In recent years, the application of passive seismic imaging techniques has gained significant traction in the industry and national programs, despite its long-standing utilization in academia. During this talk, we will highlight several innovative techniques that our team has developed and successfully implemented in a scalable and efficient manner. These techniques have proven instrumental in identifying fundamental structures within the Earth's subsurface, providing valuable insights previously untapped by conventional methods. Join us as we delve into the transformative potential of passive seismic imaging and its emerging role in advancing our understanding of Earth's 3D structure.

Cratonic margins host many of the natural resources upon which our society depends. Despite this, little is known about the dynamic evolution of these regions and the stability of substantial steps in plate thickness that delineate their boundaries with adjacent mantle. Here, we investigate the spatio-temporal evolution of Australian cratonic lithosphere and underlying asthenospheric mantle by using the geochemical composition of mafic volcanic or shallow intrusive rocks preserved throughout the continent’s history. We have collated a large database of mafic samples that were screened to remove data affected by crystal fractionation or assimilation of cumulate material. We use forward and inverse modelling of igneous trace element compositions to calculate the depth and extent of melting for 28 distinct igneous provinces in the North Australian Craton. These results are used to infer mantle potential temperature and lithospheric thickness at the time of eruption. The majority of Paleoproterozoic magmatic events record high mantle potential temperatures of 1350–1450 °C and relatively low lithospheric thicknesses of ≤50 km. In contrast, younger igneous provinces show a gradual decrease in potential temperature and an increase in lithospheric thickness with time. These constraints on the mantle lay the foundation for the development of a quantitative geodynamic understanding of the evolution of the Australian lithosphere and its resources. <b>Citation:</b> Klöcking, M., Czarnota, K., Champion, D.C., Jaques, A.L. and Davies, D. R., 2020. Mapping the cover in northern Australia: towards a unified national 3D geological model. 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.

There is a growing recognition that lithospheric structure places first-order controls on the distribution of resources within the upper crust. While this structure is increasingly imaged using geophysical techniques, there is a paucity of geological constraints on its morphology and temporal evolution. Cenozoic intraplate volcanic rocks along Australia’s eastern seaboard provide a significant opportunity to constrain mantle conditions at the time of their emplacement and thereby benchmark geophysical constraints. This volcanic activity is subdivided into two types: age-progressive provinces generated by the passage of mantle plumes beneath the plate; and age-independent provinces, which may arise from edge-driven convection at a lithospheric step. In this study, we collected and analysed 78 igneous rock samples from both types of volcanoes across Queensland. We combined these analyses with previous studies to create and augment a comprehensive database of Australian Cenozoic volcanism. Geochemical modelling techniques were used to estimate mantle temperatures and lithospheric thicknesses beneath each province. Our results show that melting occurred at depths of 45–70 km across eastern Australia. Mantle temperatures are inferred to be ~50–100 °C higher beneath age-progressive provinces than beneath age-independent provinces. These results agree with geophysical observations used to aid resource assessments and indicate that upper mantle temperatures have varied over Cenozoic times. <b>Citation:</b> Ball, P.W., Czarnota, K., White, N.J. and Champion, D.C. 2020. Exploiting Cenozoic volcanic activity to quantify upper mantle structure beneath eastern 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.

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.

The clean energy transition will require a vast increase in metal supply, yet discoveries of new mineral deposits are declining. Recently, several case studies have demonstrated links between electrical conductors imaged using magnetotelluric (MT) data and mineral deposits. Use of MT methods for exploration is therefore growing but the general applicability has not yet been tested. We look at spatial relationships between conductors and three deposit styles and find that volcanic hosted massive sulfide (VHMS) and copper porphyry deposits show weak to moderate correlations with conductors in the upper mantle. In contrast, orogenic gold deposits show strong correlations with mid-crustal conductors. These differences likely reflect differences in the way these deposits form, and suggest a metamorphic-fluid source for orogenic gold is significant. The resistivity signature can be preserved for hundreds of millions of years, and therefore MT can be a powerful tool for mineral exploration.

The North Australian Zinc Belt is the largest zinc–lead province in the world, containing 3 of the 10 largest individual deposits known. Despite this pedigree, exploration in this province during the past two decades has not been particularly successful, yielding only one significant deposit (Teena). One of the most important aspects of exploration is to choose regions or provinces that have greatest potential for discovery. Here, we present results from zinc belts in northern Australia and North America, which highlight previously unused datasets for area selection and targeting at the craton to district scale. Lead isotope mapping using analyses of mineralised material has identified gradients in μ (238U/204Pb) that coincide closely with many major deposits. Locations of these deposits also coincide with a gradient in the depth of the lithosphere–asthenosphere boundary determined from calibrated surface wave tomography models converted to temperature. In Australia, gradients in upward-continued gravity anomalies and a step in Moho depth corresponding to a pre-existing major crustal boundary are also observed. The change from thicker to thinner lithosphere is interpreted to localise prospective basins for zinc–lead and copper–cobalt mineralisation, and to control the gradient in lead isotope and other geophysical data. <b>Citation:</b> Huston, D.L., Champion, D.C., Czarnota, K., Hutchens, M., Hoggard, M., Ware, B., Richards, F., Tessalina, S., Gibson, G.M. and Carr, G., 2020. Lithospheric-scale controls on zinc–lead–silver deposits of the North Australian Zinc Belt: evidence from isotopic and geophysical data. 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.

To improve exploration success undercover, the UNCOVER initiative identified high-resolution 3D seismic velocity characterisation of the Australian plate as a high priority. To achieve this goal, the Australian Government and academia have united around the Australian Passive Seismic Array Project (AusArray). The aim is to obtain a national half-degree data coverage and an updatable 3D national velocity model, which grows in resolution as more data become available. AusArray combines data collected from the Australian National Seismological Network (ANSN), multiple academic transportable arrays (supported by AuScope and individual grants) and the Seismometers in Schools program. The Exploring for the Future program has enable the unification of these datasets and a doubling of the national rate of data acquisition. Extensive quality control checks have been applied across the AusArray dataset to improve the robustness of subsequent tomographic inversion and interpretation. These data and inversion code framework allow robust national-scale imaging of the Earth to be rapidly undertaken at depths of a few metres to hundreds of kilometres. <b>Citation:</b> Gorbatov, A., Czarnota, K., Hejrani, B., Haynes, M., Hassan, R., Medlin, A., Zhao, J., Zhang, F., Salmon, M., Tkalčić, H., Yuan, H., Dentith, M., Rawlinson, N., Reading, A.M., Kennett, B.L.N., Bugden, C. and Costelloe, M., 2020. AusArray: quality passive seismic data to underpin updatable national velocity models of the lithosphere. 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. http://dx.doi.org/10.11636/135284 <b>Data for this product are available on request from clientservices@ga.gov.au (see data description). Last updated 08/08/2024 - Quote eCat# 135284</b>