U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica
We report ion-microprobe U-Pb zircon ages from charnockites of a large Proterozoic composite batholith, Mawson Coast, Australian Antarctic Territory. The charnockites crystallized from orogenic magmas of intermediate composition (mainly 54–68% SiO 2 ) intruded into a granulite-facies metasedimentary...
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Cambridge University Press (CUP)
1991
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Online Access: | http://dx.doi.org/10.1017/s095410209100024x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S095410209100024X |
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crcambridgeupr:10.1017/s095410209100024x 2024-09-15T17:40:45+00:00 U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica Young, David N. Black, Lance P. 1991 http://dx.doi.org/10.1017/s095410209100024x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S095410209100024X en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Antarctic Science volume 3, issue 2, page 205-216 ISSN 0954-1020 1365-2079 journal-article 1991 crcambridgeupr https://doi.org/10.1017/s095410209100024x 2024-07-31T04:02:45Z We report ion-microprobe U-Pb zircon ages from charnockites of a large Proterozoic composite batholith, Mawson Coast, Australian Antarctic Territory. The charnockites crystallized from orogenic magmas of intermediate composition (mainly 54–68% SiO 2 ) intruded into a granulite-facies metasedimentary gneiss sequence between the second and third recognized deformations. A sample of low-Ti charnockite provides an age of 954 ± 12 Ma and a high-Ti charnockite is dated at 985 ± 29 Ma (all ages quoted at 95% confidence). The age difference is not significant at the 95% confidence level. Both these ages were obtained from zircons with igneous zoning and/or morphology and thus are thought to date igneous crystallization. Zircons from a felsic gneiss xenolith within the charnockite have cores of various ages, many from 1.7 to 2.0 Ga, but with other grains between 1.0 and 1.5 Ga and a single 2.5 Ga zircon. These zircon cores are direct evidence for an early to middle Proterozoic age for the supracrustal basement sequence in this mobile belt. Many of these zircon cores are concordant but abundant discordant grains suggest a complex history of multiple Pb-loss events. Zircon rims grew at 921 ± 19 Ma, probably during the post-charnockite deformation (D 3 ). Previously obtained Rb-Sr dates for charnockite of 886 ± 48 Ma and 910 ± 18 Ma were probably also rest during D 3 . A Rb-Sr isochron date of 1061 ± 36 Ma previously reported for high-Ti charnockite from Mawson Rock is thought to be erroneous, and a new date of 959 ± 58 Ma (consistent with both the igneous and reset dates above) is interpreted from those data. Article in Journal/Newspaper Antarc* Antarctic Antarctic Science Antarctica East Antarctica Cambridge University Press Antarctic Science 3 2 205 216 |
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English |
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We report ion-microprobe U-Pb zircon ages from charnockites of a large Proterozoic composite batholith, Mawson Coast, Australian Antarctic Territory. The charnockites crystallized from orogenic magmas of intermediate composition (mainly 54–68% SiO 2 ) intruded into a granulite-facies metasedimentary gneiss sequence between the second and third recognized deformations. A sample of low-Ti charnockite provides an age of 954 ± 12 Ma and a high-Ti charnockite is dated at 985 ± 29 Ma (all ages quoted at 95% confidence). The age difference is not significant at the 95% confidence level. Both these ages were obtained from zircons with igneous zoning and/or morphology and thus are thought to date igneous crystallization. Zircons from a felsic gneiss xenolith within the charnockite have cores of various ages, many from 1.7 to 2.0 Ga, but with other grains between 1.0 and 1.5 Ga and a single 2.5 Ga zircon. These zircon cores are direct evidence for an early to middle Proterozoic age for the supracrustal basement sequence in this mobile belt. Many of these zircon cores are concordant but abundant discordant grains suggest a complex history of multiple Pb-loss events. Zircon rims grew at 921 ± 19 Ma, probably during the post-charnockite deformation (D 3 ). Previously obtained Rb-Sr dates for charnockite of 886 ± 48 Ma and 910 ± 18 Ma were probably also rest during D 3 . A Rb-Sr isochron date of 1061 ± 36 Ma previously reported for high-Ti charnockite from Mawson Rock is thought to be erroneous, and a new date of 959 ± 58 Ma (consistent with both the igneous and reset dates above) is interpreted from those data. |
format |
Article in Journal/Newspaper |
author |
Young, David N. Black, Lance P. |
spellingShingle |
Young, David N. Black, Lance P. U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
author_facet |
Young, David N. Black, Lance P. |
author_sort |
Young, David N. |
title |
U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
title_short |
U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
title_full |
U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
title_fullStr |
U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
title_full_unstemmed |
U-Pb zircon dating of Proterozoic igneous charnockites from the Mawson Coast, East Antarctica |
title_sort |
u-pb zircon dating of proterozoic igneous charnockites from the mawson coast, east antarctica |
publisher |
Cambridge University Press (CUP) |
publishDate |
1991 |
url |
http://dx.doi.org/10.1017/s095410209100024x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S095410209100024X |
genre |
Antarc* Antarctic Antarctic Science Antarctica East Antarctica |
genre_facet |
Antarc* Antarctic Antarctic Science Antarctica East Antarctica |
op_source |
Antarctic Science volume 3, issue 2, page 205-216 ISSN 0954-1020 1365-2079 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s095410209100024x |
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Antarctic Science |
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3 |
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2 |
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205 |
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216 |
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1810486779318370304 |