Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica
Zircons from two paragneisses (from Mount Sones and Dallwitz Nunatak) and one orthogneiss (from Gage Ridge) in the Tula Mountains, Napier Complex (East Antarctica) were analyzed for U-Pb age, oxygen isotopes, REEs and by scanning ion imaging. A large number of zircons from all samples are reversely...
| Main Authors: | , , , , , , |
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| Format: | Journal Article |
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American Journal of Science
2013
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| Online Access: | http://hdl.handle.net/20.500.11937/14603 |
| _version_ | 1848748666933739520 |
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| author | Kusiak, M. Whitehouse, M. Wilde, Simon Dunkley, Daniel Menneken, M. Nemchin, Alexander Clark, Christopher |
| author_facet | Kusiak, M. Whitehouse, M. Wilde, Simon Dunkley, Daniel Menneken, M. Nemchin, Alexander Clark, Christopher |
| author_sort | Kusiak, M. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Zircons from two paragneisses (from Mount Sones and Dallwitz Nunatak) and one orthogneiss (from Gage Ridge) in the Tula Mountains, Napier Complex (East Antarctica) were analyzed for U-Pb age, oxygen isotopes, REEs and by scanning ion imaging. A large number of zircons from all samples are reversely discordant. Mount Sones zircons show an age range from 3.0 Ga to 2.5 Ga and underwent high-grade metamorphism at both ~2.8 Ga and 2.5 Ga. Zircons from Dallwitz Nunatak record detrital ages between 3.5 Ga and 2.5 Ga. Zircons from Gage Ridge record multiple age groups, with concordant data between 3.6 Ga and 3.3 Ga and reversely discordant data that form a discrete ~3.8 Ga population. All of the grains show evidence of Pb mobility during metamorphism. Ion imaging of zircons reveals Y and U zonation, characteristic of magmatic zircon, together with a micro-scale patchy distribution of 206Pb and 207Pb that does not correspond to either growth zonation or crystal imperfections. Some of these patches yield 207Pb/206Pb ages >4 Ga, whereas others yield ages younger than the magmatic crystallization age. Reversely discordant data are the result of ancient Pb mobilization, which is independent of the degree of metamictisation, oxygen isotope and REE content of the zircons. This mobilization can result in spurious ages and was most likely caused by polymetamorphism under anhydrous conditions; that is two high-grade events; one poorly defined at ~2.8 Ga and the other ultra-high temperature (UHT) metamorphism at 2.5 Ga. |
| first_indexed | 2025-11-14T07:08:41Z |
| format | Journal Article |
| id | curtin-20.500.11937-14603 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T07:08:41Z |
| publishDate | 2013 |
| publisher | American Journal of Science |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-146032017-09-13T14:05:39Z Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica Kusiak, M. Whitehouse, M. Wilde, Simon Dunkley, Daniel Menneken, M. Nemchin, Alexander Clark, Christopher Antarctica geochronology ion imaging zircon SIMS More than any other mineral introduction Zircons from two paragneisses (from Mount Sones and Dallwitz Nunatak) and one orthogneiss (from Gage Ridge) in the Tula Mountains, Napier Complex (East Antarctica) were analyzed for U-Pb age, oxygen isotopes, REEs and by scanning ion imaging. A large number of zircons from all samples are reversely discordant. Mount Sones zircons show an age range from 3.0 Ga to 2.5 Ga and underwent high-grade metamorphism at both ~2.8 Ga and 2.5 Ga. Zircons from Dallwitz Nunatak record detrital ages between 3.5 Ga and 2.5 Ga. Zircons from Gage Ridge record multiple age groups, with concordant data between 3.6 Ga and 3.3 Ga and reversely discordant data that form a discrete ~3.8 Ga population. All of the grains show evidence of Pb mobility during metamorphism. Ion imaging of zircons reveals Y and U zonation, characteristic of magmatic zircon, together with a micro-scale patchy distribution of 206Pb and 207Pb that does not correspond to either growth zonation or crystal imperfections. Some of these patches yield 207Pb/206Pb ages >4 Ga, whereas others yield ages younger than the magmatic crystallization age. Reversely discordant data are the result of ancient Pb mobilization, which is independent of the degree of metamictisation, oxygen isotope and REE content of the zircons. This mobilization can result in spurious ages and was most likely caused by polymetamorphism under anhydrous conditions; that is two high-grade events; one poorly defined at ~2.8 Ga and the other ultra-high temperature (UHT) metamorphism at 2.5 Ga. 2013 Journal Article http://hdl.handle.net/20.500.11937/14603 10.2475/09.2013.05 American Journal of Science fulltext |
| spellingShingle | Antarctica geochronology ion imaging zircon SIMS More than any other mineral introduction Kusiak, M. Whitehouse, M. Wilde, Simon Dunkley, Daniel Menneken, M. Nemchin, Alexander Clark, Christopher Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title | Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title_full | Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title_fullStr | Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title_full_unstemmed | Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title_short | Changes in zircon chemistry during archean UHT metamorphism in the Napier complex, Antarctica |
| title_sort | changes in zircon chemistry during archean uht metamorphism in the napier complex, antarctica |
| topic | Antarctica geochronology ion imaging zircon SIMS More than any other mineral introduction |
| url | http://hdl.handle.net/20.500.11937/14603 |