U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland
Thanks to precise analyses of uranium series radioactive disequilibria, permitted by improvements of mass spectrometry data acquisition and optimization of chemistry, two questions were tackled and answers about the periods of glaciation in Iceland and the petrogenesis of andean lavas were proposed....
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Other Authors: | , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
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HAL CCSD
2005
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Online Access: | https://theses.hal.science/tel-00011187 https://theses.hal.science/tel-00011187/document https://theses.hal.science/tel-00011187/file/These_chmeleff.pdf |
id |
ftinsu:oai:HAL:tel-00011187v1 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
French |
topic |
fluids TIMS Iceland Geochronology U-series disequilibria Déséquilibres radioactifs traçage magmatique fluides géochronologie spéctrométrie de masse Islande Andes adakites [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry |
spellingShingle |
fluids TIMS Iceland Geochronology U-series disequilibria Déséquilibres radioactifs traçage magmatique fluides géochronologie spéctrométrie de masse Islande Andes adakites [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry Chmeleff, Jérôme U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
topic_facet |
fluids TIMS Iceland Geochronology U-series disequilibria Déséquilibres radioactifs traçage magmatique fluides géochronologie spéctrométrie de masse Islande Andes adakites [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry |
description |
Thanks to precise analyses of uranium series radioactive disequilibria, permitted by improvements of mass spectrometry data acquisition and optimization of chemistry, two questions were tackled and answers about the periods of glaciation in Iceland and the petrogenesis of andean lavas were proposed. Two methods were used to date lava flows from the Reykjanes peninsula and the island of Heimaey, in Iceland, directly linked to the periods of deglaciation or reheating around the last ice age. An original method based on the use of segregation veins present in the lava flows has been developed. Thanks to the formation of this particular geological object this methods permits to be freed from xenocrysts when using the internal isochron method in the 238U-230Th system. Using this method some constraints are brought both on the quaternary geology of the area of Reykjavik and on the age of the end of the Würm glaciation on Heimaey. In parallel, due to the homogeneity of the historical and Holocene lavas of the Reykjanes peninsula, regarding the (230Th/232Th) and Th/U ratios, it is possible to derive the (230Th/232Th) ratio in time to determine the age of lava flows installed during the ice age. Thus we confirmed that the magnetic excursion recorded in the Skálamælifell lava flow is most probably the same one as that of Laschamp-Olby and that at this time (approximately 48.000 years) the Reykjanes peninsula was entirely covered with a glacier. Thanks to this method the extent of the glacier was also constrained by dating of a picritic shield around 22.000 years, thus the peninsula has to be free of any ice cap despite the fact that glaciation is the most intense around this time. Then andean arc magmas petrogenesis was constrained in time and space. Almost systematic excesses of 226Ra compared to 230Th in lavas of austral, southern and northern volcanic zones of the Andes (AVZ, SVZ and NVZ) constrain the ascending time from the source to the surface after their formation which is necessarily fast (less than 8.000 years ... |
author2 |
Laboratoire Magmas et Volcans (LMV) Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS) Université Blaise Pascal - Clermont-Ferrand II Olgeir Sigmarsson(olgeir@opgc.univ-bpclermont.fr) |
format |
Doctoral or Postdoctoral Thesis |
author |
Chmeleff, Jérôme |
author_facet |
Chmeleff, Jérôme |
author_sort |
Chmeleff, Jérôme |
title |
U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
title_short |
U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
title_full |
U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
title_fullStr |
U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
title_full_unstemmed |
U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland |
title_sort |
u-series radioactive disequilibria 238u-230th-226ra : discussions on sources and processes responsible for volcanism of the anden cordillera and on the deglaciation in iceland |
publisher |
HAL CCSD |
publishDate |
2005 |
url |
https://theses.hal.science/tel-00011187 https://theses.hal.science/tel-00011187/document https://theses.hal.science/tel-00011187/file/These_chmeleff.pdf |
long_lat |
ENVELOPE(164.333,164.333,-71.483,-71.483) ENVELOPE(-22.486,-22.486,65.099,65.099) ENVELOPE(-22.250,-22.250,65.467,65.467) |
geographic |
Austral Freed Heimaey Reykjanes |
geographic_facet |
Austral Freed Heimaey Reykjanes |
genre |
glacier Heimaey Ice cap Iceland Islande |
genre_facet |
glacier Heimaey Ice cap Iceland Islande |
op_source |
https://theses.hal.science/tel-00011187 Géochimie. Université Blaise Pascal - Clermont-Ferrand II, 2005. Français. ⟨NNT : 2005CLF21601⟩ |
op_relation |
NNT: 2005CLF21601 tel-00011187 https://theses.hal.science/tel-00011187 https://theses.hal.science/tel-00011187/document https://theses.hal.science/tel-00011187/file/These_chmeleff.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1769005978062159872 |
spelling |
ftinsu:oai:HAL:tel-00011187v1 2023-06-18T03:40:44+02:00 U-series radioactive disequilibria 238U-230Th-226Ra : discussions on sources and processes responsible for volcanism of the Anden cordillera and on the deglaciation in Iceland Les déséquilibres radioactifs 238U-230Th-226Ra : discussions sur les sources et processus responsables du volcanisme de la Cordillère des Andes et sur la déglaciation en Islande Chmeleff, Jérôme Laboratoire Magmas et Volcans (LMV) Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS) Université Blaise Pascal - Clermont-Ferrand II Olgeir Sigmarsson(olgeir@opgc.univ-bpclermont.fr) 2005-10-28 https://theses.hal.science/tel-00011187 https://theses.hal.science/tel-00011187/document https://theses.hal.science/tel-00011187/file/These_chmeleff.pdf fr fre HAL CCSD NNT: 2005CLF21601 tel-00011187 https://theses.hal.science/tel-00011187 https://theses.hal.science/tel-00011187/document https://theses.hal.science/tel-00011187/file/These_chmeleff.pdf info:eu-repo/semantics/OpenAccess https://theses.hal.science/tel-00011187 Géochimie. Université Blaise Pascal - Clermont-Ferrand II, 2005. Français. ⟨NNT : 2005CLF21601⟩ fluids TIMS Iceland Geochronology U-series disequilibria Déséquilibres radioactifs traçage magmatique fluides géochronologie spéctrométrie de masse Islande Andes adakites [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry info:eu-repo/semantics/doctoralThesis Theses 2005 ftinsu 2023-06-05T19:14:09Z Thanks to precise analyses of uranium series radioactive disequilibria, permitted by improvements of mass spectrometry data acquisition and optimization of chemistry, two questions were tackled and answers about the periods of glaciation in Iceland and the petrogenesis of andean lavas were proposed. Two methods were used to date lava flows from the Reykjanes peninsula and the island of Heimaey, in Iceland, directly linked to the periods of deglaciation or reheating around the last ice age. An original method based on the use of segregation veins present in the lava flows has been developed. Thanks to the formation of this particular geological object this methods permits to be freed from xenocrysts when using the internal isochron method in the 238U-230Th system. Using this method some constraints are brought both on the quaternary geology of the area of Reykjavik and on the age of the end of the Würm glaciation on Heimaey. In parallel, due to the homogeneity of the historical and Holocene lavas of the Reykjanes peninsula, regarding the (230Th/232Th) and Th/U ratios, it is possible to derive the (230Th/232Th) ratio in time to determine the age of lava flows installed during the ice age. Thus we confirmed that the magnetic excursion recorded in the Skálamælifell lava flow is most probably the same one as that of Laschamp-Olby and that at this time (approximately 48.000 years) the Reykjanes peninsula was entirely covered with a glacier. Thanks to this method the extent of the glacier was also constrained by dating of a picritic shield around 22.000 years, thus the peninsula has to be free of any ice cap despite the fact that glaciation is the most intense around this time. Then andean arc magmas petrogenesis was constrained in time and space. Almost systematic excesses of 226Ra compared to 230Th in lavas of austral, southern and northern volcanic zones of the Andes (AVZ, SVZ and NVZ) constrain the ascending time from the source to the surface after their formation which is necessarily fast (less than 8.000 years ... Doctoral or Postdoctoral Thesis glacier Heimaey Ice cap Iceland Islande Institut national des sciences de l'Univers: HAL-INSU Austral Freed ENVELOPE(164.333,164.333,-71.483,-71.483) Heimaey ENVELOPE(-22.486,-22.486,65.099,65.099) Reykjanes ENVELOPE(-22.250,-22.250,65.467,65.467) |