Browsing by Author "Southam, G"

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    Bioaugmentation with Acidithiobacillus species accelerates mineral weathering and formation of secondary mineral cements for hardpan development in sulfidic Pb-Zn tailings
    (Elsevier, 2021-06) Liu, Y; Wu, S; Southam, G; Chan, TS; Lu, YR; Paterson, DJ; Huang, L
    The development of hardpan caps has great potential in rehabilitating sulfidic and metallic tailings, which may be accelerated by using exogenous Acidithiobacillus species. The present study aims to establish a bioaugmentation process with exogenous Acidithiobacillus species for accelerating the weathering of sulfidic minerals and formation of secondary mineral gels as precursors for hardpan structure development in a microcosm experiment. Exogenous Acidithiobacillus thiooxidans (ATCC 19377) and A. ferrooxidans (DSM 14882) were inoculated in a sulfidic Pb-Zn tailing containing negligible indigenous Acidithiobacillus species for accelerating the weathering of pyrite and metal sulfides. Microspectroscopic analysis revealed that the weathering of pyrite and biotite-like minerals was rapidly accelerated by exogenous Acidithiobacillus species, leading to the formation of secondary jarosite-like mineral gels and cemented profile in the tailings. Meanwhile, approximately 28% Zn liberated from Zn-rich minerals undergoing weathering was observed to be re-immobilized by Fe-rich secondary minerals such as jarosite-like mineral. Moreover, Pb-bearing minerals mostly remained undissolved, but approximately 30% Pb was immobilized by secondary Fe-rich minerals. The present findings revealed the critical role of exogenous Acidithiobacillus species in accelerating the precursory process of mineral weathering and secondary mineral formation for hardpan structure development in sulfidic Pb-Zn tailings. © 2020 Elsevier B.V.
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    Cooper Basin REM gas shales after CO2 storage or acid reactions: metal mobilisation and methane accessible pore changes
    (Elsevier, 2023-05-15) Pearce, JK; Blach, T; Dawson, GKW; Southam, G; Paterson, DJ; Golding, SD; Bahadur, J; Melnichenko, YB; Rudolph, V
    Shale - water - CO2 reactions may occur during CO2 geological storage, enhanced gas recovery, enhanced oil recovery, or supercritical CO2 fracturing. Shale-acid reactions occur during fracturing or acid stimulation. The mobilisation of metals from these processes can be an environmental concern if production water leaks or is released at surface. In addition, reactions may cause changes at the pore scale and affect gas or fluid flow. Three gas shales from the Australian Cooper Basin REM sequence were characterised for metals in minerals by synchrotron X-ray fluorescence microscopy. Metals including Zn, As, Ni, Cr were hosted in sphalerite associated with organic matter, Pb was in pyrite cement, and Mn was hosted in siderite. The shales were separately reacted with brine and supercritical CO2, with CO2-SO2, with dilute HCl, or with N2 at 100 °C and 20 MPa in batch reactors. The solution pH decreased during mineral reactions releasing metals to solution with the general concentrations from reaction with HCl > CO2-SO2 > CO2 > N2 and brine. Of the total available Pb, As, Li, and Zn in the shales, from 0 to 17%, 0.3 to 23%, 3 to 13%, and 0.4 to 28% was released to solution respectively. Corrosion of siderite and ankerite was observed after the CO2 reactions, with precipitation of Fe-oxides. After CO2-SO2 reaction siderite and ankerite were dissolved with pyrite, barite, and Fe-rich precipitates. HCl reactions resulted in complete dissolution of carbonates, with dissolution pits and no mineral precipitation observed. The changes to the fractions of gas accessible mesopores were characterised by small angle neutron scattering (SANS). The Epsilon Formation had the greatest fraction of open accessible pores in the SANS range of 10 to 150 nm, followed by the Murteree and Roseneath shale samples. After CO2 or CO2-SO2 reactions a small decrease in pore accessibility was more pronounced in the Murteree and Roseneath shales, consistent with mineral precipitation. HCl reaction resulted in opening of pores at 150 nm and closing of the smallest measured pores at 10 nm. Metals were mobilised from siderite, ankerite and sulphide minerals mainly, and were dependent on the mineral and metal content but also on the injected gas stream or fluid composition. CO2 based fluids may result in cleaner flow back water, than HCl based fluids. Geochemical reactions during CO2 storage or acid treatment in reactive shales cause pore changes that can affect gas migration. Mineral precipitation during CO2 and CO2-SO2 reactions can result in favourable self-sealing. © 2023 The Authors. Published by Elsevier B.V. Open Access - CC-BY.
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    The critical role of bacteria in mineral carbonation of kimberlite
    (Goldschmidt, 2022-07-12) Jones, TR; Poitras, J; Senzani, K; Ndlovu, S; Vietti, A; Paterson, DJ; Wilson, SA; Southam, G
    The breakdown of ultramafic rock during natural weathering captures carbon dioxide from the atmosphere to form carbonate minerals. Kimberlite, an ultramafic rock that can produce diamond weathers when exposed to water. These water-rock interactions also contribute to the growth of bacteria, which accelerate the weathering process. Yellow ground (oxidized Kimberlite found at the surface) samples from the South African Voorspoed and Kareevlei mines contained both molecular signatures (16SrDNA) and viable bacteria. Our molecular analyses highlighted a bacterial population consistent with serpentinite soils and demonstrated that bacteria play a role in yellow ground formation. These yellow ground cultures can grow using only kimberlite as a substrate, promoting weathering in order to live, and providing cultures that are important to natural weathering, yellow ground formation and subsequent mineral carbonation. In order to demonstrate the importance of biology in mineral carbonation of kimberlite, we performed X-Ray Fluorescent Microscopy (XFM) at the Australian Synchrotron to obtain structural and compositional analysis of the South African Venetia mine’s massive volcaniclastic kimberlite (MVK) Coarse Residue Deposit (CRD) with and without biofilm (weathering), 50-year-old Cullinan CRD and definitive, friable Kareevlei yellow ground. These analyses demonstrated that calcium, potassium and iron can be used as tracers for weathering and mineral carbonation. Our small laboratory and larger (1000 L) field-based mineral carbonation experiments both demonstrated the importance of photosynthetic biofilms in the carbonation of kimberlite residue. All of our experiments produced intergranular cements, which stabilised the CRD residue, providing a strategy to increase mine safety while sequestering carbon. We observed continued mineral carbonation with depth demonstrating that carbonation will continue as the kimberlite is buried on the mine site, which will achieve even greater carbon offsets than anticipated. Our pilot scale field experiment demonstrated that we offset 20% (on a mass equivalent) of the annual mine emissions in one year using bacterial carbonation, with the likelihood of continued carbonation ensuring that we will have the capacity to produce a carbon neutral mine.
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    Historical diamond mine waste reveals carbon sequestration resource in kimberlite residue
    (Elsevier, 2023-02) Jones, TR; Poitras, J; Paterson, DJ; Southam, G
    Mined sub-aerially stored kimberlite provided a natural laboratory in which to examine the potential for carbon sequestration in ultramafic materials. A 15 cm hand sample of ∼50-year-old ‘cemented’ coarse residue deposit (CRD) collected from a cemented surface layer in the Cullinan Diamond Mine tailings in Gauteng, South Africa, demonstrated the encouraging effects of weathering on mineral carbonation of kimberlite. The examination of petrographic sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron – energy dispersive spectroscopy demonstrated that weathering produced extensive, secondary Ca/Mg carbonates that acted as an inter-granular cement, increasing the competency of the CRD, i.e., producing a hand sample. Nearly every grain in the sample, including primary, un-weathered angular carbonate clasts were coated in secondary, μm- to mm-scale carbonate layers, which are interpreted as secondary materials. DNA analysis of an internal, aseptic sample of secondary carbonate revealed that the weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation that was found within the secondary carbonate, interpreted as a biomaterial. The formation of secondary carbonate demonstrates that ‘waste kimberlite’ from diamond mining can serve as a resource for carbon sequestration. © 2022 Elsevier B.V.
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    Predicted CO2 water rock reactions in naturally altered CO2 storage reservoir sandstones, with interbedded cemented and coaly mudstone seals
    (Elsevier, 2022-03-15) Pearce, JK; Dawson, GW; Golding, SD; Southam, G; Paterson, DJ; Brink, F; Underschultz, JR
    Geological storage of CO2 captured from industrial processes such as coal combustion or from direct air capture is part of the transition to low emissions. The Jurassic Precipice Sandstone of the southern Surat Basin, Queensland, Australia, is undergoing feasibility studies for industrial scale CO2 geological storage, however regional data has so far been lacking. Precipice Sandstone reservoir drill core samples from the Southwood 1 and Tipton 153 wells in the southern Surat Basin include favourably quartz rich sandstone regions with quartz grain fracturing. A mudstone layer is also present in the reservoir. The overlying lower section of the Evergreen Formation seals consist of clay rich sandstones, interbedded mudstones, coal layers, Fe-Mg-Mn siderite, and Mg-calcite cemented sandstones. K-feldspars are weathered creating localised secondary porosity and pore filling kaolinite and illite. Layers of coal, pore filling cements, and framework grain compaction introduce vertical heterogeneity. Heavy minerals including pyrite, mixed composition sulphides, and barite are associated with disseminated coals in mudstones. Precipice Sandstone mercury intrusion porosities (MIP) ranged from 9 to 22% with favourably low reservoir injection threshold pressures, and the QEMSCAN measured open porosity between 2 and 22%. Evergreen Formation seal porosities were 7.5 to 16% by MIP or 1 to 19% by QEMSCAN, with the smallest pore throat distribution associated with the low permeability coal rich mudstone. Synchrotron XFM shows Rb mainly hosted in K-feldspars and muscovite, with metals including Mn mainly hosted in siderite. Zn and As are present in sulphides; and calcite and apatite cements mainly hosted Sr. Twenty kinetic geochemical CO2-water-rock models were run for 30 and 1000 years with Geochemist Workbench, with calcite and siderite initially dissolving. In the Precipice Sandstone reservoir variable alteration of carbonates, feldspars and chlorite to kaolinite, silica, siderite and smectite were predicted with the pH remaining below 5.5. CO2 was mineral trapped through alteration of chlorite to siderite in three of the four cases, with −0.02 to 1.43 kg/m3 CO2 trapped after 1000 years. In the calcite and siderite cemented Evergreen Formation seal, plagioclase conversion to ankerite trapped the most CO2 with 2.6 kg/m3 trapped after 1000 years. The Precipice Sandstone in both wells appears to be generally suitable as a storage reservoir, with mineral trapping predicted to mainly occur in the overlying lower Evergreen Formation and in interbedded mudstones. Heterogeneity in interbedded sandstone, mudstone, and coal layers are likely to act as baffles to CO2 and encourage mineral trapping. Quartz grain fractures may influence preferential migration pathways in the reservoir but this would need future experimental investigation. Experimental CO2 water rock reactions to understand porosity and permeability changes were out of scope here but are recommended in future validation, along with investigating the potential for CO2 adsorption trapping in coal and mudstone layers. © 2022 Elsevier B.V. All rights reserved.
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    Preservation of terrestrial microorganisms and organics within alteration products of chondritic meteorites from the Nullarbor Plain, Australia
    (Mary Ann Liebert, Inc., 2022-04-13) Tait, AW; Wilson, SA; Tomkins, AG; Hamilton, JL; Gagen, EJ; Holman, AI; Grice, K; Preston, LJ; Paterson, DJ; Southam, G
    Meteorites that fall to Earth quickly become contaminated with terrestrial microorganisms. These meteorites are out of chemical equilibrium in the environments where they fall, and equilibration promotes formation of low-temperature alteration minerals that can entomb contaminant microorganisms and thus preserve them as microfossils. Given the well-understood chemistry of meteorites and their recent discovery on Mars by rovers, a similarly weathered meteorite on Mars could preserve organic and fossil evidence of a putative past biosphere at the martian surface. Here, we used several techniques to assess the potential of alteration minerals to preserve microfossils and biogenic organics in terrestrially weathered ordinary chondrites from the Nullarbor Plain, Australia. We used acid etching of ordinary chondrites to reveal entombed fungal hyphae, modern biofilms, and diatoms within alteration minerals. We employed synchrotron X-ray fluorescence microscopy of alteration mineral veins to map the distribution of redox-sensitive elements of relevance to chemolithotrophic organisms, such as Mn-cycling bacteria. We assessed the biogenicity of fungal hyphae within alteration veins using a combination of Fourier-transform infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry, which showed that alteration minerals sequester and preserve organic molecules at various levels of decomposition. Our combined analyses results show that fossil microorganisms and the organic molecules they produce are preserved within calcite–gypsum admixtures in meteorites. Furthermore, the distributions of redox-sensitive elements (e.g., Mn) within alteration minerals are localized, which qualitatively suggests that climatically or microbially facilitated element mobilization occurred during the meteorite's residency on Earth. If returned as part of a sample suite from the martian surface, ordinary chondrites could preserve similar, recognizable evidence of putative past life and/or environmental change. © 2022 Mary Ann Liebert, Inc
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    Transition metal mobility and recoverability from weathered serpentinite and serpentinite skarn tailings from Lord Brassey Mine, Australia and Record Ridge, British Columbia, Canada
    (Goldschmidt, 2022-07-14) Honda-McNeil, M; Wilson, SA; Locock, A; Mililli, B; Zeyen, N; Wang, B; Turvey, C; Vessey, CJ; Patel, AS; Hamilton, J; Southam, G; Poitras, J; Jones, TR; Jowitt, S; Lowock, A
    As mineral resources become scarcer, companies are lowering their ore cut-off grades and resorting to exploring deeper underground and in more isolated areas. Incorporating tailings storage facilities and tailings reprocessing as part of the ore processing circuit can potentially extend the lives of mines and save on future exploration costs. Ultramafic and mafic mine tailings host resources including first and second row transition metals, such as nickel (Ni), cobalt (Co), and platinum group elements (PGE), whose high value and recovery could serve as a motivator for existing mines to reprocess their tailings. Many of these target metals are initially hosted by olivine, are repartitioned during serpentinization to form sulfides, oxides and alloys, and then are remobilized during weathering to form authigenic carbonates, sulfates and oxyhydroxides. Reprocessing tailings may further provide environmental benefits, including a reduction in waste output and the ability to offset greenhouse gas emissions by enhanced silicate-weathering and carbonation reactions. Here we use powder X-ray diffraction, scanning electron microscopy, electron probe micro-analysis and synchrotron X- ray fluorescence mapping to demonstrate how first and second row transition metals are mobilized to their final sinks. Samples of serpentinite, skarn and weathered tailings from the historical Lord Brassey nickel mine in Tasmania, Australia and weathered outcrops of serpentinite ore from the proposed magnesium mine in Record Ridge, BC, Canada are analyzed and compared. Preliminary results from these climatically similar localities indicate clear transition metal dissemination patterns across alteration zones and distinct partitioning behavior (ex. homogenous distribution of Ni within sulfides) in weathering products. By developing an understanding of the sinks for metals across the mining lifecycle, we aim to cultivate an economically