Throughout New Zealand, the Torlesse Supergroup forms an extensive Permian to Cretaceous accretionary wedge of rather monotonous, sandstone-dominated turbidites. In contrast to contemporaneous rocks in neighbouring terranes within the accretionary wedge, the turbidites have less intermediate-volcaniclastic compositions, and show more quartzose, continent-derived, plutonic provenances. Petrographic, geochemical, isotopic and detrital mineral age characteristics all indicate that they did not originate at the contemporary Gondwanaland margin in New Zealand, but rather, constitute a suspect terrane (Torlesse Terrane), having sediment sources elsewhere along the margin. This latter subject has been controversial, with sediment sources suggested in Antarctica, southern South America and northeast Australia, but detailed Torlesse detrital mineral (zircon and mica) age data and bulk rock Sr-isotope patterns can be best matched for the most part with Carboniferous, Permian and Triassic sources in the New England Orogen, and the remainder with Cambrian and Ordovician sources in its hinterland.

Amino acid racemization (AAR) dating of the eolianite on Lord Howe Island is used to correlate several disparate successions and provides a geochronological framework that ranges from Holocene to Middle Pleistocene time. The reliability of the AAR data is assessed by analysing multiple samples from individual lithostratigraphic units, checking the stratigraphic order of the D/L ratios and the consistency of the relative extents of racemization for a suite of seven amino acids. Three aminozones are defined on the basis of the extent of racemization of amino acids in land snails (Placostylus bivaricosus) and 'whole-rock' eolianite samples. Aminozone A includes Placostylus from modern soil horizons (e.g. mean D/L-leucine ratio of 0.03±0.01) and whole-rock samples from unconsolidated lagoonal and beach deposits (0.10±0.01-0.07±0.03). Aminozone B includes Placostylus (0.45±0.03) and whole-rock samples from beach (0.48±0.01) and dune (0.45±0.02-0.30±0.02) units of the Neds Beach Formation, deposited during OIS 5. The oldest, Aminozone C, comprises Placostylus recovered from paleosols (0.76±0.02) and whole-rock eolianite samples (0.62±0.00) from the Searles Point Formation, which indicate the formation was likely deposited over several Oxygen Isotope Stages (OIS), during and prior to OIS 7. These data support independent lithostratigraphic interpretations and are in broad agreement with U/Th ages of speleothems from the Searles Point Formation and corals from the Neds Beach Formation, and with several TL ages of dune units in both formations. The AAR data reveal that eolianite deposition extends over a significantly longer time interval than previously appreciated and indicate that the deposition of the large dune units is linked to periods of relatively high sea level.

The development of a regional stratigraphy in Palaeoproterozoic basins within the Tanami region, Northern Australia has been hindered by the difficulty of discriminating sedimentary units and facies across isolated and poorly exposed basins. A regional stratigraphy is important as it provides constraints on sedimentary basin evolution and assists in gold exploration, as mineralisation is more abundant in certain rock formations. Based on geochemistry, five main sedimentary basin events have been identified in the Tanami region, ranging from poorly mixed local sedimentary sources to well mixed distal sources. Within the basins, major gold bearing lithologies are characterised by mafic source indicators: (1) high Cr/Th ratios; (2) low Th/Sc ratios; (3) low (La/Yb)N ratios relative to Post-Archaean Average Shale; (4) Eu anomaly equal to ~1 and, (5) distinctive ranges in initial Nd values, which together define vertical stratigraphic position. Potential future exploration target areas have been identified in the Tanami region at the Cashel and Sunline prospects using these geochemical parameters.

Earth is the only terrestrial planet in the solar system with continents, and hence understanding their evolution is vital to unravelling what makes Earth special – our liquid oceans, oxygenated atmosphere, and ultimately, life. The continental crust is also host to all our mineable mineral deposits, and hence it has played a key role in the establishment of human civilisation. This link between the crust and human development will be even more prominent through the need for critical metals, as our society transitions toward green technologies. In this talk, we will discuss the link between the time-space evolution of the continental crust and the location of major mineral systems. By using isotopic data from micron-scale zircon crystals, we can map the crustal architectures that control the large-scale localisation of numerous mineral provinces. This work demonstrates the intimate link between the evolution of the continents, the understanding of mineral systems, and ultimately our continued evolution as an industrialised society.

Aspects of the tectonic history of Paleo- to Mesoproterozoic Australia are recorded by metasedimentary basins in the Mt Isa, Etheridge Provinces, and Coen Inlier in northern Australia and in the Curnamona Province of southern Australia. These deformed and metamorphosed basins are interpreted to have been deposited in a tectonically-linked system based on similarities in depositional ages and stratigraphy (Giles at al 2002). Neodymium isotope compositions of sediments and felsic volcanics, when combined with U-Pb geochronology, are independent data that are important tools for inferring tectonic setting, palaeogeography and sediment provenance in deformed and metamorphosed terrains.

Exploring for the Future (EFTF) is a four-year (2016-20) geoscience data and information acquisition program that aims to better understand on a regional scale the potential mineral, energy and groundwater resources concealed under cover in northern Australia and parts of South Australia. Hydrogeochemical surveys utilise groundwater as a passive sampling medium to reveal the chemistry of the underlying geology including hidden mineralisation. These surveys also potentially provide input into regional baseline groundwater datasets that can inform environmental monitoring and decision making. Geoscience Australia, as part of the Australian Government’s EFTF program, undertook an extensive groundwater sampling survey in collaboration with the Northern Territory Geological Survey and the Geological Survey of Queensland. During the 2017, 2018 and 2019 dry season, 224 groundwater samples (including field duplicate samples) were collected from 203 pastoral and water supply bores in the Tennant Creek-Mt Isa EFTF focus area of the Northern Territory and Queensland. An additional 38 groundwater samples collected during the 2013 dry season in the Lake Woods region from 35 bores are included in this release as they originate from within the focus area. The area was targeted to evaluate its mineral potential with respect to iron oxide copper-gold, sediment-hosted lead-zinc-silver and Cu-Co, and/or lithium-boron-potash mineral systems, among others. The 2017-2019 surveys were conducted across 21 weeks of fieldwork and sampled groundwater for a comprehensive suite of hydrogeochemical parameters, including isotopes, analysed over subsequent months. The present data release includes information and atlas maps of: 1) sampling sites; 2) physicochemical parameters (EC, pH, Eh, DO and T) of groundwater measured in the field; 3) field measurements of total alkalinity (HCO3-), dissolved sulfide (S2-), and ferrous iron (Fe2+); 4) major cation and anion results; 5) trace element concentrations; 6) isotopic results of water (δ18O and δ2H), DIC (δ13C), dissolved sulfate (δ34S and δ18O), dissolved strontium (87Sr/86Sr), and dissolved lead (204Pb, 206Pb, 207Pb, and 208Pb) isotopes; 7) dissolved hydrocarbon VFAs, BTEX, and methane concentrations, as well as methane isotopes (δ13C and δ2H); and 8) atlas of hydrogeochemical maps representing the spatial distribution of these parameters. Pending analyses include: CFCs and SF6; tritium; Cu isotopes; and noble gas concentrations (Ar, Kr, Xe, Ne, and 4He) and 3He/4He ratio. This data release (current as of July 2021) is the second in a series of staged releases and interpretations from the Northern Australia Hydrogeochemical Survey. It augments and revises the first data release, which it therefore supersedes. Relevant data, information and images are available through the GA website (https://pid.geoscience.gov.au/dataset/ga/133388) and GA’s EFTF portal (https://portal.ga.gov.au/).

This report is published in two volumes; Volume I: Bowen-Surat and Cooper-Eromanga Basins, Volume II: Gippsland, Bass, Otway, Stansbury, McArthur, Amadeus, Adavale, Galilee and Drummond Basins. Following the basin-by-basin analysis of geochemical characteristics of eastern Australia's oils, a selection of oils that best represented the major families of each region were selected. These oils were statistically analysed using a subset of geochemical (OilMod) parameters derived from GC, GC-MS and carbon isotopic analyses. This exercise was intended to display the variability in oil compositions across the whole of the eastern part of the continent. The chemical classification of oils follows closely upon, and verifies the analysis based on, palaeogeography and the supersystem concepts.

The New England Orogen contains a geological record dominated by subduction-related rocks, indicating that the orogen has been part of, or adjacent to, convergent plate margins of eastern Gondwanaland from at least the Cambrian until the end of the Early Cretaceous (~95 Ma). In the late Devonian, the orogen records the change from an island arc setting to an Andean-style convergent continental plate margin (e.g., Flood & Aitchison 1992; Skilbeck and Cawood, 1994). The rock record prior to the Middle Devonian is fragmentary, but the Late Devonian to Carboniferous components of the continental margin magmatic arc, forearc basin and accretionary wedge system are well preserved in the New England Orogen, with the Lachlan Orogen, Thomson Orogen and Drummond Basin to the west being in a backarc setting at this time. This system ended in the Late Carboniferous, with the subduction zone stepping to the east (Cawood, 1984). Nevertheless, until at least the Early Cretaceous, the Australian component of the continental margin of East Gondwanaland faced the Proto-Pacific (Panthalassan) Ocean, and has been interpreted to form part of a subduction-related convergent plate margin (e.g. Powell 1984; Cawood 2005; Glen 2005). Here, we examine aspects of the southern New England Orogen from the Cambrian to the Early Permian to further document the nature of the convergent plate margin over this period of time. We are interested especially in the Tamworth Belt, where the changeover is recorded from the Cambrian-Late Devonian island arc setting, to the development of the Devonian-Carboniferous continental margin in a convergent plate setting, with its well developed forearc basin and accretionary wedge. The island arc component is referred to as the Gamilaroi Terrane by Aitchison and Flood (1995) and Offler and Gamble (2002).

<p>Lu-Hf isotopic analysis of zircon is becoming a common way to characterise the source signature of granite. The data are collected by MC-LA-ICP-MS (multi-collector laser ablation inductively coupled plasma mass spectrometry) as a series of spot analyses on a number of zircons from a single sample. These data are often plotted as spot analyses, and variable significance is attributed to extreme values, and amount of scatter. <p>Lu-Hf data is used to understand the origin of granites, and often a distribution of εHf values is interpreted to derive from heterogeneity in the source or from mixing processes. As with any physical measurement, however, before the data are used to describe geologic processes, care ought to be taken to account for sources of analytical variability. The null hypothesis of any dataset is that there is no difference between measurements that cannot be explained by analytical uncertainty. This null hypothesis must then be disproven using common statistical methods. <p>There are many sources of uncertainty in any analytical method. First is the uncertainty associated with the counting statistics of each analysis. This uncertainty is usually recorded as the SE (standard error) uncertainty attributed to each spot. This uncertainty commonly underestimates the total uncertainty of the population, as it only contains information about the consistency of the measurement within a single analysis. The other source of uncertainty that needs to be characterised is similarity over multiple analyses. This is very difficult to assess in an unknown material, but can be assessed by measuring well-understood reference zircons. <p>Reference materials are characterised by homogeneity in the isotope of interest, and multiple analyses of this material should produce a single statistical population. Where these populations display significant excess scatter, manifested as a MSWD value that far exceeds 1, this means that counting statistics are not the sole source of uncertainty. This can be addressed by expanding the uncertainty on the analyses until the standard zircons form a coherent statistical population. This expansion should then be applied to the unknown zircons to accommodate this ‘spot-to-spot-uncertainty’ or ‘repeatability’ factor. This approach is routinely applied to SHRIMP U-Pb data, and here is similarly applied to Lu-Hf data from granites of the northeast Lachlan Orogen. <p>By applying these uncertainty factors appropriately, it is then possible to assess the homogeneity of unknown materials by calculating weighted means and MSWD factors. The MSWD is a measure of scatter away from a single population (McIntyre et al., 1966; Wendt and Carl, 1991). Where the MSWD is 1, the scatter in data points can be explained solely by analytical means. The higher the MSWD, the less likely it is that the data can be described as a single population. Data which disperses over several εHf units can still be attributed to a single population if the uncertainty envelopes of analyses largely overlap each other. These concepts are illustrated using the data presented in Figure 1. Four out of five of the εHf datasets on zircons from granites form statistically coherent populations (MSWD = 0.69 to 2.4). <p>A high MSWD does not necessarily imply that variation is due to processes occurring during granite formation. Although zircon is a robust mineral, isotopic disturbances are still possible. In the U-Pb system, there is often evidence of post-crystallisation ‘Pb-loss’ which leads to erroneously young apparent U-Pb ages. The Lu-Hf system in zircon is generally thought to be more robust than the U-Pb system, but that does not mean that it is impervious to such effects. In the data set presented in Figure 1, the sample with the most scatter in Lu-Hf (Glenariff Granite, εHf = -0.2 ± 1.5, MSWD = 7.20) is also the sample which had the most rejections in the SHRIMP U-Pb data due to Pb-loss. The subsequent Hf analyses targeted only those grains which fell within the magmatic population (i.e., no observed Pb-loss), but the larger volume excavated by laser Hf analysis means that it is likely that disturbed regions of these grains were incorporated into the measurement. This gives an explanation for the scatter that has nothing to do with geological source characteristics. <p>This line of logic can similarly be applied to all types of multi-spot analyses, including O-isotope analyses. While most of the εHf datasets presented here form coherent populations, the O-isotope data are significantly more scattered (MSWD = 2.8 to 9.4). The analyses on the unknowns scatter much more than on the co-analysed TEMORA2 reference zircon. This implies a source of scatter additional to those described above. In addition to the above described sources of uncertainty, O-isotope analysis by SIMS is also extremely sensitive to topography on the surface of the epoxy into which zircons are mounted (Ickert et al., 2008). O isotopes may also be susceptible to post-formation disturbance and so care should also be taken when interpreting O data, before assigning geological meaning. <p>While it is possible for Lu-Hf and O analyses of zircons in granites to reflect heterogeneous sources and/or complex formation processes, it is important to first exclude other sources of heterogeneity such as analytical sources of uncertainty, and post-formation isotopic disturbances.

The Victoria and Birrindudu Basins of the Victoria River region, NW Northern Territory, represent a pair of stacked unmetamorphosed Palaeoproterozoic to Neoproterozoic basins unconformably overlying low-grade metamorphic basement. SHRIMP U-Pb analysis of detrital zircons provide a basis for lithostratigraphic correlations with other Proterozoic Basins across northern Australia. The Palaeoproterozoic Stirling Sandstone (basal Limbunya Group) is tentatively correlated with the Mount Charles Formation in the Tanami region. The Jasper Gorge Sandstone (basal Auvergne Group) correlates with basal units of the lower Cryogenian Supersequence 1 of the Centralian Superbasin (Heavitree Quartzite and its correlatives). A third correlation, previously proposed elsewhere and further explored here, suggests that the Duerdin Group may correlate with the upper Cryogenian ca. 635 Ma 'Marinoan' glacigenic units of Supersequence 3 of Centralian Superbasin. In particular, the Cryogenian pre-glacigenic Black Point Sandstone Member (basal Duerdin Group) is dominated by detrital zircons with age components characteristic of the Musgrave Complex, implying significant exhumation and erosion of the Musgrave Complex occurred, at least partially, prior to the end of the Cryogenian (<ca. 635 Ma) far earlier than generally thought. The latter two correlations suggest that the Victoria Basin in the Victoria River region represents yet another relic component of the extensive former Centralian Superbasin, at least during Cryogenian time. Sm-Nd whole rock determinations overwhelmingly, and unsurprisingly, are consistent with clastic derivation from the evolved North Australian Craton and, for the Black Point Sandstone Member, from the Musgrave Complex. A relatively juvenile signature ('Ndt ' +1) is observed coincident with aerial volcanism within the Birrindudu Basin at ca. 1640 Ma as has been recently noted in other Australian Palaeoproterozoic terrains.