This Record presents new zircon U-Pb geochronological data, obtained using a Sensitive High Resolution Ion MicroProbe (SHRIMP), and thin section descriptions for four samples of plutonic and sedimentary rocks from the Captains Flat 1:50, 000 special map sheet, Eastern Lachlan 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 2012 and 2013. The four samples (Table 1.1 and Figure 1.1) were collected from CANBERRA (small and large capitals refer to map sheet names in the 1:100 000 and 1:250 000 Topographic Series respectively); one sample from CANBERRA (northcentral CANBERRA), two from MICHELAGO (southcentral CANBERRA) and one from ARALUEN (southcentral CANBERRA).

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

The late Permian Wandsworth Volcanic Group (WVG) in the southern New England Orogen (SNEO) is dominated by a monotonous series of amalgamated rhyodacitic to felsic eruptives, with minor interbedded flows, intrusives and sediments. The area enclosing known exposures of the WVG cover more than 30,000 km2, with a minimum thickness of 2 km. The top of the succession, as well as the vast majority of the pile representing non-welded material, has not been preserved. Field relationships indicate a broadly contemporaneous (though not necessarily genetic) relationship with late Permian granite magmatism, while Triassic plutons (typically in the range 246-243 Ma) intrude the WVG. SHRIMP U-Pb zircon dating indicates ages around 256.4 ± 1.6 Ma for basal units of the WVG, and 254.1 ± 2.2 Ma for the youngest preserved member of the WVG (Dundee Rhyodacite), defining a short period of substantial intermediate to acid eruptive volcanism. The compositionally unevolved Drake Volcanics to the northeast are older (264.4 ± 2.5 Ma) while those at Halls Peak are older still (Early Permian). Granites of the I-type Moonbi and Uralla Supersuites are dominantly 256-251 Ma and thus overlap in timing (and space) with the WVG event. Interestingly, many mineralized leucogranites (e.g. Parlour Mountain, Oban River, Gilgai) which were formerly regarded as Triassic are now established as synchronous with the Moonbi and Uralla Supersuites and the WVG. The age range of eruption of the WVG permitted by the SHRIMP results (~6 Ma) has been further constrained by CA-ID-TIMS U-Pb zircon analysis which yielded oldest and youngest ages of 255.54 ± 0.16 Ma and 253.26 ± 0.15 Ma respectively, indicating a maximum eruptive time range of ~2 Ma for the preserved pile. Our new results coincide with those determined from CA-ID-TIMS dating of tuffs in the Sydney and Gunnedah Basins. WVG exposures at Attunga are exactly (within ~0.1 Ma) coincident with the age of tuffs within the Trinkey Formation located in the Gunnedah Basin to the west, and the Dundee Rhyodacite is similarly closely matched to the thick Awaba Tuff in the Sydney Basin. Notably, much of the late Permian volcanic and plutonic magmatism in the SNEO is restricted to a remarkably small time range, which coincides exactly with the range of ash fall events in the Sydney and Gunnedah Basins, and possibly further afield. This suggests the SNEO, and the WVG in particular, was the dominant source of volcanic material erupted into these adjacent basins. Further, the adjacent basins may provide a more complete record of Permo-Triassic magmatism in the SNEO than currently preserved within the orogen itself.

<div>This Record is the fourth of a series of reports detailing the results of U–Pb dating of samples collected during investigations of the Mary Kathleen Domain and adjacent areas of the Mount Isa Inlier in 2018–19 by the Geological Survey of Queensland and co-workers (Kositcin <em>et al</em>., 2019, 2021, Bodorkos <em>et al</em>., 2020). It presents new Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronological results for five samples collected from the inlier. Two of the samples are from units in the Kalkadoon–Leichhardt Domain and the remaining three from units in the adjacent Mary Kathleen Domain (Figure i). The ages of these units are poorly constrained and various ages have been proposed for most of them by different investigators.</div><div> <b>Bibliographic Reference:</b> Kositcin, N., Bultitude, R. J., Purdy, D. J. 2023. <i>Summary of results. Joint GSQ–GA Geochronology Project: Kalkadoon–Leichhardt and Mary Kathleen Domains, 2018–2020. </i>GSQ Record 2023/04, Geological Survey of Queensland. GA Record 2023/41, Geoscience Australia, Canberra. http://dx.doi.org/10.26186/148600 https://geoscience.data.qld.gov.au/data/report/cr141810

This web service provides access to the Geoscience Australia (GA) ISOTOPE database containing compiled age and isotopic data from a range of published and unpublished (GA and non-GA) sources. The web service includes point layers (WFS, WMS, WMTS) with age and isotopic attribute information from the ISOTOPE database, and raster layers (WMS, WMTS, WCS) comprising the Isotopic Atlas grids which are interpolations of the point located age and isotope data in the ISOTOPE database.

This web service provides access to the Geoscience Australia (GA) ISOTOPE database containing compiled age and isotopic data from a range of published and unpublished (GA and non-GA) sources. The web service includes point layers (WFS, WMS, WMTS) with age and isotopic attribute information from the ISOTOPE database, and raster layers (WMS, WMTS, WCS) comprising the Isotopic Atlas grids which are interpolations of the point located age and isotope data in the ISOTOPE database.

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. This Record presents new U-Pb zircon geochronology from the Loch-Lilly Kars and Lake Wintlow (as described by Clark et al. 2024) Belts of the central Delamerian Orogen (Foden et al., 2020; Gilmore et al., 2023; Mole et al., 2023), performed on Geoscience Australia’s (GA) sensitive high-resolution ion microprobe (SHRIMP). The eight samples presented here (three sedimentary and five igneous rocks; Table i) were collected during Geoscience Australia’s drilling campaign across the region, which consisted of 17 drill-holes (Pitt et al., 2023), using two drilling techniques (coiled-tube rotary and conventional diamond). This work was performed as part of the MinEx CRC National Drilling initiative (NDI) and Geoscience Australia’s Darling-Curnamona-Delamerian project of the Exploring for the Future program (EFTF; <a href="https://www.eftf.ga.gov.au/">https://www.eftf.ga.gov.au/</a>). The primary aims of this drilling were to (1) understand and constrain the geology of the southern Loch-Lilly Kars Belt; and (2) assess whether Cambrian magmatic rocks continued to the south-west in the Lake Wintlow Belt, marking a possible continuation of the Stavely Belt volcanic arc rocks observed in western Victoria (Bowman et al., 2019; Lewis et al., 2016; Lewis et al., 2015; Schofield, 2018; Figure i). As both these regions are covered, this new drilling and the geochronology they allow provide the first constraints on the age of these rock units. In addition, due to the lack of surface correlation and detailed geological mapping, these units currently have no officially-defined stratigraphic nomenclature and remain unnamed. For detailed information on all drill-holes completed as part of the survey, we direct readers to the summary report by Pitt et al. (2023): <a href="https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/148639">eCat 148639</a>.

<p>The Mesoproterozoic South Nicholson Basin (SNB) in northern Australia extends across an area approximately the size of Tasmania. It is flanked by the resource rich Mt Isa Orogen and McArthur Basin. Limited outcrop and a dearth of drilling has hampered understanding of the evolution of the Basin, its relationship to other tectonic elements in northern Australia and its resource potential. The lack of any identified interbedded volcanic rocks within the studied sections has led us to concentrate on an extensive SHRIMP U-Pb detrital zircon geochronology program that so far exceeds 40 samples. In addition, we have undertaken SHRIMP U-Pb geochronology of authigenic xenotime. <p>Detrital zircon U–Pb maximum depositional ages (MDA) for the South Nicholson Group (SNG) are up to 100 My younger than previously reported [1]. The new MDA for the Constance Sandstone is ~1470 Ma and is the youngest so far recorded in the SNB. Additionally, it accords with an MDA for the underlying Crow Formation of ~1483 Ma. SHRIMP U–Pb xenotime analyses of authigenic overgrowths on detrital zircons from the Constance Sandstone gave an age of ~1266 Ma. This new data brackets the deposition of the SNG to between 1470 Ma and ~1266 Ma and provides the first evidence that the SNG is broadly contemporaneous with the 1500–1320 Ma Roper Group of the McArthur Basin. Using Multidimensional Scaling of the detrital age distributions has also added an extra dimension to our evolving understanding of the development of the SNB. <p>[1] Carson (2011) Queensland Geological Record 2011/03.

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 using a Sensitive High Resolution Ion MicroProbe (SHRIMP) for thirty-five samples of plutonic rocks from the New England 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 2012-2014.