Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland
This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma fo...
Published in: | Geoscience Frontiers |
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Format: | Article in Journal/Newspaper |
Language: | English |
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China University of Geosciences (Beijing) and Peking University
2018
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Online Access: | https://lup.lub.lu.se/record/f616b4d7-b33e-4734-b679-152c13668170 https://doi.org/10.1016/j.gsf.2017.05.003 |
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ftulundlup:oai:lup.lub.lu.se:f616b4d7-b33e-4734-b679-152c13668170 2023-05-15T16:17:22+02:00 Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland Szilas, Kristoffer van Hinsberg, Vincent McDonald, Iain Næraa, Tomas Rollinson, Hugh Adetunji, Jacob Bird, Dennis 2018-05-01 https://lup.lub.lu.se/record/f616b4d7-b33e-4734-b679-152c13668170 https://doi.org/10.1016/j.gsf.2017.05.003 eng eng China University of Geosciences (Beijing) and Peking University https://lup.lub.lu.se/record/f616b4d7-b33e-4734-b679-152c13668170 http://dx.doi.org/10.1016/j.gsf.2017.05.003 scopus:85017163120 Geoscience Frontiers; 9(3), pp 689-714 (2018) ISSN: 1674-9871 Geology Archaean Dunite Fiskefjord North Atlantic Craton Platinum-group elements Ultra-depleted mantle contributiontojournal/article info:eu-repo/semantics/article text 2018 ftulundlup https://doi.org/10.1016/j.gsf.2017.05.003 2023-02-01T23:36:30Z This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite (s.s.), peridotite (s.l.), as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth's mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust. Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian (Mg# ∼ 80), near-anhydrous magma, as olivine-dominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting (>40%). This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle (SCLM) in this region, which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the large-scale melting event(s), which resulted in the ultra-depleted ... Article in Journal/Newspaper Fiskefjord Greenland North Atlantic Lund University Publications (LUP) Greenland Geoscience Frontiers 9 3 689 714 |
institution |
Open Polar |
collection |
Lund University Publications (LUP) |
op_collection_id |
ftulundlup |
language |
English |
topic |
Geology Archaean Dunite Fiskefjord North Atlantic Craton Platinum-group elements Ultra-depleted mantle |
spellingShingle |
Geology Archaean Dunite Fiskefjord North Atlantic Craton Platinum-group elements Ultra-depleted mantle Szilas, Kristoffer van Hinsberg, Vincent McDonald, Iain Næraa, Tomas Rollinson, Hugh Adetunji, Jacob Bird, Dennis Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
topic_facet |
Geology Archaean Dunite Fiskefjord North Atlantic Craton Platinum-group elements Ultra-depleted mantle |
description |
This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite (s.s.), peridotite (s.l.), as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth's mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust. Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian (Mg# ∼ 80), near-anhydrous magma, as olivine-dominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting (>40%). This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle (SCLM) in this region, which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the large-scale melting event(s), which resulted in the ultra-depleted ... |
format |
Article in Journal/Newspaper |
author |
Szilas, Kristoffer van Hinsberg, Vincent McDonald, Iain Næraa, Tomas Rollinson, Hugh Adetunji, Jacob Bird, Dennis |
author_facet |
Szilas, Kristoffer van Hinsberg, Vincent McDonald, Iain Næraa, Tomas Rollinson, Hugh Adetunji, Jacob Bird, Dennis |
author_sort |
Szilas, Kristoffer |
title |
Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
title_short |
Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
title_full |
Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
title_fullStr |
Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
title_full_unstemmed |
Highly refractory Archaean peridotite cumulates : Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland |
title_sort |
highly refractory archaean peridotite cumulates : petrology and geochemistry of the seqi ultramafic complex, sw greenland |
publisher |
China University of Geosciences (Beijing) and Peking University |
publishDate |
2018 |
url |
https://lup.lub.lu.se/record/f616b4d7-b33e-4734-b679-152c13668170 https://doi.org/10.1016/j.gsf.2017.05.003 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Fiskefjord Greenland North Atlantic |
genre_facet |
Fiskefjord Greenland North Atlantic |
op_source |
Geoscience Frontiers; 9(3), pp 689-714 (2018) ISSN: 1674-9871 |
op_relation |
https://lup.lub.lu.se/record/f616b4d7-b33e-4734-b679-152c13668170 http://dx.doi.org/10.1016/j.gsf.2017.05.003 scopus:85017163120 |
op_doi |
https://doi.org/10.1016/j.gsf.2017.05.003 |
container_title |
Geoscience Frontiers |
container_volume |
9 |
container_issue |
3 |
container_start_page |
689 |
op_container_end_page |
714 |
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1766003223302242304 |