Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield
The Tuntsa Suite is a polymetamorphic Archean complex mainly consisting of metasedimentary gneisses. At least two strong metamorphic events can be distinguished in the area. The first took place at high temperatures in the Neoarchean at around 2.70–2.64 Ga, indicated by migmatisation and U-Pb ages o...
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ftmdpi:oai:mdpi.com:/2075-163X/10/11/1034/ 2023-08-20T04:06:27+02:00 Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield Pentti Hölttä Tiia Kivisaari Hannu Huhma Gavyn Rollinson Matti Kurhila Alan R. Butcher agris 2020-11-19 application/pdf https://doi.org/10.3390/min10111034 EN eng Multidisciplinary Digital Publishing Institute Mineral Geochemistry and Geochronology https://dx.doi.org/10.3390/min10111034 https://creativecommons.org/licenses/by/4.0/ Minerals; Volume 10; Issue 11; Pages: 1034 Archean Paleoproterozoic metamorphism age determination Fennoscandian Shield Finland Text 2020 ftmdpi https://doi.org/10.3390/min10111034 2023-08-01T00:29:42Z The Tuntsa Suite is a polymetamorphic Archean complex mainly consisting of metasedimentary gneisses. At least two strong metamorphic events can be distinguished in the area. The first took place at high temperatures in the Neoarchean at around 2.70–2.64 Ga, indicated by migmatisation and U-Pb ages of metamorphic zircon. During the Paleoproterozoic, metasedimentary gneisses were penetratively deformed and recrystallized under medium pressures producing staurolite, kyanite and garnet-bearing mineral assemblages. The suggested Paleoproterozoic PT path was clockwise where the temperature and pressure first increased to 540–550 °C and 6 kbar, crystallizing high Ca/low Mg garnet cores. The mineral compositions show that commonly garnet core was not in chemical equilibrium with staurolite but crystallized earlier, although garnet-staurolite-kyanite assemblages are common. The temperature and pressure increased to c. 650 °C and 8 kbars where staurolite and kyanite coexist. This was followed by decompression down to c. 550–600 °C and 3–4 kbars, shown by andalusite crystallization and cordierite formed in the breakdown of staurolite and biotite + kyanite. The observed garnet zoning where Mg increases and Ca decreases from the core to the rim was developed with both increasing and decreasing pressure, depending on the effective bulk composition. The U-Pb and Sm-Nd age determinations for monazite and garnet show that the Paleoproterozoic metamorphic cycle took place at 1.84–1.79 Ga, related with thrusting of the Lapland granulites onto the adjacent terranes and subsequent exhumation. Text Fennoscandian Lapland MDPI Open Access Publishing Tuntsa ENVELOPE(29.696,29.696,67.597,67.597) Minerals 10 11 1034 |
institution |
Open Polar |
collection |
MDPI Open Access Publishing |
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ftmdpi |
language |
English |
topic |
Archean Paleoproterozoic metamorphism age determination Fennoscandian Shield Finland |
spellingShingle |
Archean Paleoproterozoic metamorphism age determination Fennoscandian Shield Finland Pentti Hölttä Tiia Kivisaari Hannu Huhma Gavyn Rollinson Matti Kurhila Alan R. Butcher Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
topic_facet |
Archean Paleoproterozoic metamorphism age determination Fennoscandian Shield Finland |
description |
The Tuntsa Suite is a polymetamorphic Archean complex mainly consisting of metasedimentary gneisses. At least two strong metamorphic events can be distinguished in the area. The first took place at high temperatures in the Neoarchean at around 2.70–2.64 Ga, indicated by migmatisation and U-Pb ages of metamorphic zircon. During the Paleoproterozoic, metasedimentary gneisses were penetratively deformed and recrystallized under medium pressures producing staurolite, kyanite and garnet-bearing mineral assemblages. The suggested Paleoproterozoic PT path was clockwise where the temperature and pressure first increased to 540–550 °C and 6 kbar, crystallizing high Ca/low Mg garnet cores. The mineral compositions show that commonly garnet core was not in chemical equilibrium with staurolite but crystallized earlier, although garnet-staurolite-kyanite assemblages are common. The temperature and pressure increased to c. 650 °C and 8 kbars where staurolite and kyanite coexist. This was followed by decompression down to c. 550–600 °C and 3–4 kbars, shown by andalusite crystallization and cordierite formed in the breakdown of staurolite and biotite + kyanite. The observed garnet zoning where Mg increases and Ca decreases from the core to the rim was developed with both increasing and decreasing pressure, depending on the effective bulk composition. The U-Pb and Sm-Nd age determinations for monazite and garnet show that the Paleoproterozoic metamorphic cycle took place at 1.84–1.79 Ga, related with thrusting of the Lapland granulites onto the adjacent terranes and subsequent exhumation. |
format |
Text |
author |
Pentti Hölttä Tiia Kivisaari Hannu Huhma Gavyn Rollinson Matti Kurhila Alan R. Butcher |
author_facet |
Pentti Hölttä Tiia Kivisaari Hannu Huhma Gavyn Rollinson Matti Kurhila Alan R. Butcher |
author_sort |
Pentti Hölttä |
title |
Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
title_short |
Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
title_full |
Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
title_fullStr |
Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
title_full_unstemmed |
Paleoproterozoic Metamorphism of the Archean Tuntsa Suite, Northern Fennoscandian Shield |
title_sort |
paleoproterozoic metamorphism of the archean tuntsa suite, northern fennoscandian shield |
publisher |
Multidisciplinary Digital Publishing Institute |
publishDate |
2020 |
url |
https://doi.org/10.3390/min10111034 |
op_coverage |
agris |
long_lat |
ENVELOPE(29.696,29.696,67.597,67.597) |
geographic |
Tuntsa |
geographic_facet |
Tuntsa |
genre |
Fennoscandian Lapland |
genre_facet |
Fennoscandian Lapland |
op_source |
Minerals; Volume 10; Issue 11; Pages: 1034 |
op_relation |
Mineral Geochemistry and Geochronology https://dx.doi.org/10.3390/min10111034 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/min10111034 |
container_title |
Minerals |
container_volume |
10 |
container_issue |
11 |
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1034 |
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1774717502720311296 |