Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway
Kvitfjell ultramafic body is one of around 20 ultramafic bodies found in the Linnajavri area of Northern Norway. These ultramafic fragments are situated within the Köli Nappe of the Upper Allochthon in the Caledonian tectonostratigraphy. At Kvitfjell ultramafic body, secondary metamorphic olivine is...
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The University of Bergen
2022
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ftunivbergen:oai:bora.uib.no:11250/2838808 2023-05-15T17:43:36+02:00 Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway Arstein, Halfdan 2022-01-21T23:00:02Z application/pdf https://hdl.handle.net/11250/2838808 eng eng The University of Bergen https://hdl.handle.net/11250/2838808 Copyright the Author. All rights reserved Geothermobarometry Decarbonation Perple_X Linnajavri 756199 Master thesis 2022 ftunivbergen 2023-03-14T17:44:14Z Kvitfjell ultramafic body is one of around 20 ultramafic bodies found in the Linnajavri area of Northern Norway. These ultramafic fragments are situated within the Köli Nappe of the Upper Allochthon in the Caledonian tectonostratigraphy. At Kvitfjell ultramafic body, secondary metamorphic olivine is observed, formed by a reaction of magnesite and antigorite which releases CO2-bearing fluids. The metasediments adjacent to Kvitfjell ultramafic body suggest that this decarbonation occurred at shallower depths than previously recorded. Peak PT conditions for Kvitfjell ultramafic body, thus peak PT conditions at which decarbonation initiated, are derived from the metasediments surrounding Kvitfjell ultramafic body which is presumed to have gone through the same metamorphic path as the ultramafic body itself. The PT estimate is acquired by conventional thermobarometry, trace element thermometry, image analyses and thermodynamic modelling based on the whole rock chemistry of the adjacent metasediment. PT estimate from garnet-biotite and garnet-biotite-aluminosilicate-quartz geothermobarometry suggest that peak PT conditions are at a temperature of 593°C ±8°C and a pressure of 7.03 kbar ±0.17 kbar. This PT estimate is further supported by pseudosection modelling, observed and modelled mineral abundances, and peak PT estimate from the Ti-in-biotite thermometer coupled with the garnet-biotite-aluminosilicate-quartz barometer. These findings reveal that the decarbonation at Kvitfjell ultramafic body occurred at shallower depths than previously recorded. Transferring the temperature estimate from Kvitfjell ultramafic body to subduction zones implies that the decarbonation processes may initiate at an earlier stage than previously assumed and that carbonates become unstable before reaching sub-arc depths. Masteroppgåve i geovitskap GEOV399 MAMN-GEOV Master Thesis Northern Norway University of Bergen: Bergen Open Research Archive (BORA-UiB) Norway |
institution |
Open Polar |
collection |
University of Bergen: Bergen Open Research Archive (BORA-UiB) |
op_collection_id |
ftunivbergen |
language |
English |
topic |
Geothermobarometry Decarbonation Perple_X Linnajavri 756199 |
spellingShingle |
Geothermobarometry Decarbonation Perple_X Linnajavri 756199 Arstein, Halfdan Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
topic_facet |
Geothermobarometry Decarbonation Perple_X Linnajavri 756199 |
description |
Kvitfjell ultramafic body is one of around 20 ultramafic bodies found in the Linnajavri area of Northern Norway. These ultramafic fragments are situated within the Köli Nappe of the Upper Allochthon in the Caledonian tectonostratigraphy. At Kvitfjell ultramafic body, secondary metamorphic olivine is observed, formed by a reaction of magnesite and antigorite which releases CO2-bearing fluids. The metasediments adjacent to Kvitfjell ultramafic body suggest that this decarbonation occurred at shallower depths than previously recorded. Peak PT conditions for Kvitfjell ultramafic body, thus peak PT conditions at which decarbonation initiated, are derived from the metasediments surrounding Kvitfjell ultramafic body which is presumed to have gone through the same metamorphic path as the ultramafic body itself. The PT estimate is acquired by conventional thermobarometry, trace element thermometry, image analyses and thermodynamic modelling based on the whole rock chemistry of the adjacent metasediment. PT estimate from garnet-biotite and garnet-biotite-aluminosilicate-quartz geothermobarometry suggest that peak PT conditions are at a temperature of 593°C ±8°C and a pressure of 7.03 kbar ±0.17 kbar. This PT estimate is further supported by pseudosection modelling, observed and modelled mineral abundances, and peak PT estimate from the Ti-in-biotite thermometer coupled with the garnet-biotite-aluminosilicate-quartz barometer. These findings reveal that the decarbonation at Kvitfjell ultramafic body occurred at shallower depths than previously recorded. Transferring the temperature estimate from Kvitfjell ultramafic body to subduction zones implies that the decarbonation processes may initiate at an earlier stage than previously assumed and that carbonates become unstable before reaching sub-arc depths. Masteroppgåve i geovitskap GEOV399 MAMN-GEOV |
format |
Master Thesis |
author |
Arstein, Halfdan |
author_facet |
Arstein, Halfdan |
author_sort |
Arstein, Halfdan |
title |
Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
title_short |
Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
title_full |
Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
title_fullStr |
Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
title_full_unstemmed |
Deciphering the metamorphic framework of ophiolite alteration and devolatilization at Linnajarvi, N-Norway |
title_sort |
deciphering the metamorphic framework of ophiolite alteration and devolatilization at linnajarvi, n-norway |
publisher |
The University of Bergen |
publishDate |
2022 |
url |
https://hdl.handle.net/11250/2838808 |
geographic |
Norway |
geographic_facet |
Norway |
genre |
Northern Norway |
genre_facet |
Northern Norway |
op_relation |
https://hdl.handle.net/11250/2838808 |
op_rights |
Copyright the Author. All rights reserved |
_version_ |
1766145720011718656 |