The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy
The 2.44 Ga Koillismaa layered igneous complex (KLIC) in northern Finland is interpreted to have formed as a consequence of early Paleoproterozoic continental rifting. Associated with the mafic layered intrusions are felsic to intermediate volcanic and plutonic rocks of approximately the same age. T...
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Geological Society of Finland
2003
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ftdoajarticles:oai:doaj.org/article:cf8fc4bbb01846a2a4c77d000660048f 2023-05-15T17:42:16+02:00 The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy L.S. Lauri T. Karinen J. Räsänen 2003-12-01T00:00:00Z https://doi.org/10.17741/bgsf/75.1-2.003 https://doaj.org/article/cf8fc4bbb01846a2a4c77d000660048f EN eng Geological Society of Finland http://www.geologinenseura.fi/bulletin/Volume75/Laurietal.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/75.1-2.003 0367-5211 1799-4632 https://doaj.org/article/cf8fc4bbb01846a2a4c77d000660048f Bulletin of the Geological Society of Finland, Vol 75, Iss 1-2, Pp 29-50 (2003) metavolcanic rocks granophyre mineralogy geochemistry lithostratigraphy layered intrusions rifting Paleoproterozoic Koillismaa Finland Geology QE1-996.5 article 2003 ftdoajarticles https://doi.org/10.17741/bgsf/75.1-2.003 2022-12-31T13:50:25Z The 2.44 Ga Koillismaa layered igneous complex (KLIC) in northern Finland is interpreted to have formed as a consequence of early Paleoproterozoic continental rifting. Associated with the mafic layered intrusions are felsic to intermediate volcanic and plutonic rocks of approximately the same age. The supracrustal rocks on top of the KLIC have been divided into three stratigraphic groups. The lowermost of these, the Sirniö Group, is thought to predate the KLIC and thus to represent the original roof. The overlying Kynsijärvi and Hautavaara Groups are somewhat younger than the layered intrusions. The Sirniö Group comprises two formations of felsic and intermediate volcanic rocks. The Sirniövaara Formation, also called as the Koillismaa granophyre, consists of a thick rhyodacitic unit with granophyric groundmass and some breccia interlayers. The Sirniövaara rhyodacite consists of plagioclase, quartz and biotite. Minor and accessory phases include ilmenite, magnetite, apatite, titanite, zircon and fluorite. Low-grade metamorphic minerals such as chlorite, epidote, carbonate and sericite are also commonly present. The granophyric texture is considered to have formed as a consequence of contact metamorphism and hydrothermal alteration associated with the emplacement of the KLIC. Above the Sirniövaara Formation is the Unijoki Formation, a heterogeneous group of felsic to intermediate volcanic rocks. The felsic rocks of the Unijoki Formation resemble the Sirniövaara rhyodacite whereas the intermediate rocks generally contain amphibole, instead of biotite, as the predominant mafic mineral. The rocks of the Sirniö Group show A-type geochemical character, e.g., high alkali content, Fe/Mg, 10000*Ga/Al, LREE,Y and Zr. In addition to primary compositional variation, metamorphic, and possibly hydrothermal, disturbance are recorded in the Sirniö Group lithologies. We consider them to be an example of early Paleoproterozoic rift-related volcanic rocks and tentatively correlative to the Salla Group in northern Finland. Similar ... Article in Journal/Newspaper Northern Finland Directory of Open Access Journals: DOAJ Articles Salla ENVELOPE(28.667,28.667,66.833,66.833) Koillismaa ENVELOPE(29.047,29.047,65.843,65.843) Kynsijärvi ENVELOPE(28.283,28.283,65.883,65.883) Sirniö ENVELOPE(28.151,28.151,65.854,65.854) Unijoki ENVELOPE(28.250,28.250,65.867,65.867) Bulletin of the Geological Society of Finland 75 1-2 29 50 |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
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language |
English |
topic |
metavolcanic rocks granophyre mineralogy geochemistry lithostratigraphy layered intrusions rifting Paleoproterozoic Koillismaa Finland Geology QE1-996.5 |
spellingShingle |
metavolcanic rocks granophyre mineralogy geochemistry lithostratigraphy layered intrusions rifting Paleoproterozoic Koillismaa Finland Geology QE1-996.5 L.S. Lauri T. Karinen J. Räsänen The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
topic_facet |
metavolcanic rocks granophyre mineralogy geochemistry lithostratigraphy layered intrusions rifting Paleoproterozoic Koillismaa Finland Geology QE1-996.5 |
description |
The 2.44 Ga Koillismaa layered igneous complex (KLIC) in northern Finland is interpreted to have formed as a consequence of early Paleoproterozoic continental rifting. Associated with the mafic layered intrusions are felsic to intermediate volcanic and plutonic rocks of approximately the same age. The supracrustal rocks on top of the KLIC have been divided into three stratigraphic groups. The lowermost of these, the Sirniö Group, is thought to predate the KLIC and thus to represent the original roof. The overlying Kynsijärvi and Hautavaara Groups are somewhat younger than the layered intrusions. The Sirniö Group comprises two formations of felsic and intermediate volcanic rocks. The Sirniövaara Formation, also called as the Koillismaa granophyre, consists of a thick rhyodacitic unit with granophyric groundmass and some breccia interlayers. The Sirniövaara rhyodacite consists of plagioclase, quartz and biotite. Minor and accessory phases include ilmenite, magnetite, apatite, titanite, zircon and fluorite. Low-grade metamorphic minerals such as chlorite, epidote, carbonate and sericite are also commonly present. The granophyric texture is considered to have formed as a consequence of contact metamorphism and hydrothermal alteration associated with the emplacement of the KLIC. Above the Sirniövaara Formation is the Unijoki Formation, a heterogeneous group of felsic to intermediate volcanic rocks. The felsic rocks of the Unijoki Formation resemble the Sirniövaara rhyodacite whereas the intermediate rocks generally contain amphibole, instead of biotite, as the predominant mafic mineral. The rocks of the Sirniö Group show A-type geochemical character, e.g., high alkali content, Fe/Mg, 10000*Ga/Al, LREE,Y and Zr. In addition to primary compositional variation, metamorphic, and possibly hydrothermal, disturbance are recorded in the Sirniö Group lithologies. We consider them to be an example of early Paleoproterozoic rift-related volcanic rocks and tentatively correlative to the Salla Group in northern Finland. Similar ... |
format |
Article in Journal/Newspaper |
author |
L.S. Lauri T. Karinen J. Räsänen |
author_facet |
L.S. Lauri T. Karinen J. Räsänen |
author_sort |
L.S. Lauri |
title |
The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
title_short |
The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
title_full |
The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
title_fullStr |
The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
title_full_unstemmed |
The earliest Paleoproterozoic supracrustal rocks in Koillismaa, northern Finland - Their petrographic and geochemical characteristics and lithostratigraphy |
title_sort |
earliest paleoproterozoic supracrustal rocks in koillismaa, northern finland - their petrographic and geochemical characteristics and lithostratigraphy |
publisher |
Geological Society of Finland |
publishDate |
2003 |
url |
https://doi.org/10.17741/bgsf/75.1-2.003 https://doaj.org/article/cf8fc4bbb01846a2a4c77d000660048f |
long_lat |
ENVELOPE(28.667,28.667,66.833,66.833) ENVELOPE(29.047,29.047,65.843,65.843) ENVELOPE(28.283,28.283,65.883,65.883) ENVELOPE(28.151,28.151,65.854,65.854) ENVELOPE(28.250,28.250,65.867,65.867) |
geographic |
Salla Koillismaa Kynsijärvi Sirniö Unijoki |
geographic_facet |
Salla Koillismaa Kynsijärvi Sirniö Unijoki |
genre |
Northern Finland |
genre_facet |
Northern Finland |
op_source |
Bulletin of the Geological Society of Finland, Vol 75, Iss 1-2, Pp 29-50 (2003) |
op_relation |
http://www.geologinenseura.fi/bulletin/Volume75/Laurietal.pdf https://doaj.org/toc/0367-5211 https://doaj.org/toc/1799-4632 doi:10.17741/bgsf/75.1-2.003 0367-5211 1799-4632 https://doaj.org/article/cf8fc4bbb01846a2a4c77d000660048f |
op_doi |
https://doi.org/10.17741/bgsf/75.1-2.003 |
container_title |
Bulletin of the Geological Society of Finland |
container_volume |
75 |
container_issue |
1-2 |
container_start_page |
29 |
op_container_end_page |
50 |
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1766144107095261184 |