Ni-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour cloud

Title:
Ni-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour cloud
Authors:
Goderis, Steven; Simonson, Bruce M.; McDonald, Iain; Hassler, Scott W.; Izmer, Andrei; Belza, Joke; Terryn, Herman; Vanhaecke, Frank; Claeys, Philippe
Abstract:
Deciphering Earthʼs impact history before ∼2 Ga relies heavily on the lunar record and terrestrial spherule layers, which are distal ejecta from large impacts. This study focuses on the Paraburdoo and Reivilo spherule layers in Western Australia and South Africa respectively, that were probably formed by one impact around 2.57 Ga. Both layers contain an aggregate thickness of ∼2 cm of spherules, known as microkrystites. These spherules are up to ∼0.6 mm in diameter and crystallized during flight, but were diagenetically replaced by K-feldspar and phlogopite with remarkable textural retention. Unlike any other Archaean layer, except for the 3.2 Ga S3 layer in the Barberton greenstone belt, the Paraburdoo and Reivilo spherules contain Ni-rich spinel crystals and high concentrations of meteoritic material (up to 357 ng g−1 Ir for bulk samples of several gram). These exceptional characteristics shed new light on the distribution of the meteoritic component carrier phases (metallic alloys dispersed in the pristine glass) and the processes involved in impact spherule formation and secondary alteration.
Citation:
Goderis, S., B.M. Simonson, I. McDonald, S.W. Hassler, A. Izmer, J. Belza, H. Terryn, F. Vanhaecke, and Ph. Claeys. August 2013. “Ni-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour cloud.” Earth and Planetary Science Letters 376: 87–98.
Publisher:
Elsevier
DATE ISSUED:
2013
Department:
Geology
Type:
Article
PUBLISHED VERSION:
10.1016/j.epsl.2013.06.027
PERMANENT LINK:
http://hdl.handle.net/11282/332552

Full metadata record

DC FieldValue Language
dc.contributor.authorGoderis, Stevenen
dc.contributor.authorSimonson, Bruce M.en
dc.contributor.authorMcDonald, Iainen
dc.contributor.authorHassler, Scott W.en
dc.contributor.authorIzmer, Andreien
dc.contributor.authorBelza, Jokeen
dc.contributor.authorTerryn, Hermanen
dc.contributor.authorVanhaecke, Franken
dc.contributor.authorClaeys, Philippeen
dc.date.accessioned2014-10-09T12:04:58Z-
dc.date.available2014-10-09T12:04:58Z-
dc.date.issued2013en
dc.identifier.citationGoderis, S., B.M. Simonson, I. McDonald, S.W. Hassler, A. Izmer, J. Belza, H. Terryn, F. Vanhaecke, and Ph. Claeys. August 2013. “Ni-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour cloud.” Earth and Planetary Science Letters 376: 87–98.en
dc.identifier.issn0012-821Xen
dc.identifier.urihttp://hdl.handle.net/11282/332552-
dc.description.abstractDeciphering Earthʼs impact history before ∼2 Ga relies heavily on the lunar record and terrestrial spherule layers, which are distal ejecta from large impacts. This study focuses on the Paraburdoo and Reivilo spherule layers in Western Australia and South Africa respectively, that were probably formed by one impact around 2.57 Ga. Both layers contain an aggregate thickness of ∼2 cm of spherules, known as microkrystites. These spherules are up to ∼0.6 mm in diameter and crystallized during flight, but were diagenetically replaced by K-feldspar and phlogopite with remarkable textural retention. Unlike any other Archaean layer, except for the 3.2 Ga S3 layer in the Barberton greenstone belt, the Paraburdoo and Reivilo spherules contain Ni-rich spinel crystals and high concentrations of meteoritic material (up to 357 ng g−1 Ir for bulk samples of several gram). These exceptional characteristics shed new light on the distribution of the meteoritic component carrier phases (metallic alloys dispersed in the pristine glass) and the processes involved in impact spherule formation and secondary alteration.en
dc.language.isoen_USen
dc.publisherElsevieren
dc.identifier.doi10.1016/j.epsl.2013.06.027en
dc.subject.departmentGeologyen
dc.titleNi-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour clouden
dc.typeArticleen
dc.identifier.journalEarth and Planetary Science Lettersen
dc.subject.keywordImpacten
dc.subject.keywordLate Archaenen
dc.subject.keywordParaburdooen
dc.subject.keywordSpherule layersen
dc.subject.keywordNi-rich spinelen
dc.subject.keywordPlatinum group elementsen
dc.identifier.volume376en
dc.identifier.startpage87en
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