The structural evolution of the South Nicholson region is not well understood, hindering full appraisal of the resource potential across the region. Here, we outline new insights from a recent deep-reflection seismic survey, collected as part of the Australian Government’s Exploring for the Future initiative. The new seismic profiles, and new field observations and geochronology, indicate that the South Nicholson region was characterised by episodic development of a series of ENE-trending half grabens. These graben structures experienced two major episodes of extension, at ca. 1725 Ma and ca. 1640 Ma, broadly correlating with extensional events identified from the Lawn Hill Platform and the Mount Isa Province to the east. Southward stratal thickening of both Calvert and Isa Superbasin sequences (Paleoproterozoic Carrara Range and McNamara groups, respectively) into north-dipping bounding faults is consistent with syndepositional extension during half graben formation. Subsequent basin inversion, and reactivation of the half graben bounding faults as south-verging thrusts, appears to have been episodic. The observed geometry and offset are interpreted as the cumulative effect of multiple tectonic events, including the Isan Orogeny, with thrust movement on faults occurring until at least the Paleozoic Alice Springs Orogeny. <b>Citation:</b> Carson, C.J.. Henson, P.A., Doublier, M.P., Williams, B., Simmons, J., Hutton, L. and Close, D., 2020. Structural evolution of the South Nicholson region: insight from the 2017 L210 reflection seismic survey. 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.

<div>Mount Isa Province in northern Australia is one of the world's most strongly endowed regions for base metals and host to major iron-oxide-copper-gold (IOCG) deposits. The Carpentaria Conductivity Anomaly at the eastern margin of the Province is a major electrical conductivity structure of the Australian continent. We have used magnetotelluric and deep seismic reflection data to image the crustal architecture in this complex region to understand the crustal-scale fluid pathways and potential mineral occurrences. The resistivity models reveal a number of prominent crustal-scale conductors, suggesting that the Carpentaria Conductivity Anomaly is likely caused by a series of isolated or interconnected bodies. These conductors characterise the position and geometry of the ancient Gidyea Suture Zone, interpreted as a west-dipping subduction zone. The conductivity anomaly may record the activity of fluid hydration involved during a subduction event, with the enhanced conductivity likely being caused by deformation or mineralisation of graphitic or sulfidic rocks during orogensis. The distribution of known gold and copper deposits shows a close spatial correlation with the suture zone, suggesting that this structure is potentially a fundamental control on IOCG deposits in its vicinity. The interpretation of the seismic image shows a good correlation with the resistivity models. The implication is that crustal-penetrating structures act as potential pathways for fluid movement to form mineral deposits in the upper crust. The significance of mapping such structures using geophysics is highlighted for mineral exploration.</div><div><br></div>This Abstract was submitted/presented to the 2022 Sub 22 Conference 28-30 November (http://sub22.w.tas.currinda.com/)

The Mesoproterozoic South Nicholson Basin, straddling the NT and QLD border, sits between, and partly overlies, the Paleoproterozoic components of the Mount Isa Province to the east and the southern McArthur Basin to the northwest. While the McArthur Basin and Mount Isa Province are comparatively well studied and considered highly prospective for both mineral and energy resources, rocks of the South Nicholson region are mostly undercover and, as such, there is incomplete understanding of their geological evolution and resource potential. Geoscience Australia (in collaboration with the Northern Territory Geological Survey and the Geological Survey of Queensland, and co-funded by AuScope) undertook the South Nicholson Basin deep crustal seismic reflection survey (e.g. Carr et al., 2019). This survey was conducted under the federally funded Exploring for the Future (EFTF) initiative, a $100.4 million, four year program to evaluate the resource potential across all of northern Australia.

Exploring for the Future (EFTF) is an ongoing multiyear initiative by the Australian Government, conducted by Geoscience Australia, in partnership with state and Northern Territory government agencies and other partner research institutes. The first phase of the EFTF program (2016-2020) aimed to improve Australia’s desirability for industry investment in resource exploration in frontier or ‘greenfield’ regions across northern Australia. As part of the program, Geoscience Australia employed a range of both established and innovative techniques to gather new precompetitive data and information to develop new insight into the energy, mineral and groundwater resource potential across northern Australia. To maximise impact and to stimulate industry exploration activity, Geoscience Australia focussed activities in greenfield areas where understanding of resource potential was limited. In order to address this overarching objective under the EFTF program, Geoscience Australia led acquisition of two deep crustal reflection seismic surveys in the South Nicholson region, an understudied area of little previous seismic data, straddling north-eastern Northern Territory and north-western Queensland. The first survey, L210 South Nicholson 2D Deep Crustal Seismic Survey acquired in 2017, consisted of five overlapping seismic lines (17GA-SN1 to SN5), totalling ~1100 line-km. Survey L210 linked directly into legacy Geoscience Australia seismic lines (06GA-M1 and 06GA-M2) in the vicinity of the world-class Pb-Zn Century Mine in Queensland. The results from survey L210 profoundly revised our geological understanding of the South Nicholson region, and led to the key discovery of an extensive sag basin, the Carrara Sub-basin, containing highly prospective late Paleoproterozoic to Mesoproterozoic rocks with strong affinities with the adjacent Mount Isa Province and Lawn Hill Platform. To complement and expand on the outstanding success of the South Nicholson survey and to continue to explore the resource potential across the underexplored and mostly undercover South Nicholson and Barkly regions, a second seismic survey was acquired in late 2019, the Barkly 2D reflection survey (L212). The Barkly seismic survey comprises five intersecting lines (19GA-B1 to B5), totalling ~813 line-km, extending from the NT-QLD border in the south-east, near Camooweal, to the highly prospective Beetaloo Sub-basin in the north-west. The survey ties into the South Nicholson survey (L210), the recently acquired Camooweal 2D reflection seismic survey by the Geological Survey of Queensland and industry 2D seismic in the Beetaloo Sub-basin, leveraging on and maximising the scientific value and impact on all surveys. The Barkly reflection seismic data images the south-western margin of the Carrara Sub-basin and identified additional previously unrecognised, structurally-disrupted basins of Proterozoic strata, bounded by broadly northeast trending basement highs. Critically, the survey demonstrates the stratigraphic continuity of highly prospective Proterozoic strata from the Beetaloo Sub-basin into these newly discovered, but as yet unevaluated, concealed basins and into the Carrara Sub-basin, further attesting to the regions outstanding potential for mineral and hydrocarbon resources. This survey, in concert with the South Nicholson seismic survey and other complementary EFTF funded regional geochemical, geochronology and geophysical data acquisition surveys, significantly improves our understanding of the geological evolution, basin architecture and the resource potential of this previously sparsely studied region.

<div>Conference abstract on seismic reflector orientation analysis from the Yilgarn Craton (Western Australia):</div> Interpretation of seismic data in hard rock areas is challenging due to lack of direct geological constraints from drilling and the more limited data available typically available from sparse 2-D profiles in comparison to hydrocarbon exploration surveys. Estimates of the 3D orientation of reflectors can help associate specific reflections, or regions of the crust, with geological structures mapped at the surface whose orientation and tectonic history are known. Here we present a method analogous to semblance velocity analysis that utilizes varying source-receiver azimuths to derive continuous estimates of 3-D reflector orientations along onshore 2-D reflection profiles. For each zero-offset time within a common depth point supergather, the semblance is calculated along 3-D travel time curves, and the dip and strike of the most coherent reflection is determined. Relative errors in these angles are derived from the range of travel time curves that have semblance values greater than a specified fraction, for example 90%, of the maximum. The potential of the method is illustrated using a section from line 10GA-YU1 from the Youanmi Terrane of the Yilgarn Craton in Australia in which the original field data have been replaced with synthetic in-line and cross-line reflections. Reflector orientations are generally well recovered where the range of available source-receiver azimuths is greater than 20o, but the method fails at lower ranges where the seismic line is almost linear, a behavior that is also observed in analysis of field data. When this approach is applied to data from the 2019 seismic survey around Kalgoorlie in the Eastern Goldfields, the orientations of both moderately dipping volcanic stratigraphy and faults are recovered. Integration of these local orientation attributes into an interpretation of migrated seismic data requires that the orientations also be migrated. We use a simple approach to the 2-D migration of these attributes that utilises the apparent dip of reflections on the unmigrated stack, and maps reflector strike, for example, to a short linear segment depending on its original position and a migration velocity. Deployment of off-line receivers during future seismic acquisition will allow the recording of a larger range of source-receiver azimuths that can produce more reliable estimates of these reflector attributes than is possible with the limited range of azimuths available from standard 2-D crooked-line acquisition. This Abstract was submitted/presented to the Target 2023 Conference 28 July (https://6ias.org/target2023/)

The Central Darling Basin seismic survey was conducted in 2021 by Coal Innovation NSW (CINSW) in collaboration with Geoscience Australia and the Geological Survey of New South Wales in the Central Darling Basin, north of Wilcannia, NSW. The primary aim of the survey was to contribute structural and other information to identify potential CO2 storage sites in the Pondie Range and Poopelloe Troughs of the Darling Basin. The acquisition and processing of the data was funded by CINSW. Velseis Processing carried out the data processing and Geoscience Australia undertook quality control of the data processing. <b>Data is available on request from clientservices@ga.gov.au - Quote eCat# 146666</b>

Geoscience Australia has undertaken a regional seismic mapping study of the offshore Otway Basin extending across the explored inner basin to the frontier deep-water region. Seismic interpretation covers over 18000 line-km of new and reprocessed data acquired in the 2020 Otway Basin seismic program and over 40000 line-km of legacy 2D seismic data. We present new basin-scale isochore maps that show the distribution of the Cretaceous depocentres. Maps for the Lower Cretaceous Crayfish and Eumeralla supersequences, together with those recently published for the Upper Cretaceous Shipwreck and Sherbrook Supersequences, completes the set of isochore maps for the main tectonostratigraphic basin intervals. Mapping of basement involved faults has revealed structural fabrics that have influenced depocentre development. The tectonostratigraphic development of depocentres and maps of deep crustal units delineate crustal thinning trends related to late Cretaceous extension phases. This work highlights the need to review and update structural elements. For example, the boundary between the Otway and Sorell basins is now geologically constrained. The refinements to the tectonostratigraphic evolution of the Otway Basin presented here have important implications for the distribution and potential maturity of petroleum systems, especially with regard to heat flow associated with crustal extension. Presented at the 2024 Australian Energy Producers Conference & Exhibition (AEP) (https://energyproducersconference.au/conference/)

Following deep seismic reflection surveys on the Yilgarn and Pilbara cratons by Geoscience Australia with the Geological Survey of Western Australia and on the Superior Craton by the Canadian Lithoprobe program, these cratons are now some of the best surveyed Archean regions on Earth. We present seismic images that highlight how variations in crustal architecture relate to differences in Archean tectonic processes between cratons. All cratons are characterized by a mostly non-reflective 4–12 km-thick uppermost crust due to the presence of large granitoid plutons and gneissic domains. Localized regions of upper crustal seismic reflectivity are typically interpreted as supracrustal rocks and mafic sills or faults and shear zones. The middle and lower Archean crust contains variably complex geometries of relatively high amplitude reflections, though in some regions, such as the Eastern Goldfields Superterrane and the Abitibi Greenstone Belt, the lower crust appears less reflective than the middle crust. Crustal thicknesses vary from 30 km in the eastern Pilbara to 35–40 km across much of the Yilgarn and Superior, though thicknesses as great as 45–52 km occur locally in the latter two cratons. The characteristics of the Archean crust-mantle boundary, or Moho, which is commonly well-defined, differs between cratons, indicating significant variations in the tectonic processes that have driven the final stages of crustal evolution. Dipping reflections in the uppermost mantle linked to convergent crustal structures are interpreted as relict subduction scars. In the southern Superior Craton, Moho offsets and northdipping reflections in the middle and lower crust arose through successive underthrusting of Meso-Neoarchean island arcs, oceanic plateaux and microcontinental fragments, as they accreted against a pre-existing northern nucleus (e.g. North Caribou and Opatica terranes). Seismic reflection lines reveal a doubly vergent orogen above north-dipping mantle reflections that indicate subduction drive accretion. Post-orogenic crustal extension, which is inferred from crustal-scale normal shear zones and dropped greenstone belts, has not erased the original accretionary crustal architecture. In contrast, in the Yilgarn Craton interior, accretionary structures are less clear and there are no prominent offsets in the Moho. In the Youanmi Terrane, which represents the cratonic nucleus, a pervasive fabric of listric east-dipping mid-crustal reflections soles out into the upper part of subhorizontal lower crustal reflections. We interpret this reflective fabric to be the result of widespread crustal collapse during the late stage of craton evolution at c. 2.65–2.6 Ga that also produced subsidence of the upper crust. Though terrane boundaries can be identified in seismic data across the Eastern Goldfields Superterrane, these boundaries have commonly been modified by extension, which also overprinted any accretionary lower crustal structures, perhaps simultaneous with widespread intrusion of post-tectonic melts. Exhumation of moderately reflective, amphibolite to granulite facies crust in the Narryer Terrane above dipping mantle reflectors indicates that shortening along the northwestern edge of the Yilgarn Craton was subduction driven. In the eastern Pilbara Craton, shallowly dipping to subhorizontal reflections in the middle and lower crust preclude crustal-scale vertical tectonic movements and imply that the vertical displacements inferred from surface mapping were largely confined to the upper crust. <div>The abstract accompanies a talk the describes the architecture and and related tectonic processes of several Archean cratons based on reflection seismic interpretations. </div> This Abstract was submitted to & presented at the 2023 6th International Archean Symposium (6IAS) 25 - 27 July (https://6ias.org/)

Geoscience Australia commissioned reprocessing of selected legacy 2D seismic data in the Pedirka-Simpson Basin in South Australia-Northern Territory as part of the Exploring for the Future (EFTF) program. 34 Legacy 2D seismic lines from the Pedirka Basin were reprocessed between May 2021 and January 2022 (phase 1). An additional 54 legacy 2D seismic lines (34 lines from Pedirka Basin, South Australia and 20 lines from Simpson Basin, Northern Territory) were reprocessed between November 2021 and June 2022 (phase 2). Geofizyka Toruń S.A. based in Poland carried out the data processing and Geoscience Australia with the help of an external contractor undertook the quality control of the data processing. The seismic data release package contains reprocessed seismic data acquired between 1974 and 2008. In total, the package contains approximately 3,806.9 km of industry 2D reflection seismic data. The seismic surveys include the Beal Hill, 1974; Pilan Hill, 1976; Koomarinna, 1980; Christmas Creek, 1982; Hogarth, 1984; Morphett, 1984; Colson 2D, 1985; Etingimbra, 1985; Fletcher, 1986; Anacoora, 1987; Mitchell, 1987; Bejah, 1987; Simpson Desert, 1979, 1984, 1986, 1987; Forrest, 1988; Eringa Trough, 1994; Amadeus-Pedirka, 2008 and covers areas within the Amadeus Basin, Simpson Basin, Pedirka Basin, Warburton Basin and Cooper Basin in South Australia and Northern Territory. The objective of the seismic reprocessing was to produce a processed 2D land seismic reflection dataset using the latest processing techniques to improve resolution and data quality over legacy processing. In particular, the purpose of the reprocessing was to image the structure and stratigraphic architecture of the Neoproterozoic to Late Palaeozoic Amadeus Basin, Triassic Simpson Basin, Cambrian–Devonian Warburton Basin, Permian–Triassic Pedirka Basin and Cooper Basin. All vintages were processed to DMO stack, Pre-stack Time Migration and Post-Stack Time Migration. <b>Data is available on request from clientservices@ga.gov.au - Quote eCat# 146309</b>

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 a low emissions economy, strong 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. The Darling-Curnamona-Delamerian (DCD) 2D reflection seismic survey was acquired during May to August 2022 in the Delamerian Orogen, the Murray-Darling basin, the Curnamona Province, and the upper Darling River floodplain regions in South Australia, Victoria and New South Wales. This project is a collaboration between Geoscience Australia (GA), the Geological Survey of South Australia (GSSA), the Geological Survey of Victoria (GSV) and the Geological Survey of New South Wales (GSNSW) and was funded by the Australian Government’s Exploring for the Future (EFTF) program. The overall objective of the EFTF Darling-Curnamona-Delamerian project is to improve the understanding of mineral and groundwater resources of the Curnamona Province and Delamerian Orogen and overlying basin systems through acquisition and interpretation of new pre-competitive geoscience data sets. The total length of acquisition was 1256 km distributed over five deep crustal 2D reflection seismic lines 22GA-DL1 (446 km), 22GA-DL2 (249 km), 22GA-CD1 (287 km), 22GA-CD2 (178 km), 22GA-CD3 (39.5 km) to image deep crustal structures, and a high-resolution 2D reflection seismic line 22GA-UDF (56 km) to explore groundwater resources. The DL lines provide coverage of fundamental geophysical data over the Flinders Range, the Delamerian Province and the Murray-Darling basin region in eastern South Australia and Victoria. The CD lines extend through the Curnamona Province and into the Darling Basin. The UDF line will assist with refining the hydrogeological model, understanding groundwater dynamics, and locating areas better suited to groundwater bores for better quality groundwater in the upper Darling River floodplain area. The data processing was performed by a contractor under the supervision of Geoscience Australia. The five deep crustal lines (22GA-DL1,DL2,CD1,CD2,CD3) were processed with record lengths of 20 and 8 seconds, while the shallow high-resolution line (22GA-UDF) was processed at a 4 second length. This processing yielded DMO Stack, Post-Stack Time Migration, and Pre-Stack Time Migration products. <strong>Raw shot gathers and processed gathers for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 147423</strong>