Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers
External 4He sources have been invoked to explain 4He concentrations in groundwater greater than those expected from in situ U and Th production. In a fractured aquifer of Ordovician age located in the St. Lawrence Lowlands (Quebec, Canada), 4He concentrations of up to 4.48 × 10−5 cm3 STP math formu...
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ftunivquebec:oai:archipel.uqam.ca:10472 2023-07-16T03:59:04+02:00 Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers Méjean, Pauline Pinti, Daniele L. Ghaleb, Bassam Larocque, Marie 2017-08 application/pdf http://archipel.uqam.ca/10472/1/Mejean_et_al_Water_Resources_Research_2017_53_5677-5689.pdf en eng http://archipel.uqam.ca/10472/ http://dx.doi.org/10.1002/2016WR020014 doi:10.1002/2016WR020014 http://archipel.uqam.ca/10472/1/Mejean_et_al_Water_Resources_Research_2017_53_5677-5689.pdf Méjean, Pauline; Pinti, Daniele L.; Ghaleb, Bassam et Larocque, Marie (2017). « Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers ». Water Resources Research, 53(7), pp. 5677-5689. 234U 238U activity ratio 4He excess groundwater age α-recoil diffusion fracturing deglaciation Article de revue scientifique PeerReviewed 2017 ftunivquebec https://doi.org/10.1002/2016WR020014 2023-06-24T23:20:51Z External 4He sources have been invoked to explain 4He concentrations in groundwater greater than those expected from in situ U and Th production. In a fractured aquifer of Ordovician age located in the St. Lawrence Lowlands (Quebec, Canada), 4He concentrations of up to 4.48 × 10−5 cm3 STP math formula were measured. Such concentrations are ∼1000 times higher than would be expected from in situ production. A concomitant increase in 4He concentration and 234U/238U activity ratio is shown, suggesting a common release process in groundwater for 234U and 4He. This process has tentatively been identified as glaciation-induced rock fracturing following the Laurentide Ice Sheet retreat. The resulting increase in exposed grain surface facilitates 234U release by α-recoil and that of radiogenic 4He by diffusion. Using a model of helium diffusion from a spherical grain, it is shown that rock fracturing facilitated the release of accumulated 4He at rates ranging from 4.2 × 10−10 to 1.06 × 10−8 cm3 STP math formula yr−1. These release rates are between 1000 and 30,000 times higher than the local U and Th steady state production rate, of 3.5 ± 1.4 × 10−13 cm3 STP math formula yr−1. Integration of 4He release rates over time yields a radiogenic 4He concentration of between 3.85 × 10−6 and 7.12 × 10−5 cm3 STP math formula, in the range of concentrations measured in the St. Lawrence Lowlands fractured aquifers. Results support the occurrence of a local radiogenic helium source to explain the excesses measured in groundwater without requiring a significant external He crustal flux. Text Ice Sheet UQAM - Université du Québec à Montréal: archipel Canada Water Resources Research 53 7 5677 5689 |
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UQAM - Université du Québec à Montréal: archipel |
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ftunivquebec |
language |
English |
topic |
234U 238U activity ratio 4He excess groundwater age α-recoil diffusion fracturing deglaciation |
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234U 238U activity ratio 4He excess groundwater age α-recoil diffusion fracturing deglaciation Méjean, Pauline Pinti, Daniele L. Ghaleb, Bassam Larocque, Marie Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
topic_facet |
234U 238U activity ratio 4He excess groundwater age α-recoil diffusion fracturing deglaciation |
description |
External 4He sources have been invoked to explain 4He concentrations in groundwater greater than those expected from in situ U and Th production. In a fractured aquifer of Ordovician age located in the St. Lawrence Lowlands (Quebec, Canada), 4He concentrations of up to 4.48 × 10−5 cm3 STP math formula were measured. Such concentrations are ∼1000 times higher than would be expected from in situ production. A concomitant increase in 4He concentration and 234U/238U activity ratio is shown, suggesting a common release process in groundwater for 234U and 4He. This process has tentatively been identified as glaciation-induced rock fracturing following the Laurentide Ice Sheet retreat. The resulting increase in exposed grain surface facilitates 234U release by α-recoil and that of radiogenic 4He by diffusion. Using a model of helium diffusion from a spherical grain, it is shown that rock fracturing facilitated the release of accumulated 4He at rates ranging from 4.2 × 10−10 to 1.06 × 10−8 cm3 STP math formula yr−1. These release rates are between 1000 and 30,000 times higher than the local U and Th steady state production rate, of 3.5 ± 1.4 × 10−13 cm3 STP math formula yr−1. Integration of 4He release rates over time yields a radiogenic 4He concentration of between 3.85 × 10−6 and 7.12 × 10−5 cm3 STP math formula, in the range of concentrations measured in the St. Lawrence Lowlands fractured aquifers. Results support the occurrence of a local radiogenic helium source to explain the excesses measured in groundwater without requiring a significant external He crustal flux. |
format |
Text |
author |
Méjean, Pauline Pinti, Daniele L. Ghaleb, Bassam Larocque, Marie |
author_facet |
Méjean, Pauline Pinti, Daniele L. Ghaleb, Bassam Larocque, Marie |
author_sort |
Méjean, Pauline |
title |
Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
title_short |
Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
title_full |
Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
title_fullStr |
Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
title_full_unstemmed |
Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers |
title_sort |
fracturing-induced release of radiogenic 4 he and 234 u into groundwater during the last deglaciation: an alternative source to crustal helium fluxes in periglacial aquifers |
publishDate |
2017 |
url |
http://archipel.uqam.ca/10472/1/Mejean_et_al_Water_Resources_Research_2017_53_5677-5689.pdf |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Ice Sheet |
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Ice Sheet |
op_relation |
http://archipel.uqam.ca/10472/ http://dx.doi.org/10.1002/2016WR020014 doi:10.1002/2016WR020014 http://archipel.uqam.ca/10472/1/Mejean_et_al_Water_Resources_Research_2017_53_5677-5689.pdf Méjean, Pauline; Pinti, Daniele L.; Ghaleb, Bassam et Larocque, Marie (2017). « Fracturing-induced release of radiogenic 4 He and 234 U into groundwater during the last deglaciation: An alternative source to crustal helium fluxes in periglacial aquifers ». Water Resources Research, 53(7), pp. 5677-5689. |
op_doi |
https://doi.org/10.1002/2016WR020014 |
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Water Resources Research |
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53 |
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7 |
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5677 |
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5689 |
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