The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland
In the Archaean Pudasjärvi Complex the pyroxene-bearing rocks are considered to form a belt, the Pudasjärvi Granulite Belt (PGB). The major rock types of the PGB are meta-igneous mafic and felsic granulites, and trondhjemite gneisses Red alaskites, white leucogranites and trondhjemitic pegmatoids ar...
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Geological Society of Finland
2003
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ftdoajarticles:oai:doaj.org/article:1e8b4b41e89d42409638c92dafb77b0f 2023-05-15T16:13:04+02:00 The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland T. Mutanen H. Huhma 2003-12-01T00:00:00Z https://doi.org/10.17741/bgsf/75.1-2.004 https://doaj.org/article/1e8b4b41e89d42409638c92dafb77b0f EN eng Geological Society of Finland http://www.geologinenseura.fi/bulletin/Volume75/MutanenHuhma.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/75.1-2.004 0367-5211 1799-4632 https://doaj.org/article/1e8b4b41e89d42409638c92dafb77b0f Bulletin of the Geological Society of Finland, Vol 75, Iss 1-2, Pp 51-68 (2003) gneisses granulites diorites alaskite chemical composition absolute age U/Pb zircon Sm/Nd Archean Siurua Pudasjärvi Ranua Finland Geology QE1-996.5 article 2003 ftdoajarticles https://doi.org/10.17741/bgsf/75.1-2.004 2022-12-31T05:53:58Z In the Archaean Pudasjärvi Complex the pyroxene-bearing rocks are considered to form a belt, the Pudasjärvi Granulite Belt (PGB). The major rock types of the PGB are meta-igneous mafic and felsic granulites, and trondhjemite gneisses Red alaskites, white leucogranites and trondhjemitic pegmatoids are locally abundant. Ion microprobe U-Pb analyses on zircons suggest a magmatic age of ca 3.5 Ga for the trondhjemite gneiss in Siurua, considered the oldest rock so far identified in the Fennoscandian Shield. The old age is supported by the Sm-Nd depleted mantle model age of 3.5 Ga, and by conventional U-Pb zircon data, which have provided a minimum age of 3.32 Ga. The U-Pb sims-data on the Siurua gneiss are, however, heterogeneous and suggest several stages of zircon growth, mostly at 3.5-3.4 Ga. An inherited core in one crystal provided an age of 3.73 Ga, whereas the youngest two analyses yield ages of 3.1 and 3.3 Ga. Metamorphic monazite formed in the Siurua gneiss ca. 2.66 Ga ago, roughly contemporaneously with the high-grade metamorphism recorded by zircon in a mafic granulite. Magmatic zircons from a felsic high-grade rock provide ages of ca. 2.96 Ga, but no zircons coeval with the 2.65 Ga metamorphism were detected by ion-microprobe. As a whole the PGB seems to be a tectonic block-mosaic containing rocks with Sm-Nd crustal formation ages ranging from 3.5 to 2.8 Ga. Article in Journal/Newspaper Fennoscandian Northern Finland Directory of Open Access Journals: DOAJ Articles Ranua ENVELOPE(27.000,27.000,65.767,65.767) Bulletin of the Geological Society of Finland 75 1-2 51 68 |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
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language |
English |
topic |
gneisses granulites diorites alaskite chemical composition absolute age U/Pb zircon Sm/Nd Archean Siurua Pudasjärvi Ranua Finland Geology QE1-996.5 |
spellingShingle |
gneisses granulites diorites alaskite chemical composition absolute age U/Pb zircon Sm/Nd Archean Siurua Pudasjärvi Ranua Finland Geology QE1-996.5 T. Mutanen H. Huhma The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
topic_facet |
gneisses granulites diorites alaskite chemical composition absolute age U/Pb zircon Sm/Nd Archean Siurua Pudasjärvi Ranua Finland Geology QE1-996.5 |
description |
In the Archaean Pudasjärvi Complex the pyroxene-bearing rocks are considered to form a belt, the Pudasjärvi Granulite Belt (PGB). The major rock types of the PGB are meta-igneous mafic and felsic granulites, and trondhjemite gneisses Red alaskites, white leucogranites and trondhjemitic pegmatoids are locally abundant. Ion microprobe U-Pb analyses on zircons suggest a magmatic age of ca 3.5 Ga for the trondhjemite gneiss in Siurua, considered the oldest rock so far identified in the Fennoscandian Shield. The old age is supported by the Sm-Nd depleted mantle model age of 3.5 Ga, and by conventional U-Pb zircon data, which have provided a minimum age of 3.32 Ga. The U-Pb sims-data on the Siurua gneiss are, however, heterogeneous and suggest several stages of zircon growth, mostly at 3.5-3.4 Ga. An inherited core in one crystal provided an age of 3.73 Ga, whereas the youngest two analyses yield ages of 3.1 and 3.3 Ga. Metamorphic monazite formed in the Siurua gneiss ca. 2.66 Ga ago, roughly contemporaneously with the high-grade metamorphism recorded by zircon in a mafic granulite. Magmatic zircons from a felsic high-grade rock provide ages of ca. 2.96 Ga, but no zircons coeval with the 2.65 Ga metamorphism were detected by ion-microprobe. As a whole the PGB seems to be a tectonic block-mosaic containing rocks with Sm-Nd crustal formation ages ranging from 3.5 to 2.8 Ga. |
format |
Article in Journal/Newspaper |
author |
T. Mutanen H. Huhma |
author_facet |
T. Mutanen H. Huhma |
author_sort |
T. Mutanen |
title |
The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
title_short |
The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
title_full |
The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
title_fullStr |
The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
title_full_unstemmed |
The 3.5 Ga Siurua trondhjemite gneiss in the Archaean Pudasjärvi Granulite Belt, northern Finland |
title_sort |
3.5 ga siurua trondhjemite gneiss in the archaean pudasjärvi granulite belt, northern finland |
publisher |
Geological Society of Finland |
publishDate |
2003 |
url |
https://doi.org/10.17741/bgsf/75.1-2.004 https://doaj.org/article/1e8b4b41e89d42409638c92dafb77b0f |
long_lat |
ENVELOPE(27.000,27.000,65.767,65.767) |
geographic |
Ranua |
geographic_facet |
Ranua |
genre |
Fennoscandian Northern Finland |
genre_facet |
Fennoscandian Northern Finland |
op_source |
Bulletin of the Geological Society of Finland, Vol 75, Iss 1-2, Pp 51-68 (2003) |
op_relation |
http://www.geologinenseura.fi/bulletin/Volume75/MutanenHuhma.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/75.1-2.004 0367-5211 1799-4632 https://doaj.org/article/1e8b4b41e89d42409638c92dafb77b0f |
op_doi |
https://doi.org/10.17741/bgsf/75.1-2.004 |
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Bulletin of the Geological Society of Finland |
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75 |
container_issue |
1-2 |
container_start_page |
51 |
op_container_end_page |
68 |
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1765998675601915904 |