Carbon Capture and Storage (CCS) is a technique for mitigating anthropogenic climate change by separating CO2 from industrial flue gas, transporting it to and storing it in a subsurface geological storage reservoir. The low-salinity (TDS<3 000 mg/L) Jurassic sandstone formations in Australia's Surat Basin have been identified as a potential reservoir system for geological CO2 sequestration. However, given the prevailing use of saline reservoirs in CCS projects elsewhere, limited data are available on CO2-water-rock dynamics during geological sequestration in such low-salinity formations. Here, a combined batch experiment and numerical modelling approach is used to characterise potential CO2-water-rock reaction pathways, to assess potential impacts of CCS on groundwater chemistry, and to identify geochemical tracers of inter- and intra-formational CO2 migration during geological sequestration within the Jurassic sandstones. Mineralogy and physical properties of the prospective reservoir are characterized for 66 core samples from stratigraphic well GSQ Chinchilla 4. Representative samples are reacted with synthetic formation water and high-purity CO2 for up to 27 days at a range of pressures to simulate conditions during carbon sequestration in the Jurassic sandstones. Results show the low formation water salinity, temperature, and mineralization in the reservoirs yield high solubility trapping capacity (1.18 mol/L at 45°C, 100 bar), while the paucity of divalent cations in groundwater and the silicate reservoir matrix result in very low mineral trapping capacity within the footprint of the supercritical CO2 (scCO2) plume. Though alkalinity buffers formation water pH under elevated CO2 pressure, the acidic pH significantly enhances mineral dissolution in reactors with heterogeneous Hutton and Boxvale Sandstone samples. Smaller TDS changes are observed for samples of the mature Precipice Sandstone than for the other formations. Non-radiogenic, regional groundwater-like 87Sr/86Sr values (0.704845 - 0.706600) in batch reactors indicate carbonate and authigenic clay dissolution as the primary reaction pathways regulating solution composition in all formations during carbon sequestration. Slightly higher Sr isotope ratios in felsic samples than in calcitic samples, and dissolved Si concentrations in mature Precipice Sandstone reactors show detrital silicate dissolution to be an ancillary process. Batch reactor degassing at the end of the incubation period was simulated to assess geochemical changes in formation waters during transport away from a scCO2 plume. Model results suggest geological sequestration in the Jurassic sandstone formations would increase regional groundwater alkalinity and redistribute carbonate minerals outside the scCO2 footprint, but is unlikely to result in net mineral trapping of CO2. Several elements are mobilised in concentrations greater than found in regional groundwater, making them viable tracers of CO2 migration. Most notable is cobalt, concentrations of which are significantly elevated regardless of CO2 pressure or sample mineralogy. Experimental results indicate manganese and cadmium concentrations may locally exceed drinking water quality guidelines, but further modelling of intra aquifer mixing is required to quantify the potential risk to regional groundwaters from trace element mobilisation.

<b>IMPORTANT NOTICE: </b>This web service has been deprecated. The Australian Onshore and Offshore Boreholes OGC service at https://services.ga.gov.au/gis/boreholes/ows should now be used for accessing Geoscience Australia borehole data. This is an Open Geospatial Consortium (OGC) web service providing access to a subset of Australian geoscience samples data held by Geoscience Australia. The subset currently relates specifically to Australian Boreholes.

<div>This report contains new whole-rock and isotope (Pb and Sr) geochemical data, associated sample metadata, an assessment of the data’s quality assurance, for 76 samples collected from the Georgina Basin of the East Tennant National Drilling Initiative (NDI) in 2021. The data can be downloaded via the Geoscience Australia EFTF portal (https://portal.ga.gov.au/persona/eftf) or in the files attached with this record (http://pid.geoscience.gov.au/dataset/ga/148954).</div><div><br></div><div>This new geochemistry data release builds on the success of the East Tennant NDI, addressing the data-gap in earlier geochemical sampling of these holes, by providing whole-rock geochemistry (and Pb+Sr isotopes) for the Georgina Basin cover sequence. Improved geochemical characterisation of Georgina Basin geology is valuable from both a hydrogeological and mineral systems perspective. The Georgina Basin extends across much of the Northern Territory and into western Queensland, comprised of Cryogenian to Devonian sediment packages.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div>

A comprehensive geochemical program was carried out on rock samples collected in the NDI Carrara 1 drill hole, the first stratigraphic test of the newly discovered Carrara Sub-basin located in the South Nicholson region of northern Australia. The drill hole recovered continuous core from 284 m to total depth at 1750 m and intersected approximately 1120 m of Proterozoic sedimentary rocks, unconformably overlain by 630 m of Cambrian Georgina Basin carbonate-rich rocks. Total organic carbon (TOC) contents from Rock-Eval pyrolysis highlight the potential for several thick black shales to be a source of petroleum for conventional and unconventional plays. Cambrian rocks contain an organic-rich section with TOC contents of up to 4.7 wt.% and excellent oil-generating potential. The Proterozoic section is overmature for oil generation but mature for gas generation, with potential for generating gas in carbonaceous mudstones showing TOC contents up to 5.5 wt.% between 680 and 725 m depth. A sustained release of methane (up to 2%) recorded during drilling from 1150 to 1500 m suggests potential for an unconventional gas system in the Proterozoic rocks from 950 to 1415 m depth, which exhibit favourable organic richness and thermal maturity. The Proterozoic rocks, which are comparable in age to the sediment-hosted deposits of the Century Mine, contain local occurrences of lead, zinc and copper sulfide minerals providing hints of mineralisation. The combined geochemical results offer the promise of a potential new resource province in northern Australia. <b>Citation:</b> E. Grosjean, A.J.M. Jarrett, C.J. Boreham, L. Wang, L. Johnson, J.M. Hope, P. Ranasinghe, J.J. Brocks, A.H.E. Bailey, G.A. Butcher, C.J. Carson, Resource potential of the Proterozoic–Paleozoic Carrara depocentre, South Nicholson region, Australia: Insights from stratigraphic drilling, <i>Organic Geochemistry</i>, Volume 186, 2023, 104688, ISSN 0146-6380, DOI: https://doi.org/10.1016/j.orggeochem.2023.104688.

<div>The Exploring for the Future (EFTF) program is an Australian government initiative aimed at stimulating investment in resource exploration and development. It operates multiple interconnected projects, such as the Australia’s Resources Framework (ARF), a continental-scale endeavor to enhance understanding of Australia's geology and resource potential. A module of ARF, the Geochemistry for Basin Prospectivity (G4BP), studies Australian basins with prospective base metal mineral systems. </div><div><br></div><div>The current report focuses on the Neoproterozoic segment of the Stuart Shelf region in South Australia, a part of the Adelaide Rift Complex. This research is conducted collaboratively with the Geological Survey of South Australia, examining sediment-hosted copper potential in the rift complex.</div><div><br></div><div>The Adelaide Rift Complex is a geological formation that underwent extensive sedimentation from the Neoproterozoic to early Cambrian, particularly within the rift zone. Stuart Shelf sediments overlay Mesoproterozoic magmatic and Paleoproterozoic metasediment layers. The complex hosts multiple copper deposits, which are usually associated with movement of basinal brines that leach metals from lower basinal layers or rift-related volcanic rocks.</div><div><br></div><div>To improve understanding of the geology of the Stuart Shelf and related copper mineralisation, two primary objectives were set: </div><div><br></div><div>1. Geochemical fingerprinting and baseline data collection: This involves compilation and reanalysis of existing data, along with new data collection aimed at providing comprehensive geochemical data for stratigraphic units within the Stuart Shelf.</div><div><br></div><div>2. Identification of mineral system components: Utilising data from the first objective, this phase aims to identify potential metal and fluid sources and potential sites of metal deposition. </div><div>In conjunction with these efforts, a GA-GSSA geochemical sampling project is underway, tying geochemistry to lithostratigraphic units and facies. The newly acquired geochemical data will be integrated into the overall GSSA-CSIRO project to contribute to a more comprehensive understanding of the sediment-hosted stratabound mineral system.</div><div><br></div>

The Neoproterozoic to Middle Ordovician sediments of the Officer Basin, Australia are difficult to correlate, in part because biostratigraphic studies of acritarchs and stromatolites are localised, isotopic studies are rare, and seismic models are technically challenged by the occurrence of basaltic and halite prone-sections. Hence, the chemostratigraphic framework presented here provides an independent stratigraphic model for the Neoproterozoic to Middle Ordovician sediments of the Officer Basin. A total of six chemostratigraphic mega-sequences have been geochemically defined and assigned to the stratigraphy; these have been further subdivided into twenty-eight chemostratigraphic sequences. The chemostratigraphic zonation has been established upon elemental changes attributed to provenance and climatic variation which can be used for correlation as they convey regional, rather than local, changes in sedimentation. The elemental data reveals that there is lateral variation within the established lithostratigraphy (e.g., within the members of the Observatory Hill and Hussar formations), which is suggestive of localised sediment source input to different areas of the basin. Presented to the 2022 Central Australian Basins Symposium IV (CABS) 29-30 August (https://agentur.eventsair.com/cabsiv/)

As part of the Exploring for the Future (EFTF) program, a chemostratigraphic framework for the Officer Basin was developed that correlates inorganic geochemical sequences between exploration wells. The Officer Basin spans 525,000 km² across Western Australia and South Australia, where it remains an unproven frontier basin which has seen little exploration. The objective of this study was to undertake a bulk rock elemental chemostratigraphy study on ten historic wells in order to better correlate the Neoproterozoic and Cambrian sections. Ten study wells, five from Western Australia and five from South Australia, were selected, and core (241) and cuttings (1,245) samples were acquired from their respective state core libraries. All samples were analysed using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), resulting in quantitative data for 50 elements. The approximate proportions of dolomite, clastics, halite and anhydrite for the samples were derived using stoichiometric geochemical calculations. Halite was identified in some formations based on mud log and wireline data, but was not always preserved in the cuttings samples. This non-detection of halite resulted in poor matches between the wireline gamma ray (GR) and ChemGR profiles for halite-bearing units in some wells (e.g. Dragoon-1, Mulyawara-1, and Yowalga-3). Key element and ratios utilised to subdivide the strata were principally chosen to highlight changes in sediment provenance, climatic, and organic matter changes, as they typically have the best correlation potential over a greater distance. The stratigraphy within the study wells has been subdivided into eight chemostratigraphic mega-sequences referred to as MS1 to MS8, which are further subdivided into a total of twenty-four sequences. Mega-Sequences MS1 to MS4 broadly correspond to the published Neoproterozoic–Cambrian Centralian Supersequences (CS1 to CS4). While overall there is broad agreement between these two schemes, there are also sections where the stratigraphy has been reassigned. For example, within Kutjara-1, the section previously assigned to Centralian Supersequence CS2, and equivalent to the Cryogenian Tapley Hill Formation, is assigned to Mega-Sequence MS3 (not MS2). Within MS4, the lithostratigraphically defined members of the Observatory Hill Formation show some significant variation to the chemostratigraphy, with differences occurring within sequences MS4-S3, MS4-S4 and MS4-S5 (e.g. Birksgate-1; Trainor Echo-1). Mega-Sequence MS6 encompasses the Mount Chandler Sandstone in Trainor Echo-1 in the east and the lithological lateral equivalent Lennis Sandstone in Lungkarta-1/ST1 and Yowalga-1 in the west; however, these two argillaceous sandstones are chemically distinct. Carbonate-containing samples from three wells (Birksgate-1, Yowalga-3, and Giles-1) were analysed for their δ13Ccarb and δ18Ocarb isotope signature using Isotope-Ratio Mass Spectrometry (IRMS), with results from the least altered carbonates being of sufficient quality to attempt preliminary age dating. Comparison of the Officer Basin isotope data to global type sections enabled tentative correlation of the Yowalga-3 carbonates to the Tonian and late Ediacaran, and the Birksgate-1 carbonates to the early Cambrian. The geochemistry analyses from 10 basin-wide wells provide a robust dataset that has been used to confirm which sections correlate within the existing lithostratigraphic and sequence stratigraphic framework. This study also highlights where further work needs to be undertaken to elucidate the spatial and temporal relationships of some Cryogenian and early Cambrian sections across the entire basin, given that rocks of these ages contain both potential source and reservoir rocks for petroleum generation and accumulation.

<b>IMPORTANT NOTICE:</b> This web service has been deprecated. The Australian Onshore and Offshore Boreholes OGC service at https://services.ga.gov.au/gis/boreholes/ows should now be used for accessing Geoscience Australia borehole data. This is an Open Geospatial Consortium (OGC) web service providing access to a subset of Australian geoscience samples data held by Geoscience Australia. The subset currently relates specifically to Australian Boreholes.

Paleoproterozoic arc and backarc assemblages accreted to the south Laurentian margin between 1800 Ma and 1600 Ma, and previously thought to be indigenous to North America, more likely represent fragments of a dismembered marginal sea developed outboard of the formerly opposing Australian-Antarctic plate. Fugitive elements of this arc-backarc system in North America share a common geological record with their left-behind Australia-Antarctic counterparts, including discrete peaks in tectonic and/or magmatic activity at 1780 Ma, 1760 Ma, 1740 Ma, 1710-1705 Ma, 1690-1670 Ma, 1650 Ma and 1620 Ma. Subduction rollback, ocean basin closure and the arrival of Laurentia at the Australian-Antarctic convergent margin first led to arc-continent collision at 1650-1640 Ma and then continent-continent collision by 1620 Ma as the last vestiges of the backarc basin collapsed. Collision induced obduction and transfer of the arc and more outboard parts of the Australian-Antarctic backarc basin onto the Laurentian margin where they remained following later breakup of the Neoproterozoic Rodinia supercontinent. North American felsic rocks generally yield Nd depleted mantle model ages consistent with arc and backarc assemblages built on early Paleoproterozoic Australian crust as opposed to older Archean basement making up the now underlying Wyoming and Superior cratons. Appeared in Lithosphere (2019) 11 (4): 551–559, June 10, 2019.

Manuscript detailing the results of chlorite dissolution experiments conducted at Geoscience Australia.