<p>The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but its poorly constrained post-depositional history has hampered resource exploration and management. The Derim Derim Dolerite occupies an important position in the regional event chronology, having intruded the Roper Group prior to deformation associated with the ‘Post-Roper Inversion’ event. It was assigned a magmatic crystallisation age of 1324 ± 4 Ma (uncertainties are 95% confidence unless otherwise indicated) in 1997, based on unpublished Sensitive High Resolution Ion Micro Probe (SHRIMP) U-Pb analyses of dolerite-hosted baddeleyite from sample 97106010, collected from the Derim Derim Dolerite type locality in outcrop within the northwestern McArthur Basin. Herein, we refine these data via Isotope Dilution-Thermal Ionisation Mass Spectrometry (ID-TIMS) analysis of baddeleyites plucked from the SHRIMP grain-mounts, which yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U-Pb ID-TIMS date of 1313.8 ± 1.3 Ma recently obtained from dolerite ALT-05, sampled in Pacific Oil and Gas Ltd drillhole Altree 2, near the northern margin of the Beetaloo Sub-basin, and 200 km south of 97106010. This pair of results indicates that Derim Derim Dolerite magmatism spanned at least 10-15 Ma. Previously documented geochemical variation in Mesoproterozoic mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma (2σ) Galiwinku Dolerite in the northern McArthur Basin, 1316 ± 40 Ma phonolites intruding the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. <p><b>Citation:</b> Bodorkos, S., Yang, B., Collins, A.S., Crowley, J., Denyszyn, S.W., Claoue-Long, J.C., Anderson, J.R. and Magee, C., 2020 Precise U–Pb baddeleyite dating of the Derim Derim Dolerite: evidence for episodic mafic magmatism in the greater McArthur Basin. 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.

This record presents new Sensitive High Resolution Ion MicroProbe (SHRIMP) U– Pb zircon results for eighteen samples from the Cairns, Cape York and Georgetown regions in Queensland. Samples from the Cairns region comprise one granite and one microgranite. Eight samples from the Cape York region and three from the Georgetown region comprise Paleozoic igneous rocks, all but one of which are part of the Carboniferous to Permian Kennedy Igneous Association. Of particular interest are the results for two rhyolitic intrusions from the Coen Inlier that are host to gold mineralisation and gave ages of approximately 280 Ma. These results are supported by similar ages reported by Kositcin et al. (2016), also from felsic dykes spatially associated with gold mineralisation. Together, they suggest a widespread, early-Permian gold (Kungurian) event in this region. The results for two felsic dykes spatially associated with gold mineralisation much farther to the south in the Georgetown region, also gave similar early-Permian ages. The geochronology of five metamorphic rocks from the Cape York region, which were analysed in support of the Coen–Cape Weymouth geology mapping project has resulted in all samples being reassigned to other formations. The work contained in this report was carried out under the auspices of the National Collaborative Framework (NCF) between Geoscience Australia and the Geological Survey of Queensland. The data and age interpretations are also available in Geoscience Australia’s Geochronology Delivery database (http://www.ga.gov.au/geochron-sapub-web/). <b>Bibliographic Reference: </b>CROSS, A.J., DHNARAM, C., BULTITUDE, R.J., BROWN, D.D., PURDY, D.J. & VON GNIELINSKI, F.E., 2019. Summary of results. Joint GSQ–GA geochronology project: Cairns, Cape York and Georgetown regions, 2015–2016. <i>Queensland Geological Record</i> <b>2019/01</b>.

New SHRIMP U-Pb zircon ages from the New England Orogen, New South Wales July 2014-June 2015

<div>This Record documents the efforts of Geoscience Australia (GA) in compiling a New South Wales (NSW) Uranium–Lead (U–Pb) geochronology interpreted age compilation (version 1.0), utilising the MinView data from the Geological Survey of New South Wales (GSNSW), GA’s ‘in house’ storage of SHRIMP (Sensitive High Resolution Ion Micro Probe) ages, and other disparate publication sources e.g. academic journal articles and university theses. Here we describe both the dataset itself and the process by which it is incorporated into the continental-scale Isotopic Atlas of Australia. This initial release of the NSW geochronology compilation comprises of 1007 U–Pb ages of named and unnamed rock units in NSW.&nbsp;</div><div><br></div><div>The Isotopic Atlas draws together age and isotopic data from across the country and provides visualisations and tools to enable non-experts to extract maximum value from these datasets. Data is added to the Isotopic Atlas in a staged approach with priorities determined by GA- and partner-driven focus regions and research questions. This NSW U–Pb compilation represents the third in a series of compilation publications (Records and Datasets) for the southern states of Australia, which are a foundation for the second phase of the Exploring for the Future initiative over the period 2020–2024. All geochronology compilations in this series of Isotopic Atlas of Australia Records are available online from the Geochronology and Isotopes Data Portal.</div><div><br></div>

This Record contains new zircon U-Pb geochronological data, obtained via Sensitive High-Resolution Ion Micro Probe (SHRIMP), from two samples of metamorphosed felsic igneous rocks of the Proterozoic Pinjarra Orogen (Western Australia), intersected in diamond drillcore at the base of deep petroleum exploration wells penetrating the Paleozoic sedimentary successions of the Perth Basin. In the southern Perth Basin, petroleum exploration well Sue 1 was terminated at depth 3074.2 m, in crystalline basement rocks of the southern Pinjarra Orogen. Abundant zircon from a biotite-bearing felsic orthogneiss at depth 3073.2-3073.7 m yielded a complex array of U-Pb isotopic data, indicative of significant post-crystallisation disturbance of the isotopic system. A Discordia regression fitted to the array yielded an upper intercept date of 1076 ± 35 Ma (all quoted uncertainties are 95% confidence intervals unless specified otherwise) interpreted to represent magmatic crystallisation of the igneous precursor to the orthogneiss, and a lower intercept date of 680 ± 110 Ma which is our best estimate of the age of the tectonothermal event responsible for post-crystallisation disturbance of the U-Pb system. Crust of known Mesoproterozoic age is rare in the southern Pinjarra Orogen: pre-1000 Ma igneous crystallisation ages in the Leeuwin Complex were previously known only from two c. 1090 Ma garnet-bearing orthogneisses at Redgate Beach (Nelson, 1999), 30 km west of Sue 1. All other dated outcrops have revealed Neoproterozoic (780-680 Ma) granitic protoliths reworked by Early Cambrian (540-520 Ma) magmatism, deformation and metamorphism (Nelson, 1996, 2002; Collins, 2003). In the northern Perth Basin, petroleum exploration well Beagle Ridge 10A was terminated at depth 1482 m, in crystalline basement rocks of the northern Pinjarra Orogen. A leucocratic orthogneiss sampled within the interval 1464.0-1467.0 m yielded only sparse zircon, but four of the seven grains analysed yielded a weighted mean 207Pb/206Pb date of 1092 ± 27 Ma, interpreted to represent magmatic crystallisation of the igneous precursor to the orthogneiss. Our data show no evidence for Neoproterozoic U-Pb resetting of the c. 1090 Ma zircons: where present, post-crystallisation isotopic disturbance is predominantly geologically recent. The two newly dated samples are located at opposite ends of the Perth Basin (about 470 km apart), and although the two magmatic crystallisation ages are imprecise, the date of 1092 ± 27 Ma from the Beagle Ridge 10A leucocratic orthogneiss is indistinguishable from the date of 1076 ± 35 Ma from the Sue 1 felsic orthogneiss. Furthermore, both rocks contain inherited zircon of Mesoproterozoic age (1620-1180 Ma in Sue 1; 1290-1210 Ma in Beagle Ridge 10A), indicating the presence of pre-1100 Ma crustal components in their parent magmas. This is consistent with a suite of Paleoproterozoic Sm-Nd model ages determined by Fletcher et al. (1985) on buried Pinjarra Orogen orthogneisses, which span 2.01 ± 0.06 Ga to 1.78 ± 0.04 Ga in the north (near BMR Beagle Ridge 10A), and including a model age of 1.80 ± 0.04 Ga from a sample of granitic gneiss obtained from Sue 1. Fletcher et al. (1985) argued that the consistency of 2.1-1.8 Ga Nd model ages obtained from crystalline basement in drillcore beneath the southern and northern Perth Basin, and from outcrop in the Northampton Complex and Mullingarra Complex of the northern Pinjarra Orogen, indicated a similar or shared crustal evolution. Our new U-Pb zircon data support this model, expanding the known extent of 1100-1050 Ma felsic magmatism in both the southern and northern Pinjarra Orogen, and indicating that Neoproterozoic tectonothermal overprinting appears to be restricted to the Leeuwin Complex, with no corresponding event discernible in the northern Pinjarra Orogen.

This Record presents new zircon U-Pb geochronological data, obtained using a Sensitive High Resolution Ion MicroProbe (SHRIMP) for five samples of plutonic and volcanic rocks from the central Lachlan Orogen and the Thomson Orogen, New South Wales. The work was carried out under the auspices of the National Geoscience Accord, as a component of the collaborative Geochronology Project between the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA) during the reporting periods 2011-2012.

This Record presents new zircon U–Pb geochronological data, obtained via Sensitive High Resolution Ion Microprobe (SHRIMP) for six samples of volcanic and intrusive rocks from the Cobar Basin, NSW. The work is part of an ongoing Geochronology Project, conducted by the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA) under a National Collaborative Framework (NCF) agreement, to better understand the geological evolution and mineralisation history of the Cobar Basin. The results herein correspond to zircon U–Pb SHRIMP analysis undertaken by the GSNSW-GA Geochronology Project during the July 2018 – June 2019 reporting period.

<div>New SHRIMP U-Pb detrital zircon geochronology on Mesoproterozoic and Paleoproterozoic siliciclastic rocks from the South Nicholson region, in concert with recently acquired complementary regional geophysical datasets, has enabled comprehensive revision of the regional Proterozoic tectono-stratigraphy. The identification of analogous detrital zircon spectra between units deposited in half-graben hanging walls of major ENE-WSW trending extensional faults, the Benmara, Bauhinia, and Maloney-Mitchiebo faults, offers compelling evidence for regional tectono-stratigraphic correlation. Units sampled from the hanging walls of these faults are characterised by immature proximal lithofacies and host a small yet persistent population of <em>ca</em> 1640–1650 Ma aged zircon and lack Mesoproterozoic detritus, consistent with deposition coincident with extension during the River Extension event at <em>ca</em> 1640 Ma, an event previously identified from the Lawn Hill Platform in western Queensland. This finding suggests the hanging wall sequences are chrono-stratigraphically equivalent to the highly prospective sedimentary rocks of the Isa Superbasin, host to world-class sediment-hosted base metal deposits across western Queensland and north-eastern Northern Territory. Subsequent inversion of the extensional faults, resulted in development of south-verging thrusts, and exhumation of late Paleoproterozoic hanging wall siliciclastic rocks through overlying Mesoproterozoic South Nicholson Group rocks as fault propagated roll-over anticlines. These geochronology data and interpretations necessitate revision of the stratigraphy and the renaming of a number of stratigraphic units in the South Nicholson region. Accordingly, the distribution of the highly prospective late Paleoproterozoic units of the McArthur Basin, Lawn Hill Platform and Mount Isa Province is greatly expanded across the South Nicholson region. These findings imply that the previously underexplored South Nicholson region is a highly prospective greenfield for energy and mineral resources.</div> <b>Citation:</b> C. J. Carson, N. Kositcin, J. R. Anderson & P. A. Henson (2023) A revised Proterozoic tectono-stratigraphy of the South Nicholson region, Northern Territory, Australia—insights from SHRIMP U–Pb detrital zircon geochronology, <i>Australian Journal of Earth Sciences,</i> DOI: 10.1080/08120099.2023.2264355

Australia's North West Shelf (NW Shelf) has been the premier hydrocarbon exploration and production province for over 30 years. Despite the large number of geological studies completed in this region, numerous geological questions remain to be answered such as the provenance of reservoir units and how this relates to reservoir quality, extent and correlation. Submission of offshore sample material by explorers on the NW Shelf has allowed U-Pb age results to be determined; providing insights into the potential provenance and sedimentary transport pathways of various Triassic to Cretaceous reservoir facies. Initial results reveal that the proximal Pilbara, Yilgarn and Kimberly cratons were not major proto-sources during the Middle to Upper Triassic. The prospective, Mungaroo Formation appears to display a Triassic volcanic signature; the source of which remains enigmatic, but numerous grain characteristics suggest a source proximal to the Exmouth Plateau. Many samples show a Gondwana Assemblage age. Sediment sources of this age are absent on the Australian continent suggesting a distal origin - most likely the Antarctic and Indian blocks. Transport pathways, for the Triassic Mungaroo Formation, are interpreted as possibly northward through a proto-Perth Basin or north-westward through the Gascoyne-Hamersley-Pilbara regions. Other results suggest subtle differences in provenance of the sediments between the Exmouth Plateau and Rankin Platform, and that the provenance signatures of the Bonaparte, Canning and Perth basins show distinctively different provenance signatures.

This Record presents new Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronological results for samples collected from the Mount Isa Inlier and covered areas to the east. The Mary Kathleen Domain is the focus of this work and 11 metasedimentary and igneous samples were analysed from across the distribution of the domain. An additional two metasedimentary samples and one igneous sample from drill cores located east of the outcropping Mount Isa Province were also analysed. <b>Bibliographic Reference: </b>Kositcin, N., Purdy, D.J., Bultitude, R.J., Brown, D.D. & Hoy, D. Summary of Results. Joint GSQ–GA Geochronology Project: Mary Kathleen Domain and rocks under younger cover east of the Mount Isa Inlier, 2019–2020. <i>Queensland Geological Record</i><b> 2021/01</b>.