the southern Flinders Ranges in a south-westerly direction, following structural trends. New magnetotelluric data acquired along two seismic transects has further refined the position and depth of the conductive zone.

Magnetotelluric (MT) measures the natural variations of the Earth' magnetic and electrical (telluric) fields. The Audio-Magnetotelluric method (AMT) samples signal frequencies in the range of 20k Hz down to ~1Hz and provides data pertaining to the upper few kilometres of the Earth' crust. Broadband MT (BBMT) measures frequencies ranging from ~400 Hz down to periods of ~5000 s, providing measures of the conductivity of the crust. AMT and BBMT data were acquired at 138 stations with an interval of 2.5-5.0 km along a 690 km transect extending from Four Ways to Longreach in the South-eastern Mount Isa region. Full-waveform time series data were acquired and processed into frequency-domain transfer functions. Remote reference was applied to eliminate uncorrelated noise. After quality assurance, processed data were exported to industry-standard EDI files containing site info, impedance tensor, apparent resistivity, phase and vertical transfer function.

Geoscience Australia (GA), in partnership with State (SA, NSW, VIC, QLD, WA and TAS) and Northern Territory Geological Surveys, has applied the magnetotelluric (MT) technique to image the resistivity structure of the Australian continent over the last decade. Data have been acquired at nearly 5000 stations across Australia through a national MT survey program and regional MT surveys. Most of the data are available at GA’s website. These data provided valuable information for multi-disciplinary interpretations that incorporate various datasets. This release package includes ArcGIS shape files and Excel files of MT station locations for the completed AusLAMP and regional surveys up to December 2017.

Magnetotelluric survey data acquired in association with the L189 Gawler-Curnamona-Arrowie Deep Crustal Seismic Survey over the Curnamona Province. This survey was funded through the Onshore Energy Security Program. Data was acquired by Quantec Geoscience. Analysis and modelling was undertaken by Geoscience Australia . The aim of the survey was to produce a two-dimensional image of electrical conductivity structure of the crust and upper mantle over the Curnamona Province. This information is complementary to the reflection seismic and gravity data acquired along the 08GA-C1 traverse. Data are supplied as EDI files with support information.

The Coompana Project is a collaborative project between Geoscience Australia (GA) and the Geological Survey of South Australia (GSSA), which aims to provide new precompetitive geological, geophysical and geochemical data in the under-explored Coompana Province in South Australia. The pre-drilling geophysics program was undertaken to assist the drilling process by reducing the uncertainty associated with intersecting the targeted stratigraphy. Firstly, the magnetotellurics (MT) technique was tested at six sites where previous drill holes were located to benchmark the application of MT method with respect to estimating cover thickness in the region. Comparison with drill-hole details indicates that the method is capable of identifying major stratigraphic structures and providing cover thickness estimates with a reasonable accuracy (within 10%). Subsequently, MT data were acquired at eight proposed drilling sites in February 2017. 1D and 2D data modelling were undertaken using different algorithms to improve confidence level. Finally, estimates of the cover thickness with specified uncertainty at proposed drilling sites are produced. This report presents MT data acquisition and processing, data inversion and preliminary interpretation of model results. Limitations and uncertainty associated with the MT technique is discussed.

Magnetotelluric (MT) measures the natural variations of the Earth’ magnetic and electrical (telluric) fields. MT data were collected at forty-three sites in the Coompana region in Apr 2016 and Feb 2017. The instruments used were Phoenix Geophysics equipment including MTU-5A receiver, MTC-150L coils and PE5 electrodes. Time series data were processed into frequency domain using remote reference and Robust Processing scheme. After quality assurance, processed data were exported to industry-standard EDI files. Time series data are available on request from clientservices@ga.gov.au.