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TitleFormation and preservation of brucite and awaruite in serpentinized and tectonized mantle in central British Columbia: implications for carbon mineralization and nickel mining
AuthorSteinthorsdottir, K; Dipple, G M; Cutts, J A; Turvey, C C; Milidragovic, DORCID logo; Peacock, S M
SourceJournal of Petrology vol. 63, no. 11, 2022 p. 1-25, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20220359
PublisherOxford University Press
Mediapaper; digital; on-line
File formatpdf
ProvinceBritish Columbia
AreaAustralia; Italy
Lat/Long WENS-126.0000 -124.0000 54.0000 53.0000
Subjectsmineralogy; igneous and metamorphic petrology; geochemistry; serpentine; carbon; brucite; nickel; mineral deposits; awaruite
Illustrationslocation maps; tables; plots; photomicrographs; schematic diagrams
Released2022 11 03
AbstractThe serpentinized and tectonized mantle in the Decar area in central British Columbia, including rocks which host the Baptiste Ni Deposit, consists of several ultramafic protolith lithologies that are variably altered to serpentinite, ophicarbonate, soapstone and listvenite. Alteration minerals include brucite (Mg[OH]2), which can be used to sequester atmospheric CO2 and awaruite (Ni3Fe), which is an economically attractive nickel alloy. This study examines the formation and preservation of brucite (up to 13 wt.%) and awaruite (up to 0.2 wt.%) in the Decar area and demonstrates that both minerals are formed during serpentinization and destroyed during carbonate alteration of mantle rocks. We distinguish five alteration stages that occurred primarily in a continental environment: 1) low-temperature lizardite serpentinization from meteoric fluids at <300 °C, 2) high-temperature antigorite (±metamorphic olivine) serpentinization from metamorphic fluids at >300 °C, 3) carbonate alteration, 4) chrysotile veining (±antigorite) serpentinization, and 5) later carbonate alteration from crustal fluids. Brucite formed primarily during late lizardite serpentinization and is most abundant in rocks that originally had high olivine-pyroxene ratios. Awaruite formed during both late lizardite serpentinization and during antigorite serpentinization and is most abundant in serpentinized olivine-rich harzburgite. The stability and abundance of brucite and awaruite are controlled by both the host rock composition and degree of serpentinization. The coexistence of brucite and awaruite reflects formation in serpentinized olivine-rich peridotite, and creates an opportunity for carbon-neutral nickel mining.
Summary(Plain Language Summary, not published)
British Columbia contains extensive volumes of serpentinized (hydrothermally altered) ultramafic rock that have potential for both nickel mining and carbon dioxide (CO2) sequestration through permanent conversion of Mg-rich silicates into Mg-rich carbonate minerals. Mineable nickel is principally hosted within mineral awaruite (Ni3Fe), whereas the potential for CO2 sequestration is related to the abundance of mineral brucite (Mg(OH)2). This paper uses the Decar deposit in central British Columbia to study the role of: 1) primary mineralogy of different ultramafic lithologies and 2) hydrothermal alteration on the formation of awaruite and brucite. The development of critical metal mines (e.g., Ni) with a high capacity for carbon dioxide mineralization represents an opportunity to decarbonize supply chains for renewable energy and reduce the greenhouse gas footprint of resource development in British Columbia.

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