Pearce, J. K.Kirste, D.Dawson, G. W.Rudolph, V.Southam, G.Brink, F.Paterson, D. J.Hall, N.Sommacal, S.Golding, S. D.2025-05-232025-05-230048-9697PubMed:39818151http://www.scopus.com/inward/record.url?scp=85214925606&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733750831The transition to net zero emissions requires the capture of carbon dioxide from industrial point sources, and direct air capture (DAC) from the atmosphere for geological storage. Dissolved CO2 has reactivity to rock core, and while the majority of previous studies have concentrated on reservoir rock or cap-rock reactivity, the underlying seal formation may also react with CO2. Drill core from the underlying seal of a target CO2 storage site was reacted at in situ conditions with pure CO2, and compared with an impure CO2 stream with SO2, NO and O2 that could be expected from hard to abate industries. Argillaceous sandstones, mudstones, coaly mudstones, and carbonate cemented sandstones of the Moolayember Formation, Bowen Basin, had significant natural alteration of feldspar to kaolinite creating porosity, with clays, siderite and textured ankerite filling and rimming porosities of 3.5 to 15.8 %. Synchrotron XFM quantified Mn mainly hosted in siderite veins and cements, Sr and Rb in feldspar, and Pb, Th and Sr in monazite. Pb was also in siderite; with As mainly in pyrite and associated with ankerite. On pure CO2 or impure CO2 reaction, ankerite and siderite dissolution, Fe-chlorite leaching, and apatite or sulphide alteration occurred. With the impure CO2 stream Fe-oxides precipitated on rock surfaces especially in argillaceous sandstone. Ferroan carbonates, calcite, and Fe oxides containing Cr were also precipitated. Ankerite and siderite dissolution released increasing concentrations of dissolved Ca, Mg and Mn from carbonate cemented core that were higher with mixed gas injection. Argillaceous sandstone however released higher concentrations Si, Rb, Co and Zn. Dissolved Fe initially increased then decreased in impure gas experiments via Fe oxide precipitation, and Pb, Ni, Cr, REE also increased and subsequently decreased. Geochemical modelling predicted that Fe was mobilised mainly from reaction of siderite and Fe chlorite. Mainly carbonates (siderite, ankerite) and chlorite dissolution released trace metals, with several metals also initially mobilised by desorption and exchange. Precipitated Fe oxides provided adsorption sites to adsorb a portion of metals from solution. These reactions are also relevant to CO2 streams from DAC that could be expected to contain O2 and to potential reactions in overlying aquifers.The authors wish to acknowledge financial assistance provided through Australian National Low Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Low Emission Technology Australia (LETA) and the Australian Government through the Clean Energy Initiative. Part of this work was funded by ANLEC R&D project 7-1116-0295 . CTSCo Pty Ltd., are thanked for access to West Wandoan 1 well core, data, and constructive discussions. The UQ Environmental Geochemistry laboratory is thanked for analyses. Part of this research was undertaken on the XFM beamline at the Australian Synchrotron, part of ANSTO. This relates to AS183/XFM/13906 \u201CNatural mineral trapping of regulated metals from groundwater by long term CO 2 -fluid-rock interactions\u201D. We acknowledge travel funding provided by the International Synchrotron Access Program (ISAP) managed by the Australian Synchrotron, part of ANSTO, and funded by the Australian Government. The XFM work was supported by the Multi-modal Australian Science Imaging and Visualisation Environment (MASSIVE) ( www.massive.org.au ). We acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy and Microanalysis, The University of Queensland. Two anonymous reviewers are thanked for their comments that improved this manuscript. The authors wish to acknowledge financial assistance provided through Australian National Low Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Low Emission Technology Australia (LETA) and the Australian Government through the Clean Energy Initiative. Part of this work was funded by ANLEC R&D project 7-1116-0295. CTSCo Pty Ltd. are thanked for access to West Wandoan 1 well core, data, and constructive discussions. The UQ Environmental Geochemistry laboratory is thanked for analyses. Part of this research was undertaken on the XFM beamline at the Australian Synchrotron, part of ANSTO. This relates to AS183/XFM/13906 \u201CNatural mineral trapping of regulated metals from groundwater by long term CO2-fluid-rock interactions\u201D. We acknowledge travel funding provided by the International Synchrotron Access Program (ISAP) managed by the Australian Synchrotron, part of ANSTO, and funded by the Australian Government. The XFM work was supported by the Multi-modal Australian Science Imaging and Visualisation Environment (MASSIVE) (www.massive.org.au). We acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy and Microanalysis, The University of Queensland. Two anonymous reviewers are thanked for their comments that improved this manuscript.20en© 2025 The Author(s)Bowen BasinCarbon geological storageGas-water-rockGeochemical reactionMoolayember formation2025-02-0110.1016/j.scitotenv.2025.17839185214925606