- Title
- Chemical and isotopic signatures of waters associated with the carbonation of ultramafic mine tailings, Woodsreef Asbestos Mine, Australia
- Creator
- Oskierski, H. C.; Dlugogorski, B. Z.; Oliver, T. K.; Jacobsen, G.
- Relation
- Chemical Geology Vol. 436, Issue 15 October 2015, p. 11-23
- Publisher Link
- http://dx.doi.org/10.1016/j.chemgeo.2016.04.014
- Publisher
- Elsevier
- Resource Type
- journal article
- Date
- 2016
- Description
- Extensive carbonate crusts have formed on the tailings of the Woodsreef Asbestos Mine, sequestering significant amounts of CO₂ directly from the atmosphere. The physico-chemical (pH, T, conductivity), chemical (cations, dissolved inorganic carbon (DIC)) and isotopic (δ²H, δ¹⁸O, δ¹³CDIC, F¹⁴C) signatures of waters interacting with the tailings and associated carbonate precipitates provide insight into the processes controlling carbonation. We observe two distinct evolutionary pathways for a set of stream and meteoric-derived water samples, respectively, with both groups generally being characterised as moderately alkaline, bicarbonate-dominated and Mg-rich waters. Stream water samples are supersaturated with CO₂ and therefore prone to degassing, which, in combination with evaporation, drives carbonate supersaturation and precipitation. Isotopic signatures indicate soil CO₂ as the main carbon source in the stream waters entering the tailings pile, whereas water emerging downstream of the tailings pile may also contain carbon from the dissolution of isotopically light bedrock magnesite in an open system with respect to soil CO₂. The evolution of meteoric-derived waters on the other hand, partly occurs under CO₂-limited conditions, which results from reduced CO₂ ingress at depth and/or a temporal lag between fluid alkalisation and kinetically hindered uptake of CO₂ into alkaline solution. A high pH, Mg-rich meteoric water absorbs atmospheric CO₂ after discharging into a tunnel within the tailings pile, resulting in high DIC concentrations with atmospheric carbon isotope signature. Evaporation of the water at the discharge point in the tunnel drives precipitation of hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O), displaying a clear atmospheric isotope signature, broadly consistent with previous estimates of carbon and oxygen isotope fractionation during precipitation of hydrated Mg-carbonate.
- Subject
- serpentinite; hydromagnesite; mine tailings; mineral carbonation; CO₂ sequestration; carbonation mechanisms; degassing of CO₂; evaporation; isotope fractionation
- Identifier
- http://hdl.handle.net/1959.13/1349090
- Identifier
- uon:30332
- Identifier
- ISSN:0009-2541
- Language
- eng
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