Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland
Numerous ultramafic rocks occur as lens-shaped bodies in the Archaean continental crust exposed in southern West Greenland. As some of the oldest exposed ultramafic bodies, determining their origin, as mantle segments or magmatic cumulates, is an important yet controversial issue. The origin of thes...
Published in: | Journal of Petrology |
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Format: | Article in Journal/Newspaper |
Language: | English |
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2022
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Online Access: | https://curis.ku.dk/portal/da/publications/metasomatic-modification-of-the-mesoarchaean-ulamertoq-ultramafic-body-southern-west-greenland(10950073-20cc-4419-9f4e-f463120e0247).html https://doi.org/10.1093/petrology/egac004 |
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ftcopenhagenunip:oai:pure.atira.dk:publications/10950073-20cc-4419-9f4e-f463120e0247 2024-06-09T07:46:22+00:00 Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland Nishio, Ikuya Morishita, Tomoaki Itano, Keita Guotana, Juan Miguel Tamura, Akihiro Szilas, Kristoffer Harigane, Yumiko Tani, Kenichiro Graham Pearson, D. 2022 https://curis.ku.dk/portal/da/publications/metasomatic-modification-of-the-mesoarchaean-ulamertoq-ultramafic-body-southern-west-greenland(10950073-20cc-4419-9f4e-f463120e0247).html https://doi.org/10.1093/petrology/egac004 eng eng info:eu-repo/semantics/closedAccess Nishio , I , Morishita , T , Itano , K , Guotana , J M , Tamura , A , Szilas , K , Harigane , Y , Tani , K & Graham Pearson , D 2022 , ' Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland ' , Journal of Petrology , vol. 63 , no. 3 , egac004 . https://doi.org/10.1093/petrology/egac004 Archaean Greenland Metamorphism Metasomatism Ultramafic rock article 2022 ftcopenhagenunip https://doi.org/10.1093/petrology/egac004 2024-05-16T11:29:23Z Numerous ultramafic rocks occur as lens-shaped bodies in the Archaean continental crust exposed in southern West Greenland. As some of the oldest exposed ultramafic bodies, determining their origin, as mantle segments or magmatic cumulates, is an important yet controversial issue. The origin of these Archaean ultramafic rocks remains unclear, in-part because these rocks have undergone metasomatic modification since their formation, yet the effects of this metasomatism have so far not been assessed in detail, despite being crucial for understanding their geochemical evolution. Here, we examined the petrology, mineral and whole-rock chemistry of the largest ultramafic body located within the Mesoarchaean Akia terrane, known as the Ulamertoq ultramafic body, to elucidate the poly-metamorphic and metasomatic events that overprinted the protolith. Pronounced lithologic zoning from hydrous mineral-rich layers to orthopyroxene-rich ultramafic rocks at the boundaries between ultramafic rocks and the granitoid country rocks was formed locally by metasomatic reactions related to the granitoids. The main body of ultramafic rocks, far from the contacts, can be classified into four types based on mineral assemblage and chemistry. The fine-grained orthopyroxene aggregates and large poikilitic orthopyroxenes have low Cr2O3 and CaO contents, suggesting a secondary origin. Trace element compositions of orthopyroxene and/or amphibole in the main ultramafic rocks indicate that at least three types of metasomatic agents were required to form these minerals and the associated whole-rock chemical variations within the ultramafic body. Variations represent differences in the proportions of metasomatic orthopyroxene and/or amphibole and phlogopite added to a dunitic protolith. The main body of Ulamertoq ultramafics experienced metasomatism under granulite-facies. Retrograde cooling occurred, to 650°C-850°C and <1.8 GPa prior to local metasomatism via country-rock reaction. The presence of titanian clinohumite and its associated ... Article in Journal/Newspaper Greenland University of Copenhagen: Research Greenland Ulamertoq ENVELOPE(-51.317,-51.317,64.933,64.933) Journal of Petrology 63 3 |
institution |
Open Polar |
collection |
University of Copenhagen: Research |
op_collection_id |
ftcopenhagenunip |
language |
English |
topic |
Archaean Greenland Metamorphism Metasomatism Ultramafic rock |
spellingShingle |
Archaean Greenland Metamorphism Metasomatism Ultramafic rock Nishio, Ikuya Morishita, Tomoaki Itano, Keita Guotana, Juan Miguel Tamura, Akihiro Szilas, Kristoffer Harigane, Yumiko Tani, Kenichiro Graham Pearson, D. Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
topic_facet |
Archaean Greenland Metamorphism Metasomatism Ultramafic rock |
description |
Numerous ultramafic rocks occur as lens-shaped bodies in the Archaean continental crust exposed in southern West Greenland. As some of the oldest exposed ultramafic bodies, determining their origin, as mantle segments or magmatic cumulates, is an important yet controversial issue. The origin of these Archaean ultramafic rocks remains unclear, in-part because these rocks have undergone metasomatic modification since their formation, yet the effects of this metasomatism have so far not been assessed in detail, despite being crucial for understanding their geochemical evolution. Here, we examined the petrology, mineral and whole-rock chemistry of the largest ultramafic body located within the Mesoarchaean Akia terrane, known as the Ulamertoq ultramafic body, to elucidate the poly-metamorphic and metasomatic events that overprinted the protolith. Pronounced lithologic zoning from hydrous mineral-rich layers to orthopyroxene-rich ultramafic rocks at the boundaries between ultramafic rocks and the granitoid country rocks was formed locally by metasomatic reactions related to the granitoids. The main body of ultramafic rocks, far from the contacts, can be classified into four types based on mineral assemblage and chemistry. The fine-grained orthopyroxene aggregates and large poikilitic orthopyroxenes have low Cr2O3 and CaO contents, suggesting a secondary origin. Trace element compositions of orthopyroxene and/or amphibole in the main ultramafic rocks indicate that at least three types of metasomatic agents were required to form these minerals and the associated whole-rock chemical variations within the ultramafic body. Variations represent differences in the proportions of metasomatic orthopyroxene and/or amphibole and phlogopite added to a dunitic protolith. The main body of Ulamertoq ultramafics experienced metasomatism under granulite-facies. Retrograde cooling occurred, to 650°C-850°C and <1.8 GPa prior to local metasomatism via country-rock reaction. The presence of titanian clinohumite and its associated ... |
format |
Article in Journal/Newspaper |
author |
Nishio, Ikuya Morishita, Tomoaki Itano, Keita Guotana, Juan Miguel Tamura, Akihiro Szilas, Kristoffer Harigane, Yumiko Tani, Kenichiro Graham Pearson, D. |
author_facet |
Nishio, Ikuya Morishita, Tomoaki Itano, Keita Guotana, Juan Miguel Tamura, Akihiro Szilas, Kristoffer Harigane, Yumiko Tani, Kenichiro Graham Pearson, D. |
author_sort |
Nishio, Ikuya |
title |
Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
title_short |
Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
title_full |
Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
title_fullStr |
Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
title_full_unstemmed |
Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland |
title_sort |
metasomatic modification of the mesoarchaean ulamertoq ultramafic body, southern west greenland |
publishDate |
2022 |
url |
https://curis.ku.dk/portal/da/publications/metasomatic-modification-of-the-mesoarchaean-ulamertoq-ultramafic-body-southern-west-greenland(10950073-20cc-4419-9f4e-f463120e0247).html https://doi.org/10.1093/petrology/egac004 |
long_lat |
ENVELOPE(-51.317,-51.317,64.933,64.933) |
geographic |
Greenland Ulamertoq |
geographic_facet |
Greenland Ulamertoq |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Nishio , I , Morishita , T , Itano , K , Guotana , J M , Tamura , A , Szilas , K , Harigane , Y , Tani , K & Graham Pearson , D 2022 , ' Metasomatic Modification of the Mesoarchaean Ulamertoq Ultramafic Body, Southern West Greenland ' , Journal of Petrology , vol. 63 , no. 3 , egac004 . https://doi.org/10.1093/petrology/egac004 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.1093/petrology/egac004 |
container_title |
Journal of Petrology |
container_volume |
63 |
container_issue |
3 |
_version_ |
1801376181616902144 |