Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland)
A recurring challenge to ion microprobe U-Pb zircon geochronology has been to discriminate between preservation of original igneous zircon populations and inherited grains. This has proved particularly problematic in studying the polyphase metamorphic rocks that dominate Early Archean gneissic terra...
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ftanucanberra:oai:digitalcollections.anu.edu.au:1885/92160 2023-05-15T16:26:47+02:00 Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) Mojzsis, Stephen Harrison, Timothy 2015-12-13T23:24:17Z http://hdl.handle.net/1885/92160 unknown Elsevier 0012-821X http://hdl.handle.net/1885/92160 Earth and Planetary Science Letters Keywords: Archean geochronology ion microprobe origin of life tonalite zircon Greenland Archean Ion probe data Life origin West Greenland Journal article 2015 ftanucanberra 2015-12-21T23:58:21Z A recurring challenge to ion microprobe U-Pb zircon geochronology has been to discriminate between preservation of original igneous zircon populations and inherited grains. This has proved particularly problematic in studying the polyphase metamorphic rocks that dominate Early Archean gneissic terranes. For example, differing interpretations exist for the origin of complex zircon populations investigated by U-Pb ion microprobe zircon geochronology from a granitoid (orthogneiss) body, previously used to establish a minimum age for a supracrustal enclave on Akilia (island) in southern West Greenland. We describe a method whereby the geochemistry of the Akilia orthogneiss, coupled with a U-Th-Pb vs. age depth profile in a zircon from the same rock, permits direct assessment of zircon inheritance. Results reveal evidence for three phases of concentric zircon growth at 3.83. Ga, ~3.6 Ga and 2.7-2.5 Ga; zircon growth at both ~3.6 Ga and 2.7-2.5 Ga is consistent with precipitation from a metamorphic fluid. Depth profile U-Th-Pb data demonstrate that only the >3.8-Ga zircon core could have crystallized from the host rock. We conclude that the magmatic age of this rock is 3.83 ± 0.01 Ga, not ~3.65 Ga as has been previously proposed. The U-Th-Pb zircon depth profile technique has wider applications to resolving other geochronological debates in high-grade metamorphic terranes where zircons populations are diverse and individual grains record complex overgrowth and dissolution/re-precipitation features. Article in Journal/Newspaper Greenland Australian National University: ANU Digital Collections Greenland |
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Australian National University: ANU Digital Collections |
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ftanucanberra |
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Keywords: Archean geochronology ion microprobe origin of life tonalite zircon Greenland Archean Ion probe data Life origin West Greenland |
spellingShingle |
Keywords: Archean geochronology ion microprobe origin of life tonalite zircon Greenland Archean Ion probe data Life origin West Greenland Mojzsis, Stephen Harrison, Timothy Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
topic_facet |
Keywords: Archean geochronology ion microprobe origin of life tonalite zircon Greenland Archean Ion probe data Life origin West Greenland |
description |
A recurring challenge to ion microprobe U-Pb zircon geochronology has been to discriminate between preservation of original igneous zircon populations and inherited grains. This has proved particularly problematic in studying the polyphase metamorphic rocks that dominate Early Archean gneissic terranes. For example, differing interpretations exist for the origin of complex zircon populations investigated by U-Pb ion microprobe zircon geochronology from a granitoid (orthogneiss) body, previously used to establish a minimum age for a supracrustal enclave on Akilia (island) in southern West Greenland. We describe a method whereby the geochemistry of the Akilia orthogneiss, coupled with a U-Th-Pb vs. age depth profile in a zircon from the same rock, permits direct assessment of zircon inheritance. Results reveal evidence for three phases of concentric zircon growth at 3.83. Ga, ~3.6 Ga and 2.7-2.5 Ga; zircon growth at both ~3.6 Ga and 2.7-2.5 Ga is consistent with precipitation from a metamorphic fluid. Depth profile U-Th-Pb data demonstrate that only the >3.8-Ga zircon core could have crystallized from the host rock. We conclude that the magmatic age of this rock is 3.83 ± 0.01 Ga, not ~3.65 Ga as has been previously proposed. The U-Th-Pb zircon depth profile technique has wider applications to resolving other geochronological debates in high-grade metamorphic terranes where zircons populations are diverse and individual grains record complex overgrowth and dissolution/re-precipitation features. |
format |
Article in Journal/Newspaper |
author |
Mojzsis, Stephen Harrison, Timothy |
author_facet |
Mojzsis, Stephen Harrison, Timothy |
author_sort |
Mojzsis, Stephen |
title |
Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
title_short |
Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
title_full |
Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
title_fullStr |
Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
title_full_unstemmed |
Establishment of a 3.83-Ga magmatic age for the Akilia tonalite (southern West Greenland) |
title_sort |
establishment of a 3.83-ga magmatic age for the akilia tonalite (southern west greenland) |
publisher |
Elsevier |
publishDate |
2015 |
url |
http://hdl.handle.net/1885/92160 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Earth and Planetary Science Letters |
op_relation |
0012-821X http://hdl.handle.net/1885/92160 |
_version_ |
1766015763976552448 |