The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny
From the 3000 km2 Eoarchean Itsaq Gneiss Complex (IGC) of Greenland, zircon U-Pb dating of numerous meta-granitoid and orthogneiss samples is integrated with geologic observations, whole rock geochemistry and a strategic subset of zircon Hf and whole rock Nd isotopic measurements. This shows that th...
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ftunivwollongong:oai:ro.uow.edu.au:smhpapers-2241 2023-05-15T13:21:43+02:00 The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny Nutman, Allen P Bennett, Vickie C Friend, Clark R. L Hidaka, Hiroshi Yi, Keewook Lee, Seung Ryeol Kamiichi, Tomoyuki 2013-01-01T08:00:00Z application/pdf https://ro.uow.edu.au/smhpapers/1223 https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2241&context=smhpapers unknown Research Online https://ro.uow.edu.au/smhpapers/1223 https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2241&context=smhpapers Faculty of Science, Medicine and Health - Papers: part A juvenile crust formation episodic 3600 3920 recycling itsaq gneiss complex southern west greenland 3660 ma GeoQuest Medicine and Health Sciences Social and Behavioral Sciences article 2013 ftunivwollongong 2020-02-25T10:58:05Z From the 3000 km2 Eoarchean Itsaq Gneiss Complex (IGC) of Greenland, zircon U-Pb dating of numerous meta-granitoid and orthogneiss samples is integrated with geologic observations, whole rock geochemistry and a strategic subset of zircon Hf and whole rock Nd isotopic measurements. This shows that there are multiple episodes of TTG suite formation from ∼3890 to 3660 Ma, characterized by zircon initial εHf≈0 and whole rock initial εNd of > +2. These rocks mostly have geochemical signatures of partial melting of eclogitized mafic sources, with a subset of high magnesian, low silica rocks indicating fusion by fluid fluxing of upper mantle sources. The TTG suites are accompanied by slightly older gabbros, basalts and andesites, which have geochemical signatures pointing to magmas originating from fluid fluxing of upper mantle sources. The data show the formation of juvenile crust domains in several discrete events from ∼3900 to 3660 Ma, probably at convergent plate boundaries in an environment analogous, but not identical to, modern island arcs. In the Isua area, a northern ∼3700 Ma terrane formed distal from a predominantly ∼3800 Ma terrane. These terranes were juxtaposed between 3680 and 3660 Ma—respectively the age of the youngest rocks unique to the northern terrane and the lithologically distinctive ultramafic-granitic Inaluk dykes common to both terranes. This shows the assembly of different domains of juvenile rocks to form a more expansive domain of “continental” crust. A rare occurrence of high-pressure granulite is dated at ∼3660 Ma, demonstrating that assembly involved tectonic crustal thickening. This continental crust was then reworked in the 3660 to 3600 Ma Isukasian orogeny. In the northern part of the Isua area, 3660 to 3600 Ma granites were emplaced into ∼3700 Ma tonalites. The earliest granites are nebulous, and sigmoidal schlieric inclusions within them demonstrate ductile extension. Younger granite sheets were emplaced into extensional ductile-brittle fractures. These granite-tonalite relationships are overprinted by widespread development of late Eoarchean (pre-3500 Ma Ameralik dyke) brittle-ductile extensional cataclastic textures, together demonstrating that extension was polybaric. The southern part of the Isua area largely escaped 3660 to 3600 Ma high temperature processes and has sparse granite sheets commonly focused into coeval shear zones. In the rest of the complex, deeper crustal levels during the Isukasian orogeny are widely preserved. These experienced upper amphibolite to granulite facies moderate- to low-pressure syn-kinematic metamorphism, forming complex migmatites rich in granitic-trondhjemitic neosome. The migmatites were intruded by composite ferrogabbro and granite bodies, in which syn-magmatic extensional features are locally preserved. Thus 3660 to 3600 Ma crustal recycling involved elevated crustal thermal gradients in an extensional regime. Crustal melts formed in the Isukasian orogeny have zircon initial εHf Article in Journal/Newspaper Ameralik Greenland University of Wollongong, Australia: Research Online Ameralik ENVELOPE(-51.000,-51.000,64.117,64.117) Greenland |
institution |
Open Polar |
collection |
University of Wollongong, Australia: Research Online |
op_collection_id |
ftunivwollongong |
language |
unknown |
topic |
juvenile crust formation episodic 3600 3920 recycling itsaq gneiss complex southern west greenland 3660 ma GeoQuest Medicine and Health Sciences Social and Behavioral Sciences |
spellingShingle |
juvenile crust formation episodic 3600 3920 recycling itsaq gneiss complex southern west greenland 3660 ma GeoQuest Medicine and Health Sciences Social and Behavioral Sciences Nutman, Allen P Bennett, Vickie C Friend, Clark R. L Hidaka, Hiroshi Yi, Keewook Lee, Seung Ryeol Kamiichi, Tomoyuki The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
topic_facet |
juvenile crust formation episodic 3600 3920 recycling itsaq gneiss complex southern west greenland 3660 ma GeoQuest Medicine and Health Sciences Social and Behavioral Sciences |
description |
From the 3000 km2 Eoarchean Itsaq Gneiss Complex (IGC) of Greenland, zircon U-Pb dating of numerous meta-granitoid and orthogneiss samples is integrated with geologic observations, whole rock geochemistry and a strategic subset of zircon Hf and whole rock Nd isotopic measurements. This shows that there are multiple episodes of TTG suite formation from ∼3890 to 3660 Ma, characterized by zircon initial εHf≈0 and whole rock initial εNd of > +2. These rocks mostly have geochemical signatures of partial melting of eclogitized mafic sources, with a subset of high magnesian, low silica rocks indicating fusion by fluid fluxing of upper mantle sources. The TTG suites are accompanied by slightly older gabbros, basalts and andesites, which have geochemical signatures pointing to magmas originating from fluid fluxing of upper mantle sources. The data show the formation of juvenile crust domains in several discrete events from ∼3900 to 3660 Ma, probably at convergent plate boundaries in an environment analogous, but not identical to, modern island arcs. In the Isua area, a northern ∼3700 Ma terrane formed distal from a predominantly ∼3800 Ma terrane. These terranes were juxtaposed between 3680 and 3660 Ma—respectively the age of the youngest rocks unique to the northern terrane and the lithologically distinctive ultramafic-granitic Inaluk dykes common to both terranes. This shows the assembly of different domains of juvenile rocks to form a more expansive domain of “continental” crust. A rare occurrence of high-pressure granulite is dated at ∼3660 Ma, demonstrating that assembly involved tectonic crustal thickening. This continental crust was then reworked in the 3660 to 3600 Ma Isukasian orogeny. In the northern part of the Isua area, 3660 to 3600 Ma granites were emplaced into ∼3700 Ma tonalites. The earliest granites are nebulous, and sigmoidal schlieric inclusions within them demonstrate ductile extension. Younger granite sheets were emplaced into extensional ductile-brittle fractures. These granite-tonalite relationships are overprinted by widespread development of late Eoarchean (pre-3500 Ma Ameralik dyke) brittle-ductile extensional cataclastic textures, together demonstrating that extension was polybaric. The southern part of the Isua area largely escaped 3660 to 3600 Ma high temperature processes and has sparse granite sheets commonly focused into coeval shear zones. In the rest of the complex, deeper crustal levels during the Isukasian orogeny are widely preserved. These experienced upper amphibolite to granulite facies moderate- to low-pressure syn-kinematic metamorphism, forming complex migmatites rich in granitic-trondhjemitic neosome. The migmatites were intruded by composite ferrogabbro and granite bodies, in which syn-magmatic extensional features are locally preserved. Thus 3660 to 3600 Ma crustal recycling involved elevated crustal thermal gradients in an extensional regime. Crustal melts formed in the Isukasian orogeny have zircon initial εHf |
format |
Article in Journal/Newspaper |
author |
Nutman, Allen P Bennett, Vickie C Friend, Clark R. L Hidaka, Hiroshi Yi, Keewook Lee, Seung Ryeol Kamiichi, Tomoyuki |
author_facet |
Nutman, Allen P Bennett, Vickie C Friend, Clark R. L Hidaka, Hiroshi Yi, Keewook Lee, Seung Ryeol Kamiichi, Tomoyuki |
author_sort |
Nutman, Allen P |
title |
The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
title_short |
The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
title_full |
The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
title_fullStr |
The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
title_full_unstemmed |
The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny |
title_sort |
itsaq gneiss complex of greenland: episodic 3900 to 3660 ma juvenile crust formation and recycling in the 3660 to 3600 ma isukasian orogeny |
publisher |
Research Online |
publishDate |
2013 |
url |
https://ro.uow.edu.au/smhpapers/1223 https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2241&context=smhpapers |
long_lat |
ENVELOPE(-51.000,-51.000,64.117,64.117) |
geographic |
Ameralik Greenland |
geographic_facet |
Ameralik Greenland |
genre |
Ameralik Greenland |
genre_facet |
Ameralik Greenland |
op_source |
Faculty of Science, Medicine and Health - Papers: part A |
op_relation |
https://ro.uow.edu.au/smhpapers/1223 https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2241&context=smhpapers |
_version_ |
1766361087754633216 |