Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer
Natural alteration of zircon takes place in melts or fluids either via dissolution coupled with overgrowth or via a coupled dissolution-reprecipitation process. The latter results in the zircon being partially or totally replaced by new, compositionally re-equilibrated zircon or a new mineral phase...
Published in: | Geochimica et Cosmochimica Acta |
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Language: | English |
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2023
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ftgfzpotsdam:oai:gfzpublic.gfz-potsdam.de:item_5022265 2024-05-19T07:46:02+00:00 Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer Harlov, D. Anczkiewicz, R. Dunkley, D. 2023 application/pdf https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265_2/component/file_5022412/5022265.pdf eng eng info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2023.05.011 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265_2/component/file_5022412/5022265.pdf Geochimica et Cosmochimica Acta info:eu-repo/semantics/article 2023 ftgfzpotsdam https://doi.org/10.1016/j.gca.2023.05.011 2024-04-23T23:30:27Z Natural alteration of zircon takes place in melts or fluids either via dissolution coupled with overgrowth or via a coupled dissolution-reprecipitation process. The latter results in the zircon being partially or totally replaced by new, compositionally re-equilibrated zircon or a new mineral phase or both. In this study, fragments (50–300 μm) from a large, inclusion-free, clear, 520–530 Ma euhedral zircon with light radiation damage from a nepheline syenite pegmatite, Seiland Igneous Province, northern Norway, were experimentally reacted in 20 mg batches with 5 mg of ThO2 + ThSiO2 + SiO2 and a series of alkali-bearing fluids in sealed Pt capsules at 900 °C and 1000 MPa for 6–11 days in the piston cylinder press using a CaF2 setup with a cylindrical graphite oven. ThO2 + ThSiO2 + SiO2 was present at the end of the experiment. In experiments involving H2O, H2O + NaCl, H2O + KCl, and 2 N KOH, no reaction textures formed other than a slight dissolution of the zircon grain fragments. Experiments involving 2 N NaOH, Na2Si2O5 + H2O, and NaF + H2O resulted in zircon reaction textures with varying degrees of intensity, which took the form of partial replacement by compositionally modified zircon via a coupled dissolution-reprecipitation process. In the NaF + H2O experiment some overgrowth also occurred. Altered zircon is separated by sharp compositional boundaries from unaltered zircon. Secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis indicates that, relative to the unaltered zircon, the altered zircon is strongly enriched in Th, and heavily to moderately depleted in U and (Y + REE). In all the experiments, 206Pb (3–5 ppm in unaltered zircon) is depleted in the altered zircon to below the SIMS detection limit and to at or below the LA-ICP-MS detection limit. Hafnium and Ti concentrations in the altered zircon retained the same approximate value (within error) as the original zircon. The results from these experiments demonstrate that zircon can ... Article in Journal/Newspaper Northern Norway GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) Geochimica et Cosmochimica Acta 352 222 235 |
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Open Polar |
collection |
GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) |
op_collection_id |
ftgfzpotsdam |
language |
English |
description |
Natural alteration of zircon takes place in melts or fluids either via dissolution coupled with overgrowth or via a coupled dissolution-reprecipitation process. The latter results in the zircon being partially or totally replaced by new, compositionally re-equilibrated zircon or a new mineral phase or both. In this study, fragments (50–300 μm) from a large, inclusion-free, clear, 520–530 Ma euhedral zircon with light radiation damage from a nepheline syenite pegmatite, Seiland Igneous Province, northern Norway, were experimentally reacted in 20 mg batches with 5 mg of ThO2 + ThSiO2 + SiO2 and a series of alkali-bearing fluids in sealed Pt capsules at 900 °C and 1000 MPa for 6–11 days in the piston cylinder press using a CaF2 setup with a cylindrical graphite oven. ThO2 + ThSiO2 + SiO2 was present at the end of the experiment. In experiments involving H2O, H2O + NaCl, H2O + KCl, and 2 N KOH, no reaction textures formed other than a slight dissolution of the zircon grain fragments. Experiments involving 2 N NaOH, Na2Si2O5 + H2O, and NaF + H2O resulted in zircon reaction textures with varying degrees of intensity, which took the form of partial replacement by compositionally modified zircon via a coupled dissolution-reprecipitation process. In the NaF + H2O experiment some overgrowth also occurred. Altered zircon is separated by sharp compositional boundaries from unaltered zircon. Secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis indicates that, relative to the unaltered zircon, the altered zircon is strongly enriched in Th, and heavily to moderately depleted in U and (Y + REE). In all the experiments, 206Pb (3–5 ppm in unaltered zircon) is depleted in the altered zircon to below the SIMS detection limit and to at or below the LA-ICP-MS detection limit. Hafnium and Ti concentrations in the altered zircon retained the same approximate value (within error) as the original zircon. The results from these experiments demonstrate that zircon can ... |
format |
Article in Journal/Newspaper |
author |
Harlov, D. Anczkiewicz, R. Dunkley, D. |
spellingShingle |
Harlov, D. Anczkiewicz, R. Dunkley, D. Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
author_facet |
Harlov, D. Anczkiewicz, R. Dunkley, D. |
author_sort |
Harlov, D. |
title |
Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
title_short |
Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
title_full |
Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
title_fullStr |
Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
title_full_unstemmed |
Metasomatic alteration of zircon at lower crustal P-T conditions utilizing alkali- and F-bearing fluids: Trace element incorporation, depletion, and resetting the zircon geochronometer |
title_sort |
metasomatic alteration of zircon at lower crustal p-t conditions utilizing alkali- and f-bearing fluids: trace element incorporation, depletion, and resetting the zircon geochronometer |
publishDate |
2023 |
url |
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265_2/component/file_5022412/5022265.pdf |
genre |
Northern Norway |
genre_facet |
Northern Norway |
op_source |
Geochimica et Cosmochimica Acta |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2023.05.011 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5022265_2/component/file_5022412/5022265.pdf |
op_doi |
https://doi.org/10.1016/j.gca.2023.05.011 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
352 |
container_start_page |
222 |
op_container_end_page |
235 |
_version_ |
1799486155321769984 |