Decoding polyphase migmatites using geochronology and phase equilibria modelling
In this study, in situ U–Pb monazite ages and Lu–Hf garnet geochronology are used to distinguish mineral parageneses developed during Devonian–Carboniferous and Cretaceous events in migmatitic paragneiss and orthogneiss from the Fosdick migmatite–granite complex in West Antarctica. SHRIMP U–Pb monaz...
Published in: | Journal of Metamorphic Geology |
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Blackwell Publishing Inc.
2015
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Online Access: | https://hdl.handle.net/20.500.11937/46610 https://doi.org/10.1111/jmg.12117 |
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ftcurtin:oai:espace.curtin.edu.au:20.500.11937/46610 2023-06-11T04:04:35+02:00 Decoding polyphase migmatites using geochronology and phase equilibria modelling Yakymchuk, C. Brown, M. Clark, C. Korhonen, F. Piccoli, P. Siddoway, C. Taylor, Richard Vervoort, J. 2015 restricted https://hdl.handle.net/20.500.11937/46610 https://doi.org/10.1111/jmg.12117 unknown Blackwell Publishing Inc. http://hdl.handle.net/20.500.11937/46610 doi:10.1111/jmg.12117 Journal Article 2015 ftcurtin https://doi.org/20.500.11937/4661010.1111/jmg.12117 2023-05-30T19:44:45Z In this study, in situ U–Pb monazite ages and Lu–Hf garnet geochronology are used to distinguish mineral parageneses developed during Devonian–Carboniferous and Cretaceous events in migmatitic paragneiss and orthogneiss from the Fosdick migmatite–granite complex in West Antarctica. SHRIMP U–Pb monazite ages define two dominant populations at 365–300 Ma (from cores of polychronic grains, dominantly from deeper structural levels in the central and western sectors of the complex) and 120–96 Ma (from rims of polychronic grains, dominantly from the central and western sectors of the complex, and from monochronic grains, mostly from shallower structural levels in the eastern sector of the complex). For five paragneisses and two orthogneisses, Lu–Hf garnet ages range from 116 to 111 Ma, c. 12–17 Ma older than published Sm–Nd garnet ages of 102–99 Ma from three of the same samples. Garnet grains in the analysed samples generally have Lu-enriched rims relative to Lu-depleted cores. By contrast, for three of the same samples, individual garnet grains have flat Sm concentrations consistent with high-T diffusive resetting. Lutetium enrichment of garnet rims is interpreted to record the breakdown of a Lu-rich accessory mineral during the final stage of garnet growth immediately prior to the metamorphic peak, and/or the preferential retention of Lu in garnet during breakdown to cordierite in the presence of melt concomitant with the initial stages of exhumation.Therefore, garnet is interpreted to be part of the Cretaceous mineral paragenesis and the Lu–Hf garnet ages are interpreted to record the timing of close-to-peak metamorphism for this event. For the Devonian–Carboniferous event, phase equilibria modelling of the metasedimentary protoliths to the paragneiss and a diatexite migmatite restrict the peak P–T conditions to 720–800 °C at 0.45–1.0 GPa. For the Cretaceous event, using both forward and inverse phase equilibria modelling of residual paragneiss and orthogneiss compositions, the P–T conditions after decompression ... Article in Journal/Newspaper Antarc* Antarctica West Antarctica Curtin University: espace West Antarctica Journal of Metamorphic Geology 33 2 203 230 |
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Open Polar |
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Curtin University: espace |
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ftcurtin |
language |
unknown |
description |
In this study, in situ U–Pb monazite ages and Lu–Hf garnet geochronology are used to distinguish mineral parageneses developed during Devonian–Carboniferous and Cretaceous events in migmatitic paragneiss and orthogneiss from the Fosdick migmatite–granite complex in West Antarctica. SHRIMP U–Pb monazite ages define two dominant populations at 365–300 Ma (from cores of polychronic grains, dominantly from deeper structural levels in the central and western sectors of the complex) and 120–96 Ma (from rims of polychronic grains, dominantly from the central and western sectors of the complex, and from monochronic grains, mostly from shallower structural levels in the eastern sector of the complex). For five paragneisses and two orthogneisses, Lu–Hf garnet ages range from 116 to 111 Ma, c. 12–17 Ma older than published Sm–Nd garnet ages of 102–99 Ma from three of the same samples. Garnet grains in the analysed samples generally have Lu-enriched rims relative to Lu-depleted cores. By contrast, for three of the same samples, individual garnet grains have flat Sm concentrations consistent with high-T diffusive resetting. Lutetium enrichment of garnet rims is interpreted to record the breakdown of a Lu-rich accessory mineral during the final stage of garnet growth immediately prior to the metamorphic peak, and/or the preferential retention of Lu in garnet during breakdown to cordierite in the presence of melt concomitant with the initial stages of exhumation.Therefore, garnet is interpreted to be part of the Cretaceous mineral paragenesis and the Lu–Hf garnet ages are interpreted to record the timing of close-to-peak metamorphism for this event. For the Devonian–Carboniferous event, phase equilibria modelling of the metasedimentary protoliths to the paragneiss and a diatexite migmatite restrict the peak P–T conditions to 720–800 °C at 0.45–1.0 GPa. For the Cretaceous event, using both forward and inverse phase equilibria modelling of residual paragneiss and orthogneiss compositions, the P–T conditions after decompression ... |
format |
Article in Journal/Newspaper |
author |
Yakymchuk, C. Brown, M. Clark, C. Korhonen, F. Piccoli, P. Siddoway, C. Taylor, Richard Vervoort, J. |
spellingShingle |
Yakymchuk, C. Brown, M. Clark, C. Korhonen, F. Piccoli, P. Siddoway, C. Taylor, Richard Vervoort, J. Decoding polyphase migmatites using geochronology and phase equilibria modelling |
author_facet |
Yakymchuk, C. Brown, M. Clark, C. Korhonen, F. Piccoli, P. Siddoway, C. Taylor, Richard Vervoort, J. |
author_sort |
Yakymchuk, C. |
title |
Decoding polyphase migmatites using geochronology and phase equilibria modelling |
title_short |
Decoding polyphase migmatites using geochronology and phase equilibria modelling |
title_full |
Decoding polyphase migmatites using geochronology and phase equilibria modelling |
title_fullStr |
Decoding polyphase migmatites using geochronology and phase equilibria modelling |
title_full_unstemmed |
Decoding polyphase migmatites using geochronology and phase equilibria modelling |
title_sort |
decoding polyphase migmatites using geochronology and phase equilibria modelling |
publisher |
Blackwell Publishing Inc. |
publishDate |
2015 |
url |
https://hdl.handle.net/20.500.11937/46610 https://doi.org/10.1111/jmg.12117 |
geographic |
West Antarctica |
geographic_facet |
West Antarctica |
genre |
Antarc* Antarctica West Antarctica |
genre_facet |
Antarc* Antarctica West Antarctica |
op_relation |
http://hdl.handle.net/20.500.11937/46610 doi:10.1111/jmg.12117 |
op_doi |
https://doi.org/20.500.11937/4661010.1111/jmg.12117 |
container_title |
Journal of Metamorphic Geology |
container_volume |
33 |
container_issue |
2 |
container_start_page |
203 |
op_container_end_page |
230 |
_version_ |
1768388984265768960 |