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 U–Pb geochronological data, obtained via Sensitive High Resolution Ion Micro Probe (SHRIMP), from 43 samples of predominantly igneous rocks collected from the East Riverina region of the central Lachlan Orogen, New South Wales. The results presented herein correspond to the reporting period July 2016–June 2020. This 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 agreement, to better understand the geological evolution and mineral prospectivity of the central Lachlan Orogen in southern NSW (Bodorkos et al., 2013; 2015; 2016, 2018; Waltenberg et al., 2019).

The Kalkadoon-Leichhardt Domain of the Mount Isa Inlier has been interpreted to represent the ‘basement’ of the larger inlier, onto which many of the younger, economically prospective sedimentary and volcanic units were deposited. The domain itself is dominated by 1860–1850 Ma granitic to volcanic Kalkadoon Supersuite rocks, but these units are interpreted to have been emplaced/erupted onto older units of the Kurbayia Metamorphic Complex. This study aims to provide insights into a number of geological questions: 1. What is the isotopic character of the pre-1860–1850 Ma rocks? 2. How do these vary laterally within the Kalkadoon-Leichhardt Domain? 3. What is the tectonic/stratigraphic relationship between the 1860–1850 Ma rocks of the Mount Isa Inlier and c. 1850 Ma rocks of the Tennant Creek region and Greater McArthur Basin basement? Detrital zircon U–Pb results indicate the presence of 2500 Ma detritus within the Kurbayia Metamorphic Complex, suggesting that the Kalkadoon-Leichhardt Domain was a sedimentary depocentre in the Paleoproterozoic and potentially had sources such as the Pine Creek Orogen, or, as some authors suggest, potential sources from cratons in northern North America. Existing Hf and Nd-isotopic data suggest that the ‘basement’ units of the Mount Isa Inlier have early Proterozoic model ages (TDM) of 2500–2000 Ma. Oxygen and Hf-isotopic studies on samples from this study will allow us to test these models, and provide further insights into the character and history of these ‘basement’ rocks within the Mount Isa Inlier, and northern Australia more broadly.

Zircon U-Pb ages, εHf(t) and δ18O isotopic data, geochemistry and limited Sm-Nd results mostly from deep basement drill cores from undercover parts of the Thomson Orogen, provide strong temporal links with outcropping regions of the orogen as well as important clues for its evolution and relationship with the Lachlan Orogen. SHRIMP U–Pb ages from three Early Ordovician volcanic samples and one granite from the undercover, Thomson Orogen shows that magmatism of this age is widespread across the central, undercover regions of the orogen and occurred in a narrow time-window between 480 Ma and 470 Ma. These rocks have evolved, εHf(t)zrn (-6.26 to -12.18), εNd (-7.1 to -11.3), and supracrustal δ18Ozrn (7.01–8.50‰) which is in stark contrast to the Early Ordovician rocks in the Lachlan Orogen, that are isotopically juvenile. Two samples have latest Silurian to earliest Devonian ages (1586685 DIO Ella 1; 425.4 ± 6.6 Ma and 2122055 Hungerford Granite; 419.1 ± 2.5) and coincide with a major period of intrusive magmatism in the southern Thomson and the Eastern and Central Lachlan Orogen. These samples have evolved εHf(t)zrn (-4.62 to -6.42) and supracrustal δ18Ozrn (9.26–10.29‰) which is similar to Lachlan Orogen rocks emplaced during this time. Four samples have mid Early to early Late Devonian ages (408–382 Ma) and appear to have been emplaced in a generally extensional tectonic regime. Two of these are from the Gumbardo Formation (1682891 PPC Carlow 1 and 1682892 PPC Gumbardo 1), the basal unit of the Adavale Basin, and constrain its opening to between 408 Ma and 403 Ma. The other two samples (1585223 AAE Towerhill 1 and 2122056 Currawinya Granite) have ages of ca. 382 Ma. These latter samples generally show a shift towards more juvenile εHf(t)zrn and mantle-like δ18Ozrn values, a trend that is also seen in rocks of this age in the Lachlan Orogen. Collectively, zircon Hf and O isotopes show that magmatism in the central, undercover part of the Thomson Orogen was initially derived from isotopically evolved magma sources but progressed to more juvenile sources during the Devonian. Furthermore, it appears that samples from the Thomson Orogen may fall along two distinct Hf-O isotopic mixing trends. One trend, appears to have incorporated an older (more evolved) supracrustal component and occurs in the northern two-thirds of the Thomson Orogen, while the other trend is generally less evolved and occurs in the southern third of the Thomson Orogen and is geographically continuous with the Lachlan Orogen. <b>Citation:</b> A. J. Cross, D. J. Purdy, D. C. Champion, D. D. Brown, C. Siégel & R. A. Armstrong (2018) Insights into the evolution of the Thomson Orogen from geochronology, geochemistry, and zircon isotopic studies of magmatic rocks, <i>Australian Journal of Earth Sciences</i>, 65:7-8, 987-1008, DOI: 10.1080/08120099.2018.1515791

This Record presents new Sensitive High Resolution Ion Micro Probe (SHRIMP) U–Pb geochronological results for five drill core samples from the Rover mineral field, an area of prospective Palaeoproterozoic rocks southwest of Tennant Creek that is entirely concealed below younger sedimentary cover rocks. The work is part of an ongoing collaborative effort between Geoscience Australia (GA) and the Northern Territory Geological Survey (NTGS) that aims to develop better understanding of the geological evolution and mineral potential of this region. It is being undertaken as part of the Northern Territory Government’s Resourcing the Territory (RTT) initiative and the Federal Government’s Exploring for the Future (EFTF) program and was carried out under the auspices of the National Collaborative Framework (NCF) between GA and NTGS. The rocks studied were sampled from drill cores acquired under the Northern Territory Government’s Geophysics and Drilling Collaborations program; the drillholes sampled comprise RVDD0002 (Wetherley and Elliston 2019), MXCURD002 (Burke 2015) and R27ARD18 (Anderson 2010). <b>Bibliographic Reference:</b> Cross A, Huston D and Farias P, 2021. Summary of results. Joint NTGS–GA geochronology project: Rover mineral field, Warramunga Province, January–June 2020. <i>Northern Territory Geological Survey</i>, <b>Record 2021-003</b>.

<p>Understanding the geological evolution and resource prospectivity of a region relies heavily on the integration of different geological and geophysical datasets. Geochronology is one key dataset, as it underpins meaningful geological correlations across large regions, and also contributes to reconstruction of past tectonic settings. Using geochronology in combination with other datasets requires the geochronology data to be available in a unified dataset with a consistent format. Northern Australia is a vast and relatively underexplored area that offers enormous potential for the discovery of mineral and energy resources. The area has a long and variably complex tectonic history, which is yet to be fully understood. Numerous geochronology studies have been completed at various scales throughout northern Australia over several decades; however, these data are scattered amongst numerous sources, limiting the ease with which they can be used collectively. <p>The objective of this work is: <p>(1) to combine Uranium–Lead (U–Pb) data across north-northeastern Australia into one consistent dataset, and <p>(2) to visualise the temporal and spatial distribution of the U–Pb age data through thematic maps as a tool for better understanding the geological evolution and resource potential of northern Australia. <p>In this contribution, over 2000 U–Pb ages from the Northern Territory, Queensland, eastern Western Australia and northern South Australia have been compiled into a single, consistent dataset. Data were sourced from Geoscience Australia, State and Territory geological surveys and from academic literature. The compilation presented here includes age data from igneous, metamorphic and sedimentary rocks. Thematic maps of magmatic crystallisation ages, high-grade metamorphic ages and sedimentary maximum depositional ages have been generated using the dataset. These maps enable spatial and temporal trends in the rock record to be visualised up to semi-continental scale and form a component of the ‘Isotopic Atlas’ of northern Australia currently being compiled by Geoscience Australia.

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 presents new Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronological results for samples collected from the Mary Kathleen Domain, which forms the western part of the Eastern Fold Belt in the Mount Isa Inlier. Eight samples, comprising three granites, one quartz diorite, two metarhyolites, one feldspathic quartzite, and one of matrix material from a breccia, have been analysed as part of ongoing investigations by GSQ in collaboration with researchers from James Cook University. The results enable a better understanding of the evolution of the domain, the associated magmatism, and any related mineralisation. <b>Bibliographic Reference:</b> Kositcin, N., Bultitude, R.J., and Purdy, D.J. Summary of Results. Joint GSQ–GA Geochronology Project: Mary Kathleen Domain, Mount Isa Inlier, 2018–2019. <i>Queensland Geological Record</i><b> 2019/02</b>.

This Record presents data collected between March and September 2018 as part of the ongoing Northern Territory Geological Survey–Geoscience Australia (NTGS–GA) SHRIMP geochronology project under the National Collaborative Framework (NCF) agreement and Geoscience Australia's Exploring for the Future Programme. Five new U–Pb SHRIMP zircon geochronological results derived from five samples of meta-igneous and metasedimentary rocks from MOUNT RENNIE (southwestern Aileron Province and northwestern Warumpi Province) in the Northern Territory are presented herein. All five samples are located at or close to the recently discovered greenfield Grapple and Bumblebee prospects that contain precious and base metal sulfide mineralisation. This Record represents the first attempt to provide temporal constraints on the country rocks that host or occur close to this mineralisation. <b>Bibliographic Reference:</b> Kositcin N, McGloin MV, Reno BL and Beyer EE, 2019. Summary of results. Joint NTGS–GA geochronology project: Cu-Au-Ag-Zn mineralisation in MOUNT RENNIE, Aileron and Warumpi provinces, March – September 2018. <i>Northern Territory Geological Survey</i>, <b>Record 2019-011</b>.

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