The Thomson Orogen of eastern Australia is a major component of the Tasmanides and has historically been poorly understood and overlooked for exploration due to extensive sedimentary cover including the Eromanga Basin. To further understanding and encourage exploration of this area, Geoscience Australia, the Geological Survey of Queensland and the Geological Survey of New South Wales (NSW) have undertaken a major multidisciplinary geoscientific programme in the southern Thomson Orogen (STO) as a part of the UNCOVER initiative. A major outcome of this project has been the completion of twelve stratigraphic diamond drill holes between 2016 and 2017. SHRIMP U–Pb zircon dating of magmatic and metasedimentary rocks intersected by the boreholes provide new insights into the geological evolution and mineral prospectivity of this region. Geochronology of three intrusive rocks intersected by new boreholes in the NSW part of STO have late Silurian ages of ~425 Ma (Tongo 1), ~421 Ma (Janina 1) and ~421 Ma (Congararra 1). The age of the granodiorite intersected by Tongo 1 is within uncertainty of the intrusion-related Mo-W and later Au-base metal mineralisation at the Cuttaburra and F1 prospects located ~20 km southeast of the Tongo 1 borehole. Additionally, previously unknown volcanic events have been revealed by a dacitic ignimbrite (~387 Ma) in borehole GSQ Eulo 2 (Queensland) and a rhyolite (~395 Ma) in borehole, Milcarpa 1 (NSW). Detrital zircon geochronology has also played an important role in characterising undercover units such as the Werewilka Formation and Nebine Metamorphics, interpreted from geophysical data sets. This abstract was submitted to and presented at the 2018 Australian Geoscience Council Convention (AGCC) (https://www.agcc.org.au/)

<div>Archean crustal evolution, and its tectonic paradigm, can be directly linked to the evolution of the mantle, the hydrosphere-atmosphere, oxygenation of the Earth, and the formation and storage of ore deposits. Hence, it is vital to understand the evolution of the early crust if we are to understand our planet’s evolution as well as transformational events in its history.</div><div> The collection of vast amounts of isotopic data, especially U-Pb, Sm-Nd, Lu-Hf, and δ18O, over the last 30 years, has significantly advanced our understanding of crustal processes and their timing. However, we rarely look at these data in a spatial context. This study aims to constrain the time-space evolution of the south-east Superior Craton, Canada, by mapping the zircon Hf-O isotopes and trace element data from 148 Archean magmatic rocks (6340 total analyses).</div><div> In Lu-Hf space, the dataset demonstrates the highly juvenile nature of this region, with the majority of values between εHfi +6 and +2. When plotted spatially, the most juvenile data (+4 to +6 εHfi) delineate an E-W oriented zone, broadly in-line and sub-parallel to the Cadillac-Larder Lake and Porcupine-Destor structures. Surrounding this juvenile region is less juvenile crust (0 to +3 εHf). Corresponding δ18O values show that light to mantle-like data (3.0-5.6‰) correlate with the most juvenile crust imaged by the εHf, with heavier δ18O (5.8-7.5‰) plotting to the south, east and west of this zone. Zircon trace element proxies for hydration (Eu/Eu*), oxidation (ΔFMQ using Ti, Ce, U), and continental vs. oceanic origin (Ui/Yb) replicate the pattern observed in the Lu-Hf and δ18O. This suggests that, broadly, the SE Superior consists of a central E-W orientated juvenile zone consisting of the most reduced, least hydrated, least continental, and most high-temperature hydrothermally-altered crust. This zone is surrounded by crust which is more hydrated, oxidised, has a greater supracrustal δ18O component, and is slightly less juvenile. The major ore systems of the Abitibi subprovince, including VMS, gold and komatiite-hosted Ni-Cu-PGE systems, fall within the E-W highly-juvenile zone.</div><div> Current tectonic models for this region of the Superior Craton range from (1) long-lived Neoarchean subduction across the whole Abitibi tectono-thermal ‘event’ (2750-<2695 Ma) – ‘horizontal’ tectonics; and (2) a variety of non-arc processes such as plume-related crustal overthickening (i.e., oceanic plateau), sagduction/drip tectonics, and subcretion, amongst others – ‘vertical’ tectonics. Models combining arc and non-arc processes have also been suggested (i.e., plume-arc interaction), and our data broadly support a combined model. We propose the E-W zone delineated by the various geochemical data represents a paleo-rift zone, driven by ambient mantle or mantle plume processes. The dry, reduced, oceanic character of the zone appears to preclude an arc or back-arc setting prior to ca. 2.7 Ga. However, temporal changes in hydration, oxidation, and the increased heavy δ18O component at ca. 2.7 Ga suggest a major geodynamic shift, potentially marking the onset of subduction and associated compression. This is contribution 2020-050 of the Mineral Exploration Research Centre (MERC) Metal Earth project.</div><div> This Abstract was submitted/presented to the 2023 6th International Archean Symposium (6IAS) 25 - 27 July (https://6ias.org/)

<div>Lithospheric and crustal architecture — the framework of major tectonic blocks, terranes and their boundaries — represents a fundamental first-order control on major geological systems, including the location of world-class mineral camps. Traditionally, lithospheric and crustal architecture are constrained using predominantly geophysical methods. However, Champion and Cassidy (2007) pioneered the use of regional Sm–Nd isotopic data from felsic igneous rocks to produce isotopic contour maps of the Yilgarn Craton, demonstrating the effectiveness of ‘isotopic mapping’, and the potential to map ‘time-constrained’ crustal architecture. Mole et al. (2013) demonstrated the association between lithospheric architecture and mineral systems, highlighting the potential of isotopic mapping as a greenfield area selection tool. Additional work, using Lu-Hf isotopes (Mole et al., 2014), demonstrated that the technique could constrain a range of temporal events via ‘time-slice mapping’, explaining how Ni-Cu-PGE mineralized komatiite systems migrated with the evolving lithospheric boundary of the Yilgarn Craton from 2.9 to 2.7 Ga. Similar studies have since been conducted in West Africa (Parra-Avila et al., 2018), Tibet (Hou et al., 2015), and Canada (Bjorkman, 2017; Mole et al., 2021; 2022). This work continues in Geoscience Australia’s $225 million Exploring for the Future program (2016-present). Isotopic mapping, which forms an integral part of a combined geology-geophysics-geochemistry approach, is currently being applied across southeast Australia, covering the eastern Gawler Craton, Delamerian Orogen, and western Lachlan Orogen, encompassing more than 3 Gyrs of Earth history with demonstrable potential for large mineral systems.</div><div> <b>Reference(s):</b></div><div> Bjorkman, K.E., 2017. 4D crust-mantle evolution of the Western Superior Craton: Implications for Archean granite-greenstone petrogenesis and geodynamics. University of Western Australia, PhD Thesis, 134 pp.</div><div> Champion, D.C. and Cassidy, K.F., 2007. An overview of the Yilgarn Craton and its crustal evolution. In: F.P. Bierlein and C.M. Knox-Robinson (Editors), Proceedings of Geoconferences (WA) Inc. Kalgoorlie '07 Conference. Geoscience Australia Record 2007/14, Kalgoorlie, Western Australia, pp. 8-13.</div><div> Hou, Z., Duan, L., Lu, Y., Zheng, Y., Zhu, D., Yang, Z., Yang, Z., Wang, B., Pei, Y., Zhao, Z. and McCuaig, T.C., 2015. Lithospheric architecture of the Lhasa terrane and its control on ore deposits in the Himalayan-Tibetan orogen. Economic Geology, 110(6): 1541-1575.</div><div> Mole, D.R., Fiorentini, M.L., Cassidy, K.F., Kirkland, C.L., Thebaud, N., McCuaig, T.C., Doublier, M.P., Duuring, P., Romano, S.S., Maas, R., Belousova, E.A., Barnes, S.J. and Miller, J., 2013. Crustal evolution, intra-cratonic architecture and the metallogeny of an Archaean craton. Geological Society, London, Special Publications, 393: pp. 23-80.</div><div> Mole, D.R., Fiorentini, M.L., Thebaud, N., Cassidy, K.F., McCuaig, T.C., Kirkland, C.L., Romano, S.S., Doublier, M.P., Belousova, E.A., Barnes, S.J. and Miller, J., 2014. Archean komatiite volcanism controlled by the evolution of early continents. Proceedings of the National Academy of Sciences, 111(28): 10083-10088.</div><div> Mole, D.R., Thurston, P.C., Marsh, J.H., Stern, R.A., Ayer, J.A., Martin, L.A.J. and Lu, Y., 2021. The formation of Neoarchean continental crust in the south-east Superior Craton by two distinct geodynamic processes. Precambrian Research, 356: 106104.</div><div> Mole, D.R., Frieman, B.M., Thurston, P.C., Marsh, J.H., Jørgensen, T.R.C., Stern, R.A., Martin, L.A.J., Lu, Y.J. and Gibson, H.L., 2022. Crustal architecture of the south-east Superior Craton and controls on mineral systems. Ore Geology Reviews, 148: 105017.</div><div> Parra-Avila, L.A., Belousova, E., Fiorentini, M.L., Eglinger, A., Block, S. and Miller, J., 2018. Zircon Hf and O-isotope constraints on the evolution of the Paleoproterozoic Baoulé-Mossi domain of the southern West African Craton. Precambrian Research, 306: 174-188.</div><div> This Abstract was submitted/presented to the Target 2023 Conference 28 July (https://6ias.org/target2023/)

<div>The Yilgarn Craton of Western Australia represents one of the largest pieces of Precambrian crust on Earth, and a key repository of information on the Meso-Neoarchean period. Understanding the crustal, tectonic, thermal, and chemical evolution of the craton is critical in placing these events into an accurate geological context, as well as developing holistic tectonic models for the Archean Earth. In this study, we collected a large U-Pb (420 collated samples) and Hf isotopic (2163 analyses) dataset on zircon to investigate the evolution of the craton. These data provide strong evidence for a Hadean-Eoarchean origin for the Yilgarn Craton from mafic crust at ca. 4000 Ma. This ancient cratonic nucleus was subsequently rifted, expanded and reworked by successive crustal growth events at ca. 3700 Ma, ca. 3300 Ma, 3000-2900 Ma, 2825-2800 Ma, and ca. 2730-2620 Ma. The <3050 Ma crustal growth events correlate broadly with known komatiite events, and patterns of craton evolution, revealed by Hf isotope time-slice mapping, image the periodic break-up of the Yilgarn proto-continent and the formation of rift-zones between the older crustal blocks. Crustal growth and new magmatic pulses were focused into these zones and at craton margins, resulting in continent growth via internal (rift-enabled) expansion, and peripheral (crustal extraction at craton margins) magmatism. Consequently, we interpret these major geodynamic processes to be analogous to plume-lid tectonics, where the majority of tonalite-trondhjemite-granodiorite (TTG) felsic crust, and later granitic crust, was formed by reworking of hydrated mafic rocks and TTGs, respectively, via a combination of infracrustal and/or drip-tectonic settings. While this process of crust formation and evolution is not necessarily restricted to a specific geodynamic system, we find limited direct evidence that subduction-like processes formed a major tectonic component, aside from re-docking the Narryer Terrane to the craton at ca. 2740 Ma. Overall, these 'rift-expansion' and 'craton margin' crustal growth process led to an intra-cratonic architecture of younger, juvenile terranes located internal and external to older, long-lived, reworked crustal blocks. This framework provided pathways that localized later magmas and fluids, driving the exceptional mineral endowment of the Yilgarn Craton.</div> This Abstract/Poster was submitted to & presented at the 2023 6th International Archean Symposium (6IAS) 25 - 27 July (https://6ias.org/)

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>.

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.

<div>New Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronological results for fifteen Proterozoic and late Paleozoic samples, thirteen from the Georgetown Region and two from the adjacent Cairns Region, are presented in this Record. Eleven of the samples are from cores of basement units intersected in drillholes that penetrated overlying rocks of the Karumba (Cenozoic) and Carpentaria (Mesozoic) basins. Three of these are gneisses from the undercover extension of the Yambo Subprovince (Etheridge Province) in the northeastern part of the Georgetown Region, four are of Mesoproterozoic granites from the Forsayth Subprovince (Etheridge Province) and Croydon Province farther south, and the remaining eight are from units forming part of the Carboniferous–Permian Kennedy Igneous Association, including two from surface outcrops in the Georgetown Region and two from surface outcrops in the adjacent Cairns Region.</div><div><br></div>

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>.

<div>The first ca. 2.2 billion years of Earth history saw significant change; from a water-world dominated by an anoxic atmosphere and tonalitic continents, to the exposed landmasses, oxygenated atmosphere, and granitic crust of the Paleoproterozoic. Precisely when, and how, these major changes occurred, remain some of the most important and controversial questions in modern geoscience. Here, we present an extensive new zircon U-Pb-Hf-O isotopic and trace element dataset from Earth’s largest preserved Archean continent, the Superior Craton, Canada. These data record a number of fundamental geochemical changes through time and indicate a major geological and geodynamic transition occurred toward the end of Archean, at ca. 2.7 Ga. Our data show that, at&nbsp;&gt;2704–2695&nbsp;Ma, the southern Superior Craton had juvenile εHf, light to mantle-like δ18O, low (Eu/Eu*)/Y (drier/shallower crust), reduced ΔFMQ, less continental initial-U (Ui)/Yb, and more mantle-like Ui/Nb. At ca. 2704–2695&nbsp;Ma, there is a marked transition in multiple datasets, including increases in δ18O, (Eu/Eu*)/Y, ΔFMQ, Ui/Yb and Ui/Nb data, together with more distinct arc-like trace element trends. These data reveal that at 2.7 Ga there was an increase in: (1) continental surface weathering, supported by increased sedimentation at &lt;2.68 Ga, (2) oxidized and hydrous magmatism, and (3) surface material in magma sources. Together, these observations suggest a major geodynamic transition from ‘vertical’ tectonics (sagduction, drips) to north-dipping subduction at 2.7 Ga. The increase in δ18O suggests that proximal continental crust, probably in the northern Superior Craton, became emergent at this time, an inference supported by detrital zircon geochronology. Hence, this dataset links major geodynamic change to the emergence of continental crust and the rise of more oxidized magmatism. These fundamental changes to the Earth’s surface environment, tectonics, and atmosphere at 2.7 Ga, provide evidence for an Earth systems turning-point at the end of the Neoarchean.</div> This Abstract was submitted/presented to the 2022 Specialist Group in Geochemistry, Mineralogy and Petrology (SGGMP) Conference 7-11 November (https://gsasggmp.wixsite.com/home/biennial-conference-2021)

<div>This record presents nine new zircon and titanite U–Pb geochronological data, obtained via Sensitive High Resolution Ion Microprobe (SHRIMP) for seven samples of plutonic rocks from the Lachlan Orogen and the Cobar Basin, plus one garnet-bearing skarn vein from the Cobar region. Many of these new ages improve existing constraints on the timing of mineralisation in the Cobar Basin, as 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 Collaboration Framework (NCF) agreement. The results herein (summarised in Table 1.1) correspond to zircon and titanite U–Pb SHRIMP analysis undertaken on GSNSW Mineral Systems projects over July 2017–June 2019.</div><div><br></div><div>Our new data establish an episode of c. 427–425 Ma I-type plutonism, coeval with regional S-type granites, which marginally predated opening of the Cobar Basin. Widespread S-type and high-level I-type magmatism accompanied 423–417 Ma basin development. At least two episodes of skarn-related mineralisation are recognised in the southern Cobar Basin: c. 387 Ma (from pre-mineralisation skarn veins) at Kershaws prospect, and c. 403 Ma at the adjacent Hera mine (Fitzherbert et al., 2021).</div><div><br></div><div>Three intrusive rocks were dated at the Norma Vale prospect in the southwestern Cobar Basin, where calcic iron-copper skarn mineralisation is thought to have been caused by I-type but compositionally complex high-level intrusive rocks emplaced along a northeast-oriented fault related to the nearby Rookery Fault (Fitzherbert et al., 2017). A 423 ± 8 Ma I-type quartz diorite potentially constrains the timing of skarn mineralisation, but is indistinguishable in age from a 421.3 ± 3.0 Ma S-type cordierite-biotite granite and a 417.5 ± 3.3 Ma coarse-grained S-type granite, both from deeper in the same drillhole. These results suggest that at least some of the coeval S-type and high-level I-type magmatic activity accompanying opening of the Cobar Basin was associated with early mineralisation, although skarn-forming processes regionally are complex and episodic (Fitzherbert et al., 2021).</div><div><br></div><div>In the Cobar mining belt, our new date of 422.8 ± 2.8 Ma for I-type rhyolitic porphyry at Carissa Shaft (which is one of the southernmost high-level intrusions associated with the Perseverance and Queen Bee orebodies) is coeval with the 423.2 ± 3.5 Ma ‘Peak rhyolite’ (Black, 2007), but marginally older than the 417.6 ± 3.0 Ma Queen Bee Porphyry (Black, 2005). At Gindoono, a 423.0&nbsp;±&nbsp;2.6&nbsp;Ma unnamed dacitic porphyry intruded and hornfelsed the undated I-type Majuba Volcanics, thereby establishing a minimum age for that unit.</div><div><br></div><div>East of Cobar, the I-type Wild Wave Granodiorite intruded the Ordovician Girilambone Group, but was exhumed and eroded to form clasts within pebble conglomerates of the lowermost Cobar Basin. Its new U–Pb SHRIMP zircon age of 424.1 ± 2.8 Ma constrains the timing of I-type plutonism which marginally predated formation of the Cobar Basin. A similar zircon age of 426.7 ± 2.3 Ma was obtained from the concealed Fountaindale Granodiorite north of Condoblin, indicating that this I-type pluton is coeval with the nearby and much larger c. 427 Ma S-type Erimeran Granite. Titanite from the same sample of Fountaindale Granodiorite yielded an age of 421.6 ± 2.7 Ma, which is significantly younger than the zircon age, and is interpreted to constrain the timing of ‘deuteric’ (chlorite-albite-epidote-titanite-sericite-carbonate) alteration during post-magmatic hydrothermal activity (e.g. Blevin, 2003b).</div><div><br></div><div>A garnet-bearing skarn vein at Kershaws prospect, adjacent to the Hera orebody (Fitzherbert et al., 2021), predates the main phase of mineralisation, and yielded a titanite age of 387.2 ±&nbsp;6.2&nbsp;Ma. This indicates that the skarn-forming hydrothermal event at Kershaws prospect is significantly younger than the c. 403 Ma age for the main mineralising event at Hera mine (Fitzherbert et al., 2021).</div>