Sequestration of atmospheric CO2 in a weathering-derived, serpentinite-hosted magnesite deposit: 14C tracing of carbon sources and age constraints for a refined genetic model

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dc.contributor.authorOskierski, HCen_AU
dc.contributor.authorDlugogorski, BZen_AU
dc.contributor.authorJacobsen, GEen_AU
dc.date.accessioned2015-10-19T23:57:57Zen_AU
dc.date.available2015-10-19T23:57:57Zen_AU
dc.date.issued2013-12-01en_AU
dc.date.statistics2015-10-15en_AU
dc.description.abstractThe Attunga magnesite deposit is texturally and geochemically distinct from other spatially associated, serpentinite-hosted magnesite deposits in the Great Serpentinite Belt, New South Wales, Australia, such as the hydrothermal Piedmont magnesite deposit or widespread silica–carbonate alteration zones. Cryptocrystalline magnesite at Attunga predominantly occurs in nodular masses and irregular, desiccated veins that occupy pre-existing cracks and pore spaces resulting from fracturing and weathering of the host rock. Incipient weathering of the serpentinite host rock is accompanied by a decrease in volume and the mobilisation of MgO and CaO from the serpentinite. Pore spaces and permeability created during weathering and fracturing of the host rock provide access for CO2-, MgO- and CaO-bearing meteoric waters which led to an increase of volume during carbonation. SiO2 is only mobilised during more advanced stages of weathering and late stage infiltration of SiO2-bearing waters and precipitation of opal-A lead to local silicification of the serpentinite. Stable carbon and oxygen isotope signatures show that nodular magnesite at Attunga has formed under near-surface conditions incorporating carbon from C3-photosynthetic plants and oxygen from meteoric waters. Radiocarbon concentrations in the magnesite preclude subducted carbonaceous sediments as the source of carbon and, together with distinct stable carbon and oxygen isotope signatures, indicate that magnesite at Attunga precipitated from low temperature, supergene fluids. Even though there is no direct geochemical and isotopic evidence, some textural observations and field relationships for weathering-derived magnesite deposits suggest the prior existence of a possibly Early Triassic, hydrothermal magnesite deposit at Attunga. The presence of a pre-existing magnesite deposit may entail the localised formation of the weathering-derived magnesite at Attunga, but the predominance of weathering-related textures and geochemical signatures indicate that weathering is the integral magnesite mineralisation process at Attunga. Conventional radiocarbon ages of about 50 ka represent a maximum age constraint for the formation of the magnesite deposit during Quaternary weathering. A significant amount of atmospheric CO2 has been sequestered via the biosphere and carbonation of serpentinite at Attunga. © 2013, Elsevier Ltd.en_AU
dc.identifier.citationOskierski, H. C., Dlugogorski, B. Z., & Jacobsen, G. (2013). Sequestration of atmospheric CO2 in a weathering-derived, serpentinite-hosted magnesite deposit: 14C tracing of carbon sources and age constraints for a refined genetic model. Geochimica Et Cosmochimica Acta, 122(0), 226-246. doi:10.1016/j.gca.2013.08.029en_AU
dc.identifier.govdoc6186en_AU
dc.identifier.issn0016-7037en_AU
dc.identifier.journaltitleGeochimica Et Cosmochimica Actaen_AU
dc.identifier.pagination226-246en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.gca.2013.08.029en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/6338en_AU
dc.identifier.volume12en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectWeatheringen_AU
dc.subjectSerpentinitesen_AU
dc.subjectOxygen isotopesen_AU
dc.subjectTriassic perioden_AU
dc.subjectCarbonen_AU
dc.subjectBiosphereen_AU
dc.titleSequestration of atmospheric CO2 in a weathering-derived, serpentinite-hosted magnesite deposit: 14C tracing of carbon sources and age constraints for a refined genetic modelen_AU
dc.typeJournal Articleen_AU
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