dc.contributor.author
Kaufmann, Felix E. D.
dc.contributor.author
O'Driscoll, Brian
dc.contributor.author
Hecht, Lutz
dc.date.accessioned
2020-10-22T12:37:52Z
dc.date.available
2020-10-22T12:37:52Z
dc.identifier.uri
https://refubium.fu-berlin.de/handle/fub188/28624
dc.identifier.uri
http://dx.doi.org/10.17169/refubium-28373
dc.description.abstract
The Rum Layered Suite, NW Scotland, hosts Cr-spinel seams at the bases of peridotite-troctolite macro-rhythmic units in the eastern portion of the intrusion. Here, we present detailed field observations together with microstructural and mineral chemical analyses for the Unit 7-8 Cr-spinel seam and associated cumulates in the Eastern Layered Intrusion. Detailed mapping and sampling reveal significant lateral variations in the structural characteristics and mineral compositions of the Unit 7-8 boundary zone rocks. Although the Cr-spinel seam is laterally continuous over similar to 3 km, it is absent towards the centre and the margins of the intrusion. The compositional characteristics of Cr-spinel and plagioclase vary systematically along strike, exhibiting a chemical evolution towards more differentiated compositions with increasing distance from the main feeder conduit of the Rum intrusion; the Long Loch Fault. On the basis of our combined datasets, we propose that the upper part of the troctolite, the anorthosite layer underlying the Cr-spinel seam and the seam itself formed during a multi-stage magma replenishment event. The stages can be summarised as follows: (1) peridotite schlieren and anorthosite autoliths formed following melt infiltration and cumulate assimilation in the crystal mush of the Unit 7 troctolite. (2) The anorthosite layer then formed from the Unit 7 troctolite crystal mush by thermal erosion and dissolution due to infiltrating magma. (3) Subsequent dissolution of the anorthosite layer by new replenishing magma led to peritectic in situ crystallisation of the Unit 7-8 Cr-spinel seam, with (4) continued magma input eventually producing the overlying Unit 8 peridotite. In the central part of the Rum Layered Suite, the aforementioned assimilation of the troctolitic footwall formed the anorthosite layer. However, the absence of anorthosite in close proximity to the Long Loch Fault can be explained by enhanced thermochemical erosion close to the feeder zone, and its absence close to the margins of the intrusion, at maximum distance from the Long Loch Fault, may be due to cooling of the magma and loss of erosion potential. In line with other recent studies on PGE-bearing chromitites in layered intrusions, we highlight the importance of multi-stage intrusive magma replenishment to the formation of spatially coupled anorthosite and Cr-spinel seams, as well as the lateral mineral chemical variations observed in the Unit 7-8 boundary zone cumulates.
en
dc.format.extent
22 Seiten
dc.rights.uri
https://creativecommons.org/licenses/by/4.0/
dc.subject
in-situ crystallization
en
dc.subject
cumulate assimilation
en
dc.subject
chromitite layers
en
dc.subject
isotope ratios
en
dc.subject
chrome-spinel
en
dc.subject
magma chamber
en
dc.subject.ddc
500 Naturwissenschaften und Mathematik::550 Geowissenschaften, Geologie::550 Geowissenschaften
dc.title
Lateral variations in the Unit 7-8 boundary zone of the Rum Eastern Layered Intrusion, NW Scotland: implications for the origin and timing of Cr-spinel seam formation
dc.type
Wissenschaftlicher Artikel
dcterms.bibliographicCitation.articlenumber
90
dcterms.bibliographicCitation.doi
10.1007/s00410-020-01732-x
dcterms.bibliographicCitation.journaltitle
Contributions to Mineralogy and Petrology
dcterms.bibliographicCitation.number
9
dcterms.bibliographicCitation.volume
175
dcterms.bibliographicCitation.url
https://doi.org/10.1007/s00410-020-01732-x
refubium.affiliation
Geowissenschaften
refubium.affiliation.other
Institut für Geologische Wissenschaften
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refubium.resourceType.isindependentpub
no
dcterms.accessRights.openaire
open access
dcterms.isPartOf.issn
0010-7999
dcterms.isPartOf.eissn
1432-0967
refubium.resourceType.provider
WoS-Alert