Strontium isotopes (87Sr/86Sr) are useful in the earth sciences (e.g., recognising geological provinces, studying geological processes) as well in archaeological (e.g., informing on past human migrations), palaeontological/ecological (e.g., investigating extinct and extant taxa’s dietary range and migrations) and forensic (e.g., validating the origin of drinks and foodstuffs) sciences. Recently, Geoscience Australia and the University of Wollongong have teamed up to determine 87Sr/86Sr ratios in fluvial sediments selected from the low-density National Geochemical Survey of Australia (www.ga.gov.au/ngsa). The initial study targeted the northern parts of the Northern Territory and Queensland in Australia. The samples were taken from a depth of ~60-80 cm depth in floodplain deposits at or near the outlet of large catchments (drainage basins). A coarse grain-size fraction (<2 mm) was air-dried, sieved, milled then digested (hydrofluoric acid + nitric acid followed by aqua regia) to release total strontium. Preliminary results demonstrate a wide range of strontium isotopic values (0.7048 < 87Sr/86Sr < 1.0330) over the survey area, reflecting a large diversity of source rock lithologies, geological processes and bedrock ages. Spatial distribution of 87Sr/86Sr shows coherent (multi-point anomalies and gradients), large-scale (>100 km) patterns that appears to be consistent, in many places, with surface geology, regolith/soil type and/or nearby outcropping bedrock. For instance, the extensive black clay soils of the Barkly Tableland define a >500 km-long northwest-southeast trending low anomaly (87Sr/86Sr < 0.7182). Where carbonate or mafic igneous rocks dominate, a low to moderate strontium isotope signature is observed. In proximity to the outcropping Proterozoic metamorphic provinces of the Tennant, McArthur, Murphy and Mount Isa geological regions, high 87Sr/86Sr values (> 0.7655) are observed. A potential link between mineralisation and elevated 87Sr/86Sr values in these regions needs to be investigated in greater detail. Our results to-date indicate that incorporating soil/regolith strontium isotopes in regional, exploratory geoscience investigations can help identify basement rock types under (shallow) cover, constrain surface processes (e.g., weathering, dispersion), and, potentially, recognise components of mineral systems. Furthermore, the resulting strontium isoscape can also be utilised in archaeological, paleontological and ecological studies that aim to investigate past and modern animal (including humans) dietary habits and migrations.

This Record contains new zircon and monazite U-Pb geochronological data obtained via Sensitive High-Resolution Ion Micro Probe (SHRIMP) from nine samples of volcanic, volcaniclastic and plutonic igneous rocks of the central Lachlan Orogen and the New England Orogen, New South Wales. These data were obtained during the reporting period July 2014-June 2015, under the auspices of the collaborative Geochronology Project between the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA), which is part of the National Collaboration Framework (NCF).

This report presents the results of an elemental and carbon and oxygen isotope chemostratigraphy study on three historic wells; Kidson-1, Willara-1 and Samphire Marsh-1, from the southern Canning Basin, Western Australia. The objective of this study was to correlate the Early to Middle Ordovician sections of the three wells to each other and to wells with existing elemental and carbonate carbon isotope chemostratigraphy data from the Broome Platform, Kidson and Willara sub-basins, and the recently drilled and fully cored stratigraphic Waukarlycarly 1 well from the Waukarlycarly Embayment.

A major concern for regulators and the public with geological storage of CO2 is the potential for the migration of CO2 via a leaky fault or well into potable groundwater supplies. Given sufficient CO2, an immediate effect on groundwater would be a decrease in pH which could lead to accelerated weathering, an increase in alkalinity, release of major and minor ions and heavy metals (particularly Pd, Ni and Cr) as well as CO2 mobilisation of trace organic contaminants. These scenarios potentially occur in a high CO2 leakage event, therefore detection of a small leak, although barely perceptible, could provide an important early warning for a subsequent and more substantial impact. Different approaches are required for the detection and quantification of these low level leaks and are the subject of this paper. A 3 year groundwater survey was recently completed in the Surat Basin, which provided comprehensive water and isotopic analysis of groundwaters together with their exsolved gases. The gases were analysed for composition, -13CCO2, -13CCH4 and -2HCH4. Methane is prevalent in the major Surat Basin aquifers (e.g. Mooga, Gubberamunda and Hutton sandstones) and is invariably associated with a bacterial (methanogenic) carbonate reduction source, evident from its isotopic signature ('13CCH4 ~ -70', '2HCH4 ~ -220'). In addition to methane and low levels of CO2, trace ethane is common. Two neighbouring wells, however, were quite different to the other 85 wells surveyed. Their exsolved gases contained comparatively high ethane, but also C1-C6 hydrocarbons in addition to methane. Methane isotope systematics were significantly different from other groundwater wells completed in the same formation. The -13C of the CO2 was similar to the surrounding groundwater wells, but the relative proportion of CO2 in the gas was significantly higher. Combined, these characteristics are consistent with hydrocarbon biodegradation. There was little difference in the groundwater chemistry for these wells compared to the regional baseline. The study provides a useful analogue study for detection, at various scales, of a leaky well associated with a geological storage site. Compositional and isotopic analysis of exsolved gases from groundwater samples could be used to demonstrate non-equilibrium conditions and intrusion of exogenic CO2. Abstract for the 2013 International Association of Hydrologist Congress, Perth

Australia has been, and continues to be, a leader in isotope geochronology and geochemistry. While new isotopic data is being produced with ever increasing pace and diversity, there is also a rich legacy of existing high-quality age and isotopic data, most of which have been dispersed across a multitude of journal papers, reports and theses. Where compilations of isotopic data exist, they tend to have been undertaken at variable geographic scale, with variable purpose, format, styles, levels of detail and completeness. Consequently, it has been difficult to visualise or interrogate the collective value of age and isotopic data at continental-scale. Age and isotopic patterns at continental scale can provide intriguing insights into the temporal and chemical evolution of the continent (Fraser et al, 2020). As national custodian of geoscience data, Geoscience Australia has addressed this challenge by developing an Isotopic Atlas of Australia, which currently (as of November 2020) consists of national-scale coverages of four widely-used age and isotopic data-types: 4008 U-Pb mineral ages from magmatic, metamorphic and sedimentary rocks 2651 Sm-Nd whole-rock analyses, primarily of granites and felsic volcanics 5696 Lu-Hf (136 samples) and 553 O-isotope (24 samples) analyses of zircon 1522 Pb-Pb analyses of ores and ore-related minerals These isotopic coverages are now freely available as web-services for use and download from the GA Portal. While there is more legacy data to be added, and a never-ending stream of new data constantly emerging, the provision of these national coverages with consistent classification and attribution provides a range of benefits: vastly reduces duplication of effort in compiling bespoke datasets for specific regions or use-cases data density is sufficient to reveal meaningful temporal and spatial patterns a guide to the existence and source of data in areas of interest, and of major data gaps to be addressed in future work facilitates production of thematic maps from subsets of data. For example, a magmatic age map, or K-Ar mica cooling age map sample metadata such as lithology and stratigraphic unit is associated with each isotopic result, allowing for further filtering, subsetting and interpretation. The Isotopic Atlas of Australia will continue to develop via the addition of both new and legacy data to existing coverages, and by the addition of new data coverages from a wider range of isotopic systems and a wider range of geological sample media (e.g. soil, regolith and groundwater).

The purpose of this study was to constrain the processes of Paleoproterozoic crustmantle evolution by investigating the Lu-Hf, Sm-Nd and oxygen isotope systematics of igneous rocks of the Lamboo Province of the Halls Creek and King Leopold Orogens, in the Kimberley region of Western Australia. The specific objectives were to: 1. Ascertain the nature of the source rocks of the granites, and to test whether granite formation involved the reworking of ancient meta-igneous protoliths in an intra-plate environment or complex crust-mantle interaction processes typical of modern plate tectonic settings; 2. Use data from granite-hosted zircons to quantify the proportion of new crust formed during discrete magmatic events, and to link this with the longer-term record of crustal evolution preserved by detrital zircons, and 3. Constrain the tectonic setting of the Lamboo Province, and thus the geodynamic controls on global crustal growth in this key time period.

The Roebuck Basin on Australia’s offshore north-western margin is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the Offshore Energy Studies section. This offshore program is designed to produce pre-competitive information to assist with the evaluation of the hydrocarbon resource potential of the central North West Shelf and facilitate exploration investment in Australia. The recent oil and gas discoveries at Phoenix South 1 (2014), Roc 1 (2015-16), Roc 2 (2016), Phoenix South 2 (2016), Phoenix South 3 (2018), Dorado 1 (2018), Dorado 2 (2019) and Dorado 3 (2019) wells in the Bedout Sub-basin demonstrate the presence of a petroleum system in Lower Triassic strata (Thompson, 2020; Thompson et al., 2015 and 2018). The current study aims to better understand this new petroleum system and establish its extent. As part of this program, a range of organic geochemical analyses were acquired on petroleum fluids from the Roc 1 and Roc 2 wells with these data released in this report.

The National Geochemical Survey of Australia (<a href="http://www.ga.gov.au/ngsa" title="NGSA website" target="_blank">NGSA</a>) is Australia’s only internally consistent, continental-scale <a href="http://dx.doi.org/10.11636/Record.2011.020" title="NGSA geochemical atlas and dataset" target="_blank">geochemical atlas and dataset</a>. The present dataset contains additional mineralogical data obtained on NGSA samples selected from the Darling-Curnamona-Delamerian (<a href="https://www.ga.gov.au/eftf/projects/darling-curnamona-delamerian" title="DCD website" target="_blank">DCD</a>) region of southeastern Australia for the first partial data release of the Heavy Mineral Map of Australia (HMMA) project. The HMMA, a collaborative project between Geoscience Australia and Curtin University underpinned by a pilot project establishing its feasibility, is part of the Australian Government-funded Exploring for the Future (<a href="https://www.ga.gov.au/eftf" title="EFTF website" target="_blank">EFTF</a>) program. The selected 223 NGSA sediment samples fall within the DCD polygon plus an approximately one-degree buffer. The samples were taken on average from 60 to 80 cm depth in floodplain landforms, dried and sieved to a 75-430 µm grainsize fraction, and the contained heavy minerals (HMs; i.e., those with a specific gravity >2.9 g/cm³) were separated by dense fluids and mounted on cylindrical epoxy mounts. After polishing and carbon-coating, the mounts were subjected to automated mineralogical analysis on a TESCAN® Integrated Mineral Analyzer (TIMA). Using scanning electron microscopy and backscatter electron imaging integrated with energy dispersive X-ray analysis, the TIMA identified over 140 different HMs in the DCD area. The dataset, consisting of over 29 million individual mineral grains identified, was quality controlled and validated by an expert team. The data released here can be visualised, explored and downloaded using an online, bespoke mineral network analysis tool (<a href="https://geoscienceaustralia.shinyapps.io/mna4hm/" title="MNA website" target="_blank">MNA</a>) built on a cloud-based platform. Accompanying this report are a data file of TIMA results and a mineralogy vocabulary file. When completed in 2023, it is hoped the HMMA project will positively impact mineral exploration and prospectivity modelling around Australia, as well as have other applications in earth and environmental sciences.

A regional hydrocarbon prospectivity study was undertaken in the onshore Canning Basin in Western Australia as part of the Exploring for the Future (EFTF) program, an Australian Government initiative dedicated to driving investment in resource exploration. As part of this program, significant work has been carried out to deliver new pre-competitive data including new seismic acquisition, drilling of a stratigraphic well, and the geochemical analysis of geological samples recovered from exploration wells. A regional, 872 km long 2D seismic line (18GA-KB1) acquired in 2018 by Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA), images the Kidson Sub-basin of the Canning Basin. In order to provide a test of geological interpretations made from the Kidson seismic survey, a deep stratigraphic well, Barnicarndy 1, was drilled in 2019 in a partnership between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA) in the Barnicarndy Graben, 67 km west of Telfer, in the southwest Canning Basin. Drilling recovered about 2100 m of continuous core from 580 mRT to the driller’s total depth (TD) of 2680.53 mRT. An extensive analytical program was carried out to characterise the lithology, age and depositional environment of these sediments. This data release presents organic geochemical analyses undertaken on rock extracts obtained from cores selected from the Barnicarndy 1 well. The molecular and stable isotope data carbon and hydrogen will be used to understand the type of organic matter being preserved, the depositional facies and thermal maturity of the Lower Ordovician sedimentary rocks penetrated in this well. This information provides complementary information to other datasets including organic petrological and palynological studies.

The Hera Au–Pb–Zn–Ag deposit in the southeastern Cobar Basin of central New South Wales preserves calc-silicate veins/skarn and remnant carbonate/sandstone-hosted skarn within a reduced anchizonal Siluro-Devonian turbidite sequence. The skarn orebody distribution is controlled by a long-lived, basin margin fault system, that has intersected a sedimentary horizon dominated by siliciclastic turbidite, with lesser gritstone and thick sandstone intervals, and rare carbonate-bearing stratigraphy. Foliation (S1) envelopes the orebody and is crosscut by a series of late-stage east–west and north–south trending faults. Skarn at Hera displays mineralogical zonation along strike, from southern spessartine–grossular–biotite–actinolite-rich associations, to central diopside-rich–zoisite–actinolite/tremolite–grossular-bearing associations, through to the northern most tremolite–anorthite-rich (garnet-absent) association in remnant carbonate-rich lithologies and sandstone horizons; the northern lodes also display zonation down dip to garnet present associations at depth. High-T skarn assemblages are pervasively retrogressed to actinolite/tremolite–biotite-rich skarn and this retrograde phase is associated with the main pulse of sulfide mineralisation. The dominant sulfides are high-Fe-Mn sphalerite–galena–non-magnetic high-Fe pyrrhotite–chalcopyrite; pyrite, arsenopyrite and scheelite are locally abundant. The distribution of metals in part mimics the changing gangue mineralogy, with Au concentrated in the southern and lower northern lode systems and broadly inverse concentrations for Ag–Pb–Zn. Stable isotope data (O–H–S) from skarn amphiboles and associated sulfides are consistent with magmatic/basinal water and magmatic sulfur inputs, while hydrosilicates and sulfides from the wall rocks display elevated δD and mixed δ34S consistent with progressive mixing or dilution of original basinal/magmatic waters within the Hera deposit by unexchanged waters typical of low latitude (tropical) meteoritic waters. High precision titanite (U–Pb) and biotite (Ar–Ar) geochronology reveals a manifold orebody commencing with high-T skarn and retrograde Pb–Zn-rich skarn formation at ≥403 Ma, Au–low-Fe sphalerite mineralisation at 403.4 ± 1.1 Ma, foliation development remobilisation or new mineralisation at 390 ± 0.2 Ma followed by thrusting, orebody dismemberment at (384.8 ± 1.1 Ma) and remobilization or new mineralisation at 381.0 ± 2.2 Ma. The polymetallic nature of the Hera orebody is a result of multiple mineralizing events during extension and compression and involving both magmatic and likely basinal fluid/metal sources. <b>Citation:</b> Fitzherbert, Joel A., McKinnon, Adam R., Blevin, Phillip L., Waltenberg, Kathryn., Downes, Peter M., Wall, Corey., Matchan, Erin., Huang Huiqin., The Hera orebody: A complex distal (Au–Zn–Pb–Ag–Cu) skarn in the Cobar Basin of central New South Wales, Australia <i>Resource Geology,</i> Vol 71, Iss 4, pp296-319 <b>2021</b>. DOI: https://doi.org/10.1111/rge.12262