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Nickel-rich metasomatism of the lithospheric mantle by pre-kimberlitic alkali-S-Cl-rich C-O-H fluids

Giuliani, Andrea; Kamenetsky, Vadim S; Kendrick, Mark; Phillips, David; Goemann, Karsten

Description

Metasomatism of the lithospheric mantle sometimes produces unusual assemblages containing native metals and alloys, which provide important insight into metasomatic processes in the mantle. In this study, we describe the metasomatic enrichment of a refractory harzburgite xenolith in Ni, Fe and, to a lesser extent, Cu, Co, As and Sb. The xenolith (XM1/422) derives from the Bultfontein kimberlite (Kimberley, South Africa) and hosts Ni mineralisation that includes native nickel (Ni84. 5-98. 0),...[Show more]

dc.contributor.authorGiuliani, Andrea
dc.contributor.authorKamenetsky, Vadim S
dc.contributor.authorKendrick, Mark
dc.contributor.authorPhillips, David
dc.contributor.authorGoemann, Karsten
dc.date.accessioned2015-12-13T22:38:10Z
dc.identifier.issn0010-7999
dc.identifier.urihttp://hdl.handle.net/1885/77432
dc.description.abstractMetasomatism of the lithospheric mantle sometimes produces unusual assemblages containing native metals and alloys, which provide important insight into metasomatic processes in the mantle. In this study, we describe the metasomatic enrichment of a refractory harzburgite xenolith in Ni, Fe and, to a lesser extent, Cu, Co, As and Sb. The xenolith (XM1/422) derives from the Bultfontein kimberlite (Kimberley, South Africa) and hosts Ni mineralisation that includes native nickel (Ni84. 5-98. 0), heazlewoodite (Ni3S2) and Ni-rich silicates (e. g. up to 37. 5 wt % NiO in olivine, and 22. 4 wt % NiO in phlogopite). The presence of several mineral phases enriched in alkali and volatile species (e. g. phlogopite, phosphates, carbonates, chlorides, djerfisherite) indicates that the transition metal cations were likely introduced during metasomatism by alkali-rich C-O-H fluids or alkali-carbonate melts. It is postulated that sulphide breakdown and fluid reaction with refractory mantle rocks contributed to the fluid's enrichment in Ni and other metallic cations. The Ni-rich assemblages of xenolith XM1/422 show local chemical disequilibrium, and modelling of the Ni diffusion profiles adjacent to olivine-native nickel and olivine-heazlewoodite grain boundaries, suggests a close temporal relationship between Ni-rich metasomatism and subsequent entrainment by the kimberlite magma. However, metal-rich metasomatism has also been observed in other lithospheric mantle domains, including orogenic peridotitic massifs and the suboceanic mantle; regions unaffected by kimberlite magmatsim. As micro-scale occurrences of metallic phases are easily overlooked, it is possible that metal-rich metasomatism is more widespread in the Earth's mantle than previously recognised.
dc.publisherSpringer
dc.sourceContributions to Mineralogy and Petrology
dc.subjectKeywords: cation; entrainment; harzburgite; host rock; kimberlite; lithospheric structure; magmatism; mantle structure; metallogenesis; metasomatism; mineralization; nickel; olivine; ore deposit; phlogopite; xenolith; Kimberley [Northern Cape]; Northern Cape; South C-O-H fluids; Kimberlite; Lithospheric mantle; Metasomatism; Native nickel; Olivine
dc.titleNickel-rich metasomatism of the lithospheric mantle by pre-kimberlitic alkali-S-Cl-rich C-O-H fluids
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume165
dc.date.issued2013
local.identifier.absfor040200 - GEOCHEMISTRY
local.identifier.ariespublicationf5625xPUB6293
local.type.statusPublished Version
local.contributor.affiliationGiuliani, Andrea, University of Melbourne
local.contributor.affiliationKamenetsky, Vadim S, University of Tasmania
local.contributor.affiliationKendrick, Mark, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationPhillips, David, University of Melbourne
local.contributor.affiliationGoemann, Karsten, University of Tasmania
local.description.embargo2037-12-31
local.bibliographicCitation.issue1
local.bibliographicCitation.startpage155
local.bibliographicCitation.lastpage171
local.identifier.doi10.1007/s00410-012-0801-1
dc.date.updated2016-02-24T09:28:04Z
local.identifier.scopusID2-s2.0-84871917376
local.identifier.thomsonID000313017500009
CollectionsANU Research Publications

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