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).

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>.

Xenotime (YPO4) occurs in a wide range of geological environments, but its potential to establish the timing of mineralisation and sediment diagenesis has been the focus of most recent studies. Xenotime in these settings usually has a low uranium content (typically < 1000 ppm) and occurs as microscopic crystals (< 20 μm diameter), either individually or as outgrowths on a zircon substrate. Large radius ion microprobes, such as the SHRIMP or Cameca 1270/1280, that have high sensitivity and spatial resolution, are well suited for the U–Pb–Th analysis of xenotime from such environments. SIMS U–Pb–Th analyses of xenotime, however, are prone to significant U–Pb–Th matrix effects (ME) that are related to the wide natural range of U (0–6 wt%) and rare earth element (REE) (ΣREE: 12–22 wt%) concentrations in this mineral. For SHRIMP U–Pb–Th xenotime analyses, a 1 wt% increase in U concentration, relative to the U–Pb–Th calibration reference material (RM), will on average cause a corresponding increase in the measured 206Pb/238U and 208Pb/232Th of approximately 15% and 14% respectively. Similarly, a 1 wt% contrast in ΣREE causes an increase of about 1.2% in 206Pb/238U and about 1.7% in 208Pb/232Th. Correction for these chemically-induced matrix effects requires the concurrent analysis of three xenotime reference materials (RMs) which have known ages and a range of U and ΣREE contents that have been determined accurately by electron probe microanalysis (EPMA). A least squares methodology is used to derive correction coefficients that relate the SHRIMP U–Pb–Th ME to the U and ΣREE concentrations for the RMs. Crucial to the success of this technique is the use of one dimensional (1-D) calibrations using 206Pb+/270[UO2]+ and 208Pb+/248[ThO]+. Processing is carried out in two steps: the first derives the correction coefficients to matrix correct the 206Pb+/270[UO2]+ and 208Pb+/248[ThO]+ ratios, the second processes the matrix corrected ratios to determine 206Pb/238U and 208Pb/232Th. <b>Citation:</b> A.J. Cross, I.S. Williams, SHRIMP U–Pb–Th xenotime (YPO4) geochronology: A novel approach for the correction of SIMS matrix effects, <i>Chemical Geology</i>, Volume 484, 2018, Pages 81-108, ISSN 0009-2541, https://doi.org/10.1016/j.chemgeo.2017.12.017.

This record presents new zircon U-Pb geochronological data, obtained via Sensitive High Resolution Ion Microprobe (SHRIMP) for eleven samples of plutonic and volcanic rocks from the Lachlan Orogen, and the New England Orogen. The work is part of an ongoing Geochronology Project (Metals in Time), 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 of New South Wales. The results herein (summarised in Table 1.1 and Table 1.2) correspond to zircon U-Pb SHRIMP analysis undertaken on GSNSW mineral systems projects for the reporting period July 2015-June 2016. Lachlan Orogen In the Lachlan Orogen, the age of 418.9 ± 2.5 Ma for the Babinda Volcanics is consistent with the accepted stratigraphy of its parent Kopyje Group, agrees with the ages of other I-type volcanic rocks within the Canbelego-Mineral Hill Volcanic Belt and indicates eruption and emplacement of this belt during a single event. The age of the Shuttleton Rhyolite Member (421.9 ± 2.7 Ma) of the Amphitheatre Group is compatible with recent U-Pb dating of the Mount Halfway Volcanics, which interfingers with the Amphitheatre Group (MacRae, 1987). The age is also similar to nearby S-type granite intrusions, which suggests that the limited eruptive volcanic activity in the region was accompanied by local coeval plutonism. The results for the Babinda Volcanics and Shuttleton Rhyolite Member, in conjunction with previous GA dating and other dating and studies (summarised in Downes et al., 2016) establishes that significant igneous activity occurred between ~423 and ~418 Ma within the Cobar region but comprised two compositionally distinct but broadly contemporaneous belts of volcanics and comagmatic granite intrusions. The new age for the unnamed quartz monzonite at Hobbs Pipe constrains the maximum age of the hosted gold mineralisation to 414.7 ± 2.6 Ma. The wide range in ages for granites along the Gilmore Suture suggests that mineralisation in this region is not necessarily constrained to a single short-lived event. The new age of 413.5 ± 2.3 Ma for volcanics at Yerranderie indicates that that the Bindook Volcanic Complex was erupted over a relatively short period, and also indicates that the epithermal mineralisation at Yerranderie was not genetically related to the host volcanics but probably to a younger rifting event in the east Lachlan. New England Orogen Four units were dated from the Clarence River Supersuite in the New England Orogen. All four are between 255 and 256 Ma, demonstrating that these granites are related chemically, spatially, and temporally. While these four ages are indistinguishable, the current age span for Clarence River Supersuite is more than 40 million years. This wide age range indicates that classification of granites into the Clarence River Supersuite needs further refinement. The new age for the Newton Boyd Granodiorite (252.8 ± 1.0 Ma) is similar to some previously dated units within the Herries Supersuite, but both the Herries Supersuite and Stanthorpe Supersuite (into which the Herries Supersuite was reclassified by Donchak, 2013) incorporate units with a broad range of ages: the age distribution for the Stanthorpe Supersuite spans 50 million years. Classification of granites in the New England Orogen in New South Wales is worth revisiting. Two units were dated from the Drake Volcanics, nominally in the Wandsworth Volcanic Group and indicate that the middle to upper section of the Drake Volcanics, including the mineralising intrusions, were emplaced within the space of 1-2 million years. These results support a genetic and temporal link between the Au-Ag epithermal mineralisation at White Rock and Red Rock and their host Drake Volcanic packages rather than to younger regional plutonism (i.e., Stanthorpe Supersuite) or volcanism (i.e., Wandsworth Volcanics). The almost 10 Ma gap between the Drake Volcanics and the next lowest units of the Wandsworth Volcanic Group supports the argument for considering the Drake Volcanics a distinct unit.

This Record presents new U-Pb geochronological data, obtained via Sensitive High Resolution Ion Micro Probe (SHRIMP), from six samples of igneous rocks and four samples of sedimentary rocks, collected from south-central New South Wales. 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 of the central Lachlan Orogen in the East Riverina region. The results presented herein correspond to the reporting period July 2015-June 2016.

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.

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 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.

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>.