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dc.contributor.authorOrvik, Alf Andre
dc.contributor.authorSlagstad, Trond
dc.contributor.authorSørensen, Bjørn Eske
dc.contributor.authorMillar, Ian
dc.contributor.authorHansen, Harald
dc.date.accessioned2022-08-08T07:04:49Z
dc.date.available2022-08-08T07:04:49Z
dc.date.issued2022-08-05
dc.description.abstractThe Karasjok–Central Lapland Greenstone Belt is one of the largest Palaeoproterozoic greenstone belts in the Fennoscandian Shield and includes multiple (ultra)mafic intrusions, some with notable ore reserves, formed during three episodes at 2.44, 2.22 and 2.05 Ga. This study presents new mineralogical, geochronological and isotopic data for the Gállojávri ultramafic intrusion, in the Karasjok Greenstone Belt, northern Norway. Previous petrogenetic modelling suggests that the intrusion was emplaced as a conduit system open for influx of melt with signs of polybaric fractionation and assimilation. Zircon U-Pb geochronology yields an age of 2051 ± 8 Ma, interpreted to reflect magmatic crystallisation. Large variations in isotopic signature over decimetres to metres indicate incomplete magma mixing. In bulk samples, εNd(t) ranges from − 15 to 4. Zircon εHf(t) ranges from − 14 to − 1. Bulk <sup>87</sup>Sr/<sup>86</sup>Sr(t) shows an apparent range from 0.5041 to 0.7072: the anomalously low values and general alteration indicates that <sup>87</sup>Sr/<sup>86</sup>Sr is non-primary, whereas the less mobile Sm-Nd/ Lu-Hf systems are interpreted to represent primary magmatic signatures. We ascribe the large variations in the Nd and Hf isotopic signatures to local melting or dissolution of xenoliths and influx of variably contaminated melt into the semi-consolidated Gállojávri magma chamber, consistent with a conduit model involving variable replenishment and crustal interaction. The most evolved isotopic signatures cannot be accounted for by interaction with the local Archaean basement, indicating the presence of unidentified crustal components at depth. The Gállojávri intrusion shows many petrogenetic similarities to other c. 2.05 Ga (ultra)mafic intrusions in the Central Lapland Greenstone Belt.en_US
dc.identifier.citationOrvik AA, Slagstad T, Sørensen BE, Millar I, Hansen H. Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics. Precambrian Research. 2022;379en_US
dc.identifier.cristinIDFRIDAID 2041316
dc.identifier.doihttps://doi.org/10.1016/j.precamres.2022.106813
dc.identifier.issn0301-9268
dc.identifier.issn1872-7433
dc.identifier.urihttps://hdl.handle.net/10037/25999
dc.language.isoengen_US
dc.publisherElsevieren_US
dc.relation.journalPrecambrian Research
dc.rights.accessRightsopenAccessen_US
dc.rights.holderCopyright 2022 The Author(s)en_US
dc.titleEvolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematicsen_US
dc.type.versionpublishedVersionen_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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