Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics
The 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 mineralogic...
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ftunivtroemsoe:oai:munin.uit.no:10037/25999 2023-05-15T16:13:06+02:00 Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics Orvik, Alf Andre Slagstad, Trond Sørensen, Bjørn Eske Millar, Ian Hansen, Harald 2022-08-05 https://hdl.handle.net/10037/25999 https://doi.org/10.1016/j.precamres.2022.106813 eng eng Elsevier Precambrian Research Orvik 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;379 FRIDAID 2041316 https://doi.org/10.1016/j.precamres.2022.106813 0301-9268 1872-7433 https://hdl.handle.net/10037/25999 openAccess Copyright 2022 The Author(s) Journal article Tidsskriftartikkel Peer reviewed publishedVersion 2022 ftunivtroemsoe https://doi.org/10.1016/j.precamres.2022.106813 2022-08-10T23:00:01Z The 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 87 Sr/ 86 Sr(t) shows an apparent range from 0.5041 to 0.7072: the anomalously low values and general alteration indicates that 87 Sr/ 86 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. Article in Journal/Newspaper Fennoscandian Karasjok Northern Norway Lapland University of Tromsø: Munin Open Research Archive Karasjok ENVELOPE(25.519,25.519,69.472,69.472) Norway Precambrian Research 379 106813 |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
description |
The 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 87 Sr/ 86 Sr(t) shows an apparent range from 0.5041 to 0.7072: the anomalously low values and general alteration indicates that 87 Sr/ 86 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. |
format |
Article in Journal/Newspaper |
author |
Orvik, Alf Andre Slagstad, Trond Sørensen, Bjørn Eske Millar, Ian Hansen, Harald |
spellingShingle |
Orvik, Alf Andre Slagstad, Trond Sørensen, Bjørn Eske Millar, Ian Hansen, Harald Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
author_facet |
Orvik, Alf Andre Slagstad, Trond Sørensen, Bjørn Eske Millar, Ian Hansen, Harald |
author_sort |
Orvik, Alf Andre |
title |
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
title_short |
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
title_full |
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
title_fullStr |
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
title_full_unstemmed |
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics |
title_sort |
evolution of the gállojávri ultramafic intrusion from u-pb zircon ages and rb-sr, sm-nd and lu-hf isotope systematics |
publisher |
Elsevier |
publishDate |
2022 |
url |
https://hdl.handle.net/10037/25999 https://doi.org/10.1016/j.precamres.2022.106813 |
long_lat |
ENVELOPE(25.519,25.519,69.472,69.472) |
geographic |
Karasjok Norway |
geographic_facet |
Karasjok Norway |
genre |
Fennoscandian Karasjok Northern Norway Lapland |
genre_facet |
Fennoscandian Karasjok Northern Norway Lapland |
op_relation |
Precambrian Research Orvik 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;379 FRIDAID 2041316 https://doi.org/10.1016/j.precamres.2022.106813 0301-9268 1872-7433 https://hdl.handle.net/10037/25999 |
op_rights |
openAccess Copyright 2022 The Author(s) |
op_doi |
https://doi.org/10.1016/j.precamres.2022.106813 |
container_title |
Precambrian Research |
container_volume |
379 |
container_start_page |
106813 |
_version_ |
1765998700394446848 |