Papers by Anita Parbhakar-Fox
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The acid rock drainage index (ARDI) was developed to predict acid formation based on intact rock ... more The acid rock drainage index (ARDI) was developed to predict acid formation based on intact rock texture. Five textural parameters which have direct control on acid formation are evaluated. The ARDI forms part of the geochemistry–mineralogy–texture (GMT) approach to undertaking acid rock drainage (ARD) predictive tests. This staged-approach involves parallel use of geochemical, mineralogical and textural analyses. Sample screening is performed at stage-one, and a general classification given. Stage-two involves the use of routine geochemical tests in order to cross-check stage-one results, and also to quantify the acid forming/neutralising potential. Stage-three uses advanced geochemical tests and microanalytical tools to cross-check any ambiguous results from the previous stages, and for detailed characterisation of acid forming sulphide phases.
Samples were obtained from two mine sites in Queensland, Australia, from which seventeen mesotextural groups were identified (A–Q). The ARDI identified mesotextural groups J (quartz–pyrite) and H (quartz–arsenopyrite–pyrite) as extremely acid forming. Routinely used geochemical classifications also identified these as the most acid forming groups. Four mesotextural groups (K–O) were classified as having acid neutralising capacity after full GMT classification. The remainder of mesotextural groups were classified as not acid forming. Mesotextural groups G (quartz–galena–sphalerite), H and J only require kinetic testing to resolve the lag-time to, and longevity of acid formation, and to measure the concentration of potentially deleterious elements released. The ARDI was not able to confidently discern between samples with the capacity to neutralise acid, and those which are not acid forming. Therefore, further refinement of the ARDI is required. However, in its current form the ARDI is suitable for mineral deposits with low-carbonate contents. This paper demonstrates its use as part of stage-one of the GMT approach at both operational and abandoned mine sites to screen and classify acid forming potential.
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Fifty-one waste-rock samples collected from the abandoned Croydon Au-mines were categorised into ... more Fifty-one waste-rock samples collected from the abandoned Croydon Au-mines were categorised into ten mesotextural groups (A to J) and characterised by routine and advanced static geochemical tests to identify which groups are currently responsible for acid generation. Traditional net-acid producing potential (NAPP) test procedures confirmed the absence of effective and longer-term neutralising minerals. Advanced NAG tests were performed and the multi-addition NAG test was identified as the most efficient and accurate relative to the single addition NAG and sequential NAG tests. Mesotexture J (massive quartz-pyrite) and H (massive quartz-arsenopyrite-pyrite) were identified as extremely acid-generating with maximum multi-addition NAG values of 446 and 433 kgH2SO4/t respectively. A new classification approach of comparing paste pH values with a site-specific mineralogical ARD Index was trialled, and confirmed the extremely acid generating nature of mesotextures J and H. Future management of the site should focus remediation efforts on the removal or encapsulation of waste rock demonstrating these two mesotextures.
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recent mining activity between 1981-1990 at several mine site in Croydon, North Queensland ha lef... more recent mining activity between 1981-1990 at several mine site in Croydon, North Queensland ha left uncapped sulfidic waste rock dumps. At the federation mine, the waste rock is characterised by typical vughy quartz pyrite veins which are the source of acidity, metals and a range of minerals produced by oxidation and acid mine drainage processes. Acid mine drainage from the major dumps seeps into the adjacent Federation Pit which contained elevated levels of dissolved metals including zinc, arsenic, cadmium, lead, copper, aluminum and manganese and relatively low concentrations of sulfate. The catch dam built below Federation pit is also acidic. There is periodic discharge at high flow times. The results of ICP-MS scans on water and sediments show anomalous concentrations of Al, Mn, As, Cu, Zn, Cd and Pb in the creeks adjacent to the site relative to background levels. While concentrations reduce at various distances from the site Cd, Mn and Zn are relatively more mobile than As and Pb.There is a positive correlation between Cu, Zn, Cd and pH of surface waters with a considerable decrease in the concentrations of metals and arsenic at 12km downstream. The experience of pit water treatment shows that planning for and assessing the site rehabilitation should be based on a measure of metal loads and not concentration alone.
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Amino acid adsorption is relevant to prebiotic processes involving possible catalytic reactions i... more Amino acid adsorption is relevant to prebiotic processes involving possible catalytic reactions in the early Solar System, as implied by the clay-organic correlation found in meteorites, and the generation and modification of organic components essential for the origin of life. Here we report the results of a study investigating the adsorption of L-lysine (0.025-0.4M) onto montmorillonite. The reaction products were studied using X-ray diffraction, chemical analysis and infrared spectroscopy. We find that lysine adsorption is first dominated by cation exchange and then by adsorption of electrically neutral lysine (as a zwitterion), as indicated by the chemical and FTIR evidence. At the maximum concentration, lysine displaces only ~1/3 of the original interlayer cations. The d-spacing of the smectite-lysine complex increases from 1.2 to 2.1nm as more lysine enters the interlayer space, and water is expelled. We propose a structural model of lysine sorption in the interlayer in which lysine is orientated at >45-90° to the plane of siloxane O atoms.
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Papers by Anita Parbhakar-Fox
Samples were obtained from two mine sites in Queensland, Australia, from which seventeen mesotextural groups were identified (A–Q). The ARDI identified mesotextural groups J (quartz–pyrite) and H (quartz–arsenopyrite–pyrite) as extremely acid forming. Routinely used geochemical classifications also identified these as the most acid forming groups. Four mesotextural groups (K–O) were classified as having acid neutralising capacity after full GMT classification. The remainder of mesotextural groups were classified as not acid forming. Mesotextural groups G (quartz–galena–sphalerite), H and J only require kinetic testing to resolve the lag-time to, and longevity of acid formation, and to measure the concentration of potentially deleterious elements released. The ARDI was not able to confidently discern between samples with the capacity to neutralise acid, and those which are not acid forming. Therefore, further refinement of the ARDI is required. However, in its current form the ARDI is suitable for mineral deposits with low-carbonate contents. This paper demonstrates its use as part of stage-one of the GMT approach at both operational and abandoned mine sites to screen and classify acid forming potential.
Talks by Anita Parbhakar-Fox
Samples were obtained from two mine sites in Queensland, Australia, from which seventeen mesotextural groups were identified (A–Q). The ARDI identified mesotextural groups J (quartz–pyrite) and H (quartz–arsenopyrite–pyrite) as extremely acid forming. Routinely used geochemical classifications also identified these as the most acid forming groups. Four mesotextural groups (K–O) were classified as having acid neutralising capacity after full GMT classification. The remainder of mesotextural groups were classified as not acid forming. Mesotextural groups G (quartz–galena–sphalerite), H and J only require kinetic testing to resolve the lag-time to, and longevity of acid formation, and to measure the concentration of potentially deleterious elements released. The ARDI was not able to confidently discern between samples with the capacity to neutralise acid, and those which are not acid forming. Therefore, further refinement of the ARDI is required. However, in its current form the ARDI is suitable for mineral deposits with low-carbonate contents. This paper demonstrates its use as part of stage-one of the GMT approach at both operational and abandoned mine sites to screen and classify acid forming potential.