Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland
The c. 30-km2 Tokkalehto metagabbro and associated sills and dykes intrude a large part of the western part of the early Proterozoic Kuusamo supracrustal belt in northern Finland. These rocks have previously been mapped as a metavolcanic unit, Greenstone Formation III, the type area of which occurs...
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Geological Society of Finland
2001
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ftdoajarticles:oai:doaj.org/article:277cacba05294107b18a33a32b8ab716 2023-05-15T17:42:13+02:00 Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland P.M. Evins K. Laajoki 2001-12-01T00:00:00Z https://doi.org/10.17741/bgsf/73.1-2.001 https://doaj.org/article/277cacba05294107b18a33a32b8ab716 EN eng Geological Society of Finland http://www.geologinenseura.fi/bulletin/Volume73/EvinsLaajoki.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/73.1-2.001 0367-5211 1799-4632 https://doaj.org/article/277cacba05294107b18a33a32b8ab716 Bulletin of the Geological Society of Finland, Vol 73, Iss 1-2, Pp 5-15 (2001) metagabbro intrusions absolute age U/Pb magmatism lithostratigraphy magnetic anomalies Proterozoic Tokkalehto Kuusamo Finland Geology QE1-996.5 article 2001 ftdoajarticles https://doi.org/10.17741/bgsf/73.1-2.001 2022-12-31T08:38:38Z The c. 30-km2 Tokkalehto metagabbro and associated sills and dykes intrude a large part of the western part of the early Proterozoic Kuusamo supracrustal belt in northern Finland. These rocks have previously been mapped as a metavolcanic unit, Greenstone Formation III, the type area of which occurs further east in the Kuusamo supracrustal belt. However, observations along the contacts of this unit (contact breccias, distinctive skarns and xenoliths) and within this unit (igneous layering and mafic enclaves) indicate that these rocks are intrusive. High resolution SIMS analysis of zircon from the metagabbro at Nurkamokumpu yields a crystallization age of 2216.2 ± 3.8 Ma. On the basis of this age and the lithological and petrographical characteristics of the metagabbro, it belongs to the c. 2.2 Ga karjalite or gabbro-wehrlite suite, which has a wide distribution in eastern and northern Finland. These results show that the strong aeromagnetic anomalies of the western part of the Kuusamo supracrustal belt do not represent Greenstone Formation III metavolcanics. A subdivision of the Kuusamo supracrustal belt into eastern and western halves is proposed along the Kitka Fault. Instead, these anomalies represent c. 2.2 Ga gabbroic intrusions, which intruded metasediments of the western Kuusamo supracrustal belt. Article in Journal/Newspaper Northern Finland Directory of Open Access Journals: DOAJ Articles Kitka ENVELOPE(28.980,28.980,66.243,66.243) Kuusamo ENVELOPE(29.183,29.183,65.967,65.967) Bulletin of the Geological Society of Finland 73 1-2 5 15 |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
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language |
English |
topic |
metagabbro intrusions absolute age U/Pb magmatism lithostratigraphy magnetic anomalies Proterozoic Tokkalehto Kuusamo Finland Geology QE1-996.5 |
spellingShingle |
metagabbro intrusions absolute age U/Pb magmatism lithostratigraphy magnetic anomalies Proterozoic Tokkalehto Kuusamo Finland Geology QE1-996.5 P.M. Evins K. Laajoki Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
topic_facet |
metagabbro intrusions absolute age U/Pb magmatism lithostratigraphy magnetic anomalies Proterozoic Tokkalehto Kuusamo Finland Geology QE1-996.5 |
description |
The c. 30-km2 Tokkalehto metagabbro and associated sills and dykes intrude a large part of the western part of the early Proterozoic Kuusamo supracrustal belt in northern Finland. These rocks have previously been mapped as a metavolcanic unit, Greenstone Formation III, the type area of which occurs further east in the Kuusamo supracrustal belt. However, observations along the contacts of this unit (contact breccias, distinctive skarns and xenoliths) and within this unit (igneous layering and mafic enclaves) indicate that these rocks are intrusive. High resolution SIMS analysis of zircon from the metagabbro at Nurkamokumpu yields a crystallization age of 2216.2 ± 3.8 Ma. On the basis of this age and the lithological and petrographical characteristics of the metagabbro, it belongs to the c. 2.2 Ga karjalite or gabbro-wehrlite suite, which has a wide distribution in eastern and northern Finland. These results show that the strong aeromagnetic anomalies of the western part of the Kuusamo supracrustal belt do not represent Greenstone Formation III metavolcanics. A subdivision of the Kuusamo supracrustal belt into eastern and western halves is proposed along the Kitka Fault. Instead, these anomalies represent c. 2.2 Ga gabbroic intrusions, which intruded metasediments of the western Kuusamo supracrustal belt. |
format |
Article in Journal/Newspaper |
author |
P.M. Evins K. Laajoki |
author_facet |
P.M. Evins K. Laajoki |
author_sort |
P.M. Evins |
title |
Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
title_short |
Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
title_full |
Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
title_fullStr |
Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
title_full_unstemmed |
Age of the Tokkalehto metagabbro and its significance to the lithostratigraphy of the early Proterozoic Kuusamo supracrustal belt, northern Finland |
title_sort |
age of the tokkalehto metagabbro and its significance to the lithostratigraphy of the early proterozoic kuusamo supracrustal belt, northern finland |
publisher |
Geological Society of Finland |
publishDate |
2001 |
url |
https://doi.org/10.17741/bgsf/73.1-2.001 https://doaj.org/article/277cacba05294107b18a33a32b8ab716 |
long_lat |
ENVELOPE(28.980,28.980,66.243,66.243) ENVELOPE(29.183,29.183,65.967,65.967) |
geographic |
Kitka Kuusamo |
geographic_facet |
Kitka Kuusamo |
genre |
Northern Finland |
genre_facet |
Northern Finland |
op_source |
Bulletin of the Geological Society of Finland, Vol 73, Iss 1-2, Pp 5-15 (2001) |
op_relation |
http://www.geologinenseura.fi/bulletin/Volume73/EvinsLaajoki.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/73.1-2.001 0367-5211 1799-4632 https://doaj.org/article/277cacba05294107b18a33a32b8ab716 |
op_doi |
https://doi.org/10.17741/bgsf/73.1-2.001 |
container_title |
Bulletin of the Geological Society of Finland |
container_volume |
73 |
container_issue |
1-2 |
container_start_page |
5 |
op_container_end_page |
15 |
_version_ |
1766144060472426496 |