Authigenic carbonates as natural analogues of mineralisation trapping in

CO2 sequestration Progress Report and Preliminary Results ANLEC Project 7-1011-0189

G. K. W. Dawson, S.D. Golding, C.J. Boreham and T. Mernagh

October 2013 | CO2CRC Report No: RPT13-4602

REPORT CO2CRC PARTICIPANTS

Core Research Industry & Government Supporting Participants Participants Participants CSIRO ANLEC R&D CanSyd Curtin University BG Group Charles Darwin University Geoscience Australia BHP Billiton Government of South Australia GNS Science BP Developments Australia Lawrence Berkeley National Laboratory Monash University Brown Coal Innovation Australia Process Group Simon Fraser University Chevron The Global CCS Institute University of Adelaide Dept. of Primary Industries - Victoria University of Queensland University of Melbourne Ministry of Business, Innovation & Employment University of New South Wales INPEX University of Western Australia KIGAM NSW Government Dept. Trade & Investment Rio Tinto SASOL Shell Total Western Australia Dept. of Mines and Petroleum Glencore Xstrata

Authigenic carbonates as natural analogues of mineralisation trapping in CO2 sequestration Progress Report and Preliminary Results Project 7-1011-0189

G. K. W. Dawson, S.D. Golding, C.J. Boreham and T. Mernagh

Date of submission October 2013 CO2CRC Report No: RPT13-4602

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Acknowledgements The authors wish to acknowledge financial assistance provided to the CO2CRC by the Australian Government through its CRC program and through Australian National Low Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Australian Coal Association Low Emissions Technology Limited and the Australian Government through the Clean Energy Initiative.

Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC)

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Reference: G. K. W. Dawson, S.D. Golding, C.J. Boreham and T. Mernagh, 2013. Authigenic carbonates as natural analogues of mineralisation trapping in CO2 sequestration. Cooperative Research Centre for Greenhouse Gas Technologies, Canberra, Australia, CO2CRC Publication Number RPT13-4602. 75pp.

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Table of Contents

Index of Figures ...... 4 Index of Tables ...... 5 Executive Summary ...... 6 1. Introduction ...... 9 2. Sampling strategy and descriptions...... 10 3. Initial geochemistry ...... 29 3.1. Calcite stable isotopes ...... 29 3.2. Calcite elemental abundances ...... 40 3.2.1. Major, minor, and trace element overview ...... 40 3.2.2. Rare earth elements plus yttrium (REY) and other related elements ...... 46 4. Fluid inclusion studies ...... 60 4.1. Summary observations of fluid inclusion occurrence in Chinchilla 4 samples ...... 61 4.2. Construction of an on-line fluid inclusion crusher ...... 64 5. Ongoing and future work for project ...... 67 6. References ...... 68

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Index of Figures

Figure 1: Map of the showing sites being assessed for evidence of significant carbonate cementation...... 12 Figure 2: Map of the Eromanga Basin showing sites being assessed for evidence of significant carbonate cementation...... 13 Figure 3: Surat Basin Kogan Creek mine massive carbonate mineralisation examples. Given that the average local coal is borderline brown coal to sub-bituminous low rank, the carbonate precipitation is expected to have occurred under relatively low temperature conditions generally and so is applicable to this study. a) and b) are samples of two up to 15 cm wide “chimneys” of massive calcite collected from within faults, c) very hard and apparently iron rich fault breccia containing large calcite veins, from clastic unit between coal seams, d) large calcite sheets with bornite and pyrite discs, from within coal master cleats (large systematic joints), e) calcite from shear surface containing brown probable syntectonic linear accessory phase, f) 4 mm thick calcite sheet from within fault, with probable syntectonic bornite and pyrite...... 16 Figure 4: Carbon and oxygen isotope compositions of Surat and Eromanga calcite cements and veins...... 35 Figure 5: Carbon and oxygen isotope composition of calcite cements and fault veins in clastic units of the Surat and Eromanga basins...... 35 Figure 6: Carbon and oxygen isotope compositions of calcite veins and chimneys in the Walloon at Kogan Creek coal mine, Surat Basin...... 36 Figure 7: Major to moderate elemental abundances measured within fracture calcite samples via ICP-MS. 40 Figure 8: Moderate to minor elemental abundances measured within fracture calcite samples via ICP-MS. 41 Figure 9: Moderate to minor elemental abundances measured within fracture calcite samples via ICP-MS. 42 Figure 10: Scandium and uranium levels track each other for most samples excluding the Eromanga faults...... 42 Figure 11: Non-REY trace elemental abundances measured within fracture calcite samples via ICP-MS...... 43 Figure 12: Fracture calcite REY concentrations compared with marine carbonate (Webb and Kamber, 2000)...... 46 Figure 13: Plot of sample La/Th ratios relative to the expected upper crustal ratio of 2.8 (centre line)...... 47 Figure 14: Plot of sample La/Sc ratios relative to the expected upper crustal ratio of 1 (centre line)...... 48 Figure 15: Plot of sample Th/U ratios relative to the expected upper crustal ratio of 3.8 (line)...... 48 Figure 16: Variation diagram first proposed by Möller (1983); field positions plotted are based upon numerous analyses of samples from across the world. Samples that plot below the carbonatite- hydrothermal-metamorphic series are classed as “sedimentary process related”, with the rough positions of marine carbonate types between the dashed lines, and sea water composition plotted for reference. .. 49 Figure 17: PAAS-normalised REE data for fracture calcite samples. The majority of samples are enriched in HREE’s relative to LREE’s...... 56 Figure 18: Calcite cemented sample #256 (Chinchilla 4– 799m) contained rare two-phase, aqueous inclusions with 5 – 10 vol.% vapour that were sufficiently large for microthermometry...... 63 Figure 19: The heated fluid inclusion crusher and transfer line interfaced with Geoscience Australia’s Agilent 5893 GC-MS: ...... 65 Figure 20: Detail of the fluid inclusion crusher block, item 4 in Figure 19: ...... 66

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Index of Tables

Table 1: Queensland Eromanga Basin sites sampled, with preliminary analyses listed...... 13 Table 2: Surat Basin sites sampled, with preliminary analyses listed...... 13 Table 3: Queensland Eromanga Basin – Potential further sampling sites assessed.* ...... 14 Table 4: South Australian Eromanga Basin – Potential further sampling sites assessed.* ...... 14 Table 5: Surat Basin – Potential further sampling sites assessed.*...... 14 Table 6: SA chipped well intervals to be sampled in relation to massive calcite cemented zones ...... 15 Table 7: SA cored well intervals found to contain significant calcite cement ...... 15 Table 8: Types of significant sandstone carbonate mineralisation identified during initial assessment of well completion reports...... 17 Table 9: Initial carbonate samples collected from Eromanga Basin wells...... 18 Table 10: Initial carbonate cemented sandstone samples collected from Surat Basin wells...... 21 Table 11: South Australian Eromanga Basin Wells with largest amount of recovered core (10 to 20 metres) – Well completion reports under assessment...... 26 Table 12: Queensland Eromanga Basin wells with recovered core – Well completion reports under assessment.* ...... 27 Table 13: Surat Basin wells with recovered core (up to entire stratigraphic sequence)...... 28 Table 14: Carbonate carbon and oxygen stable isotopes for Eromanga Basin calcites – both cemented sandstone and fault-mineralisation intervals...... 30 Table 15: Carbonate carbon and oxygen stable isotopes for Surat Basin Calcites – from cemented sandstone intervals...... 31 Table 16: Carbonate carbon and oxygen stable isotopes for Kogan Creek Coal Mine calcite samples...... 32 Table 17: Modelled carbon and oxygen isotope composition of the mineralising fluids...... 33 Table 18: Non-REY element concentrations within fracture calcite samples (ppm), Surat Basin unless otherwise specified.* ...... 44 Table 19: REY element concentrations within fracture calcite samples (ppm), Surat Basin unless otherwise specified.* ...... 50 Table 20: Selected useful elemental ratios...... 51 Table 21: Y + REE data (PAAS normalised).* ...... 54 Table 22: Y + REE data (CN normalised).* ...... 55 Table 23: Selected ratios of PAAS normalised elements.* ...... 57 Table 24: Equations used to calculate expected normalised values of selected elements...... 57 Table 25: REE anomalies (PAAS or Chondrite normalised)...... 59

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Executive Summary

This project aims to support CO2 storage projects in Australian sedimentary basins through investigation of the controls on carbonate authigenesis in freshwater aquifers of the Great Artesian Basin. This report primarily summarizes the progress made to date for Part 1 of the project – the petrological, fluid inclusion and geochemical investigation of the controls on carbonate authigenesis in freshwater aquifers as a natural analogue for mineralisation trapping. Parameters derived from Part I will feed into the Part II simulation to produce a model for authigenic carbonate diagenesis, which will be developed concurrently with experiments designed using knowledge gleaned during the desktop study to evaluate the potential for engineered accelerated mineral trapping within sandstone formations (Part III). The fluid inclusion crusher and transfer line designed to process gram quantities of fluid inclusion-containing sediments, has been constructed using staff and resources from Geoscience Australia’s Field and Engineering Services and the Isotope and Organic Geochemistry Laboratory.

The sampling campaign is spread across both the Queensland and South Australian regions of the Great Artesian Basin, to capture the greatest degree of variability in sandstone carbonate cementation conditions. Samples of carbonate cemented sandstone as well as carbonate fracture mineralisation, including fault chimney calcite up to 15 cm thick, have been taken from 20 localities thus far. A further 14 chipped wells have been identified as having high potential for significant carbonate cementation. Future sampling will be targeted around structures for which there is possible evidence of petroleum migration associated with some of the carbonate cementation analysed. The scattered sampling approach will also continue, to ensure that samples containing the highest abundances of carbonate cementation are made available for the various analyses underway.

Most recently, over 200 wells for which core was recovered have been identified across both South Australia and Queensland, and first-pass assessment is being made of the well completion reports to determine which cores contain strong carbonate mineralisation. Cores are much easier to use and provide more definitive information than cuttings can for fluid inclusion studies, and isotope, trace element, and petrographic analyses, given that in-situ textural relationships between compositional elements are preserved in rock core. The well cuttings obtained thus far were too fine-grained to be suitable for fluid inclusion studies. The lengths of the Queensland cores range from metres to the entire sedimentary sequence, whereas the South Australian cores are no more than 20 m long but at least cover some formations that are primary targets for this study.

Carbon and oxygen isotopic compositions were determined for 17 calcite cements and 3 fault veins in Eromanga Basin sandstones, 26 calcite cements in Surat Basin sandstones, and 21 calcite veins, 2 calcite chimneys and 1 fault breccia in the Walloon Coal Measures (Kogan Creek coal mine). The mine sample analyses were funded by an internal UQ grant separate from this project, but the data are relevant to determining the range of conditions under which carbonates have precipitated within the Surat Basin,

6 especially given that dissolved sulfur species and deeply-source CO2-rich fluid migration through faults may have played roles in the massive carbonate precipitation.

The Surat cements exhibit a range of δ18O values from 4.6 to 17.0 ‰ (n=25), with the exception of a heavily carbonate-cemented Hutton Sandstone sample (Chinchilla 4-799.6m) that has a δ18O value of 24.7 ‰. The Surat cements exhibit a range of δ13C from -11.1 to 3.0 ‰ (n=26). Eromanga cements and fault veins have an overlapping range of δ18O and δ13C values (relative to the Surat) from 6.6 to 22.3 ‰ and -15.9 to 0.0 ‰ (n=20), respectively. Modelled fluid oxygen isotope compositions for the majority of calcite cements indicate they precipitated in the temperature range of 80 oC to 120oC across both basins. Preliminary fluid inclusion data reported here as well as literature apatite fission track analysis of Surat-Bowen samples indicate that the Hutton Sandstone experienced paleotemperatures ≥ 110oC in the eastern Surat Basin. The sandstone cement samples with the most depleted 13C signatures are generally from wells located adjacent to major faults in the Surat and Eromanga basins, which support the proposal that zones of significant carbonate cementation may form where hydrocarbons and associated CO2 migrate up leaking faults and emerge in a shallow aquifer system. Additional samples from these and adjacent wells will be a focus of the next analytical campaign. Mixing between low salinity groundwaters of meteoric origin and evolved basinal brines across a range of temperatures may explain the wide range of calculated oxygen isotope compositions from -17.0 to 7.9 ‰ of fluids precipitating calcite cements and fault veins in Great Artesian Basin sediments. Future fluid inclusion studies will allow a detailed investigation of this hypothesis.

Massive calcite filled chimneys are a feature of fault systems in the Surat Basin. Two calcite chimney samples from the Walloon Coal Measures at Kogan Creek have an identical 18O value of 24.4 ‰ and 13C values of 0.1 and 1.3 ‰ similar to many of the calcite veins that fill cleat, shears and joints. A third sample has a similar carbon isotope value but is strongly depleted in 18O relative to the other samples, and the calcite oxygen isotope value is not in equilibrium with the fluid because of CO2 degassing and rapid precipitation in the fault chimney. Calcite veins filling cleat, shears and joints in the Walloon Coal Measures at Kogan Creek in the Surat Basin exhibit an unusually wide range of 13C values from -17.8 to 18.9 ‰ (n=21) that are negatively correlated with 18O values ranging from 15.2 to 25.8 ‰ (R2 = 0.9482). Only two joint-fill calcite samples reflect low temperature, near surface conditions of abiotic or microbial oxidation of

13 methane or coal; those with highly negative  C values. The microbially enhanced precipitation of CO2 is a potential engineered sequestration solution, as methanogens assist precipitation of carbonates by lowering the partial pressure of CO2 within a system, making it sufficiently alkaline for minerals such as calcite to form. Methanogenesis involving fermentation or the CO2 reduction pathway is the only process that can produce the highly positive 13C values that lie at the other end of the negative C-O correlation trend obtained. A model temperature range of 40oC to 80oC for the mineralising fluids is consistent with temperatures of 48oC to 71oC calculated from vitrinite reflectance of coal abutting the Kogan Creek calcite veins.

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Fracture calcite mineralisation was chosen for an initial assessment of elemental abundances measured via high precision ICP-MS, for the purposes of demonstrating the utility of elemental abundance analyses. REE and related element abundances, fractionation between LREE and HREE, and anomalous concentrations of specific REE’s can be indicative of mineral precursor compositions, mineralising fluid composition (including ligands involved), the conditions of the environment/s through which the fluid migrated prior to precipitation, and whether the present carbonate mineralisation is primary or remobilised carbonate. Most of the Kogan Creek samples are derived from deeply-sourced CO2 precipitated under either reducing or else less oxidising conditions, generally at depths greater than 1 km and up to 2 km assuming a geothermal gradient of about 35 oC. An exception was the joint calcite with the highest Y/Ho ratio measured, which indicated that the mineralising fluid was well oxygenated; this agreed with modelling of the oxygen and carbon isotopes which indicated that the fluid CO2 composition was consistent with oxidation of methane or coal. Given that enrichment of elements within the calcites appears to generally be associated with faults, this implies that the adjacent coal and carbonaceous shales are not the primary source of these. All except one of the samples plot within the hydrothermal veins field with respect to Yb/Ca and Yb/La ratios, but the fact that the fluids were not high temperature during precipitation (as indicated by vitrinite reflectance data) matches well with the modelled stable isotopes scenario of deeper fluids mixing with meteoric water and then precipitating calcite.

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1. Introduction

The primary focus of this project is development of a better understanding of the controls on the formation of authigenic carbonates in low salinity, siliclastic aquifers of the Great Artesian Basin (GAB) as a natural analogue of mineralisation trapping in CO2 sequestration. The objective is to determine whether there are differences in groundwater composition or reservoir conditions that encourage mineralisation of CO2, and if so, then what are the key parameters. It is also intended to undertake mineralisation experiments on Wandoan Project Precipice and Hutton Formation core under simulated in-situ conditions to evaluate the potential for engineered accelerated mineralisation trapping to maximise the use of storage porosity in the Precipice Sandstone and serve as a mitigation option for the Hutton Sandstone aquifer above the Evergreen

Formation seal in the event of CO2 leakage from the Precipice storage reservoir.

This is a sister project to three projects funded by ANLEC and will have access to data sets and insights obtained in these projects. The work program includes stable and radiogenic isotope and fluid inclusion analysis of carbonate and other cements in addition to microscopic and geochemical studies. Fluid inclusion data together with stable (C, O) and radiogenic (Sr, Sm, Nd) isotope compositions of mineral precipitates are excellent indicators of thermal and fluid flow histories, providing essential information on the physicochemical conditions and time scales of CO2 trapping in sedimentary reservoirs. Reliable age dating and isotope tracing of carbonate cements require a detailed petrographic investigation to establish mineral paragenesis. The thin section petrology, XRD and SEM mineralogy, trace elements, and stable and radiogenic isotope analyses are being undertaken at UQ using facilities in the Centre for Geoanalytical Mass Spectrometry and Isotope Science (CGMSIS) and the Centre for Microscopy and Microanalysis (CMM).

The fluid inclusion studies are being carried out at Geoscience Australia (GA) that is equipped with state-of- the-art facilities for the analysis of fluid inclusions including a Linkam MDS 600 heating/freezing stage. The Raman laboratory has a HORIBA Jobin Yvon SuperLabram laser Raman microprobe, which has a fully confocal microscope and is used for the rapid and non-destructive analysis of solids, liquids and gases.

Those authigenic carbonates with fluid inclusion containing entrapped hydrocarbons and/or CO2 will be subjected to more detailed compositional analysis. The origin of carbonates can be inferred indirectly from the carbon isotopic composition of CO2 trapped within the fluid inclusions and directly from the carbon isotope composition of the authigenic carbonates. However, the carbon isotopic composition of the gaseous hydrocarbons is a more sensitive measure of the involvement of abiotic oxidative or microbially- mediated processes. The molecular and isotopic (C and H) analyses of the gases will be determined using GA’s gas chromatographs and gas chromatograph-combustion/pyrolysis-isotope ratio mass spectrometers. These results will be compared with similar analyses on natural gases and dissolved gaseous hydrocarbons in formation waters in the region and used to identify genetic relationships between the fluid inclusion gases and free gases. In this progress report we outline the sampling strategy employed to date, present the first geochemistry and fluid inclusion results for carbonate cements and veins from the Eromanga and Surat basins and document the development of the online inclusion decrepitation system at GA.

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2. Sampling strategy and descriptions

The Queensland and South Australian regions of the Mesozoic Surat-Eromanga Basin system plus overlying Cenozoic basins collectively form the major part of what has historically been called the Great Artesian Basin (Figures 1 and 2). This group of basins overlie the Pennsylvanian to Early Bowen-Galilee and Cooper Basins as well as older sedimentary basins, metamorphic and igneous units. Abundant coal, oil, and gas accumulations occur within the entire basin system. Most coal units are generally thin, gas is derived from both coals and conventional sources, and oil tends to be associated with structures that have been reactivated since primary migration. Whilst mostly a relatively closed intracratonic system overall, the basins have been open to a number of marine incursions at times, most significantly during the ; occurs alongside paralic coal measures in some areas (Adamson and Dorsch, 1988; Anon., 1964, 1982, 1984, 1991, 1994, 2001; Baily, 1996; Battrick et al., 1985; Brown, 1984; Burnett and Darling, 1986; Dabney, 1965; Espiritu and James, 1999; Estensen et al., 1986; Freeman, 1967; French, 1989; Green, 1963; Haak, 1999; Hall and Gagen, 1989; Harrison and Higginbotham, 1964; Jenkins, 1984; Knauer and Delbaere, 1992; Kyranis, 1963; Laing, 1966, 1967; Longley and Batt, 1985a, b; Lowman, 2003a, b; Moore, 1981; Nguyen et al., 1996; O'Neill, 1985; Ostler, 1989; Pyle, 1965a, b, 1966a, b; Pyle et al., 1963; Pyle and Dabney, 1963; Robbie and Mitchell, 1996; Salomon et al., 1990; Slijderink, 1998; Surka and Rouse, 1984; Taylor, 1985; Thornton, 1984; Thornton and Elliott, 1982; Titheridge, 2010; Tolliday and How, 1986).

With the exception of petroleum fields, structures tend to be poorly mapped throughout the system due to deep Cenozoic sediments covering most of the basin units and accessibility issues due to lack of seismic data in currently non-resource prospective areas. Whilst large-scale structural geologic data is available in digital format for Queensland, digitized smaller-scale company structure maps have not been made publically available online, and even less digitized structural information is available for South Australia. Low amplitude folding and faulting has occurred throughout the Great Artesian Basin system a number of times including recently during the Cenozoic (e.g. Etheridge et al., 1991; Fergusson, 1991; Finlayson, 1993; Foster et al., 1994; Mathur, 1983; Shaw, 1991). Localised intrusions and related mineralisation also occur in places, with the most significant possibly associated with a line of Oligocene-Miocene hot spot volcanos along the eastern-most margin of the Surat Basin (Cohen et al., 2007; Knesel et al., 2008).

Sampling of drill core and cuttings was spread as broadly as possible across the basin system in an attempt to capture the greatest degree of variability in sandstone carbonate cementation conditions, with samples from different intervals of the same or adjacent wells also taken in selected areas to help account for local variability. More than 75 well completion reports have been assessed in detail thus far for the presence of significant carbonate mineralisation with samples taken from 50 localities, of which 19 have preliminary analytical results (Tables 1 and 2) and a further 17 have been identified as having high potential for significant carbonate cementation (Tables 3, 4, 5, 6 and 7). Joint and fault carbonate mineralisation was also taken wherever this was found during sampling of carbonate cemented sandstones, and also from

10 near-surface coal measure deposits at a site of known significant carbonate vein mineralisation within the central Surat Basin. The latter analyses were funded by an internal UQ grant separate from this project, but the data are relevant to determining the range of conditions under which carbonates have precipitated within the Surat Basin, especially given that dissolved sulfur species and fluid migration through faults may have played roles in the massive carbonate precipitation observed at the mine site (e.g. Figure 3).

The significant carbonate cemented intervals identified during the initial assessment of well completion reports were classified into a number of categories based upon characteristics such as sandstone mineralogy and whether samples were likely marine influenced or not (Table 8). This was to ensure that as wide a spread of sample types as possible were collected during the first-pass sampling for initial analyses (Tables 9 and 10). Due to availability of supporting information and ease of assessing this, the initial sample search was centred on Queensland petroleum drill wells (Figures 1 and 2). The Queensland Government IRTM, QPED, and QDEX web products were used to assess the spread of wells spatially, the existence of wells for which core of relevant age and locality was recovered, and open file well completion report information, respectively. The South Australian Government equivalent of QDEX – PEPS – was also used to search for relevant wells, but the Queensland material was housed in Brisbane and so was easier to recover for initial analysis. A South Australian sampling campaign is planned to occur before year’s end.

Most recently, over 200 wells for which core was recovered have been identified across both South Australia and Queensland (Tables 11, 12, and 13). Cores are much easier to use and provide more definitive information than cuttings can for fluid inclusion studies, and isotope, trace element, and petrographic analyses, given that in-situ textural relationships between compositional elements are preserved in rock core. Unfortunately, none of the South Australian cores are longer than 20 m, but these are at least from formations that are of prime interest to this study. Whilst the Queensland cores may in some cases include the entire stratigraphic sequence from surface to basement, no indication is given in the database records as to which formations were cored. Each of the cored wells identified is undergoing a brief preliminary assessment for evidence of zones of significant carbonate cementation recorded within the well completion reports. Due to time constraints, less detailed assessment is being made of these wells than those which were originally sampled. In light of preliminary results, future sampling will be targeted around structures for which there is possible evidence of petroleum migration associated with some of the carbonate cementation analysed. The scattered sampling approach will also continue to ensure that samples containing the highest abundances of carbonate cementation are made available for the various analyses underway. The combination of analyses such as carbonate isotopes (e.g. C, O, Sm, Sr, Nd), elemental concentrations (majors, minors, trace including rare earth elements + yttrium – REY), fluid inclusions, and vitrinite reflectance (where possible) will give fluid composition, pressure, temperature, timing of precipitation, and provenance parameters (among others) for the conditions under which the significant carbonate cementation occurred in nature.

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Figure 1: Map of the Surat Basin showing sites being assessed for evidence of significant carbonate cementation.

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Figure 2: Map of the Eromanga Basin showing sites being assessed for evidence of significant carbonate cementation.

Table 1: Queensland Eromanga Basin sites sampled, with preliminary analyses listed. Sample Site Latitude Longitude Sample Type Preliminary Analyses Well Completion Report Bodalla South 2 -26.46 143.43 Chips CO-stable isotopes (Longley and Batt, 1985a) Bodalla South 9 -26.45 143.42 Chips CO-stable isotopes (Robbie and Mitchell, 1996) Inland 3 -25.54 141.64 Chips CO-stable isotopes (Baily, 1996) Kenmore 12 -26.65 143.44 Chips CO-stable isotopes (Salomon et al., 1990) Mirintu 1 -28.83 143.33 Core CO-stable isotopes (Anon., 1984) Saltern Creek 1 -23.35 144.94 Core CO-stable isotopes (Anon., 1964) Widnerpool 1 -24.12 143.67 Chips CO-stable isotopes (Hall and Gagen, 1989) Winna 1 -27.73 142.55 Core CO-stable isotopes (Burnett and Darling, 1986) Yongala 1 -25.50 143.93 Chips CO-stable isotopes (Laing, 1966)

Table 2: Surat Basin sites sampled, with preliminary analyses listed. Sample Site Latitude Longitude Sample Type Preliminary Analyses Well Completion Report Brigalow 1 -27.47 148.90 Chips CO-stable isotopes (Tolliday and How, 1986) CO-stable isotopes, fluid Chinchilla 4 -26.73 150.20 Core (Almond, 1985) inclusions Davidson 1 -27.20 150.17 Chips CO-stable isotopes (Pyle, 1965b) Green Swamp 1 -27.46 150.46 Chips CO-stable isotopes (Nguyen et al., 1996) CO-stable isotopes, trace Kogan Creek -26.93 150.78 Mined Rocks N/A (Minesite) elements, fluid inclusions? Moonie 40 -27.73 150.27 Chips CO-stable isotopes (Lowman, 2003a) Moonie Corner 1 -27.77 150.19 Chips CO-stable isotopes (Anon., 1994) Strathpine 1 -26.39 150.23 Chips CO-stable isotopes (Knauer and Delbaere, 1992) Sussex Downs 1 -27.77 150.14 Chips CO-stable isotopes (Pyle, 1966b)

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Table 3: Queensland Eromanga Basin – Potential further sampling sites assessed.* Sample Site Latitude Longitude Potential for Significant Calcite Well Completion Report Cementation Bodalla South 1 -26.45 143.42 High (Battrick et al., 1985) Challum 1 -27.39 141.58 High (Thornton, 1984) Denbigh Downs 1 -22.23 141.44 High (French, 1989) Ghina 1 -27.05 142.18 High (Slijderink, 1998) Gibba 1 -28.74 141.55 High (Anon., 1991) Kenmore 5 -26.65 143.45 Low (Estensen et al., 1986) Maryvale 1 -26.67 146.86 Low (Freeman, 1967) Morney 1 -25.44 141.59 Low (Moore, 1981) Mount Bellalie 1 -26.52 143.12 High (Longley and Batt, 1985b) Tartulla 1 -27.23 142.17 High (Thornton and Elliott, 1982) Tintaburra 1 -26.93 143.10 High (Surka and Rouse, 1984) Yanda 1 -27.46 141.81 High (Jenkins, 1984) Yongala 2 -25.53 143.89 High (Laing, 1967) *Only chipped samples available in carbonate cemented intervals of these wells.

Table 4: South Australian (SA) Eromanga Basin – Potential further sampling sites assessed.* Sample Site Latitude Longitude Potential for Significant Well Completion Report Calcite Cementation Gidgealpa 1 -27.95 140.08 Low (Harrison and Higginbotham, 1964) Gidgealpa 18 -27.97 140.03 High (Taylor, 1985) Kerna 3 -28.24 140.98 High (Brown, 1984) Muteroo 1 -28.13 139.89 High (O'Neill, 1985) Spencer West 1 -28.18 139.80 High (Ostler, 1989) Strzelecki 15 -28.25 140.66 Low (Anon., 1985) *Only chipped samples available in carbonate cemented intervals of these wells.

Table 5: Surat Basin – Potential further sampling sites assessed.* Sample Site Latitude Longitude Potential for Significant Well Completion Report Calcite Cementation Bennet 1 -27.22 150.22 Low (Pyle, 1965a) Bennet 2 -27.22 150.23 Low (Pyle, 1966a) Deep Crossing 1 -27.47 150.49 High (Adamson and Dorsch, 1988) Duke S3 -27.11 150.23 Low (Titheridge, 2010) Kogan 1 -27.09 150.81 Low (Kyranis, 1963) Kogan South 1 -27.14 150.80 Low (Green, 1963) Moonie 1 -27.74 150.26 Low (Anon., 1994) Moonie 13 -27.76 150.23 Low (Pyle and Dabney, 1963) Moonie 37 -27.74 150.26 High (Anon., 1982) Moonie 41 -27.75 150.24 High (Lowman, 2003b) Southwood 1 -27.71 150.23 Low (Pyle et al., 1963) Strathpine 2 -26.40 150.23 High (Knauer and Delbaere, 1992) Strathpine 3 -26.42 150.24 High (Espiritu and James, 1999) Tipton 26A -27.45 151.13 High (Espiritu and James, 1999) Weringa 1 -26.09 150.04 High (Dabney, 1965) Wyalla 1 -26.90 150.73 Low (Anon., 2001) *Only chipped samples available in carbonate cemented intervals of these wells.

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Table 6: SA chipped well intervals to be sampled in relation to massive calcite cemented zones

Intervals (feet) Well Formation Notes Calcite Non-calc 5515, 5540, 5580, 5300 poor oil show, 5900 just Gidgealpa 18 Namur Sandstone 5620, 5650 below 10 feet below oil show

5700 Birkhead Formation 5000, 5300 Namur Sandstone 5900, 6100 Hutton Sandstone 4750, 5050, 5125, 4750, 5050, 5125, 5210, 5600 5210, 5300, 5385, 4950, 5420 Namur Sandstone trace oil show, 5500 oil Strzelecki 15 5400, 5430 5500 Birkhead Formation

5600, 5750, Hutton Sandstone 5850 5500, 5640, 5670, 5220, 5350, 5700, 5750, 5880, Namur Sandstone 5414 has coal 5415, 5475 Kerna 3 5910

6150, 6230, Hutton Sandstone 6250 has coal 6250 4820, 4930, 5150, 5240, 5290, 5120, 5400- Namur Sandstone 5400-5420 is coal Muteroo 1 5350 5420

5700, 5760, Hutton Sandstone 5760 has coal and oil show 6000, 6170 4825, 4870, 4910, 4500, 4630, Spencer 4950, 5000, 5020, Namur Sandstone 5130 West 1 5050 5400, 5500, Hutton Sandstone 5600, 5700

Table 7: SA cored well intervals found to contain significant calcite cement

Well Intervals (feet) Formation Notes Burke 002 5063-5065 Murta (Mooga) Some microfaulting Dullingari 036 4889-4892 Murta (Mooga) Oil Dullingari 037 5067-5069 Murta (Mooga) Dullingari 039 5018-5025, 5033-5038 Murta (Mooga) Jena 002 3882-3885 Murta (Mooga) 3932-3939 has minor oil, 3951-3953 Jena 006 3932-3936, 3951-3953 Murta (Mooga) vertical fracs filled with "limestone" & oil 3886-3889 is calcitutite surrounded by Jena 012 3886-3889, 3921-3922 Murta (Mooga) siltstone, 3921-3922 has oil Marabooka 004 3390-3396, 3427-3431 Oodnadatta Fm 3390-3396 has limestone inclusions 6037-6044 has faults and coal, 6063-6066 Merrimelia 032 6037-6044, 6063-6066 Birkhead Fm has oil Narcoonowie 4372-4376 just below oil, 4389-4390 with 004 4372-4376, 4389-4390 Murta (Mooga) oil Ulandi 005 3914-3916 Cadna-Owie Fm Wilpinnie 001 4689-4698 Murta (Mooga)

15

a b

c d

e f

Figure 3: Surat Basin Kogan Creek mine massive carbonate mineralisation examples. Given that the average local coal is borderline brown coal to sub-bituminous low rank, the carbonate precipitation is expected to have occurred under relatively low temperature conditions generally and so is applicable to this study. a) and b) are samples of two up to 15 cm wide “chimneys” of massive calcite collected from within faults, c) very hard and apparently iron rich fault breccia containing large calcite veins, from clastic unit between coal seams, d) large calcite sheets with bornite and pyrite discs, from within coal master cleats (large systematic joints), e) calcite from shear surface containing brown probable syntectonic linear accessory phase, f) 4 mm thick calcite sheet from within fault, with probable syntectonic bornite and pyrite.

16

Table 8: Types of significant sandstone carbonate mineralisation identified during initial assessment of well completion reports. Probable sandstone type (italicised = provisional) Basin & arbitrary corresponding code (e.g. 2a) for ease of analysis Carbonate type Eromanga Eromanga Marine influenced Probable terrestrial 1st pass* 1st pass* Surat 1st pass* (QLD) (SA) Siderite Probably N/A S – plus sandstone code if applicable 1 1 0 4 1 (with calcite in Surat) Dolomite D – plus sandstone code if applicable Probably N/A 1 1 0 7 4 (1 core)

F – (fault mineralisation) plus sandstone code if 1 1 (core) 0 0 0 applicable L? – Possible limestone or sandy limestone, rather than 1 1 0 3 2 cement? 1a – Quartzose sandstone with lithic fragments & 3 2 1 0 0 sometimes feldspars, clay, etc. 1a – Quartzose sandstone with lithic fragments & 4 4 (1 core) 2 4 3 sometimes feldspars, clay, etc. 1b – Feldspathic quartzose sandstone 1 1 (core) 1 0 0

1c – Quartzose sandstone with clay matrix & minor 2 1 2 0 0 accessory phases 1c – Quartzose sandstone with clay matrix & minor 4 2 (1 core) 2 5 3 accessory phases 1d – Quartzose sandstone with minor accessory phases 1 0 0 0 0 Calcite 1d – Quartzose sandstone with minor accessory phases 0 0 0 2 0

F – (fault mineralisation) plus sandstone code if 0 0 0 0 applicable 2a – Quartzose sandstone with lithic fragments & 1 1 0 5 5 (1 core) sometimes feldspars, clay, etc. 2a – Quartzose sandstone with lithic fragments & 0 0 0 0 0 sometimes feldspars, clay, etc.

2b – Feldspathic quartzose sandstone 0 0 0 0 0

2c – Quartzose sandstone with clay matrix & minor 6 (2 core) 3 (1 core) 0 25 13 accessory phases 2c – Quartzose sandstone with clay matrix & minor 1 0 2 0 0 accessory phases 2d – Quartzose sandstone with minor accessory phases 2 2 0 11 6 (1 core)

2d – Quartzose sandstone with minor accessory phases 1 1 3 2 2

Total marine influenced 18 13 8 0 21 12

Total terrestrial 12 8 5 0 47 27 Total for Basin/Region 30 21 13 0 68 39

Total first pass sample 60 ALL FOUND 110 *The 1st pass columns indicate the target intervals for initial sampling.

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Table 9: Initial carbonate samples collected from Eromanga Basin wells. Thickness of Associated Depth Depth carbonate Preliminary Hole Code Lithology from well completion report petroleum, Formation (m) (ft) cemented Analyses coal, etc. zone/s 70% SANDSTONE: "Light grey to medium green grey, friable to hard, very fine, rarely 450 m (net sand fine, subangular to subrounded, quartz Possibly about 250 m, grains with abundant red, green, grey, black marine/ interbedded Bodalla & white lithics, common argillaceous & silt estuarine 150 1a with siltstone, Winton South 2 matrix in part, abundant calcareous cement carbonate, and claystone, in part, rare mica flakes and carbonaceous also coal dolostone and material, no visual porosity. 30% present coal) CLAYSTONE: medium green, firm, massive, mod silty & very finely arenaceous in part." "100% SANDSTONE, light grey, pale brown in part, fine to coarse, angular to sub round, poorly sorted, patchy hard calcite cement, 1596 2d trace argillaceous matrix, trace lithics & Oil show Carbonate stable carbonaceous specks, rare mica, trace isotopes, XRD garnet, firm in aggregates, good porosity, no Bodalla 150 m fluorescence" Hutton Sandstone South 9 sandstone "100% SANDSTONE, light brown, fine to coarse, common very coarse, common patchy hard calcite cement, trace 1617 2d Trace oil show argillaceous matrix, trace lithics & rare mica, firm to moderately hard in aggregates, fair porosity" "SANDSTONE: gy brn, pl-med brn, f-med, pred med. Occ c. Ang-sbang, pr-mod srt i/p., 4430- wk-mod sil cmt. Loc mod-str calc cmt. Com 100 ft below Inland 3 2c 150 ft Namur Sandstone 4440 brn gy arg mtx, tr tan FeO stns, occ carb & trace oil show slty liths, tr rock flour, fri-v hd i/p, pr vis por, pred no oil fluor" "SANDSTONE: pl-dk brn, f-c, pred m, ang- 5570- sbang, pr-mod str, abt sideritic cmt, occ calc Carbonate stable Inland 3 S – 2c Trace oil show 50 ft Hutton Sandstone 5580 cmt, tr-com arg mtx, com slty & carb liths, isotopes, XRD fri-hd, pr vis por" 18

Table 9 continued: Initial carbonate samples collected from Eromanga Basin wells. Thickness of Associated Depth carbonate Preliminary Hole Depth (ft) Code Lithology from well completion report petroleum, Formation (m) cemented Analyses coal, etc. zone/s "SANDSTONE: lt gy-off wh, lt grnsh gy, f occ med, mod Limestone 510 1d srt, sa-sr, v strng calc cmt, tr carb spks/liths, tr wh arg 100 m Mackunda associated mtx, hd-v hd, pvis porosity, n/s". Just below limestone

"SANDSTONE: lt gy-dk grn gy, f, mod w srt, sa-sr, strng 100 m above 920 1d 20 m Wallumbilla calc cmt, tr dk grn liths, glauc, frm-hd, p vis porosity, n/s" oil show Kenmore 12 "SANDSTONE: lt gy-off wh, vf-f, occ med, sa-sr, mod srt, 30 m below oil 1075 1c strng calc cmt, frm-hd, tr wh arg mtx ip, pyritic, rr 75 m Cadna-Owie show dolomitic frags, p-fr vis porosity, n/s, tr minrl fluo" "SANDSTONE: lt gy-wh, clr-trn sl, sldy-off wh, f-med, occ 10 m below 1350 1c vf, com calc & sil cmt, tr wh arg mtx, frm-mod hd, tr lit, 25 m Birkhead coal seam carb frgs, occ lse qtz, tr pyr, pr vis porosity, n/s" (Only gas in Mooga Saltern Creek 1 1650'10''- "SANDSTONE, light grey, fine to medium grain, (Log in poor 2c well is (Namur (Core) 1651'4'' subangular, poorly sorted, calcareous, white clay matrix." condition) CSG) Sandstone?) Carbonate stable “SANDSTONE: gy, gn, vf-f g, wll srt, glauc, v calc cmt, frm- 25 m above 130 m (net Widnerpool 1 559-562 1c Wallumbilla fri.” limestone sand 40 m) isotopes, XRD 70% "SANDSTONE: off wh, crm, f, sb ang, mod wl srt, 20 m below v calc cmt, arg mtx, tr lit, mod hd, ti, n vis por, n/s. 30% coal, 100 m 50 m (net Widnerpool 1 862-865 2c Westbourne SILTSTONE: med-dk brn, gy brn ip, aren, tr arg, mic, frm, above sand 30 m) sb blky." limestone "SANDSTONE: V. Lt bn, L. Vf, V well std, sa, mod sil & strg Winna 1 1008- calc cmt, comm-abund wh cly mtx, V. Sl mic, tr weath Good oil 1c 20 m Murta (Core) 1008.12 feld, V. Pr-pr porosity & 100% V. Dull pale yelll fl & pr sl shows str'g cut and pr thin blooming ring cut, minor carb lam" "SANDSTONE: light grey to beige ochre, fine to very fine grained, moderately sorted angular to sub angular quartz, green lithic rock fragments (illegible word) 2500- 50 ft below 500 ft (net Yongala 1 1a mineral, rare red mineral, and some yellow (illegible Winton 2510 coal sand 400 ft) word), in a calcareous matrix, slightly porous, but very calcareous and light from 2400 to 2530". Minor mudstone. 19

Table 9 continued: Initial carbonate samples collected from Eromanga Basin wells. Carbonate Associated Depth Preliminary cemented Hole Code Lithology from well completion report petroleum, Formation (m) Analyses zone coal, etc. thickness 70 m below limestone, Carbonate 675.21- Coarse sandstone, "trace to 15% dull orange spotted fluorescence, very slow crush but 2 m 1b stable 675.33 cut," poor to fair visual porosity, calcite cemented above isotopes, XRD calcite-filled faults Sandstone & interlaminated siltstone. “SANDSTONE: Fine grained, light grey. Quartzose- Carbonate feldspathic. Angular to sub-rouned, predominantly stable sub angular. Moderately well sorted. Rare to isotopes and occasional lithic grains, occasional biotite, rare ICP-MS carbonaceous fragments, rare to occasional black measured opaque? heavy mineral grains. Slight to common 677.6- elemental F - 1c argillaceous matrix. Slight siliceous. Occasional Fault calcite 677.64 calcareous." "SILTSTONE: Light to medium grey, concentrations 30 m (net arenaceous occasional grading to very fine grained for each of the sand 15 m, sandstone in parts. Quartzose-feldspathic with two but veins occasional to common carbonaceous lamellae. generations of and faults Mirintu Abundant argillaceous matrix." fault-fill calcite filled with Cadna- 1 4 mm thick (two generations each 2 mm thick) calcite vein-type fault-fill mineralisation calcite Owie (CORE) mineralisation. "SANDSTONE: White to light grey. Fine to medium. Quartzose. Sub-angular to sub- Between present in Carbonate 680.36- rounded, poorly to moderately well sorted. Occasional feldsapar and ? lithic grains, calcite-filled the shale as 1c stable 680.54 common black, hard ? heavy mineral grains. Rare biotite flecks. Microcrystalline faulted well as the isotopes, XRD matrix, calcareous cement." intervals sandstone) (Within siltstone) "Fracture 55 degrees Carbonate dip. Filled with 1mm calcite vein. Sub- stable vertical slickenslides." "SILTSTONE: isotopes Medium grey. Transitional to very fine analysis and Fault calcite sandstone in parts. Laminated and cross ICP-MS (also 30 m 695.87- F – laminated. Bioturbated (worm burrows) measured above minor 696.03 N/A in parts. Rare carbonaceous fragments. elemental “sandy Very slightly calcareous in parts. concentrations limestone”) CLAYSTONE: Dark grey. Laminated and within the bioturbated." fault-fill calcite Calcite vein-type fault-fill in multiple closely spaced faults. mineralisation

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Table 10: Initial carbonate cemented sandstone samples collected from Surat Basin wells. Thickness of Associated Depth carbonate Preliminary Hole Depth (ft) Code Lithology from well completion report petroleum, Formation (m) cemented Analyses coal, etc. zone/s "Sandstone. Lt - med gy, soft to firm, qtzose, lithic, feldspathic, glauconitic, calcareous, vfn-fn, 100 ft (net (Rolling Brigalow 1 890 1a Not specified (illegible; gen light?)" – Later found to have sand 60 ft) Downs Group) insufficient calcite for analysis. Scattered coaly wood Coarse to very coarse, fair to poorly sorted, Hutton Chinchilla 4 799.6 2a fragments. 50 m strongly calcite cemented quartzose sandstone Sandstone 45 m above micro-faults 5440-5450. "60% SANDSTONE, light grey, fine to coarse Original bag grained, poorly sorted, quartzose, trace lithics, 10 ft above mislabelled strongly calcareous, firm to loose, no OCSF. 20% minor coal Hutton Davidson 1 2d 100 ft as duplicate SILTSTONE: light to medium grey-brown, soft. seam (in upper Sandstone Carbonate of 5450- SHALE: light to dark brown and grey, Evergreen Fm) stable 5460 carbonaceous trace coal fragments." "50% SANDSTONE, light grey, fine to coarse isotopes, XRD grained, poorly sorted, quartz-lithics subangular, 150 ft (100 ft calcareous, white clay matrix, firm, tight, no Coal fragments Davidson 1 5840-5850 Evergreen, Evergreen 2a OCSF. 30% SILTSTONE: grey, grey-brown, trace common carbonaceous, soft. 20% SHALE: black, grey- 50 ft Precipice) brown, dark brown, carbonaceous, firm, coal fragments common." "70% SANDSTONE, light grey-white, fine grained, quartzose, trace coarse to granular, slight trace 150 ft (100 ft Precipice lithic grains, extremely calcareous, patches of Trace coal Evergreen, Davidson 1 6010-6020 2c Sandstone porkish white tuffaceous? Matrix, firm, tight, no 50 ft Precipice) OSCF. 30% SHALE: mid grey, dark grey, finely micaceous, soft to firm, trace coaly."

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Table 10 continued: Initial carbonate cemented sandstone samples collected from Surat Basin wells. Thickness of Associated Depth Depth carbonate Preliminary Hole Code Lithology from well completion report petroleum, coal, Formation (m) (ft) cemented Analyses etc. zone/s "30% SST - lt gy-brn, f-vc grnd, SR-A, PS, pred clr & occ wh, yell, org, gy qtz, occ liths - gy, gy-grn, buff, pred loose but occ soft-fm aggs, abund wht mtx & sil/calc cmt, nil-poor por, no sho. 40% COAL - black, btl, blocky, mass, arg frags with conch Walloon Green fract, vit lustre, occ arg with minor fissility, only minor arg & Common minor 250 m (120 m 1000 2c Coal Swamp 1 silty subfissile grading to SHALE. 30% SLST - lt-med gy & brn, v coal seams net sand) Measures carb w flecks & laminae ip, fm, blocky, mass, non-calc, v arg ip, highly mic with silver musc flakes & micromic. Tr CLST/TUFF - buff, fm, bladed to platy ip, mass to amorphous cryptocrystalline translucent ip, non calc." "90% SST - minor amt losse m-vc & pebbles of clr & wh qtz & rare lithics, pred f-m aggs; pred lt grn-gy & lt brn, vf-f, SA-SR, WS, pred clr, wh, gy qtz, rare gy, fuff, blk liths, in fm-hd aggs, Carbonate Green mod sil-calc cmt, abund wh-lt brn arg mtx, occ lt gy-grn mtx, Common minor 100 m (60 m Hutton stable 1500 2a Swamp 1 occ carb lenses & thin laminae, grading to SLST ip, poor por, coal seams net sand) Sandstone isotopes, no show. 10% SLST - lt-mod gy & brn, fm, blocky-tabular, XRD mass, non calc, aren ip grading to vf grnd lithic SST, occ carb streaks. Tr CLST, Tr TUFF, Tr COAL." "60% SST - minor amount loose, c-vc & occ pebbles, clr qtz, minor gy & grn-gy lithics, SA-A, med grn-ty lithic vf-f aggs, only occ hd - pred soft - fm, wk-mod sil & calc cmt, abund gy & gy grn arg mtx, (much washed out of sample) occ carb streaks, Green silty ip grading to lithic aren SLST, no por, no sho. 30% SLST - Common minor 70 m (35 m Evergreen 1620 2c Swamp 1 med gy & brn ip, sft-fm, (less sil), blocky, mass, non calc, carb coal seams net sand) Formation flecks & occ streaks, mic & micromic, v aren with qtz & lithics - grading to vf lithic SST. 10% CLST - only minor v dk gy - pred lt-med ty & brn, sft-fm, tabular, mass-subfiss, non calc, wk sil, carb flecks, micromic, silty grading to aren SLST."

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Table 10 continued: Initial carbonate cemented sandstone samples collected from Surat Basin wells. Associated Thickness of Depth Depth Preliminary Hole Code Lithology from well completion report petroleum, carbonate Formation (m) (ft) Analyses coal, etc. cemented zone/s "SANDSTONE: gry-t gry, loc trnsl, vf-f, wl srt, s bang-s brnd, Minor coal 450 ft (net sand (Blythesdale com strg calc cmt, tr off wh-lt gry arg mtx, tr vf liths & carb 1000 1c spks, fri-mod hd aggs, ti-v pr vis por. COAL: blk, dll-sbvit, seam 175 ft) Group) Moonie hd-brit i/p, fiss-sbblky, unevn-sbconch, loc slty i/p." 40 500 ft split over Minor Walloon and Hutton 4830 D “Dolomite” methane Hutton, (net sand Sandstone 300 ft) 60% SST: "lt gy-off wh, occ trnsl, dom vf-f aggs, occ crs, s- sa, pr srtd, rr wh arg mtx, strg calc cmt on aggs, tr lse qtz, rr lt gnsh liths, rr carb detrl, pr inf por, tr calc min fluor, n/s. 1270 1a 20% SLTST: med-dk gy, brn blk, arg-aren mtx, grdg to vf SST ip, com carb spk & mic-lam, tr micmic, sl calc ip, frm-mod Carbonate hd, sblky-fiss. 20% COAL: blk, mod hd, brtl, blky-sbfiss, occ stable isotopes, slty, conch frac, vit lus, tr woody tex." XRD 40% COAL: “blk, brn blk, tr v dk brn, grdg to carb SLTST, Coal seams dull-vit+bri, brit-mod hd, fiss+conc. 30% SLTST: med-dk gy, 1371 1c and frm-hd, sblky-sbfiss, sl calc ip, tr dol strks, com car flk + 450 m (net sand Walloon Coal apparently miclam, rr micmic, occ aren mtx. < 100 m though) Measures Moonie 40% COAL: "v dk brn-blk. Dull-vit. Sbbit, fiss-sbconc, brit- minor Corner 1 mod hd. 10% LYST: med lt gy-brn gy, sli-mod calc, swig, tr carb & lith spks, aren, tr vf sd amorph, stkyv sft. 30% SST: med gy-dk gy, vf-f, sr-occ sa, mod-w srtd, com-abun mod 1437 1c hd calc cmt, com off wh arg mtx, occ carb & lith grs, tr pyr, slty ip, grdg to aren SLTST, rr lse vf & crs-v crs qtz, fri-hd, v pr por, n/s. 20% SLTST: med-dk gy, brn gy-brn blk, cren-arg, n calc occ carb spks & mic lams, tr diss pyr, sandy drdg to vf SST ip, frm crmbly-blky." 1497 D Dolomite 450 m (net sand Walloon Coal XRD; insufficient 1455 D Dolomite As above < 100 m though) Measures carbonate

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Table 10 continued: Initial carbonate cemented sandstone samples collected from Surat Basin wells. Associated Thickness of Depth Depth Preliminary Hole Code Lithology from well completion report petroleum, carbonate Formation (m) (ft) Analyses coal, etc. cemented zone/s 70% SST: "lt-dk gy, vf-med, occ lse crs-v crs qtz, a-sa, mod srtd, 200 m, mostly in com strng sil & calc cmt, com arg & slty mtx, tr grdg to aren Minor coal lower Evergreen Moonie SLTST, tr micmic, com feld & lith grs, fri-mod hd, ti-v pr por, n/s. Evergreen 1818 2c Corner 1 30% SLTST: med-dk gy, dk brn, frm-hd, occ v hd-indrtd, com car seams (net sand about spk & miclam & strks, aren mtx ip, grdg to vf-f SST, rr lith, rr lt 125 m) grnsh chamosltic? grs, blky-sb-lss." 100% "SST: v lt-lt gy aggs, clr-trnsl grs, dom f-med, mod-w srtd, Moonie 1905 2d strg sil & cal cmt, tr wk arg cmt, frm-v hd, tr lith rr carb Corner 1 spks/miclam, rr qtz ovrgth, pr por-ti, tr min fluor, n/s." 200 m, mostly in 50% SST: "lt-med gy, occ off wh-clr, dom f-med, occ crs, a-sr, Minor coal lower Evergreen Precipice mod srtd, v strg sil & cal cmt, wk arg cmt ip, tr lith/carb miclam, seams (net sand approx. Sandstone Moonie rr carb detrl, grdng & intbd-interlam w/SLTST, tr qtz ovrgth, pr 1923 2d 125 m) Corner 1 por-ti, tr min flu, n/s. 50% SLTST: gy-med gy, sblky-sbflss, frm-v hd abund carb miclam, aren mtx, grdg to f-vf SST, tr grded bdngs, tr carb/COAL strks." Carbonate “60% SLTST: gy-gy brn, frm, blky, fiss-sb fi sip., qtzose, blk org stable spk & len, grdg to SANDSTONE. 30% SST: wh, sft-fri, vf-m gr, Walloon isotopes, Minor coal 100 m (net sand pred f gr. Sa-sr, h sph, med w srt, qtzose, minor lith, occ org & Coal XRD Strathpine 1 270 2c seams approx. 20 m) hvy mins, abn wh cly mtx, pred abd carb cmt, pvp, ns, grdg to Measures SILTSTONE. 10% COAL: blk, med hd, blky-sh fiss, bri conch frac, sb bit-bit.” "50% SST: wh-gy, qtzose, vf-med pred f, wl srtd, sb ang-sb mdd, hi sphr, mod-abd wh cly mtx, mod-abd calc cmt, sil cmt ip, mod hd-hd, occ yel brn fgr cmt, acc lith, poor-fr vis por, no shws. Strathpine 1 390 2c 45% SLTST: gy-dk gy brn, qtzose, fm-hd, blky-sb fis, org spks & lam, grad to sst, occ arg. 5% Coal: blk-blk bm, hd, sb conch frac, Hutton sb blky-sb fis, occ ea." 200 m (net sand Trace coal "80% SST: wh, qtzose, vf-med pred f, sb ang-sb rndd, hi sphr, wl approx. 140 m) Sandstone srtd, mod abd wh cly mtx, abd calc cmt, mod hd-hd, occ fri, poor-fr vis por, no shws. 15% SLTST: gy-gy brn, qtzose, fm, arg Strathpine 1 500 2c ip & mic mic, sb blky-sb, fis, org spks & lam grad to SST & SH. 5% Coal: blk, brt-prly lust, fm-hd, sb blky-sb fis, ea ip conch frac."

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Table 10 continued: Initial carbonate cemented sandstone samples collected from Surat Basin wells. Thickness of Associated Depth Depth carbonate Preliminary Hole Code Lithology from well completion report petroleum, Formation (m) (ft) cemented Analyses coal, etc. zone/s “70% SLTST: gy, qtzose – aren, sb blky-sb fis, fm-md hd, org spks + lam, grad to vf sst r.r., mic mic. 30% SST: wh, qtzose, f, s bang-sb Strathpine 1 618 2c rndd, hi sphr, wl srtd-v wl srtd, abd wh cly mtx, abd calc cmt, acc Trace coal Evergreen lith, org + hvy mins, poor vis por, no shws. COAL – tr: blk-v dk brn, hd-md hd, brt-prly lustr, sb conch frac, ea i.p. sb fix.” “70% SLTST: gy-bl gy, aren-sil, occ mic mic, fm, sb blky-sb fis, org spks, grad to SST and SH. 15% SST: gy-wh, brn whr fgr, qtz-qtx lith, Strathpine 1 vf-f, occ f-med, fm, s bang-sb rndd, hi sphr, well srtd, mod wh-gy 633 2c Trace coal cly mtx, abd cmt i.p., abd sil cmt i.p., app 40% brn fg cmt this vhd- hd, acc org + hvy mins, poor, vis por no Shows”. 15% SH: gy brn-yel Evergreen brn, aren-sil, arg + mic mic i.p., fm-sft, org spks, grad to SLST.” (Boxvale “60% SLTST: gy-gy bl also dk brn, aren-sil-org, occ mic mic, fm, sb SST MBR) blky-sb fiss, org spks, grad to SST + SH. 30% SH: dk brn-brn, arg, mic Strathpine 1 mic, org, abd org lam, fis, fm, grad to sltst. 10% SST: wh, qtzose, vf- 200 m 678 2c Trace coal f, s bang-sb rndd, hi sphr, wl srtd, abd whi cly mtx, abd calc cmt (net sand 65 m) Carbonate i.p., sil cmt i.p., acc org + lith + hvy mins, poor vis por, no Shws. stable COAL: trace.” isotopes, “75% SLTST: gy also brn-dk brn, aren i.p. to arg-org with abd org XRD lam, sb blky- occ sb fiss-fiss, fm-mod hd, mic mic i.p., org spks + 10 m below Strathpine 1 lam, grad to Sst. 15% SST: pred lse gr, qtz, clr, crs-f, wht, pred med, 753 2c minor oil s bang-wl rndd, hi sphr, mod srtd, aggs abd wh cly mtx, sft, abd show calc cmt, fr por, no shws. 10% SH: dk brn-blk brn, arg-org, fm, sb fis-fis, mic mic i.p., abd org lam, grad to sltst.” Precipice Sandstone "60% SST: wh, qtzose, f, sb ang-sb rndd, hi sphr, wl srtd, fm-fri, abd Strong oil wh cly mtx, abd calc cmt, r.r. Lith, poor vis por due to mtx & cmt, show, just Strathpine 1 801 2c shw 30%-40% dull yell flur, wk pale yel-whi crsh cut, res dull yel res above ring. 40% SLTST: gy-dk gy, sil-aren, fm, sb blky-sb fis, abd org spks & Kuttung lam, occ bec arg & mic mic grad to f sst." Volcanics

"70% SANDSTONE: light grey-white, medium to coarse grained, Sussex 6800- quartzose, trace dark grains, poor sorting, abundant white to Precipice 100 ft (net sand 2c Trace coal Downs 1 6810 cream calcareous clay matrix, well cemented, tight. 30% Sandstone 60 ft) SILTSTONE: grey, sandy, firm."

25

Table 11: South Australian Eromanga Basin Wells with largest amount of recovered core (10 to 20 metres) – Well completion reports under assessment. Well Latitude Longitude Formation/s Cored Well Latitude Longitude Formation/s Cored Biala 006 -28.51 140.38 Murta Fm Jena 003 -28.52 140.32 Murta Fm Biala 007 -28.54 140.37 Murta Fm Jena 006 -28.51 140.31 Murta Fm Bookabourdie 005 -27.54 140.48 Birkhead Fm Jena 011 -28.51 140.30 Murta Fm Burke 002 -28.13 140.93 Murta Fm Jena 012 -28.50 140.31 Cadna-Owie Fm Calamia West 001 -28.51 140.27 Murta Fm Limestone Creek 007 -28.52 140.39 Murta Fm Corkwood 001 -28.02 140.80 Birkhead Fm Limestone Creek 008 -28.52 140.40 Cadna-Owie Fm Dirkala 001 -28.52 140.04 Birkhead Fm Limestone Creek 009 -28.52 140.38 Murta Fm Dirkala 003 -28.52 140.03 Murta Fm Marabooka 004 -28.20 140.61 Oodnadatta Fm Dullingari 020 -28.09 140.87 Cadna-Owie Fm Mawson 002 -28.05 139.93 Poolowanna Fm Dullingari 028 -28.12 140.87 Murta Fm McKinlay 001 -28.47 140.48 Oodnadatta Fm Dullingari 035 -28.10 140.88 Murta Fm McKinlay 002 -28.45 140.48 Murta Fm Dullingari 036 -28.14 140.89 Murta Fm Merrimelia 006 -27.74 140.18 Murta Fm, Namur Sandstone Dullingari 037 -28.08 140.90 Cadna-Owie Fm Merrimelia 008 -27.73 140.19 Murta Fm Dullingari 039 -28.10 140.90 Murta Fm Merrimelia 009 -27.75 140.18 Murta Fm Dullingari 040 -28.14 140.88 Murta Fm Merrimelia 016 -27.74 140.18 Murta Fm Dullingari 043 -28.14 140.88 Murta Fm Merrimelia 030 -27.73 140.18 Birkhead Fm Dullingari 047 -28.11 140.89 Murta Fm Merrimelia 031 -27.73 140.18 Birkhead Fm Fly Lake 004 -27.61 139.99 Murta Fm Merrimelia 032 -27.74 140.18 Birkhead Fm Gidgealpa 029 -28.02 139.98 Birkhead Fm Narcoonowie 004 -28.49 140.72 Murta Fm Gidgealpa 030 -28.03 139.97 Birkhead Fm Strzelecki 004 -28.23 140.64 Birkhead Fm, Murta Fm Gidgealpa 031 -28.01 139.98 Birkhead Fm Three Queens 001 -28.00 140.78 Cadna-Owie Fm, Hutton Sandstone Gidgealpa 032 -28.02 139.99 Birkhead Fm Ulandi 005 -28.54 140.31 Cadna-Owie Fm Gidgealpa 034 -28.04 140.00 Hutton Sandstone Wilpinnie 001 -28.06 140.73 Murta Fm Jena 002 -28.52 140.31 Cadna-Owie Fm

26

Table 12: Queensland Eromanga Basin wells with recovered core – Well completion reports under assessment.* WELL_NAME Latitude Longitude WELL_NAME Latitude Longitude (CLEEVE) 1 -23.43 144.39 KATHERINE 1 -23.59 143.75 AUGATHELLA 1 -25.80 146.43 KATHERINE WEST 1 -23.59 143.76 AUGATHELLA 2-3R -25.19 146.15 KENNEDY HIGHWAY DDH1 -22.75 141.32 BARROLKA EAST 1 -26.85 141.80 KENNEDY HIGHWAY KHD01A -22.75 141.32 BESSIES 1 -23.40 143.22 MACHATTIE 1 -24.82 140.31 BLACKALL 1 -24.36 145.34 MACHATTIE LMDDH001 -24.91 139.73 BLACKALL 2 -24.16 144.22 MOUNT WHELAN 1 -23.31 138.88 BODALLA SOUTH 1 -26.45 143.42 MOUNT WHELAN 2 -23.48 138.68 BRAIDWOOD 1 -24.75 142.92 MULLIGAN MULDDH001 -24.90 138.55 BULLOO 1 -28.40 143.77 MUNKAH 2 -27.44 141.90 CONNEMARA 1 -24.50 141.40 PRAIRIE 1/1A -22.63 144.24 DARR 1 -23.09 144.17 QUILPIE 1 -26.63 145.04 DILKERA 1 -27.75 142.64 ROCKY CREEK 1 -23.54 143.21 EPSILON 1 -28.15 141.15 TAMBO 2 -24.87 146.37 EPSILON 2 -28.14 141.13 TAMBO 4 -24.82 145.85 EROMANGA 1 -26.61 143.88 THARGOMINDAH 1-1A -27.29 143.46 EUSTON 1 -23.16 143.64 THARGOMINDAH 2 -27.73 142.92 FITTLEWORTH 1 -23.75 144.18 THARGOMINDAH 3 -27.28 142.93 JACKSON SOUTH 2 -27.65 142.43 TICKALARA 1 -28.64 142.16 JACKSON SOUTH 7 -27.66 142.45 WYANDRA 1 -27.09 146.14 JUNDAH 1 -24.53 142.70 YANKO 1 -28.08 141.86 *No indication of the actual formations cored was given in the summary database obtained.

27

Table 13: Surat Basin wells with recovered core (up to entire stratigraphic sequence). WELL_NAME Latitude Longitude WELL_NAME Latitude Longitude (BLYTHDALE) 11 -26.59 148.96 MOONIE 4 -27.77 150.24 (BLYTHDALE) 14 -26.50 148.99 MOONIE 5 -27.75 150.24 (BLYTHDALE) 4 -26.58 148.96 MOONIE 7 -27.77 150.23 (BLYTHDALE) 4 -26.59 148.95 MOONIE 8 -27.74 150.26 (BLYTHDALE) 5 -26.58 148.97 MOONIE 9 -27.78 150.23 (CORNWALL) 6 -26.14 148.42 MOONIE 10 -27.74 150.26 (GUBBERAMUNDA) 2 -26.27 148.75 MOONIE 18 -27.75 150.25 (HOSPITAL HILL) 3 -26.57 148.78 MOONIE 19 -27.76 150.24 (HOSPITAL HILL) 4 -26.57 148.77 MOONIE 20 -27.76 150.25 (MOOGA) 3 -26.40 148.85 MOONIE 21 -27.77 150.24 (MOUNT BASSETT) 1 -26.46 148.86 MOONIE 22 -27.76 150.24 (MOUNT BASSETT) 2 -26.48 148.88 MOONIE 23 -27.74 150.26 (MOUNT BASSETT) 3 -26.49 148.85 MOONIE 26 -27.77 150.23 (MOUNT BASSETT) 4 -26.49 148.83 MOONIE 27 -27.76 150.24 (ORALLO) 10 -26.34 148.57 MOONIE 28 -27.76 150.25 (SOLITARY CREEK) 7 -26.31 148.94 MOONIE 29 -27.75 150.25 (WALLUMBILLA) 19 -26.58 149.18 MOONIE 12 -27.78 150.22 (WAROOBY) 1 -26.56 148.90 MOONIE 13 -27.76 150.23 ALTON 2 -27.93 149.36 MOONIE 14 -27.75 150.26 ALTON 3 -27.94 149.37 MOONIE 15 -27.76 150.24 ALTON 4 -27.95 149.37 MOONIE 16 -27.72 150.28 ALTON 5 -27.95 149.37 MOONIE 17 -27.74 150.25 ALTON 6 -27.94 149.36 MOONIE 30 -27.73 150.27 ALTON 8 -27.94 149.37 MOONIE 31 -27.75 150.25 AVONDALE 3 -26.97 148.66 MOONIE 32 -27.75 150.25 AVONDALE 4 -26.94 148.68 MOONIE 33 -27.76 150.24 AVONDALE NORTH 1 -26.92 148.68 MOONIE 34 -27.76 150.24 BINKEY 1 -26.35 150.26 MOONIE 37 -27.74 150.26 BLYTHDALE NORTH 2 -26.53 148.95 MOONIE 38 -27.76 150.25 BONY CREEK 19I -26.74 148.96 MOUNT HOPE 2 -26.42 149.10 BOOMI 1 -28.76 149.56 PARADISE DOWNS 2 -26.22 149.90 CAMERON 1 -26.16 149.63 PEGASUS 1 -26.12 148.90 CHINCHILLA 3 -26.94 150.37 PELHAM 1 -26.39 150.29 CHINCHILLA 4 -26.73 150.20 PICKANJINNIE 12-12A -26.57 149.14 COMBARNGO EAST 1 -26.86 149.18 PICKANJINNIE 2 -26.62 149.13 DALBY 1 -27.34 150.74 PICKANJINNIE 22I -26.59 149.12 DANIEL 1 -26.07 149.55 PICKANJINNIE 23I -26.59 149.13 GLENEARN SWC -27.49 148.99 PLEASANT HILLS 31 -26.41 149.02 KUMBARILLA EAST 1 -27.43 150.79 PLEASANT HILLS 32 -26.38 149.00 LACERTA 10 -26.30 149.02 PLEASANT HILLS 34 -26.41 149.00 LACERTA 13 -26.33 149.04 RASLIE 7 -26.49 149.08 LACERTA 3 -26.31 149.03 ROMA 8 -26.55 148.60 LATEMORE 1 -26.59 149.08 ROWALLON 13 -26.39 149.05 LATEMORE EAST 1 -26.59 149.10 ROWALLON 3 -26.44 149.14 LATEMORE SOUTH 1 -26.64 149.11 SOUTHEAST TEATREE 1 -27.14 150.70 MEELEEBEE 5 -26.24 149.20 STRATHPINE 3 -26.42 150.24 MEGAN 1A -27.46 150.53 WASHPOOL 1 -27.16 148.98 MITCHELL 1 -26.42 147.12 WIDARA 1 -27.98 150.28 MITCHELL 2 -26.34 148.13 YAPUNYAH 1 -27.33 148.75 MOONIE 3 -27.73 150.27 *No indication of the actual formations cored was given in the summary database obtained. 28

3. Initial geochemistry

3.1. Calcite stable isotopes Carbon and oxygen isotopic compositions were determined for 26 calcite cements in Surat Basin sandstones, 21 calcite veins, 2 calcite chimneys and 1 fault breccia in the Walloon Coal Measures (Kogan Creek coal mine), and 17 calcite cements and 3 fault veins in Eromanga Basin sandstones (Tables 14, 15 and 16); Figures 4, 5 and 6). The Surat cements exhibit a range of δ18O values from 4.6 to 17.0 ‰ (n=25), with the exception of a heavily carbonate-cemented Hutton Sandstone sample (Chinchilla 4-799.6m), which has a δ18O value of 24.7 ‰ (Figure 5). The Surat cements exhibit a range of δ13C from -11.1 to 3.0 ‰ (n=26). Eromanga cements and fault veins have an overlapping range of δ18O and δ13C values from 6.6 to 22.4 ‰ and -15.9 to 0.0 ‰ (n=20), respectively (Figure 5). The range of δ18O and δ13C values for Eromanga samples becomes 6.6 to 15.7 ‰ and -10.7 to 0.0 ‰ (n=17) when CO-58, CO-63 and CO-66 are excluded.

In order to determine the fluid source, we used model temperatures of 80°C and 120°C and the oxygen isotope fractionation curve for calcite-water to calculate the oxygen and carbon isotope compositions of the fluid in equilibrium with Eromanga and Surat sandstone calcites (Table 17) (O'Neil et al., 1969). Low temperature formation (<80°C) of the calcite cements and fault veins is unlikely because this would imply unrealistically low fluid oxygen isotope compositions. Considering a higher temperature range between 80°C and 120°C gives more realistic calculated fluid oxygen isotope compositions from -15.0 to -1.1 ‰ (n=17) and -17.0 to 0.2 ‰ (n=25) for the main populations of Eromanga and Surat sandstone calcites, respectively (Table 17). The calculated oxygen isotope compositions of fluids in equilibrium with the majority of calcite samples are much lower than those reported for most mid to low-latitude sedimentary basins (Clayton et al., 1966) and to those attained during burial diagenesis in many sedimentary basins (Clauer and Chaudhuri, 1995). This suggests meteoric dominated waters were involved in the precipitation of the majority of calcite cements and the fault veins. Four samples with higher δ18O values from 21.6 to 24.7 ‰ (CO-10, CO- 58, CO-63 and CO-66) precipitated under lower temperature conditions and/or from 18O-enriched fluids such as basinal brines.

29

Table 14: Carbonate carbon and oxygen stable isotopes for Eromanga Basin calcites – both cemented sandstone and fault-mineralisation intervals. XRD (or SEM in brackets) sample screening results Sandstone Associated Sample Location Formation 13C  18O  Carbonate relative proportions (%) Code* Structure VPDB VSMOW Calcite Siderite Ankerite Dolomite

CO-1 Inland 3, 4430-4440' Birkhead Fm. 2c Fault 0.0 12.9

CO-2 Mirintu-1 B 696 m Fault Fill Cadna-Owie Fm. F Fault -0.3 8.8 (100) Mirintu-1 A1 Bottom layer of fault Cadna-Owie Fm. CO-3 F – 1c Fault -1.6 9.7 (100) 677 m Cadna-Owie Fm. CO-4 Mirintu-1 A2 Top layer of fault 677 m F – 1c Fault -1.6 10.6 (100)

CO-5a Mirintu-1 680.36-680.395 m Cadna-Owie Fm. Fault -2.8 9.5 1c CO-5b Fault -2.8 9.5 Cadna-Owie Fm: CO-6 Mirintu-1 675.29-675.33 m Wyandra 1b Fault -3.4 9.5 Sandstone CO-7 Saltern Creek 1, 1651'2" - 1651'4" Namur Sandstone 2c Fold -2.6 9.0 CO-8 Winna 1, 1008.08 - 1008.12 m Murta Fm. 1c Fold -4.2 6.6

CO-9 Yongala-1, 2500-2510' Mackunda Fm. 1a Fault -10.7 14.3

CO-51 Bodalla South 9, 1596 m Hutton Sandstone 2d Fold -4.7 8.4 100 CO-52 Bodalla South 9, 1617 m Hutton Sandstone 2d Fold -7.4 13.9 70 30 CO-52R (replicate isotope analysis) -7.4 13.8 CO-56 Kenmore 12, 1075 m Cadna-Owie 1c Fold -2.9 13.6 100

CO-57 Kenmore 12, 1350 m Birkhead 1c Fold -1.4 12.4 100 CO-58 Widnerpool 1, 559-562 m Wallumbilla 1c Fault -15.9 22.4 100 CO-59 Widnerpool 1, 862-865 m Westbourne 2c Fault -3.2 13.3 100 CO-63 Bodalla South 2, 150 m Winton 1a Fold -10.3 22.3 100 CO-64 Inland 3, 5570-5580 ft Hutton Sandstone S – 2c Fold -10.0 13.7 64 CO-65 Kenmore 12, 510 m Mackunda 1d Fold -5.7 15.7 100 CO-65R (replicate isotope analysis) -5.7 15.7 CO-66 Kenmore 12, 920 m Wallumbilla 1d Fold -13.8 21.6 100 *Refer to tables 6 and 7.

30

Table 15: Carbonate carbon and oxygen stable isotopes for Surat Basin Calcites – from cemented sandstone intervals. XRD sample screening results Sandstone Associated Sample Location Formation 13C 18O Carbonate relative proportions (%) Code* Structure VPDB VSMOW Calcite Siderite Ankerite Dolomite CO-10 Chinchilla-4, 799.6 m Hutton Sandstone 2a Fault 0.8 24.7 90? 10?

CO-11 Davidson-1, 5840-5850' Precipice Sandstone 2a Fault -3.6 4.9 100 CO-12 Davidson-1, 6010-6020' Precipice Sandstone 2c Fault -9.2 6.4 78 22 CO-13 Green Swamp-1, 1500 m Hutton Sandstone 2a Fault -2.5 7.0 100 CO-14 Strathpine-1, 500 m Hutton Sandstone 2c Fault -2.4 5.2 100 CO-15 Sussex Downs-1, 6800-6810' Precipice Sandstone 2c Fault -4.7 6.3 100? CO-35 Brigalow 1, 890 m Rolling Downs Grp 1a Fault -6.5 15.2 100 CO-36 Davidson 1 5440-5450 ft Hutton Sandstone 2d Fault -2.0 10.6 100 CO-37 Green Swamp 1, 1000 m Walloon CM 2c Fault 0.8 14.2 60 40 CO-38 Green Swamp 1, 1620 m Hutton Sandstone 2a Fault -3.4 13.8 54 46 CO-39 Moonie 40, 1000 ft Blythesdale Group Fault -9.3 16.4 52 48 CO-40 Moonie Corner 1, 1270 m Walloon CM 1a Fault -11.1 14.1 100 CO-40R (replicate isotope analysis) Fault -11.1 14.1 CO-41 Moonie Corner 1, 1371 m Walloon CM 1c Fault -0.2 14.1 54 46 CO-42 Moonie Corner 1, 1437 m Walloon CM 1c Fault -2.2 13.3 59 41 CO-43 Moonie Corner 1, 1818 m Evergreen Fm 2c Fault -2.1 11.9 100 CO-43R (replicate isotope analysis) Fault -2.1 11.9 CO-44 Moonie Corner 1, 1905 m Precipice Sandstone 2d Fault -4.9 9.0 100 CO-46 Strathpine 1, 270 m Walloon CM 2c Fault 3.0 12.2 58 42 CO-47 Strathpine 1, 390 m Hutton Sandstone 2c Fault 2.3 14.4 100 CO-48 Strathpine 1, 618 m Evergreen Fm 2c Fault -0.3 12.2 100 CO-49 Strathpine 1, 633 m Evergreen Fm 2c Fault 0.2 13.3 54 46 CO-50 Strathpine 1, 801 m Precipice Sandstone 2c Fault -7.6 8.4 100 CO-50R (replicate isotope analysis) Fault -7.6 8.4 CO-53 Moonie 40, 4830 ft Hutton Sandstone D Fault -7.0 13.6 68 32 CO-55 Moonie Corner 1, 1497 m Walloon CM D Fault -0.6 17.0 42 58 CO61 Strathpine 1, 753 m Precipice Sandstone 2c Fault -1.7 8.3 62 38 CO62 Strathpine 1, 678 m Evergreen Fm 2c Fault -7.0 8.7 63 37 CO67 West Wandoan 1, Hutton 6 Hutton Sandstone Fault 1.1 4.6 100 *Refer to tables 6 and 7.

31

Table 16: Carbonate carbon and oxygen stable isotopes for Kogan Creek Coal Mine calcite samples. Associated 13 18 Fracture Type Source Location Sample  CPDB  OVSMOW Sample Description structure

S9B19d CO-30 0.1 24.4 Massive calcite from a 15 cm wide “chimney” of mineralisation in a fault. Also clay present. S9B16-17.7 CO-31a -1 6.6 Massive calcite from a 15 cm wide “chimney” of mineralisation in a fault. Also clay present. Faults in coal: 15 cm wide massive calcite S9B16-17.7 (fresh crush) CO-31b 1.3 24.4 Massive calcite from a 15 cm wide “chimney” of mineralisation in a fault. Also clay present. S10B11M5 CO-19 14.1 17.4 Calcite from shear surface in coal. Faults in coal: calcite sheet-type veins S8 End Wall O1 CO-26 5.4 20.8 Calcite from shear surface in coal. Fault in coal with abundant sulfides, minor calcite S8B3N7 CO-33 - - Fault through coal with abundant sulphides and minor calcite 10 mm thick mineralisation of fault through coal seams; syntectonic bornite on/within this Fault in coal: calcite sheet with syntectonic bornite S10B4M7 CO-20 16.8 16.8 calcite was separated prior to analysis. Large calcite vein in very hard boulder from top of large fault, non-coal interval above Fault: breccia with calcite veins S8B5N6 CO-22 -13.6 11.1 middle coal seam sequence. Calcite separated from significant bornite prior to analysis. Coal master cleat mineralisation CO-21a 8.5 18.3 (different cleats tested; “A”). Calcite separated from significant bornite prior to analysis. Coal master cleat mineralisation CO-21b -1.8 21.9 (different cleats tested; “B”). CO-21c 8.2 18.3 (S8B6N5 fresh sub-sample) S8B6N5 CO-21d 2.8 20.1 Small coal cleat calcite separated from sulphides.

Coal: master cleats with bornite S8B6M5 CO-32 - - Master cleat calcite with abundant fine crystals of bornite and pyrite Faults S10B17&20O5 large grains CO-28a -17.8 25.8 Granular calcite from subvertical joint through coal. Coal: subvertical joints S10B17&20O5 thin sheet CO-28b -14.3 24.3 Sheet calcite from subvertical joint through coal. S10B19&40O1 CO-24 7 18.7 Coal master cleat calcite, separated from sulphides. Coal: master cleats with pyrite S10B24/25O1 CO-25 4 19.4 Coal master cleat calcite, separated from pyrite hemispheres. S10B12M1 CO-16 15 16.7 Calcite from coal master cleats. S10B23HO O1 CO-23 6.3 18.9 Calcite from coal master cleats. CO-27a 12.7 18.2 Coal master cleat calcite. CO-27b 2.3 21.4 Coal master cleat calcite. S9B1(&20)O1 CO-27c 4.9 20.8 Coal master cleat calcite. Coal: master cleats S10B17(&10?)O1 CO-34 - - Non-cleat joint swarm through coal, filled with calcite and coal detritus CO-17a 16.4 16.8 Prismatic calcite from small coal cleats, with minor sulphides. Coal: minor cleats with sulfides S10B14M1 CO-17b 16.3 17.3 Prismatic calcite from small coal cleats, separated from sulphides. S10B20/21 M13 CO-18 18.9 15.2 Coal cleat calcite, some with brown tinge. CO-29a 5.4 19.5 Brown calcite from small coal cleats. Coal: minor cleats with brown calcite S10B24/25 mid O5? CO-29b 5.5 19.5 Brown calcite from small coal cleats. - Samples 32 to 34 not analysed for CO stable isotopes; sample 32 and 34 are inseparable from sulphides and coal fines respectively, sample 33 has insufficient mass of calcite. 32

Table 17: Modelled carbon and oxygen isotope composition of the mineralising fluids. Calcite Modelled fluids at different temperatures Sample  C  C 40oC 80oC 120oC 40oC 80oC 120oC CO-1 12.9 0.0 -8.7 -3.9 -1.3 -1.3 CO-2 8.8 -0.3 -12.8 -7.9 -1.6 -1.6 CO-3 9.7 -1.6 -11.9 -7.1 -2.9 -2.9 CO-4 10.6 -1.6 -11.0 -6.2 -2.9 -2.9 CO-5a 9.5 -2.8 -12.1 -7.2 -4.1 -4.1 CO-5b 9.5 -2.8 -12.1 -7.2 -4.1 -4.1 CO-6 9.5 -3.4 -12.1 -7.2 -4.7 -4.7 CO-7 9.0 -2.6 -12.6 -7.8 -3.9 -3.9 CO-8 6.6 -4.2 -15.0 -10.2 -5.5 -5.5 CO-9 14.3 -10.7 -7.3 -2.4 -11.9 -11.9 CO-10 24.7 0.8 3.1 7.9 -0.5 -0.5 CO-11 4.9 -3.6 -16.7 -11.9 -4.9 -4.9 CO-12 6.4 -9.2 -15.2 -10.3 -10.4 -10.4 CO-13 7.0 -2.5 -14.6 -9.8 -3.8 -3.8 CO-14 5.2 -2.4 -16.4 -11.5 -3.7 -3.7 CO-15 6.3 -4.7 -15.3 -10.5 -6.0 -6.0 CO-16 16.7 15.0 -11.8 -4.9 12.9 13.7 CO-17a 16.8 16.4 -11.6 -4.8 14.4 15.1 CO-17b 17.3 16.3 -11.1 -4.3 14.2 15.0 CO-18 15.2 18.9 -13.2 -6.4 16.9 17.6 CO-19 17.4 14.1 -11.0 -4.2 12.1 12.8 CO-20 16.8 16.8 -11.6 -4.8 14.8 15.6 CO-21a 18.3 8.5 -10.1 -3.3 6.5 7.2 CO-21b 21.9 -1.8 -6.5 0.3 -3.9 -3.1 CO-21c 18.3 8.2 -10.1 -3.3 6.2 6.9 CO-21d 20.1 2.8 -8.3 -1.5 0.8 1.6 CO-22 11.1 -13.6 -17.3 -10.5 -15.7 -14.9 CO-23 18.9 6.3 -9.5 -2.7 4.3 5.0 CO-24 18.7 7.0 -9.7 -2.9 5.0 5.7 CO-25 19.4 4.0 -9.0 -2.2 1.9 2.7 CO-26 20.8 5.4 -7.6 -0.8 3.4 4.1 CO-27a 18.2 12.7 -10.2 -3.4 10.7 11.4 CO-27b 21.4 2.3 -7.0 -0.2 0.3 1.0 CO-27c 20.8 4.9 -7.6 -0.8 2.9 3.6 CO-28a 25.8 -17.8 -2.6 4.2 -19.8 -19.1 CO-28b 24.3 -14.3 -4.1 2.7 -16.3 -15.6 CO-29a 19.5 5.4 -8.9 -2.1 3.4 4.2 CO-29b 19.5 5.5 -8.9 -2.1 3.4 4.2 CO-30 24.4 0.1 -4.0 2.8 -1.9 -1.2 CO-31a 6.6 -1.0 -21.8 -15.0 -3.0 -2.3 CO-31b 24.4 1.3 -4.0 2.8 -0.7 0.0

33

Table 17 continued: Modelled carbon and oxygen isotope composition of the mineralising fluids. Calcite Modelled fluids at different temperatures Sample  C  C 40oC 80oC 120oC 40oC 80oC 120oC CO-35 15.2 -6.5 -6.4 -1.6 -7.8 -7.8 CO-36 10.6 -2.0 -11.0 -6.1 -3.3 -3.3 CO-37 14.2 0.8 -7.4 -2.6 -0.5 -0.5 CO-38 13.8 -3.3 -7.8 -3.0 -4.6 -4.6 CO-39 16.4 -9.3 -5.2 -0.4 -10.6 -10.6 CO-40 14.1 -11.1 -7.5 -2.7 -12.4 -12.4 CO-41 14.1 -0.2 -7.5 -2.7 -1.5 -1.5 CO-42 13.3 -2.2 -8.3 -3.4 -3.5 -3.5 CO-43 11.9 -2.1 -9.7 -4.9 -3.4 -3.4 CO-44 9.0 -4.9 -12.6 -7.8 -6.2 -6.2 CO-46 12.2 3.0 -9.4 -4.6 1.7 1.7 CO-47 14.4 2.3 -7.2 -2.4 1.0 1.0 CO-48 12.2 -0.3 -9.4 -4.6 -1.6 -1.6 CO-49 13.3 0.2 -8.3 -3.4 -1.1 -1.1 CO-50 8.4 -7.6 -13.2 -8.4 -8.9 -8.9 CO-51 8.4 -4.7 -13.2 -8.4 -6.0 -6.0 CO-52 13.9 -7.4 -7.7 -2.9 -8.7 -8.7 CO-53 13.6 -7.0 -8.0 -3.2 -8.3 -8.3 CO-55 17.0 -0.6 -4.6 0.2 -1.9 -1.9 CO-56 13.6 -2.9 -8.0 -3.2 -4.2 -4.2 CO-57 12.4 -1.4 -9.2 -4.4 -2.7 -2.7 CO-58 22.4 -15.9 0.8 5.6 -17.2 -17.2 CO-59 13.3 -3.2 -8.3 -3.5 -4.5 -4.5 CO61 8.3 -1.7 -13.3 -8.4 -3.0 -3.0 CO62 8.7 -7.0 -12.9 -8.0 -8.3 -8.3 CO-63 22.3 -10.3 0.7 5.6 -11.6 -11.6 CO-64 13.7 -10.0 -7.9 -3.1 -11.3 -11.3 CO-65 15.7 -5.7 -5.9 -1.1 -7.0 -7.0 CO-66 21.6 -13.8 0.0 4.8 -15.1 -15.1 CO-67 4.6 1.1 -17.0 -12.2 -0.2 -0.2

34

25.0

20.0

15.0

10.0 Surat Basin - Faults & Coal 5.0 Joints PDB

C Surat Basin - Sandstones 13

 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 -5.0 Eromanga Basin - Sandstones & Faults -10.0

-15.0

-20.0 18  OVSMOW

Figure 4: Carbon and oxygen isotope compositions of Surat and Eromanga calcite cements and veins.

4 Winton Fm

2 Mackunda Fm

Wallumbilla 0 0 5 10 15 20 25 30 (Surat) Rolling Downs Group -2 Cadna-Owie Fm.

(Surat) Blythesdale Group -4 (Hooray equiv) Murata Fm PDB

C -6

13 (Hooray equiv) Namur Sandstone 

-8 Walloon CM

Westbourne Fm -10 Birkhead Fm

-12 Hutton Sandstone

Hutton Sandstone with U- -14 monazite & Mn-calcite Evergreen Fm -16 18 Precipice Sandstone  OVSMOW

Figure 5: Carbon and oxygen isotope composition of calcite cements and fault veins in clastic units of the Surat and Eromanga basins.

35

25.0 Faults in coal: 15 cm wide massive calcite 20.0 Faults in coal: calcite sheet-type veins 15.0 Fault in coal: calcite sheet with syntectonic bornite 10.0 Fault: breccia with calcite veins

5.0 Coal: master cleats with bornite VPDB C

13 0.0

 Coal: master cleats with pyrite 0 10 20 30 -5.0 Coal: master cleats

-10.0 Coal: subvertical joints

-15.0 Coal: minor cleats with sulfides

-20.0 Coal: minor cleats with brown 18  OVSMOW calcite

Figure 6: Carbon and oxygen isotope compositions of calcite veins and chimneys in the Walloon Coal Measures at Kogan Creek coal mine, Surat Basin.

It is likely that those samples with somewhat more negative calculated fluid oxygen isotope compositions were deposited at the higher temperature end of the model temperature range (120oC). In this context preliminary fluid inclusion data reported subsequently in this report as well as apatite fission track analysis of Surat-Bowen samples indicate that the Hutton Sandstone experienced paleotemperatures ≥ 110oC (Raza et al., 2009). Surat calcite cements apart from Chinchilla 4-799.6m are interpreted to have precipitated from meteoric fluids with calculated oxygen isotope compositions of -17.0 to 0.2 ‰ that are consistent with the mid to high latitude position of eastern Australia during the Early to mid-Cretaceous (Veevers and Conaghan, 1984). On the other hand, the calculated fluid oxygen isotope composition for Chinchilla 4-799.6m at 120oC of 7.9 ‰ is enriched in 18O relative to seawater and meteoric waters, which suggests the calcite precipitated from deep-basin brine composed of highly evolved meteoric water. Magmatic fluids and evaporated seawater may have similar 18O values but can be excluded on the basis of the fluid inclusion data for this sample that indicate the carbonate cement precipitated from low salinity fluids with up to 1.74 wt.%

NaCl equivalent. The ultimate source of the CO2 is discussed in a subsequent section.

The timing and temperature of precipitation of calcite cements in the Eromanga Basin are less well constrained because of the complex hydrogeology of the basin. Fluid inclusion data for underlying Cooper Basin sandstones provide an indication of maximum paleotemperatures (≤160oC) and also record a shift in salinity towards values similar to modern groundwaters (Toupin et al., 1997). Mixing between low salinity groundwaters of meteoric origin and evolved basinal brines across a range of temperatures may explain the wide range of calculated oxygen isotope compositions from -15.0 to 5.6 ‰ of fluids precipitating calcite

36 cements and fault veins in Eromanga Basin sediments. Future fluid inclusion studies will allow a detailed investigation of this hypothesis.

Modelling of fluid carbon isotope composition is more complex than for oxygen isotopes as the carbon isotope fractionation under aqueous conditions depends on the pH of the fluid. Under near neutral to acidic

o - conditions, H2CO3 is the dominant aqueous carbonate species at temperatures less than 200 C, whereas HCO3 is the dominant species under near neutral to mildly alkaline conditions (Large et al., 2001). The precipitation of calcite in reservoir settings occurs under near neutral to alkaline conditions so the modelling of carbon

- isotope fractionation has been undertaken for the HCO3 -dominant case using the fractionation equations of (Ohmoto and Rye, 1979) (Table 17). The majority of Surat and Eromanga sandstone calcites have calculated carbon isotope fluid compositions at model temperatures of 80oC and 120oC that are consistent with inorganic sources, specifically marine carbonate (13C value of 0 ‰) and magmatic/mantle carbon dioxide (13C value of -5 ‰) (Hoefs, 1987).

Eight calcite cement samples from both basins are more depleted in 13C, with calculated carbon fluid compositions less than -10 ‰ across the model temperature range (Table 17). This necessarily requires an organic carbon source most likely associated with hydrocarbon generation at deeper levels (Hoefs, 1987). Bicarbonate production related to modification (degradation) of organic matter and hydrocarbons may result from aerobic microbial oxidation, bacterial sulfate reduction (BSR), bacterial fermentation (methanogenesis), thermally induced abiotic decarboxylation (thermal maturation) and thermochemical sulfate reduction (TSR). Microbial (bacterial) oxidation is unlikely in this setting as it is the first reaction that occurs after sediment deposition in shallow ground water environments (Carothers and Kharaka, 1980). Bacterial sulfate reduction is commonly observed in areas affected by shallow formation waters (below the microbial oxidation zone)

2- 13 -1 with SO4 concentrations higher than 25mg/l and temperatures lower than 80°C. The  C value of HCO3 related to this process depends on the carbon isotopic composition of the organic carbon source and is about -20‰ for degradation of organic matter with a bulk 13C value of about -25‰ (Irwin and Barnes, 1975; Carothers and Kharaka, 1980). The presence of sulfate-rich waters away from subcrop is related to underlying or interbedded evaporite lithologies not observed in the Great Artesian basin system. Bacterial fermentation or methanogenesis operates in shallow sediments in both marine and freshwater environments and results in a wide range of bicarbonate carbon isotope compositions up +16‰ as observed in the Kogan Creek carbonates. This is discussed further in the following paragraphs. Thermal degradation of organic matter that occurs at temperatures greater than 80°C produces CO2 and CH4 in addition to hydrocarbons. Significant CO2 is produced through the catagenesis and metagenesis of humic or coaly (type III kerogen) source rocks, whereas only minor CO2 is generated from sapropelic (type I/II kerogen) source rocks (Hunt, 1979).

13 Thermogenic CO2 from hydrocarbon deposits have  C values ranging generally between -26.1 and -2.9‰ (mean of -9.4‰) for Australian gas fields (Pallasser, 2000). The isotopically heaviest gases may be mixtures with an additional inorganic CO2 input that is implied by the relationship between concentration and carbon isotopic composition (Figure 2; Boreham et al., 2001). Thermochemical sulphate reduction occurs at higher 37 temperatures typically above 140oC in deep hydrocarbon reservoirs that contain sufficient sulfate and can be excluded because of this requirement (e.g. Machel et al., 1995; Worden and Smalley, 1996; Heydari, 1997). Five of the samples in question are from wells located adjacent to major faults in the Surat and Eromanga basins (Figures 1 and 2) as is the anomalous Chinchilla 4-799.6m sample, which support the proposal that zones of significant carbonate cementation may form where hydrocarbons and associated CO2 migrate up leaking faults and emerge in a shallow aquifer system (so-called hydrocarbon-related diagenetic zones (HrDZs); Rollet et al. (2006)). However, the majority of cement samples analysed thus far are from wells located within 10 km of mapped major faults and those which are not are situated on the flanks of major folds (Figures 1 and 2; Tables 14, 15 and 16), which may potentially be related to unmapped faults at depth. Additional samples from these wells and adjacent wells will be a focus of the next analytical campaign.

Calcite veins filling cleat, shears and joints in the Walloon Coal Measures at Kogan Creek in the Surat Basin exhibit an unusually wide range of 13C values from -17.8 to 18.9 ‰ (n=21) that are negatively correlated with 18O values ranging from 15.2 to 25.8 ‰ (R2 = 0.9482). Sample CO-22, a fault breccia in a non-coal interval is different from the other samples and likely formed under similar conditions to Surat calcite cements, albeit from an organic carbon source (Table 17). Excluding CO-22, two populations are evident in the Kogan Creek carbonate stable isotope data (Figure 6). Two samples of joint filling calcite have highly negative 13C (-17.8 and -14.3‰) and highly positive 18O (25.8 and 24.3 ‰) values, whereas the other samples have somewhat less positive 18O (15.2 to 21.9 ‰) values, and low negative to highly positive 13C (-1.8 to 18.9 ‰) values. The anomalous, highly negative 13C values of the two large joint filling calcites likely record abiotic or microbial oxidation of methane or coal under relatively low temperature, near surface conditions. On the other hand, methanogenesis involving fermentation or the CO2 reduction pathway is the only process that can produce the highly positive 13C values that lie at the other end of the negative C-O correlation trend (Golding et al., 2013a).

The calcite 18O values reflect not only the fluid source but also the temperature of precipitation that should not be greater than 80oC in view of the carbon isotope evidence for methanogenesis and methane oxidation in the coal measures. A model temperature range of 40oC to 80oC is consistent also with temperatures of 48oC to 71oC calculated from vitrinite reflectance of coal abutting the Kogan Creek calcite veins using the method of Barker and Pawlewicz (1994), which would correspond to a depth range of 1 to 2 km assuming a geothermal gradient of 35 degrees C per km. An alternative is that hot fluids migrating up faults resulted in elevated precipitation temperature at shallower depths. The calculated oxygen isotope compositions of fluids in equilibrium with the calcite veins at these temperatures range from -21.8 to 4.4 ‰; however, much of this range likely reflects the model temperature range rather than actual variation in fluid composition. We previously argued that the two joint filling calcite samples with highly negative 13C values formed under low temperature, near surface conditions. Using a model temperature of 40oC for the formation of these calcites gives more realistic calculated fluid oxygen isotope compositions from -4.1 to -2.6 ‰ that overlaps the

38 composition of rainwater and shallow groundwater in the area (Pacey, 2011). If we assume that the calcites that lie at the other end of the negative C-O correlation trend with mineral 18O values less than 20 ‰ (Figure 6) formed under higher temperature conditions approaching 80oC, the calculated fluid oxygen isotope compositions range from -6.4 to -2.1 ‰ and also overlap the composition of groundwater in the area (Pacey, 2011). Although it is possible that the population of calcite veins with somewhat less positive 18O values, and low negative to highly positive 13C values could be derived from present day groundwater, it is more likely they precipitated in the past from groundwater with similar isotope values to the present day waters in view of the elevated temperatures indicated by the vitrinite reflectance data.

Massive calcite filled chimneys are a feature of fault systems in the Surat Basin and thought to be related to gas migration up faults from underlying source rocks. Two calcite chimney samples from the Walloon Coal Measures at Kogan Creek have an identical 18O value of 24.4 ‰ and 13C values of 0.1 and 1.3 ‰ similar to many of the calcite veins that fill cleat, shears and joints (Figure 6). A third sample has a similar carbon isotope value but is strongly depleted in 18O relative to the other samples (Figure 6). There are several possible explanations for this heterogeneity among samples from the same fault chimney. It is possible the anomalous calcite chimney sample formed from a different fluid or under higher temperature conditions that would suggest multiple episodes of fluid migration. Vitrinite reflectance for the adjacent coal, however, indicates a maximum paleotemperature of 65oC that results in an unrealistically low calculated fluid oxygen isotope composition (<-17 ‰). The other alternative is that the calcite oxygen isotope value is not in equilibrium with the fluid because of CO2 degassing and rapid precipitation in the fault chimney. The calculated carbon isotope compositions of the fluid depositing calcite chimney fill (-1 to 1.3 ‰) overlap the range of marine carbonate

13 but could also have incorporated C-enriched CO2 residual from methanogenesis of the deeply-derived parent CO2 source.

39

3.2. Calcite elemental abundances

Fracture calcite mineralisation was chosen for an initial assessment of elemental abundances measured via high precision ICP-MS. It is much easier to separate fracture calcite from non-calcite phases than it is to do this for sandstone carbonate cementation. Whilst it is possible to use a weak acid to dissolve a portion of the carbonate cementation without affecting the majority of non-carbonate phases, some other minerals may still dissolve and ions affiliated with clays and organics may also be liberated and add to the measured elemental signatures. ICP-MS analysis of sandstone carbonate cementation will still be attempted but for the purposes of demonstrating the utility of elemental abundance analyses, relatively pure fracture carbonates are easier to interpret. Strontium, neodymium, and samarium isotope analyses are in progress, and these will provide further information regarding the fluid sources and absolute timing of precipitation.

3.2.1. Major, minor, and trace element overview

All of the initially analysed fracture carbonates were calcite, and broadly contain similar amounts of the same major elements. Even so, there are some significant variations in the data. The Eromanga Basin fault calcite samples (R 2, 3, and 4) all contain almost an order of magnitude less iron, magnesium, strontium, and barium than the majority of samples collected from the Surat Basin mine site (Figure 7, Table 18). The precipitation rate of calcite at a given ionic strength is greatly inhibited by the presence of magnesium ions in solution (Mitchell et al., 2010) and to a lesser extent strontium ions as well (Lumsden et al., 1989), so it is possible that the Eromanga samples precipitated much faster than most of the Surat mine samples, if this occurred under similar conditions of pressure, pH, temperature, and salinity. An exception is sample R 30, a fault chimney sample analysed, and the mineralising fluid stable isotope modelling for this sample as well as the facts that it has a powdery microcrystalline habit (Figure 3b) and lower magnesium and strontium levels indicates that this sample did precipitate rapidly in comparison to other mine samples, which tend to be blocky to prismatic in habit, probably via rapid CO2 degassing up the fault. Analysis of the more clay-rich calcite chimney sample (Figure 3a) is pending, and is expected to be similar. Major to moderate elements in fracture calcites 1.E+09

1.E+08

1.E+07 Ba Ca 1.E+06 Fe Mg 1.E+05 calcite (ppb) calcite P 1.E+04 Sr

Elemental concentration within concentration Elemental 1.E+03 R-2 R-3 R-4 R-16 R-18 R-20 R-22 R-23 R-24 R-25 R-26 R-29 R-30 R-32 R-33 R-34 R-17c R-27c R-17a R-19a R-21a R-27a R-28a R-17b R-19b R-27b R-27d R-28b Sample

Figure 7: Major to moderate elemental abundances measured within fracture calcite samples via ICP-MS.

40

Barium tends to mirror both the magnesium and strontium concentrations for most samples, implying that it is also incorporated within the calcite crystal lattice rather than being present in an accessory mineral. The calcite samples from a large sub-vertical joint through coal (R 28a and 28b) contain elevated iron and magnesium implying a relatively lower rate of precipitation than most of the other samples, and also contain the highest quantity of zinc measured, up to 90 ppm (Figure 8, Table 18) as well as relatively higher phosphorous and lower barium content than most samples. They have the second lowest amount of scandium after the fault breccia (R 22) though, which contains lower levels of most moderate to minor elements and yet contains the highest measured copper concentration; about 4 ppm. The fault chimney calcite analysed (R 30) as well as calcite of a nearby fault containing abundant sulphides (R 33) have the highest titanium levels as well as elevated scandium and zinc. One of the relatively nearby large coal cleat calcites (R 27a) has the highest scandium concentration as well as elevated titanium but not zinc. (Cleats are systematic joint sets within coal). The sample with the highest zirconium concentration (R 30 at 5 ppm) also contains bornite (Figure 3d), but with the exception of sample R 20 (Figure 3e) there appears to be no association between zirconium and bornite content. Both the Surat fault breccia and the Eromanga fault calcites have very low zirconium levels, and yet whilst everything except copper is present in low abundance in the Surat breccia, the Eromanga faults are relatively enriched in scandium and zinc and contain the most nickel. The relatively constant lithium concentration for all samples gives confidence that the concentrations were correctly calibrated to the mass of sample originally dissolved for the analysis as abundance of lithium, a fairly ubiquitous element, within carbonates should be fairly constant except under exceptional circumstances such as evaporite deposits. Although the stable isotopes modelling of the mineralising fluid/s indicated the presence of meteoric fluid during precipitation of most of the samples, it is clear that if that is so then other fluid/s more enriched in elements not found in abundance within groundwater have mixed with the meteoric water, unless those elements were leached from host units.

Moderate to minor elements in fracture calcites 1.E+05

Cu 1.E+04 Li Ni 1.E+03 Sc Ti 1.E+02 Zn Zr 1.E+01 R-2 R-3 R-4 Elemental concentrationwithin calcite (ppb) R-16 R-18 R-20 R-22 R-23 R-24 R-25 R-26 R-29 R-30 R-32 R-33 R-34 R-17c R-27c R-17a R-19a R-21a R-27a R-28a R-17b R-19b R-27b R-27d R-28b Sample

Figure 8: Moderate to minor elemental abundances measured within fracture calcite samples via ICP-MS.

41

The Eromanga fault calcites have the lowest uranium and highest gallium levels (over 1 ppm), as well as high vanadium (1 ppm) which is variably abundant within the Surat samples (Figure 9), with maximum abundance (2.8 ppm vanadium) occurring together with highest cobalt (1.4 ppm) in a fault chimney calcite sample (R 30). The highest lead level (8.7 ppm) was detected within calcite from the heavily sulphide mineralised fault sample (R 34) along with the highest uranium (2.7 ppm), thorium (3 ppm), and tin (420 ppb) levels, and elevated vanadium, cobalt, and gallium as well. Interestingly, whilst the calcite chimney sample has high vanadium, cobalt and lead levels, it has relatively low uranium (only 200 ppb). High uranium was also found within two of the coal master cleat calcite samples (R 27 pure calcite and R 32 with bornite and pyrite), as well as dark brown calcite extracted from a minor cleat (R 29). For most samples, excepting the Eromanga faults, uranium and scandium concentrations follow the same pattern and so their occurrence is likely related in most circumstances (Figure 10). A separate study is investigating levels of these elements present within the associated sulphide and other mineralisation within the faults and other samples.

Minor to trace elements in fracture calcites 1.E+04

Co 1.E+03 Ga Th 1.E+02 U V Pb 1.E+01 Sn

1.E+00 Elemental concentration within calcite (ppb) calcite within concentration Elemental R-2 R-3 R-4 R-16 R-18 R-20 R-22 R-23 R-24 R-25 R-26 R-29 R-30 R-32 R-33 R-34 R-17c R-27c R-17a R-19a R-21a R-27a R-28a R-17b R-19b R-27b R-27d R-28b Sample Figure 9: Moderate to minor elemental abundances measured within fracture calcite samples via ICP-MS.

1.E+05

1.E+04

1.E+03

1.E+02 Sc

calcite (ppb) calcite U 1.E+01

Elemental concentration within concentration Elemental 1.E+00 R-2 R-3 R-4 R-16 R-18 R-20 R-22 R-23 R-24 R-25 R-26 R-29 R-30 R-32 R-33 R-34 R-17c R-27c R-17a R-19a R-21a R-27a R-28a R-17b R-19b R-27b R-27d R-28b Sample Figure 10: Scandium and uranium levels track each other for most samples excluding the Eromanga faults.

42

The Eromanga faults, together with calcite from the two largest faults sampled in the Surat mine (R 30 fault chimney and R 33 massive sulphides) contain the most abundant chromium (up to 480 ppb), rubidium (up to 660 ppb), beryllium (up to 275 ppb), cesium (up to 150 ppb) and thallium (up to 120 ppb) levels (Figure 11). The fault breccia sample (R 22) that generally contains low levels of other elements (excepting copper and lead) has the second highest amount of rubidium. The minor coal cleat with brown calcite (R 29), which contained high uranium (1.5 ppm), has the highest cadmium level (160 ppb). Given that enrichment of elements within calcites appears to generally be associated with faults, this implies that the adjacent coal and carbonaceous shales are not the primary source of these elements.

Selected trace elements in fracture calcites 1.E+03 Be Cd 1.E+02 Cr Cs 1.E+01 Rb Tl W 1.E+00 Hf Mo 1.E-01 Nb R-2 R-3 R-4 R-16 R-18 R-20 R-22 R-23 R-24 R-25 R-26 R-29 R-30 R-32 R-33 R-34 R-17c R-27c R-17a R-19a R-21a R-27a R-28a R-17b R-19b R-27b R-27d R-28b

Elemental concentration within calcite (ppb) calcite within concentration Elemental 1.E-02 Sample

Figure 11: Non-REY trace elemental abundances measured within fracture calcite samples via ICP-MS.

The association of sulphide minerals with many of the Surat Basin fracture calcites is important, as sulphur phases in solution can greatly affect mineral leaching, cation stability during fluid transport, and the conditions of mineral precipitation. Co-contaminant gases such as SO2 are present in gas streams from oil or coal burning and oxy fuel power plants, and so it is possible that in practice sequestered CO2 will contain a component of SO2. Examining the conditions under which natural analogue systems containing both CO2 and SO2 precipitated carbonate minerals in the basins of interest to this study is beneficial for obtaining basin-specific parameters for attempts at developing enhanced artificial mineral trapping of CO2 in the presence of dissolved sulfur species. Co-contaminant injection (e.g., minor SO2 within CO2) could aid eventual enhanced carbonate precipitation; initial dissolution of silicates and reduction of transition metals by aqueous SO2 would result in more divalent cations available for carbonate precipitation than were originally present within formation waters (Golding et al., 2013b; Pearce et al., in prep.; Pearce et al., 2013).

43

Table 18: Non-REY element concentrations within fracture calcite samples (ppm), Surat Basin unless otherwise specified.* Fracture Type Source Location Sample Li Be Mg P Ca Sc Ti V Cr Fe Co Ni Cu Zn Ga B Mirintu-1 Multiple R-2 1.52E+00 2.87E-02 4.06E+02 5.01E+01 4.11E+05 1.38E+01 9.69E-01 1.06E+00 2.66E-01 3.01E+03 2.36E-01 3.29E+00 4.50E-01 6.48E+00 7.24E-01 Small Faults, 696 m A1 Mirintu-1 Bottom Eromanga Basin Layer in Fault , R-3 1.50E+00 3.47E-02 4.26E+02 4.79E+01 4.21E+05 1.31E+01 7.81E-01 9.16E-01 2.41E-01 2.99E+03 2.33E-01 3.19E+00 5.88E-01 5.40E+00 5.79E-01 Faults 677.6 m A2 Mirintu-1 Top Layer R-4 1.46E+00 1.83E-02 3.02E+02 6.28E+01 4.22E+05 1.37E+01 6.50E-01 3.85E-01 1.95E-01 2.30E+03 2.41E-01 3.49E+00 5.06E-01 1.22E+01 1.01E+00 in Fault, 677.6 m Faults in coal: 15 cm wide massive S9B19d R-30 1.86E+00 2.74E-01 6.33E+02 2.76E+02 4.00E+05 6.48E+00 1.19E+01 2.78E+00 4.82E-01 1.24E+04 1.36E+00 2.54E+00 2.07E+00 1.86E+01 3.25E-01 calcite

Faults in coal: S10B11M5 Stripy R-19a 1.56E+00 1.46E-02 2.56E+03 7.91E+01 4.13E+05 3.22E+00 1.27E+00 3.21E-01 5.56E-02 1.16E+04 1.99E-01 1.88E+00 9.67E-01 5.55E+00 6.49E-02 calcite sheet-type S10B11M5 R-19b 1.43E+00 1.76E-02 2.49E+03 8.41E+01 4.23E+05 3.42E+00 1.14E+00 2.42E-01 4.70E-02 1.19E+04 2.03E-01 1.90E+00 1.70E+00 2.96E+00 5.02E-02 veins S8 End Wall O1 R-26 1.74E+00 8.84E-03 1.60E+03 1.22E+02 4.15E+05 4.85E+00 6.95E-01 7.66E-02 8.14E-02 1.04E+04 2.02E-01 1.97E+00 5.87E-01 3.32E+00 9.62E-02 Fault in coal with abundant sulfides, S8B3N7 R-33 1.80E+00 5.43E-02 2.00E+03 1.75E+02 3.99E+05 1.06E+01 9.29E+00 7.62E-01 4.76E-01 1.62E+04 1.94E-01 2.20E+00 1.65E+00 2.21E+01 3.37E-01 minor calcite Fault in coal: calcite sheet with S10B4M7 R-20 1.54E+00 1.68E-02 2.43E+03 1.40E+02 4.19E+05 1.79E+00 1.74E+00 4.09E-01 3.65E-02 1.29E+04 1.98E-01 1.77E+00 1.98E+00 3.71E+00 9.41E-02 syntectonic bornite Fault: breccia with S8B5N6 R-22 1.54E+00 7.47E-02 3.15E+03 7.81E+01 3.58E+05 3.38E-01 3.36E-01 8.37E-02 4.38E-02 1.23E+04 2.04E-01 1.37E+00 3.71E+00 2.27E+00 5.99E-03 calcite veins Coal: master cleats S8B6N5 R-21 1.57E+00 2.35E-02 2.81E+03 1.82E+02 4.27E+05 3.45E+00 7.91E-01 3.36E-01 8.12E-02 9.82E+03 2.12E-01 2.23E+00 1.42E+00 4.44E+00 5.39E-02 with bornite S8B6M5 R-32 1.70E+00 3.24E-02 2.34E+03 1.74E+02 4.20E+05 7.25E+00 9.56E-01 1.12E-01 6.18E-02 6.09E+03 2.18E-01 2.60E+00 1.78E+00 8.32E+00 1.28E-01 S10B17&20O5 Round R-28a 1.58E+00 1.73E-02 4.89E+03 2.77E+02 4.22E+05 7.69E-01 1.64E+00 4.48E-02 5.12E-02 1.89E+04 2.12E-01 1.69E+00 1.30E+00 1.91E+01 2.28E-02 Coal: subvertical Calcite joints S10B17&20O5 R-28b 1.96E+00 2.49E-02 4.50E+03 2.97E+02 3.82E+05 6.73E-01 7.76E-01 2.58E-02 3.00E-02 1.73E+04 1.78E-01 2.55E+00 7.33E-01 8.79E+01 1.96E-02 Coal: master cleats S10B19&40O1 R-24 1.62E+00 2.05E-02 1.74E+03 1.26E+02 4.02E+05 2.55E+00 7.96E-01 7.42E-02 5.46E-02 1.43E+04 1.96E-01 1.53E+00 5.72E-01 2.69E+00 5.23E-02 with pyrite S10B24/25O1 R-25 1.60E+00 4.05E-02 1.64E+03 1.12E+02 4.16E+05 6.19E+00 1.05E+00 1.18E-01 7.12E-02 9.46E+03 1.92E-01 1.89E+00 3.86E-01 1.43E+00 1.37E-01 S10B12M1 R-16 1.44E+00 1.65E-02 7.26E+02 6.38E+01 4.14E+05 1.69E+00 5.49E-01 3.47E-02 4.57E-02 1.71E+04 2.39E-01 1.73E+00 6.66E-01 3.41E+00 4.50E-02 S10B23HO O1 R-23 1.56E+00 4.20E-02 1.86E+03 8.27E+01 4.11E+05 5.65E+00 1.15E+00 1.89E-01 6.01E-02 1.14E+04 2.05E-01 1.93E+00 8.11E-01 2.99E+00 6.33E-02 S9B1(&20)O1 R-27a 1.84E+00 3.41E-02 2.91E+03 2.50E+02 4.20E+05 1.64E+01 7.73E+00 1.19E-01 7.96E-02 1.21E+04 2.30E-01 1.92E+00 1.05E+00 4.43E+00 1.10E-01 (one bag)

Coal: master cleats S9B1(&20)O1 Prismatic R-27b 1.53E+00 2.36E-03 1.39E+03 8.41E+01 4.23E+05 9.83E+00 1.34E+00 2.38E-01 7.13E-02 1.00E+04 1.97E-01 1.98E+00 7.52E-01 5.40E+00 8.85E-02 S9B1(&20)O1 R-27c 1.57E+00 7.32E-03 1.19E+03 7.64E+01 4.30E+05 4.95E+00 1.86E+00 2.97E-01 2.09E-01 9.01E+03 2.28E-01 2.22E+00 8.13E-01 4.02E+00 7.00E-02 (another bag) S9B1(&20)O1 R-27d 1.63E+00 3.64E-03 1.35E+03 9.96E+01 4.25E+05 3.79E+00 8.05E-01 5.66E-02 6.09E-02 9.51E+03 2.10E-01 2.30E+00 5.14E-01 3.15E+00 8.59E-02 (combined) S10B17(&10?)O1 R-34 1.65E+00 5.59E-03 1.27E+03 1.04E+02 4.30E+05 6.97E+00 8.67E-01 1.31E-01 1.36E-01 9.62E+03 2.11E-01 1.97E+00 2.26E+00 3.51E+00 9.12E-02 S10B14M1 B (clear) R-17a 1.50E+00 1.28E-02 1.36E+03 1.02E+02 4.11E+05 2.53E+00 1.55E+00 6.09E-01 7.97E-02 1.26E+04 2.09E-01 1.68E+00 6.52E-01 2.21E+00 2.54E-01 Coal: minor cleats S10B14M1 A (cloudy) R-17b 1.57E+00 7.57E-03 1.51E+03 1.16E+02 4.21E+05 2.65E+00 1.15E+00 3.37E-01 6.81E-02 1.23E+04 2.21E-01 2.07E+00 7.79E-01 3.10E+00 1.94E-01 with sulfides S10B14M1 R-17c 1.57E+00 8.97E-03 1.46E+03 9.76E+01 4.18E+05 3.24E+00 2.17E+00 5.65E-01 7.04E-02 1.27E+04 2.05E-01 1.73E+00 5.66E-01 2.37E+00 2.07E-01 Coal: minor cleats S10B20/21 M13 R-18 1.36E+00 9.36E-03 3.71E+03 6.46E+01 4.20E+05 1.08E+00 5.71E-01 4.50E-02 1.77E-01 9.44E+03 2.13E-01 2.60E+00 8.27E-01 7.79E+00 5.10E-02 with brown calcite S10B24/25 mid O5? R-29 1.57E+00 1.13E-02 1.88E+03 1.02E+02 4.16E+05 1.64E+01 4.08E+00 2.19E-01 1.33E-01 9.90E+03 2.29E-01 1.86E+00 1.09E+00 5.95E+00 1.84E-01 *NB: The sample number numerals match those of the stable isotope sample numbers; however, the a, b, c, etc. discriminators DO NOT MATCH as the sub-samples taken were slightly different for each overall sample tested. for REE and CO-stable isotopes. Missing sample numbers indicate tests yet to be undertaken for carbonate cemented sandstones already analysed for carbon and oxygen stable isotopes. 44

Table 18 continued: Non-REY element concentrations within fracture calcite samples (ppm), Surat Basin unless otherwise specified.* Fracture Type Source Location Sample Rb Sr Zr Nb Mo Cd Sn Cs Ba Hf W Tl Pb Th U B Mirintu-1 Multiple R-2 1.20E-01 2.71E+02 3.94E-02 2.15E-03 1.13E-02 7.30E-03 1.54E-01 4.13E-02 6.65E+00

3.2.2. Rare earth elements plus yttrium (REY) and other related elements Something immediately apparent from measured REE abundances (Table 19) is that the total concentration present in the fracture calcite samples analysed is up to three orders of magnitude higher than for marine carbonates (Figure 12), with the only exceptions being the fault breccia calcite (R 22), and the thulium levels of the subvertical joint calcite (R 28a and 28b), master cleat R 16 and one of the minor coal cleat calcites (R 18).

Eromanga Faults Surat Faults 1000 100

100 10

10 1

1 0.1

0.1 0.01 Concentration (ppm) Concentration (ppm)

0.01 0.001 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Element Element R-30 R-19a R-19b R-2 R-3 R-4 Marine carbonate R-26 R-33 R-20

Master cleat calcite with sulfides Master cleat calcite, no sulfides 100 100

10 10

1 1

0.1 0.1 Concentration (ppm) Concentration (ppm)

0.01 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Element Element R-21 R-24 R-25 R-32 Marine carbonate R-16 R-23 R-27a R-27b

Minor cleat calcite Subvertical joints 1000 10

100 1 10

1 0.1 0.1 Concentration (ppm) Concentration (ppm)

0.01 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Element Element R-17a R-17b R-17c R-18 R-29 Marine carbonate R-28a R-28b Marine carbonate

Figure 12: Fracture calcite REY concentrations compared with marine carbonate (Webb and Kamber, 2000).

46

The concentration of cerium in one of the Eromanga fault samples (R 4) is of the same order of magnitude as magnesium and strontium (> 100 ppm). The ranges of selected elemental ratios (Table 20) can be used to help tease out the conditions under which precipitation occurred, as well as the history of the mineralising fluid/s. The Y/Ho ratio (46) of a large subvertical joint calcite sample (R 28b) falls within the lower range expected for marine carbonate (Bau, 1996), and the Nd/Yb ratio (3.14) is close to 2.98 that is the typical value for well oxygenated shallow western Pacific ocean water (Webb and Kamber, 2000). This does not necessarily mean that the sample precipitated in sea water, rather the conditions under which precipitation occurred may have been somewhat similar to those of well oxygenated sea water. Modelling of the mineralising fluid oxygen and carbon supports this finding, as the fluid CO2 composition is consistent with oxidation of methane or coal. The Y/Ho ratios for the Eromanga faults, largest Surat faults and some of the other samples are close to 28, the expected value for terrestrial sediments and volcanic ash (Webb and Kamber, 2000), with the rest of the samples ranging in between this and marine values (Table 20).

The values expected for upper crust La/Th, Th/Sc and Th/U ratios are 2.8, 1, and 3.8 respectively (McLennan et al., 1990), and comparing the ratios for the samples with these values can give an indication of processes that the mineralising fluids have undergone. Only calcite from the fault with highly abundant sulphide mineralisation (R 33) falls roughly within the expected upper crustal range of La/Th (Figure 13) and Th/Sc (Figure 14) ratios, whilst the rest of the samples are enriched in both lanthanum and scandium relative to thorium. As the samples contain abundant LREE’s and scandium is of similar size and valence to LREE minerals, it is not surprising that most of the samples have abundant scandium. The Eromanga fault samples have a lot more thorium than uranium, whereas all of the measured Surat fracture calcite samples have more uranium than thorium (Figure 15). The sample with the highest Th and U is from a fault that is dominantly mineralised with sulphides rather than carbonates (R 33), which may be why it stands out from the rest of the samples.

100.000 Eromanga Basin Faults

Faults in coal: 15 cm wide massive calcite 10.000 Faults in coal: calcite sheet- type veins Fault in coal with abundant sulfides, minor calcite Fault in coal: calcite sheet 1.000 with syntectonic bornite Fault: breccia with calcite veins Coal: master cleats with

La (ppm) bornite 0.100 Coal: subvertical joints

Coal: master cleats with pyrite 0.010 Coal: master cleats Coal: minor cleats with sulfides Coal: minor cleats with 0.001 brown calcite 0.0 0.1 10.0 1000.0 Th (ppm) Figure 13: Plot of sample La/Th ratios relative to the expected upper crustal ratio of 2.8 (centre line).

47

100 Eromanga Basin Faults

Faults in coal: 15 cm wide massive calcite 10 Faults in coal: calcite sheet- type veins Fault in coal with abundant sulfides, minor calcite Fault in coal: calcite sheet 1 with syntectonic bornite Fault: breccia with calcite veins Coal: master cleats with bornite Th (ppm) 0.1 Coal: subvertical joints Coal: master cleats with pyrite Coal: master cleats 0.01 Coal: minor cleats with sulfides Coal: minor cleats with brown calcite 0.001 0.001 0.1 10 1000 Sc (ppm) Figure 14: Plot of sample La/Sc ratios relative to the expected upper crustal ratio of 1 (centre line).

10.00 Eromanga Basin Faults

Faults in coal: 15 cm wide massive calcite Faults in coal: calcite sheet- type veins 1.00 Fault in coal with abundant sulfides, minor calcite Fault in coal: calcite sheet with syntectonic bornite Fault: breccia with calcite veins 0.10 Coal: master cleats with bornite Th (ppm) Coal: subvertical joints

Coal: master cleats with pyrite

0.01 Coal: master cleats

Coal: minor cleats with sulfides Coal: minor cleats with brown 0.00 calcite 0.00 0.01 0.10 1.00 10.00 U (ppm) Figure 15: Plot of sample Th/U ratios relative to the expected upper crustal ratio of 3.8 (line).

REE abundances, fractionation between LREE and HREE, and anomalous concentrations of specific REE’s can be indicative of mineral precursor compositions, mineralising fluid composition, the conditions of the environment/s through which the fluid migrated prior to precipitation, and whether the present carbonate mineralisation is primary or remobilised carbonate precipitation (Bau and Möller, 1992). High magnitude Yb/La, Tb/Ca, and Ce/Yb ratios can be indicative of fluid REE load derived from a high temperature source (Möller, 1983). The Yb/La ratio is also used as the REE fractionation index, with higher values indicating HREE enrichment and lower values LREE enrichment, and when cross-plotted with Yb/Ca ratios (Figure 16) the context of carbonate mineralisation for specific samples can be classified (Möller, 1983).

48

1.E-03 Faults in coal: calcite sheet-type veins Eromanga Basin Faults 1.E-04 Faults in coal: 15 cm wide massive High grade calcite Fault in coal with abundant 1.E-05 regional metamorphism sulfides, minor calcite Fault in coal: calcite sheet with fissure calcite syntectonic bornite Fault: breccia with calcite veins 1.E-06 Yb/Ca Carbonatite Hydrothermal Coal: master cleats with bornite veins 1.E-07 Coal: subvertical joints

Coal: master cleats with pyrite

1.E-08 Coal: master cleats, no pyrite Limestone Seashells, corals Coal: minor cleats with sulfides 1.E-09 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 Coal: minor cleats with brown calcite Yb/La Sea Water

Figure 16: Variation diagram first proposed by Möller (1983); field positions plotted are based upon numerous analyses of samples from across the world. Samples that plot below the carbonatite- hydrothermal-metamorphic series are classed as “sedimentary process related”, with the rough positions of marine carbonate types between the dashed lines, and sea water composition plotted for reference.

Vertical trends on the plot (Figure 16) can indicate fluid-rock interactions such as contact with limestones or clays, which due to dilution or loss of REE’s sorbed onto clay paticles can alter the Y/Ca ratio. Horizontal trends indicate remobilisation processes, and diagonal trends are indicative of primary crystallisation fractionation (Möller, 1983). Carbonate remobilisation typically results in loss of LREE content relative to the original carbonate, as HREE’s complex more effectively with carbonate and bicarbonate anions and other ligands than the LREE’s (Bau and Möller, 1992). The master cleat calcites lacking pyrite display a near- perfect primary mineralisation fractionation trend, and the majority of cleat calcite samples analysed are more fractionated than the fault samples.

The fact that all except one of the fracture calcite samples analysed plot within the hydrothermal veins field does not mean that the mineralising fluids were high temperature during carbonate precipitation. The original process of fluid REE enrichment may have been related to active hydrothermal processes, or perhaps just acidic breakdown of material that had been originally associated with high temperature processes and contained high REE content (e.g. relatively fresh volcanic debris acid leached by migrating fluids). For the fluid to be sufficiently acidic to cause significant breakdown of REE-rich minerals, it probably would have had to contain a combination of sulphurous and carbonic acid though (i.e. been an igneous process-derived fluid). Alternatively, a formerly high temperature fluid containing abundant REE could have migrated into and mixed with a lower temperature, perhaps meteoric and therefore REE-poor, fluid resulting in low temperature precipitation of minerals with high REE contents.

49

Table 19: REY element concentrations within fracture calcite samples (ppm), Surat Basin unless otherwise specified.* Fracture Type Source Location Sample La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Total Ln Y B Mirintu-1 Multiple Small R-2 2.96E+01 7.58E+01 7.91E+00 2.56E+01 3.74E+00 1.12E+00 3.07E+00 5.29E-01 3.14E+00 6.39E-01 1.69E+00 2.30E-01 1.38E+00 2.02E-01 154.6 1.95E+01 Faults, 696 m Eromanga Basin A1 Mirintu-1 Bottom R-3 1.61E+01 4.06E+01 4.44E+00 1.48E+01 2.42E+00 7.49E-01 2.56E+00 4.27E-01 2.71E+00 5.77E-01 1.63E+00 2.52E-01 1.74E+00 2.57E-01 89.3 1.64E+01 Faults Layer in Fault , 677.6 m A2 Mirintu-1 Top Layer in R-4 4.90E+01 1.30E+02 1.42E+01 4.75E+01 6.94E+00 2.08E+00 4.92E+00 8.80E-01 4.91E+00 9.33E-01 2.44E+00 3.44E-01 2.22E+00 3.28E-01 267.2 2.69E+01 Fault, 677.6 m Faults in coal: 15 cm wide massive S9B19d R-30 4.50E+00 1.20E+01 1.80E+00 8.17E+00 2.08E+00 7.35E-01 2.17E+00 3.61E-01 2.21E+00 4.58E-01 1.26E+00 1.81E-01 1.13E+00 1.70E-01 37.2 1.27E+01 calcite Faults in coal: S10B11M5* Stripy R-19a 5.66E+00 1.04E+01 1.27E+00 5.15E+00 1.06E+00 2.83E-01 8.93E-01 1.52E-01 8.83E-01 1.86E-01 5.29E-01 7.44E-02 4.86E-01 7.68E-02 27.1 6.42E+00 calcite sheet-type S10B11M5 R-19b 5.06E+00 9.25E+00 1.20E+00 4.87E+00 1.06E+00 2.48E-01 1.01E+00 1.67E-01 1.02E+00 2.16E-01 6.23E-01 9.34E-02 5.94E-01 9.22E-02 25.5 7.86E+00 veins S8 End Wall O1 R-26 7.26E+00 1.57E+01 2.20E+00 9.86E+00 2.36E+00 6.50E-01 2.26E+00 3.88E-01 2.27E+00 4.62E-01 1.22E+00 1.64E-01 9.18E-01 1.33E-01 45.8 1.38E+01 Fault in coal with abundant sulfides, S8B3N7 R-33 2.06E+01 5.71E+01 7.57E+00 2.97E+01 5.71E+00 1.09E+00 3.27E+00 6.09E-01 3.06E+00 5.40E-01 1.30E+00 1.61E-01 8.86E-01 1.35E-01 131.8 1.65E+01 minor calcite Fault in coal: calcite sheet with S10B4M7 R-20 6.00E+00 1.06E+01 1.28E+00 5.09E+00 1.04E+00 2.69E-01 9.16E-01 1.55E-01 9.08E-01 1.86E-01 5.13E-01 7.10E-02 4.16E-01 5.95E-02 27.5 6.65E+00 syntectonic bornite Fault: breccia with S8B5N6 R-22 8.73E-02 1.92E-01 3.02E-02 1.63E-01 4.45E-02 1.19E-02 6.27E-02 1.04E-02 6.00E-02 1.36E-02 3.68E-02 4.66E-03 2.53E-02 3.90E-03 0.7 5.67E-01 calcite veins Coal: master cleats S8B6N5 R-21 3.34E+00 8.23E+00 1.28E+00 6.03E+00 1.59E+00 4.54E-01 1.74E+00 2.82E-01 1.74E+00 3.72E-01 9.85E-01 1.34E-01 7.71E-01 1.05E-01 27.1 1.34E+01 with bornite S8B6M5 R-32 1.00E+01 2.00E+01 2.79E+00 1.21E+01 3.15E+00 8.34E-01 4.22E+00 6.55E-01 4.43E+00 1.03E+00 3.08E+00 4.71E-01 2.90E+00 4.29E-01 66.1 3.22E+01 S10B17&20O5 Round R-28a 1.19E+00 2.20E+00 2.91E-01 1.28E+00 3.17E-01 8.88E-02 4.44E-01 7.00E-02 4.60E-01 1.09E-01 3.22E-01 4.51E-02 2.69E-01 3.99E-02 7.1 4.49E+00 Coal: subvertical Calcite joints S10B17&20O5 R-28b 5.64E-01 8.96E-01 1.26E-01 6.03E-01 1.59E-01 4.96E-02 2.78E-01 4.11E-02 2.92E-01 7.45E-02 2.18E-01 3.10E-02 1.92E-01 2.82E-02 3.6 3.43E+00 Coal: master cleats S10B19&40O1 R-24 3.05E+00 5.98E+00 9.07E-01 4.71E+00 1.25E+00 3.71E-01 1.65E+00 2.56E-01 1.67E+00 4.03E-01 1.20E+00 1.74E-01 1.07E+00 1.58E-01 22.8 1.60E+01 with pyrite S10B24/25O1 R-25 1.50E+01 3.15E+01 4.55E+00 2.25E+01 5.67E+00 1.58E+00 6.37E+00 1.03E+00 6.20E+00 1.45E+00 4.22E+00 6.21E-01 3.86E+00 6.25E-01 105.2 5.68E+01 S10B12M1 R-16 3.90E+00 8.35E+00 1.09E+00 4.74E+00 1.00E+00 2.64E-01 9.86E-01 1.68E-01 9.63E-01 1.99E-01 5.19E-01 6.88E-02 3.72E-01 5.42E-02 22.7 7.93E+00 S10B23HO O1 R-23 4.04E+00 1.08E+01 1.91E+00 1.06E+01 3.46E+00 1.07E+00 4.78E+00 7.66E-01 4.87E+00 1.07E+00 2.92E+00 4.11E-01 2.40E+00 3.34E-01 49.4 3.65E+01 S9B1(&20)O1 R-27a 7.38E+00 2.39E+01 4.15E+00 2.01E+01 6.37E+00 2.06E+00 1.12E+01 1.80E+00 1.20E+01 2.63E+00 7.09E+00 9.57E-01 5.34E+00 7.15E-01 105.6 6.97E+01 (one bag) Coal: master cleats S9B1(&20)O1* Prismatic R-27b 7.71E+00 1.70E+01 2.49E+00 1.13E+01 2.68E+00 7.23E-01 3.09E+00 4.89E-01 3.14E+00 7.08E-01 2.03E+00 3.02E-01 1.85E+00 2.88E-01 53.8 2.52E+01 S9B1(&20)O1 R-27c 5.32E+00 1.19E+01 1.71E+00 7.82E+00 1.83E+00 5.01E-01 1.89E+00 3.10E-01 1.90E+00 4.31E-01 1.25E+00 1.74E-01 1.07E+00 1.61E-01 36.2 1.54E+01 (another bag) S9B1(&20)O1 (combined) R-27d 6.91E+00 1.66E+01 2.45E+00 1.13E+01 2.68E+00 7.29E-01 2.58E+00 4.41E-01 2.58E+00 5.30E-01 1.43E+00 1.91E-01 1.08E+00 1.49E-01 49.6 1.55E+01 S10B17(&10?)O1 R-34 7.57E+00 1.63E+01 2.36E+00 1.06E+01 2.46E+00 6.69E-01 2.55E+00 4.25E-01 2.56E+00 5.57E-01 1.55E+00 2.19E-01 1.28E+00 1.91E-01 49.3 1.83E+01 S10B14M1 B (clear) R-17a 2.37E+01 4.62E+01 5.42E+00 2.06E+01 4.14E+00 6.85E-01 3.65E+00 6.26E-01 3.63E+00 7.57E-01 2.06E+00 2.87E-01 1.62E+00 2.34E-01 113.6 2.82E+01 Coal: minor cleats S10B14M1 A (cloudy) R-17b 1.99E+01 3.86E+01 4.55E+00 1.75E+01 3.57E+00 6.39E-01 3.41E+00 5.77E-01 3.43E+00 7.30E-01 2.00E+00 2.73E-01 1.58E+00 2.23E-01 97.0 2.56E+01 with sulfides S10B14M1 R-17c 1.95E+01 3.90E+01 4.80E+00 1.86E+01 3.86E+00 6.73E-01 4.08E+00 6.68E-01 4.17E+00 9.09E-01 2.55E+00 3.59E-01 2.11E+00 3.00E-01 101.6 3.26E+01 Coal: minor cleats S10B20/21 M13 R-18 1.93E+00 3.96E+00 5.39E-01 2.25E+00 4.52E-01 1.08E-01 3.86E-01 6.40E-02 3.84E-01 8.25E-02 2.51E-01 3.73E-02 2.38E-01 3.71E-02 10.7 3.20E+00 with brown calcite S10B24/25 mid O5? R-29 2.11E+01 4.44E+01 6.19E+00 3.04E+01 7.90E+00 2.35E+00 1.06E+01 1.67E+00 1.06E+01 2.70E+00 8.59E+00 1.34E+00 8.75E+00 1.45E+00 158.1 1.03E+02 *NB: The sample number numerals match those of the stable isotope sample numbers; however, the a, b, c, etc. discriminators DO NOT MATCH as the sub-samples taken were slightly different for each overall sample tested for REE and CO-stable isotopes. Missing sample numbers indicate tests yet to be undertaken for carbonate cemented sandstones already analysed for carbon and oxygen stable isotopes. 50

Table 20: Selected useful elemental ratios. Fractionation Index Fracture Type Source Location Sample Y/Ho La/Th Th/Sc Th/U Yb/La Ln/Ca Yb/Ca Tb/Ca Tb/La Ce/Yb Eu/Sm Nd/Yb B Mirintu-1 Multiple Small Faults, 696 m R-2 30.47 365.83 5.86E-03 8.85 4.65E-02 3.77E-04 3.35E-06 1.29E-06 1.79E-02 55.1 0.298 18.61 A1 Mirintu-1 Bottom Layer in Fault , 677.6 Eromanga Basin Faults m R-3 28.37 246.72 5.00E-03 6.93 1.07E-01 2.12E-04 4.12E-06 1.01E-06 2.64E-02 23.4 0.309 8.50 A2 Mirintu-1 Top Layer in Fault, 677.6 m R-4 28.79 492.87 7.25E-03 12.68 4.53E-02 6.33E-04 5.26E-06 2.08E-06 1.79E-02 58.8 0.300 21.42 Faults in coal: 15 cm wide massive calcite S9B19d R-30 27.70 12.46 4.83E-02 1.30 2.51E-01 9.28E-05 2.82E-06 9.01E-07 8.02E-02 10.6 0.354 7.23 S10B11M5* Stripy R-19a 34.45 199.87 3.68E-02 0.77 8.59E-02 6.58E-05 1.18E-06 3.67E-07 2.68E-02 21.4 0.266 10.60 Faults in coal: calcite sheet- type veins S10B11M5 R-19b 36.31 315.03 1.84E-02 0.45 1.17E-01 6.02E-05 1.40E-06 3.94E-07 3.30E-02 15.6 0.235 8.20 S8 End Wall O1 R-26 29.83 185.29 2.17E-02 0.18 1.27E-01 1.11E-04 2.21E-06 9.35E-07 5.34E-02 17.1 0.276 10.74 Fault in coal with abundant sulfides, minor calcite S8B3N7 R-33 30.57 0.65 2.83E-01 1.11 4.29E-02 3.30E-04 2.22E-06 1.53E-06 2.95E-02 64.5 0.191 33.49 Fault in coal: calcite sheet with syntectonic bornite S10B4M7 R-20 35.75 248.00 1.27E-02 0.42 6.94E-02 6.56E-05 9.92E-07 3.70E-07 2.59E-02 25.5 0.257 12.24 Fault: breccia with calcite 4762.3 veins S8B5N6 R-22 41.60 8 3.14E-03 0.082 2.89E-01 2.08E-06 7.06E-08 2.90E-08 1.19E-01 7.6 0.266 6.46 Coal: master cleats with S8B6N5 R-21 36.11 110.85 1.57E-02 1.07 2.31E-01 6.34E-05 1.81E-06 6.62E-07 8.46E-02 10.7 0.285 7.82 bornite S8B6M5 R-32 31.26 7.28 6.33E-02 0.25 2.90E-01 1.57E-04 6.90E-06 1.56E-06 6.55E-02 6.9 0.264 4.18 S10B17&20O5 Round Calcite R-28a 41.16 6.79 1.67E-02 0.03 2.25E-01 1.69E-05 6.36E-07 1.66E-07 5.87E-02 8.2 0.280 4.76 Coal: subvertical joints S10B17&20O5 R-28b 46.08 378.31 1.59E-02 0.02 3.40E-01 9.29E-06 5.02E-07 1.07E-07 7.28E-02 4.7 0.311 3.14 Coal: master cleats with S10B19&40O1 R-24 39.73 126.61 9.46E-03 0.14 3.51E-01 5.68E-05 2.67E-06 6.36E-07 8.38E-02 5.6 0.296 4.39 pyrite S10B24/25O1 R-25 39.23 148.35 1.63E-02 0.34 2.57E-01 2.53E-04 9.26E-06 2.47E-06 6.87E-02 8.2 0.278 5.85 S10B12M1 R-16 39.75 388.89 1.11E-02 0.20 9.54E-02 5.48E-05 8.99E-07 4.05E-07 4.30E-02 22.5 0.263 12.75 S10B23HO O1 R-23 34.07 185.50 7.04E-03 0.12 5.93E-01 1.20E-04 5.82E-06 1.86E-06 1.90E-01 4.5 0.310 4.42 S9B1(&20)O1 (one bag) R-27a 26.55 107.82 4.36E-03 0.19 7.24E-01 2.52E-04 1.27E-05 4.28E-06 2.43E-01 4.5 0.323 3.76 Coal: master cleats S9B1(&20)O1* Prismatic R-27b 35.51 32.26 1.68E-02 0.10 2.40E-01 1.27E-04 4.38E-06 1.16E-06 6.34E-02 9.2 0.270 6.08 S9B1(&20)O1 (another bag) R-27c 35.64 72.79 1.92E-02 0.08 2.01E-01 8.43E-05 2.49E-06 7.22E-07 5.83E-02 11.1 0.273 7.31 S9B1(&20)O1 (combined) R-27d 29.32 10.77 2.92E-02 0.28 1.57E-01 1.17E-04 2.54E-06 1.04E-06 6.39E-02 15.3 0.272 10.45 S10B17(&10?)O1 R-34 32.90 5.33 1.52E-02 0.15 1.69E-01 1.15E-04 2.97E-06 9.88E-07 5.61E-02 12.8 0.272 8.29 S10B14M1 B (clear) R-17a 37.25 182.58 4.57E-02 1.07 6.83E-02 2.76E-04 3.94E-06 1.52E-06 2.64E-02 28.5 0.166 12.73 Coal: minor cleats with sulfides S10B14M1 A (cloudy) R-17b 35.02 118.57 1.43E-02 0.24 7.96E-02 2.30E-04 3.76E-06 1.37E-06 2.91E-02 24.4 0.179 11.08 S10B14M1 R-17c 35.91 221.23 1.40E-02 0.31 1.09E-01 2.43E-04 5.06E-06 1.60E-06 3.43E-02 18.5 0.175 8.79 1534.8 Coal: minor cleats with S10B20/21 M13 R-18 38.80 7 1.24E-02 0.21 1.23E-01 2.56E-05 5.66E-07 1.53E-07 3.32E-02 16.7 0.239 9.49 brown calcite S10B24/25 mid O5? R-29 38.22 50.58 9.13E-03 0.10 4.14E-01 3.80E-04 2.10E-05 4.02E-06 7.93E-02 5.1 0.298 3.47

51

The fractionation exhibited by the REE’s can shed light upon the mineralising fluid migration history as well as the precipitation environment. REE mobilisation and fractionation occurs via two fundamental processes; sorption-controlled and ligand-controlled (Bau and Möller, 1992). Fluids containing divalent and therefore strong ligands such as carbonate and sulphate anions will preferentially mobilise HREE over LREE as the smaller ionic radius HREE are more tightly bound to ligands than the larger LREE ions. If significant carbonate and sulphate were able to exist in solution, this indicates that the pH was alkaline. For LREE enrichment to occur, strong ligands cannot be involved in any significant way; conditions under which this occurs include high temperature and/or acidic conditions. Significant dissolved carbon and sulphur species can still be present during sorption-controlled LREE enrichment, but they would be present as acidic species such as carbonic and sulphurous acids.

The Ce/Yb ratio provides an indication of the extent of LREE or HREE enrichment, with large values indicating LREE enrichment and vice versa for HREE enrichment (Möller, 1983). The samples with the highest Ce/Yb ratios (Table 20) include the Surat fault chimney calcite sample (R 30) and two of the three Eromanga fault calcite samples (R 2 and 4). It is interesting to note that there is a considerable difference between the top and bottom layers of one of the Eromanga Basin faults in terms of the Ce/Yb ratio (samples R 3 and 4), which implies that the mineralising fluid evolved during fault activation and mineralisation.

REE data is usually normalised with respect to a standard appropriate for the samples. Mineralisation derived from igneous-related processes is generally normalised to chondritic meteoroid elemental compositions (CN) (Anders and Grevesse, 1989) as this is representative of the undifferentiated mantle. On the other hand, sedimentary-hosted mineralisation is generally normalised with respect to a sedimentary standard such as the Post Aachean Australian Shale (PAAS) (McLennan, 1989). If there is doubt as to which process/s were involved in the mineralisation then it is useful to normalise to more than one standard (Bau and Möller, 1992). Whilst the fracture carbonate data has been normalised to both PAAS (Table 21) and Chondrite (Table 22), most of this discussion involves the PASS normalised data (Figure 17) as it seems most appropriate for the majority of samples.

Ratios of selected PAAS-normalised elements show very clear patterns (Table 23). All Surat fracture calcites have (La/Sm)SN of less than one, whereas Eromanga fault calcites have a 1:1 to slightly positive (>1)

(La/Sm)SN relationship. In contrast to both one of the Eromanga faults sampled and the top calcite layer of the second, the bottom layer calcite (R 3) in the latter fault is HREE-enriched with (Pr/Yb)SN < 1 (Lawrence et al., 2006), likely due to the fact that a ligand-rich fluid was involved in that specific mineralisation event as evidenced by the (Tb/Yb)SN ratio being < 1 (Bau and Möller, 1992).

A similarly ligand-rich fluid was associated with precipitation of at least four of the Surat fracture calcite samples. These include the cadium and uranium enriched minor cleat calcite (R 29), zinc-enriched large subvertical joint calcite (especially R 28b), the zirconium and uranium enriched calcite (R 32) of one of the

52 bornite-containing master cleats, and the calcite (R 24 and 25) of master cleats containing significant pyrite mineralisation. Especially for those of these samples associated with sulphide mineralisation, it is possible that both carbonate and sulphate anions were abundant ligands, with the sulphate being reduced by native bacteria eventually resulting in the pyrite mineralisation. Given that spherules of pyrite and bornite have been observed to have grown upon calcite sheets (e.g. Figure 3d) it is possible that carbonate precipitation preceded significant sulphide mineralisation. Sixteen of the twenty-five Surat fracture calcite samples display middle-REE enrichment as indicated by (Pr/Tb)SN < 1 coupled with (Tb/Yb)SN > 1 (Lawrence et al., 2006). Only one Surat fracture calcite sample is LREE-enriched (R 33); calcite from a fault containing significant sulphide mineralisation.

The majority of fracture calcite samples have precipitated from fluids for which sorption processes dominated the REE fractionation as their (Tb/Yb)SN ratio is > 1 (Bau and Möller, 1992), with the most extreme example of this being the R-33. This calcite sample also contained the highest concentrations of lead, uranium, thorium, and chromium measured. The highest vitrinite reflectance measurement obtained thus far for this study also came from coal of the surface of this fault, which together with the (Tb/Yb)SN ratio and high sulphide content indicates that the mineralising fluid was of relatively elevated temperature, probably also more acidic than that for each of the other fracture calcite samples, and of a deep and potentially igneous origin. However, unlike all of the other samples, R-33 has a neutral (Eu/Sm)SN ratio. Hot, reducing, and acidic hydrothermal solutions generally have high (Eu/Sm)SN coupled with slightly positive

(Tb/Yb)SN (e.g. Michard et al., 1983), and if these mix with lower temperature reduced waters then massive sulfide precipitation may occur; this would be coupled with elevated levels of arsenic, cobalt, and zinc within the minerals precipitated (e.g. Bau and Möller, 1992). The (Eu/Sm)SN and (Tb/Yb)SN ratios were > 1 for almost all other Surat fracture calcite samples (excepting the minor cleat calcites), indicating that this mineralisation would have been hydrothermal fluid related (Michard et al., 1983). Given that the measured vitrinite reflectance values for coal inclusions in the major fracture mineralisation of the Surat mine samples are all higher than that for the minor cleat calcite (R 29), and that the (Eu/Sm)SN ratios of the minor cleat calcites are all less than 1, it is probably that the temperature of the fluid from which those three minor calcite samples precipitated was lower than the fluids involved in precipitation of calcite within the major fractures.

53

Table 21: Y + REE data (PAAS normalised).* Fracture Type Source Location Sample La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y B Mirintu-1 Faults 696 m R-2 7.78E-01 9.48E-01 8.89E-01 8.00E-01 6.68E-01 1.01E+00 6.54E-01 6.87E-01 7.13E-01 6.39E-01 5.84E-01 5.75E-01 4.91E-01 4.70E-01 7.21E-01 A1 Mirintu-1 Eromanga Basin Bottom Layer in Faults Fault , 677.6 m R-3 4.25E-01 5.08E-01 4.99E-01 4.61E-01 4.33E-01 6.81E-01 5.45E-01 5.55E-01 6.17E-01 5.77E-01 5.61E-01 6.31E-01 6.20E-01 5.97E-01 6.06E-01 A2 Mirintu-1 Top Layer in Fault, 677.6 m R-4 1.29E+00 1.63E+00 1.60E+00 1.49E+00 1.24E+00 1.89E+00 1.05E+00 1.14E+00 1.12E+00 9.33E-01 8.40E-01 8.59E-01 7.93E-01 7.62E-01 9.95E-01 Faults in coal: 15 cm wide massive calcite S9B19d R-30 1.18E-01 1.49E-01 2.03E-01 2.55E-01 3.71E-01 6.68E-01 4.62E-01 4.68E-01 5.01E-01 4.58E-01 4.36E-01 4.53E-01 4.04E-01 3.95E-01 4.70E-01 S10B11M5* Stripy R-19a 1.49E-01 1.30E-01 1.43E-01 1.61E-01 1.90E-01 2.57E-01 1.90E-01 1.97E-01 2.01E-01 1.86E-01 1.83E-01 1.86E-01 1.74E-01 1.79E-01 2.38E-01 Faults in coal: calcite sheet-type veins S10B11M5 R-19b 1.33E-01 1.16E-01 1.34E-01 1.52E-01 1.88E-01 2.25E-01 2.15E-01 2.17E-01 2.31E-01 2.16E-01 2.15E-01 2.33E-01 2.12E-01 2.15E-01 2.91E-01 S8 End Wall O1 R-26 1.91E-01 1.96E-01 2.47E-01 3.08E-01 4.21E-01 5.91E-01 4.81E-01 5.04E-01 5.15E-01 4.62E-01 4.19E-01 4.11E-01 3.28E-01 3.10E-01 5.10E-01 Fault in coal with abundant sulfides, minor calcite S8B3N7 R-33 5.43E-01 7.14E-01 8.51E-01 9.27E-01 1.02E+00 9.93E-01 6.96E-01 7.91E-01 6.95E-01 5.40E-01 4.50E-01 4.03E-01 3.16E-01 3.13E-01 6.11E-01 Fault in coal: calcite sheet with syntectonic bornite S10B4M7 R-20 1.58E-01 1.32E-01 1.44E-01 1.59E-01 1.87E-01 2.44E-01 1.95E-01 2.01E-01 2.06E-01 1.86E-01 1.77E-01 1.78E-01 1.49E-01 1.38E-01 2.46E-01 Fault: breccia with calcite veins S8B5N6 R-22 2.30E-03 2.40E-03 3.39E-03 5.11E-03 7.95E-03 1.08E-02 1.33E-02 1.35E-02 1.36E-02 1.36E-02 1.27E-02 1.17E-02 9.03E-03 9.08E-03 2.10E-02 Coal: master cleats S8B6N5 R-21 8.79E-02 1.03E-01 1.44E-01 1.89E-01 2.85E-01 4.13E-01 3.71E-01 3.67E-01 3.96E-01 3.72E-01 3.40E-01 3.35E-01 2.75E-01 2.44E-01 4.97E-01 with bornite S8B6M5 R-32 2.63E-01 2.50E-01 3.13E-01 3.79E-01 5.63E-01 7.58E-01 8.98E-01 8.50E-01 1.01E+00 1.03E+00 1.06E+00 1.18E+00 1.04E+00 9.97E-01 1.19E+00 S10B17&20O5 Coal: subvertical Round Calcite R-28a 3.14E-02 2.75E-02 3.27E-02 3.99E-02 5.66E-02 8.07E-02 9.44E-02 9.09E-02 1.05E-01 1.09E-01 1.11E-01 1.13E-01 9.59E-02 9.28E-02 1.66E-01 joints S10B17&20O5 R-28b 1.48E-02 1.12E-02 1.42E-02 1.88E-02 2.84E-02 4.51E-02 5.92E-02 5.33E-02 6.63E-02 7.45E-02 7.53E-02 7.76E-02 6.85E-02 6.56E-02 1.27E-01 Coal: master cleats S10B19&40O1 R-24 8.03E-02 7.47E-02 1.02E-01 1.47E-01 2.24E-01 3.37E-01 3.51E-01 3.32E-01 3.79E-01 4.03E-01 4.13E-01 4.35E-01 3.83E-01 3.67E-01 5.92E-01 with pyrite S10B24/25O1 R-25 3.94E-01 3.94E-01 5.12E-01 7.04E-01 1.01E+00 1.43E+00 1.36E+00 1.34E+00 1.41E+00 1.45E+00 1.45E+00 1.55E+00 1.38E+00 1.45E+00 2.10E+00 S10B12M1 R-16 1.03E-01 1.04E-01 1.23E-01 1.48E-01 1.79E-01 2.40E-01 2.10E-01 2.18E-01 2.19E-01 1.99E-01 1.79E-01 1.72E-01 1.33E-01 1.26E-01 2.94E-01 S10B23HO O1 R-23 1.06E-01 1.35E-01 2.15E-01 3.31E-01 6.17E-01 9.72E-01 1.02E+00 9.95E-01 1.11E+00 1.07E+00 1.01E+00 1.03E+00 8.56E-01 7.76E-01 1.35E+00 S9B1(&20)O1 (one bag) R-27a 1.94E-01 2.98E-01 4.66E-01 6.27E-01 1.14E+00 1.87E+00 2.38E+00 2.33E+00 2.73E+00 2.63E+00 2.44E+00 2.39E+00 1.91E+00 1.66E+00 2.58E+00 S9B1(&20)O1* Coal: master cleats Prismatic R-27b 2.03E-01 2.13E-01 2.80E-01 3.52E-01 4.78E-01 6.57E-01 6.57E-01 6.35E-01 7.15E-01 7.08E-01 7.00E-01 7.54E-01 6.61E-01 6.71E-01 9.32E-01 S9B1(&20)O1 (another bag) R-27c 1.40E-01 1.48E-01 1.92E-01 2.44E-01 3.27E-01 4.55E-01 4.02E-01 4.03E-01 4.31E-01 4.31E-01 4.30E-01 4.36E-01 3.82E-01 3.74E-01 5.69E-01 S9B1(&20)O1 (combined) R-27d 1.82E-01 2.07E-01 2.75E-01 3.53E-01 4.79E-01 6.62E-01 5.50E-01 5.73E-01 5.87E-01 5.30E-01 4.92E-01 4.77E-01 3.86E-01 3.46E-01 5.75E-01 S10B17(&10?)O1 R-34 1.99E-01 2.04E-01 2.65E-01 3.31E-01 4.39E-01 6.08E-01 5.43E-01 5.51E-01 5.82E-01 5.57E-01 5.35E-01 5.48E-01 4.56E-01 4.44E-01 6.79E-01 S10B14M1 B (clear) R-17a 6.24E-01 5.77E-01 6.09E-01 6.44E-01 7.39E-01 6.23E-01 7.77E-01 8.13E-01 8.25E-01 7.57E-01 7.12E-01 7.17E-01 5.78E-01 5.44E-01 1.04E+00 Coal: minor cleats S10B14M1 A with sulfides (cloudy) R-17b 5.23E-01 4.82E-01 5.11E-01 5.48E-01 6.38E-01 5.81E-01 7.26E-01 7.50E-01 7.80E-01 7.30E-01 6.90E-01 6.84E-01 5.65E-01 5.19E-01 9.47E-01 S10B14M1 R-17c 5.12E-01 4.88E-01 5.40E-01 5.81E-01 6.88E-01 6.12E-01 8.68E-01 8.67E-01 9.49E-01 9.09E-01 8.80E-01 8.98E-01 7.55E-01 6.97E-01 1.21E+00 Coal: minor cleats S10B20/21 M13 R-18 5.08E-02 4.96E-02 6.05E-02 7.05E-02 8.08E-02 9.85E-02 8.21E-02 8.32E-02 8.73E-02 8.25E-02 8.66E-02 9.32E-02 8.48E-02 8.62E-02 1.19E-01 with brown calcite S10B24/25 R-29 5.56E-01 5.55E-01 6.95E-01 9.48E-01 1.41E+00 2.14E+00 2.26E+00 2.17E+00 2.42E+00 2.70E+00 2.96E+00 3.35E+00 3.12E+00 3.36E+00 3.82E+00 *(PAAS) = Post Archean Australian Shale (PAAS) Normalised (McLennan, 1989). 54

Table 22: Y + REE data (CN normalised).* Fracture Type Source Location Sample La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y B Mirintu-1 Faults, 696 m R-2 9.27E+01 9.25E+01 6.54E+01 4.16E+01 1.87E+01 1.47E+01 1.15E+01 1.07E+01 9.51E+00 8.46E+00 7.84E+00 6.99E+00 6.22E+00 6.12E+00 9.18E+00 A1 Mirintu-1 Eromanga Basin Bottom Layer in Faults Fault , 677.6 m R-3 5.06E+01 4.96E+01 3.67E+01 2.40E+01 1.21E+01 9.84E+00 9.60E+00 8.66E+00 8.22E+00 7.64E+00 7.53E+00 7.67E+00 7.85E+00 7.78E+00 7.72E+00 A2 Mirintu-1 Top Layer in Fault, 677.6 m R-4 1.54E+02 1.59E+02 1.18E+02 7.73E+01 3.47E+01 2.73E+01 1.84E+01 1.78E+01 1.49E+01 1.24E+01 1.13E+01 1.04E+01 1.00E+01 9.92E+00 1.27E+01 Faults in coal: 15 cm wide massive calcite S9B19d R-30 1.41E+01 1.46E+01 1.49E+01 1.33E+01 1.04E+01 9.66E+00 8.12E+00 7.32E+00 6.68E+00 6.06E+00 5.86E+00 5.50E+00 5.11E+00 5.15E+00 5.98E+00 S10B11M5* Stripy R-19a 1.77E+01 1.27E+01 1.05E+01 8.38E+00 5.32E+00 3.71E+00 3.35E+00 3.07E+00 2.68E+00 2.47E+00 2.45E+00 2.26E+00 2.20E+00 2.33E+00 3.03E+00 Faults in coal: calcite sheet-type veins S10B11M5 R-19b 1.59E+01 1.13E+01 9.88E+00 7.92E+00 5.28E+00 3.26E+00 3.78E+00 3.38E+00 3.08E+00 2.87E+00 2.89E+00 2.84E+00 2.69E+00 2.80E+00 3.71E+00 S8 End Wall O1 R-26 2.27E+01 1.92E+01 1.82E+01 1.60E+01 1.18E+01 8.54E+00 8.47E+00 7.87E+00 6.87E+00 6.12E+00 5.63E+00 5.00E+00 4.15E+00 4.04E+00 6.50E+00 Fault in coal with abundant sulfides, minor calcite S8B3N7 R-33 6.47E+01 6.97E+01 6.26E+01 4.82E+01 2.85E+01 1.44E+01 1.23E+01 1.24E+01 9.26E+00 7.15E+00 6.04E+00 4.90E+00 4.01E+00 4.08E+00 7.79E+00 Fault in coal: calcite sheet with syntectonic bornite S10B4M7 R-20 1.88E+01 1.29E+01 1.06E+01 8.28E+00 5.22E+00 3.53E+00 3.43E+00 3.15E+00 2.75E+00 2.46E+00 2.37E+00 2.16E+00 1.88E+00 1.80E+00 3.14E+00 Fault: breccia with calcite veins S8B5N6 R-22 2.74E-01 2.34E-01 2.49E-01 2.66E-01 2.22E-01 1.56E-01 2.35E-01 2.10E-01 1.82E-01 1.80E-01 1.71E-01 1.42E-01 1.14E-01 1.18E-01 2.67E-01 Coal: master cleats S8B6N5 R-21 1.05E+01 1.00E+01 1.06E+01 9.81E+00 7.97E+00 5.97E+00 6.53E+00 5.73E+00 5.28E+00 4.93E+00 4.56E+00 4.07E+00 3.49E+00 3.17E+00 6.33E+00 with bornite S8B6M5 R-32 3.13E+01 2.44E+01 2.30E+01 1.97E+01 1.58E+01 1.10E+01 1.58E+01 1.33E+01 1.34E+01 1.36E+01 1.43E+01 1.43E+01 1.31E+01 1.30E+01 1.52E+01 S10B17&20O5 Coal: subvertical Round Calcite R-28a 3.74E+00 2.69E+00 2.40E+00 2.08E+00 1.59E+00 1.17E+00 1.66E+00 1.42E+00 1.39E+00 1.44E+00 1.49E+00 1.37E+00 1.21E+00 1.21E+00 2.12E+00 joints S10B17&20O5 R-28b 1.77E+00 1.09E+00 1.05E+00 9.80E-01 7.96E-01 6.51E-01 1.04E+00 8.33E-01 8.84E-01 9.86E-01 1.01E+00 9.44E-01 8.68E-01 8.55E-01 1.62E+00 Coal: master cleats S10B19&40O1 R-24 9.56E+00 7.29E+00 7.50E+00 7.66E+00 6.26E+00 4.87E+00 6.17E+00 5.19E+00 5.05E+00 5.33E+00 5.55E+00 5.29E+00 4.85E+00 4.78E+00 7.54E+00 with pyrite S10B24/25O1 R-25 4.70E+01 3.85E+01 3.76E+01 3.67E+01 2.83E+01 2.07E+01 2.39E+01 2.09E+01 1.88E+01 1.92E+01 1.95E+01 1.89E+01 1.74E+01 1.89E+01 2.68E+01 S10B12M1 R-16 1.22E+01 1.02E+01 9.05E+00 7.71E+00 5.01E+00 3.47E+00 3.69E+00 3.40E+00 2.92E+00 2.64E+00 2.40E+00 2.09E+00 1.68E+00 1.64E+00 3.74E+00 S10B23HO O1 R-23 1.27E+01 1.32E+01 1.58E+01 1.72E+01 1.73E+01 1.41E+01 1.79E+01 1.55E+01 1.48E+01 1.42E+01 1.35E+01 1.25E+01 1.08E+01 1.01E+01 1.72E+01 S9B1(&20)O1 (one bag) R-27a 2.31E+01 2.91E+01 3.43E+01 3.26E+01 3.18E+01 2.70E+01 4.18E+01 3.64E+01 3.64E+01 3.48E+01 3.28E+01 2.91E+01 2.42E+01 2.17E+01 3.29E+01 S9B1(&20)O1* Coal: master cleats Prismatic R-27b 2.42E+01 2.07E+01 2.06E+01 1.83E+01 1.34E+01 9.50E+00 1.16E+01 9.92E+00 9.53E+00 9.38E+00 9.40E+00 9.17E+00 8.37E+00 8.74E+00 1.19E+01 S9B1(&20)O1 (another bag) R-27c 1.67E+01 1.45E+01 1.41E+01 1.27E+01 9.16E+00 6.58E+00 7.08E+00 6.29E+00 5.74E+00 5.71E+00 5.78E+00 5.30E+00 4.84E+00 4.87E+00 7.24E+00 S9B1(&20)O1 (combined) R-27d 2.17E+01 2.02E+01 2.02E+01 1.84E+01 1.34E+01 9.57E+00 9.68E+00 8.95E+00 7.83E+00 7.01E+00 6.60E+00 5.80E+00 4.89E+00 4.51E+00 7.32E+00 S10B17(&10?)O1 R-34 2.37E+01 1.99E+01 1.95E+01 1.72E+01 1.23E+01 8.79E+00 9.56E+00 8.61E+00 7.77E+00 7.38E+00 7.19E+00 6.66E+00 5.78E+00 5.79E+00 8.64E+00 S10B14M1 B (clear) R-17a 7.43E+01 5.63E+01 4.48E+01 3.35E+01 2.07E+01 9.00E+00 1.37E+01 1.27E+01 1.10E+01 1.00E+01 9.56E+00 8.72E+00 7.32E+00 7.09E+00 1.33E+01 Coal: minor cleats S10B14M1 A with sulfides (cloudy) R-17b 6.23E+01 4.70E+01 3.76E+01 2.85E+01 1.79E+01 8.40E+00 1.28E+01 1.17E+01 1.04E+01 9.67E+00 9.26E+00 8.31E+00 7.16E+00 6.76E+00 1.21E+01 S10B14M1 R-17c 6.10E+01 4.76E+01 3.97E+01 3.02E+01 1.93E+01 8.84E+00 1.53E+01 1.35E+01 1.26E+01 1.20E+01 1.18E+01 1.09E+01 9.57E+00 9.08E+00 1.54E+01 Coal: minor cleats S10B20/21 M13 R-18 6.05E+00 4.83E+00 4.45E+00 3.67E+00 2.26E+00 1.42E+00 1.45E+00 1.30E+00 1.16E+00 1.09E+00 1.16E+00 1.13E+00 1.07E+00 1.12E+00 1.51E+00 with brown calcite S10B24/25 R-29 6.62E+01 5.42E+01 5.11E+01 4.94E+01 3.95E+01 3.09E+01 3.98E+01 3.40E+01 3.22E+01 3.57E+01 3.98E+01 4.07E+01 3.96E+01 4.38E+01 4.86E+01 *CN = Chondrite ("Mean C1 Chondr." of Table 1 in A&G 1989, multiplied by 1.36) Normalised (Anders and Grevesse, 1989). 55

Eromanga Faults Surat Faults 10 10

1

0.1 1

0.01

0.001 0.1 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu R-30 R-19a R-19b R-26 R-2 R-3 R-4 R-33 R-20 R-22

Master cleat calcite with sulfides Master cleat calcite with no sulfides 10 10

1 1

0.1 0.1

0.01 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu R-16 R-23 R-27a R-27b R-27c R-21 R-32 R-24 R-25 R-27d R-34 R-28a R-28b

Minor cleat calcite The most "depleted" samples 10 1

1 0.1

0.1 0.01

0.01 0.001 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

R-17a R-17b R-17c R-18 R-29 R-22 R-18 R-28a R-28b

Figure 17: PAAS-normalised REE data for fracture calcite samples. The majority of samples are enriched in HREE’s relative to LREE’s.

56

Table 23: Selected ratios of PAAS normalised elements.*

Sample (La/Sm)SN (Tb/Yb)SN (Eu/Sm)SN (Pr/Yb)SN (Pr/Tb)SN R-2 1.17 1.40 1.52 1.81 1.29 R-3 0.98 0.89 1.57 0.80 0.90 R-4 1.04 1.44 1.53 2.02 1.40 R-30 0.32 1.16 1.80 0.50 0.43 R-19a 0.78 1.13 1.35 0.82 0.73 R-19b 0.71 1.02 1.20 0.63 0.62 R-26 0.45 1.54 1.40 0.75 0.49 R-33 0.53 2.50 0.97 2.69 1.08 R-20 0.85 1.36 1.31 0.97 0.71 R-22 0.29 1.49 1.36 0.38 0.25 R-21 0.31 1.33 1.45 0.52 0.39 R-32 0.47 0.82 1.35 0.30 0.37 R-28a 0.55 0.95 1.43 0.34 0.36 R-28b 0.52 0.78 1.59 0.21 0.27 R-24 0.36 0.87 1.51 0.27 0.31 R-25 0.39 0.97 1.42 0.37 0.38 R-16 0.57 1.64 1.34 0.93 0.56 R-23 0.17 1.16 1.58 0.25 0.22 R-27a 0.17 1.22 1.65 0.24 0.20 R-27b 0.42 0.96 1.37 0.42 0.44 R-27c 0.43 1.05 1.39 0.50 0.48 R-27d 0.38 1.48 1.38 0.71 0.48 R-34 0.45 1.21 1.39 0.58 0.48 R-17a 0.84 1.41 0.84 1.05 0.75 R-17b 0.82 1.33 0.91 0.90 0.68 R-17c 0.74 1.15 0.89 0.71 0.62 R-18 0.63 0.98 1.22 0.71 0.73 R-29 0.39 0.70 1.52 0.22 0.32 > 1 (green) may be indicative Middle REE enrichment if of sorption dominated > 1 (green) coupled to > 1 LREE & < 1 HREE < 1 (green) may be both (Pr/Tb)SN < 1 and processes during REE slightly high (Tb/Yb)SN can enriched. Neither Pr indicative of (Tb/Yb)SN < 1 (bold font mobilisation, vice versa for indicate hot reducing acidic nor Yb behave metasomatism text if this is so), assuming ligand dominated REE hydrothermal solutions anomalously (Lawrence (Bau and Möller, 1992) no Tb anomaly fractionation (Michard et al., 1983) et al., 2006) (Bénézeth et al., 2007) (Bau and Möller, 1992) * SN means “shale normalised” and in this case the shale is PAAS.

Although the REE’s tend to behave very similarly chemically, evidently there are still some slight differences in the behaviour of some individual elements or else it would not be possible to fractionate this group into different concentrations of the various elements under given environmental conditions. Normalised REE values that are substantially different to what would be expected given the values of near-neighbouring elements are considered to be anomalous, and this can also provide information regarding mineralising fluid provenance, migration history and conditions of mineral precipitation (McLennan, 1989). The geometric average method used to calculate the expected normalised values for elements that may behave anomalously, using equations 1 to 5 (Table 24) assume that the normalised ratios of near-neighbouring elements are constant (McLennan, 1989), the values of closely related elements display linearly on log-linear plots (Figure 17) and that the elements used in the equations do not themselves behave anomalously (Lawrence et al., 2006).

Table 24: Equations used to calculate expected normalised values of selected elements. # 1 2 3 4 5 2 푃푟 푇푏 푃푟 푃푟푛 푛 3 2 푛 푛 Equation 퐿푎푛∗ = 푃푟푛 × ( ) 퐶푒푛∗ = 푃푟푛 × ( ) 퐸푢푛∗ = √(푆푚푛 × 푇푏푛) 퐺푑푛∗ = 푇푏푛 × ( ) 퐶푒푛∗ = 푃푟푛 × ( ) 푁푑푛 푁푑푛 퐷푦푛 푁푑푛 57

REE anomalies are calculated by dividing the measured normalised REE value by the expected normalised value (Table 25). Ratios greater than 1 are positive, less than 1 are negative, and close to 1 are not anomalous. If calcite has a negative Ce anomaly, this implies that the oxygen fugacity of the source region of the mineralising fluid was at least high enough for Ce oxidation to occur, which would have resulted in precipitation of other cerium- containing minerals such as oxy-hydroxides as soon as the oxidation had occurred (Möller, 1983). The Ce anomaly is also a function of pH as well as fO2 (Bau and Möller, 1992). Most of the samples have either an only slightly negative Ce anomaly or else none at all. Notable exceptions include the Eromanga fault samples, the Surat fault chimney calcite (R 30) and the fault containing abundant sulphides (R 33) and some of the coal cleat calcites which have clearly negative Ce anomalies. A large cleat calcite sample (27 a) that apparently formed under the most oxidising conditions also had the highest measured scandium concentration as well elevated titanium.

Compared with chondrites, PAAS has a negative Eu anomaly due to the fact that the major source of the shales is ultimately felsic and recycled material which is itself depleted in Eu due to preferential incorporation of Eu into plagioclase (e.g. Möller, 1983; Philpotts, 1970). Two of the samples do not have a Eu anomaly; the chimney calcite (R 30) and the top layer calcite (R 4) of one of the Eromanga Basin faults. The rest of the samples have negative Eu anomalies with respect to chondrites, yet all but three have positive Eu anomalies with respect to PAAS. In order to be enriched in Eu with respect to PAAS the mineralising fluid probably had either a mafic igneous origin or involved the thermal and/or acidic breakdown of plagioclase-containing rocks under reducing conditions (Bau and Möller, 1992; McLennan, 1989; Möller, 1983). Minerals inherit a positive Eu anomaly if formed under oxidising conditions, and the mineralising solution may also have had much greater sulphate than hydrogen sulphide concentration (Möller, 1983). The samples with the most negative Eu anomalies are minor coal cleat calcite occurring with sulphides. If mineralising conditions are reducing or else become reducing due to bacterial activity transforming sulphate to hydrogen sulphide, then minerals formed will have a negative Eu anomaly because reduced Eu2+ will preferentially stay in solution (Möller, 1983). Therefore, it is possible that the sulphides occurring with the calcite in the small cleats may have been the result of sulphate reducing bacteria metabolism. Interestingly, at least one of those small cleat calcites has a strong methanogenesis signature, and as methanogens are not productive in the presence of highly active sulphate producing bacteria (Abram and Nedwell, 1978), the two process would have had to have either occurred at separate times in these cleats, or else concurrently in two different locations with the products of such reactions being transported to the cleats in which they precipitated together.

58

Table 25: REE anomalies (PAAS or Chondrite normalised).

LaN/LaN* CeN/CeN* EuN/EuN* GdN/GdN* LuN/LuN* Fracture Type Source Sample PAAS C PAAS C PAAS C PAAS C PAAS C Mirintu-1 696 m R-2 0.71 0.57 0.96 0.90 1.51 0.94 0.99 0.95 1.12 1.11 Mirintu-1 677.6 m bottom layer Eromanga Basin Faults R-3 0.73 0.59 0.94 0.88 1.45 0.91 1.09 1.05 0.98 0.97 Mirintu-1 696 m top layer R-4 0.69 0.56 0.95 0.89 1.57 0.98 0.89 0.86 1.04 1.03 Faults in coal: 15 cm wide massive calcite S9B19d R-30 0.93 0.75 0.93 0.87 1.67 1.04 1.05 1.01 1.10 1.08 Faults in coal: S10B11M5* calcite Stripy R-19a 1.33 1.08 1.03 0.97 1.34 0.84 0.98 0.95 1.10 1.09 sheet-type S10B11M5 R-19b 1.27 1.03 0.97 0.91 1.14 0.72 1.06 1.02 1.11 1.10 veins S8 End Wall O1 R-26 1.20 0.97 0.99 0.93 1.32 0.83 0.98 0.94 1.19 1.17 Fault in coal with abundant sulfides, minor calcite S8B3N7 R-33 0.76 0.61 0.91 0.86 1.06 0.66 0.77 0.74 1.26 1.24 Fault in coal: calcite sheet with syntectonic bornite S10B4M7 R-20 1.35 1.09 1.02 0.96 1.28 0.80 0.99 0.95 1.11 1.10 Fault: breccia with calcite veins S8B5N6 R-22 1.54 1.24 1.06 1.00 1.14 0.71 1.00 0.96 1.30 1.28 Coal: master S8B6N5 R-21 1.05 0.85 0.94 0.88 1.33 0.84 1.09 1.05 1.08 1.06 cleats with bornite S8B6M5 R-32 1.23 1.00 0.96 0.91 1.17 0.74 1.25 1.20 1.09 1.08 S10B17&20O5 Coal: conchoidal subvertical grains R-28a 1.44 1.16 1.03 0.97 1.22 0.76 1.20 1.15 1.14 1.12 joints S10B17&20O5 R-28b 1.83 1.48 1.04 0.98 1.29 0.81 1.38 1.33 1.09 1.07 Coal: master S10B19&40O1 R-24 1.64 1.33 1.06 0.99 1.32 0.83 1.21 1.16 1.09 1.08 cleats with pyrite S10B24/25O1 R-25 1.46 1.18 1.06 1.00 1.29 0.81 1.07 1.03 1.19 1.17 S10B12M1 R-16 1.21 0.98 1.02 0.96 1.26 0.79 0.97 0.93 1.23 1.21 S10B23HO O1 R-23 1.18 0.95 0.97 0.91 1.34 0.84 1.14 1.09 1.09 1.08 S9B1(&20)O1 (one bag) R-27a 0.75 0.61 0.86 0.81 1.30 0.81 1.19 1.15 1.09 1.08 Coal: master S9B1(&20)O1* cleats Prismatic R-27b 1.15 0.93 0.95 0.90 1.25 0.78 1.16 1.12 1.16 1.14 S9B1(&20)O1 (another bag) R-27c 1.19 0.96 0.99 0.93 1.30 0.81 1.07 1.03 1.11 1.10 S9B1(&20)O1 (combined) R-27d 1.09 0.89 0.97 0.91 1.30 0.82 0.98 0.95 1.11 1.09 S10B17(&10?)O1 R-34 1.17 0.95 0.96 0.90 1.28 0.81 1.04 1.00 1.17 1.15 S10B14M1 B Coal: minor (clear) R-17a 1.15 0.93 1.00 0.94 0.82 0.51 0.97 0.93 1.17 1.15 cleats with S10B14M1 A sulfides (cloudy) R-17b 1.18 0.95 1.01 0.95 0.86 0.54 1.01 0.97 1.11 1.10 S10B14M1 R-17c 1.10 0.89 0.97 0.91 0.82 0.52 1.10 1.05 1.10 1.08 Coal: minor S10B20/21 M13 R-18 1.14 0.92 0.95 0.90 1.21 0.76 1.04 1.00 1.12 1.10 cleats with S10B24/25 mid brown calcite O5? R-29 1.49 1.21 1.09 1.02 1.31 0.82 1.15 1.11 1.15 1.14 > 1 means < 1 can indicate > 1 generally implies thermal > 1 means > 1 means enriched with oxidising conditions or acidic decomposition of enriched with enriched with lanthanum (McLennan, 1989) feldspars under conditions of gadolinium lutetium low oxygen fugacity (McLennan, 1989)

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4. Fluid inclusion studies

Samples were selected from the Chinchilla 4 well for fluid inclusion studies of authigenic carbonate. Two thin sections from the Hutton Sandstone and six thin sections from the Evergreen Formation were selected for petrographic analyses (see section 4.1. for detailed descriptions). Samples from the Evergreen Formation did not contain any suitable carbonate for fluid inclusion studies and only one sample (#256 Chinchilla 4– 799m) of the Hutton Sandstone contained enough carbonate cement for fluid inclusion work (Figure 18). Even then, fluid inclusions were very scarce in the carbonate cement and only a few were large enough for further study.

A doubly-polished thin section, 50 microns thick was prepared from sample # 256 from the Hutton Sandstone. It consisted of angular to sub-rounded grains of quartz and minor carbonate cement in the previous pore spaces. This carbonate was mostly optically clear but occasionally contained rare, two-phase, aqueous inclusions with 5 – 10 vol.% vapour.

Fluid inclusion microthermometric measurements were undertaken using a Linkam MDS600 heating/freezing stage. The stage was calibrated with synthetic fluid inclusions (pure CO2 in a CO2-H2O mixture, and pure H2O). The uncertainty in ice melting temperatures was less than ±0.2°C, whereas the uncertainty in homogenisation temperatures was less than ±2°C.

Ice melting temperatures ranged from -1.0 to 3.0 °C. Temperatures above 0.0 °C are attributed to metastable behaviour due to the small size of these inclusions (typically less than 3 microns diameter). This indicates that the fluid was of slow salinity with maximum values around 1.74 wt.% NaCl equivalent. All inclusions homogenised to the liquid phase and homogenisation temperatures ranged from 112.2 to 135.3 °C. No pressure corrections have been applied to these temperatures as the depth at which the carbonate cement was precipitated is unknown at this stage.

In summary, limited fluid inclusion data from carbonate cement in the Hutton Sandstone indicates that it precipitated from low salinity fluids with up to 1.74 wt.% NaCl equivalent and at temperatures ranging from 112.2 to 135.3oC. The Chinchilla 4 well, from which this sample was obtained, is located within 10 km of one of the most significant fault systems in eastern Australia – the Hunter-Goondiwindi-Moonie-Leichardt- Burunga fault-line, which could help to explain this anomalously high temperature value for the Hutton relative to expectations in the wider Great Artesian basin system. The next phase of our studies will examine fluid inclusions in carbonate cements from Eromanga and Surat basin petroleum cores as well as carbonate cements in faults in these cores. Stable isotope analysis of carbonates has highlighted a subset of samples with depleted carbon isotope values indicative of an organic carbon source that are good candidates not only for fluid inclusion studies but also carbon isotopic analyses of CO2 trapped in the inclusions using the on-line fluid inclusion crusher described in the next section.

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4.1. Summary observations of fluid inclusion occurrence in Chinchilla 4 samples

Hutton Sandstone Box 256 799.47 – 799.57m

Description

This sample contains irregularly shaped quartz crystals, often with embayments indicating partial dissolution. No overgrowths were observed. The quartz crystals are cemented together by carbonate, clays and minor sericite.

Abundance of Inclusions

The quartz crystals contain abundant, small (< 2 µm) fluid inclusions (FI). The carbonate cement contains a few, isolated, small (< 2 µm) FI.

Sizes and Shapes of Inclusions

Small FI (< 2 µm) in quartz and carbonate. FI in quartz and carbonate are rounded to irregular.

Origins of Inclusions

Mostly secondary FI in quartz. Primary FI in carbonate.

L/V Ratios

Variable L/V ratios in quartz. L/V ratios hard to determine in carbonate due to small size of FI but typically around 10 – 15 vol.%.

Types of Inclusions

Liquid- and Vapor-rich inclusion observed in both quartz and carbonate.

Hutton Sandstone Box 268 835.40 – 835.55 m

Description

This sample contains irregularly shaped quartz crystals in a brownish cement of kaolinite, chlorite and carbonate. There are abundant small (< 2µm) FI in quartz but the groundmass is too fine for any decent sized FI and with too many solid inclusions.

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Evergreen Formation: Box 256 946.97 – 947.07 m

Description

Abundant, slightly rounded anhedral quartz crystals in close-packed arrangement. Several small (1-2 mm) kspar crystals also observed.

Abundance of Inclusions

Abundant secondary FI in quartz crystals. Possible, small (< 1 µm) FI in carbonate crystals. Occasional overgrowths but TI in these are too small.

Evergreen Formation Box: 328 1017.27 – 1017.32 m

Description

Very small quartz + siderite? grains (< 500 µm) in fine grained matrix (ankerite, glauconite, sericite). No observable FI.

Evergreen Formation: Box 340 1053.09 – 1053.20 m

Description

Irregular – rounded quartz + minor albite crystals in a groundmass of Kspar, kaolinite, chlorite and ankerite? Abundant secondary FI in quartz but no usable FI in carbonate.

Evergreen Formation: Box 349 1082.39– 1082.50 m

Description

Abundant, irregular – rounded quartz grains in a kaolinite, chlorite, biotite, ankerite? cement. Abundant secondary FI in quartz but no observable carbonate in this sample.

Evergreen Formation: Box 364 1126.37 – 1126.46 m

Description

Irregular – anhedral quartz grains + minor muscovite in a fine-grained matrix of albite, Kspar, smectite and carbonate? Abundant secondary FI in quartz but no observable carbonate in this sample.

Evergreen Formation: Box 368 1138.10 – 1138.21 m

Description

Irregular – rounded quartz, Kspar, albite crystals in a fine-grained groundmass of kaolinite, chlorite and carbonate? Abundant secondary FI in quartz but no observable carbonate. Overgrowths observed on a few quartz grains.

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Figure 18: Calcite cemented Hutton Sandstone sample #256 (Chinchilla 4– 799m) contained rare two-phase, aqueous inclusions with 5 – 10 vol.% vapour that were sufficiently large for microthermometry.

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4.2. Construction of an on-line fluid inclusion crusher In order to process gram quantities of fluid inclusion-containing sediments, construction of a fluid inclusion crusher and transfer line was commissioned using staff and resources from GA’s Field and Engineering Services, and the Isotope and Organic Geochemistry Laboratory. The design of the fluid inclusion crusher was based on the ‘crusher’ depicted in Andrawes et al. (1984) but with modifications to heat above 100oC and to remove released moisture before the analysis of the released gases (gaseous hydrocarbons and

CO2). Analysis is performed by interfacing the heated transfer line with the injection port of a gas chromatography-mass spectrometer (GC-MS) and gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS). Figures 19 and 20 show the current version of the equipment attached to a split injector on an Agilent 5893 GCMS.

Current testing was able to raise the temperature of the sample block/holder to 105 ± 5oC (4a-e in Figure

1 20) while an insulated heating trace wrapped around the nafion tube and the /16” SS tubing transfer line could only reach 70oC. Immediate future work will involve the replacement of the ‘on/off’ temperature controller (4f in Figure 20) with a proportional temperature controller resulting in a fluctuation of < ± 2oC around the set temperature. Also a more efficient heating trace is being sort in order for the temperature of the nafion tube and transfer line to reach 105oC.

64

7

8 5 1 0 9

7

6 4 5

3 2 He flo

1 w

Figure 19: The heated fluid inclusion crusher and transfer line interfaced with Geoscience Australia’s Agilent 5893 GC-MS:

1) He carrier gas supply; 2) N gas supply for nafion tubing; 2 3) Electronic flow contoller 0-30 ml/min flow rate; 4) Heated crusher block; 5) Pneumatic press – force up to 20 atm; 6) Nafion tubing holder; 7) Heated transfer line (heating trace removed); 8) Heated split injector; 9) Liq. N trap for cryo-focussing of released gases; and 2 10) GCMS for gas analysis.

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g

N2

a 6 flo w He flo f w

e b d c

He flo w

Figure 20: Detail of the fluid inclusion crusher block, item 4 in Figure 19:

4a) Plunger with viton O-ring seals - applies downward force to crush the sample; 4b) He flow by-pass to apply positive pressure below top O-ring; 4c) He flow into sample placed between 16mm Ø W-carbide discs; 4d) Cartridge heater positioned below sample; 4e) Thermocouple to heated block; 4f) Temperature controller for heating block (heated to 105oC); 4g) Temperature controller for heating trace wrapped around nafion tube holder and transfer line (heated to 105oC); and 6) SS ⅛” tubing with He carrier flow inside the nafion tubing and outside counter-flow of N – to strip H O 2 2 from gas. A low dead volume 2-micron filter is placed before nafion tube.

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5. Ongoing and future work for project

The determination of groundwater chemistry and reservoir conditions responsible for natural carbonate mineralisation within the Great Artesian Basin is ongoing. The remainder of the carbonate cemented samples collected during the initial sampling campaign are undergoing preparation for analyses, and samples suitable for Sr, Sm and Nd isotope analysis are being processed. The next set of samples collected will be carbonate cemented cores that have recently been identified, from both South Australia and Queensland. Supplementary drill chip samples will be collected from both within wells that have already been sampled, and wells adjacent to significantly cemented wells especially proximal to large faults. The most significant samples will undergo detailed petrographic, cathodoluminescence and SEM analysis in addition to XRD, carbonate stable isotopes, ICP-MS elemental abundance, fluid inclusion studies, and radiogenic isotope studies (where applicable).

On the basis of information obtained from the natural carbonate mineralisation studies, a model will be developed for carbonate authigenesis in sandstone aquifers. This will also utilise GA’s PetroModTM burial history modelling program to integrate the geohistory of the Surat/Eromanga/Bowen basins with compositional kinetics for hydrocarbon and CO2 generation from the Permian source rocks to infer volumetrics and migration pathways at the time of carbonate mineralisation. Model development will be done in conjunction with laboratory studies of mineralisation of CO2 for Precipice and Hutton Sandstone core samples under simulated in situ conditions. Parameters affecting carbonate precipitation and techniques for potentially accelerating this process, identified during the desktop study (Golding et al., 2013b), will be experimentally investigated using both bench-top low pressure tests as well as higher temperatures and pressures in custom built geochemical reactors.

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