Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland
This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki carbonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennosc...
Published in: | Bulletin of the Geological Society of Finland |
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Language: | English |
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Geological Society of Finland
1997
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Online Access: | https://doi.org/10.17741/bgsf/69.1-2.001 https://doaj.org/article/e9d6e5aa797d4fd48a36b0fcf32854fd |
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ftdoajarticles:oai:doaj.org/article:e9d6e5aa797d4fd48a36b0fcf32854fd 2023-05-15T16:12:56+02:00 Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland J. Nykänen K. Laajoki J. Karhu 1997-12-01T00:00:00Z https://doi.org/10.17741/bgsf/69.1-2.001 https://doaj.org/article/e9d6e5aa797d4fd48a36b0fcf32854fd EN eng Geological Society of Finland http://www.geologinenseura.fi/bulletin/Volume69/sgs_bt_069_pages_005_030.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/69.1-2.001 0367-5211 1799-4632 https://doaj.org/article/e9d6e5aa797d4fd48a36b0fcf32854fd Bulletin of the Geological Society of Finland, Vol 69, Iss 1-2, Pp 5-30 (1997) phlogopite amphibole group magnetite ilmenite olivine apatite monazite allanite geochemistry trace elements rare earths stable isotopes Proterozoic Kortejärvi Laivajoki Petäikkö-Suvantovaara Finland Geology QE1-996.5 article 1997 ftdoajarticles https://doi.org/10.17741/bgsf/69.1-2.001 2022-12-31T00:20:58Z This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki carbonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennoscandian Shield. They are not exposed, but have been penetrated by a couple of deep drill holes. In terms of modal mineralogy, both intrusions contain calcite carbonatite and dolomite-calcite carbonatite as their main rock types, but Kortejärvi also contains dolomite carbonatite and calcite-dolomite carbonatite, some glimmerite and olivine-magnetite rock and Laivajärvi tremolite-calcite carbonatite, tremolite-dolomite carbonatite, serpentine-talc-dolomite rock and glimmerite. The main country rock is an amphibolite which is not fenitized. No alkaline rocks have been detected in these intrusions. Calcite is most common mineral in both occurrences. Other carbonate minerals include dolomite with minor ankerite and occassional siderite. In addition to low-Ti phlogopite, tetraferriphlogopite is also encountered. Fresh olivine is rare, and its alteration products include titaniferous clinohumite. The amphiboles are mainly calcic amphiboles, including actinolite, tremolite and edenite. The only sodic-calcic amphibole is accessory richterite. Other essential minerals are Ti-poor magnetite with ilmenite exsolutions, fluorapatite (3.95-4.89 wt. % F), monazite, and allanite-(Ce). Geochemically, the Kortejärvi rocks are mostly magnesiocarbonatites, whereas those of Laivajärvi, due to their higher magnetite content, are ferrocarbonatites. Of the trace elements, Nb is much lower (8-30 ppm) in proper carbonatites than the average for carbonatites and U and Th (<0.9 ppm and<2.4 pm, respectively) lower than average. Sr is typical, but not high (1830-3480 ppm), and Ba is rather low (27-348 ppm). The REEs are hosted by allanite and monazite and their concentrations in the proper carbonatites are relatively low (REE(Y)tot 737-1452 ... Article in Journal/Newspaper Fennoscandian Northern Finland Directory of Open Access Journals: DOAJ Articles Kortejärvi ENVELOPE(27.917,27.917,65.700,65.700) Bulletin of the Geological Society of Finland 69 1-2 5 30 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
phlogopite amphibole group magnetite ilmenite olivine apatite monazite allanite geochemistry trace elements rare earths stable isotopes Proterozoic Kortejärvi Laivajoki Petäikkö-Suvantovaara Finland Geology QE1-996.5 |
spellingShingle |
phlogopite amphibole group magnetite ilmenite olivine apatite monazite allanite geochemistry trace elements rare earths stable isotopes Proterozoic Kortejärvi Laivajoki Petäikkö-Suvantovaara Finland Geology QE1-996.5 J. Nykänen K. Laajoki J. Karhu Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
topic_facet |
phlogopite amphibole group magnetite ilmenite olivine apatite monazite allanite geochemistry trace elements rare earths stable isotopes Proterozoic Kortejärvi Laivajoki Petäikkö-Suvantovaara Finland Geology QE1-996.5 |
description |
This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki carbonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennoscandian Shield. They are not exposed, but have been penetrated by a couple of deep drill holes. In terms of modal mineralogy, both intrusions contain calcite carbonatite and dolomite-calcite carbonatite as their main rock types, but Kortejärvi also contains dolomite carbonatite and calcite-dolomite carbonatite, some glimmerite and olivine-magnetite rock and Laivajärvi tremolite-calcite carbonatite, tremolite-dolomite carbonatite, serpentine-talc-dolomite rock and glimmerite. The main country rock is an amphibolite which is not fenitized. No alkaline rocks have been detected in these intrusions. Calcite is most common mineral in both occurrences. Other carbonate minerals include dolomite with minor ankerite and occassional siderite. In addition to low-Ti phlogopite, tetraferriphlogopite is also encountered. Fresh olivine is rare, and its alteration products include titaniferous clinohumite. The amphiboles are mainly calcic amphiboles, including actinolite, tremolite and edenite. The only sodic-calcic amphibole is accessory richterite. Other essential minerals are Ti-poor magnetite with ilmenite exsolutions, fluorapatite (3.95-4.89 wt. % F), monazite, and allanite-(Ce). Geochemically, the Kortejärvi rocks are mostly magnesiocarbonatites, whereas those of Laivajärvi, due to their higher magnetite content, are ferrocarbonatites. Of the trace elements, Nb is much lower (8-30 ppm) in proper carbonatites than the average for carbonatites and U and Th (<0.9 ppm and<2.4 pm, respectively) lower than average. Sr is typical, but not high (1830-3480 ppm), and Ba is rather low (27-348 ppm). The REEs are hosted by allanite and monazite and their concentrations in the proper carbonatites are relatively low (REE(Y)tot 737-1452 ... |
format |
Article in Journal/Newspaper |
author |
J. Nykänen K. Laajoki J. Karhu |
author_facet |
J. Nykänen K. Laajoki J. Karhu |
author_sort |
J. Nykänen |
title |
Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
title_short |
Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
title_full |
Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
title_fullStr |
Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
title_full_unstemmed |
Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland |
title_sort |
geology and geochemistry of the early proterozoic kortejärvi and laivajoki carbonatites, central fennoscandian shield, finland |
publisher |
Geological Society of Finland |
publishDate |
1997 |
url |
https://doi.org/10.17741/bgsf/69.1-2.001 https://doaj.org/article/e9d6e5aa797d4fd48a36b0fcf32854fd |
long_lat |
ENVELOPE(27.917,27.917,65.700,65.700) |
geographic |
Kortejärvi |
geographic_facet |
Kortejärvi |
genre |
Fennoscandian Northern Finland |
genre_facet |
Fennoscandian Northern Finland |
op_source |
Bulletin of the Geological Society of Finland, Vol 69, Iss 1-2, Pp 5-30 (1997) |
op_relation |
http://www.geologinenseura.fi/bulletin/Volume69/sgs_bt_069_pages_005_030.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/69.1-2.001 0367-5211 1799-4632 https://doaj.org/article/e9d6e5aa797d4fd48a36b0fcf32854fd |
op_doi |
https://doi.org/10.17741/bgsf/69.1-2.001 |
container_title |
Bulletin of the Geological Society of Finland |
container_volume |
69 |
container_issue |
1-2 |
container_start_page |
5 |
op_container_end_page |
30 |
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1765998546977292288 |