Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts
International audience U-series studies in oceanic basalts are critical for understanding melting and melt extraction in the Earth's mantle. The combined results of a detailed geochemical study of melting and melt extraction at Theistareykir, northern Iceland, provide a strong case for melt ext...
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ftsorbonneuniv:oai:HAL:hal-00271233v1 2024-09-15T18:14:32+00:00 Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts Stracke, Andreas Bourdon, Bernard Mckenzie, Dan Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) Bullard Laboratories University of Cambridge UK (CAM) 2006 https://hal.science/hal-00271233 https://doi.org/10.1016/j.epsl.2006.01.057 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2006.01.057 hal-00271233 https://hal.science/hal-00271233 doi:10.1016/j.epsl.2006.01.057 ISSN: 0012-821X Earth and Planetary Science Letters https://hal.science/hal-00271233 Earth and Planetary Science Letters, 2006, 244 (1-2), pp.97-112. ⟨10.1016/j.epsl.2006.01.057⟩ U-series MORB OIB melt extraction dynamic melting [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry info:eu-repo/semantics/article Journal articles 2006 ftsorbonneuniv https://doi.org/10.1016/j.epsl.2006.01.057 2024-07-25T23:47:59Z International audience U-series studies in oceanic basalts are critical for understanding melting and melt extraction in the Earth's mantle. The combined results of a detailed geochemical study of melting and melt extraction at Theistareykir, northern Iceland, provide a strong case for melt extraction via channeled melt flow at an active spreading ridge. It has often been argued, however, that widely used melting and melt extraction models, which simulate channeled melt extraction (i.e. fractional and/or dynamic melting), can only partially explain the global U-series systematics in oceanic basalts. As a consequence, more complicated models have been invoked, which suggest different styles of melt extraction at different depths/pressures in the mantle, so-called “two-porosity models”. Alternatively, diffusion-controlled mechanisms have been proposed. Here we show that U–Th–Pa–Ra systematics in oceanic basalts can indeed be explained by models where melt transport occurs without chemical equilibrium between melt and solid when variations in all three critical melting parameters (residual porosity, upwelling rate of the solid mantle and melt velocity) are taken into account. Melting at ridges requires systematic variation of at least two critical melting parameters, most likely upwelling and melt extraction rate. Melts generated with increasing lateral distance to the ridge axis are generated with slower upwelling rates and are extracted with lower velocities than melts created closer to the ridge axis. Melting at ocean islands, on the other hand, can successfully be explained by variations in upwelling rate only. Global U-series systematics in OIB originate from superimposed global variations in upwelling velocity due to different buoyancy fluxes and from local variation in upwelling velocity as a function of radial distance to the plume center. The model proposed here is consistent with other geochemical data for oceanic basalts and strongly supports melt extraction via high-porosity channels as a general ... Article in Journal/Newspaper Iceland HAL Sorbonne Université Earth and Planetary Science Letters 244 1-2 97 112 |
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Open Polar |
collection |
HAL Sorbonne Université |
op_collection_id |
ftsorbonneuniv |
language |
English |
topic |
U-series MORB OIB melt extraction dynamic melting [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry |
spellingShingle |
U-series MORB OIB melt extraction dynamic melting [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry Stracke, Andreas Bourdon, Bernard Mckenzie, Dan Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
topic_facet |
U-series MORB OIB melt extraction dynamic melting [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry |
description |
International audience U-series studies in oceanic basalts are critical for understanding melting and melt extraction in the Earth's mantle. The combined results of a detailed geochemical study of melting and melt extraction at Theistareykir, northern Iceland, provide a strong case for melt extraction via channeled melt flow at an active spreading ridge. It has often been argued, however, that widely used melting and melt extraction models, which simulate channeled melt extraction (i.e. fractional and/or dynamic melting), can only partially explain the global U-series systematics in oceanic basalts. As a consequence, more complicated models have been invoked, which suggest different styles of melt extraction at different depths/pressures in the mantle, so-called “two-porosity models”. Alternatively, diffusion-controlled mechanisms have been proposed. Here we show that U–Th–Pa–Ra systematics in oceanic basalts can indeed be explained by models where melt transport occurs without chemical equilibrium between melt and solid when variations in all three critical melting parameters (residual porosity, upwelling rate of the solid mantle and melt velocity) are taken into account. Melting at ridges requires systematic variation of at least two critical melting parameters, most likely upwelling and melt extraction rate. Melts generated with increasing lateral distance to the ridge axis are generated with slower upwelling rates and are extracted with lower velocities than melts created closer to the ridge axis. Melting at ocean islands, on the other hand, can successfully be explained by variations in upwelling rate only. Global U-series systematics in OIB originate from superimposed global variations in upwelling velocity due to different buoyancy fluxes and from local variation in upwelling velocity as a function of radial distance to the plume center. The model proposed here is consistent with other geochemical data for oceanic basalts and strongly supports melt extraction via high-porosity channels as a general ... |
author2 |
Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) Bullard Laboratories University of Cambridge UK (CAM) |
format |
Article in Journal/Newspaper |
author |
Stracke, Andreas Bourdon, Bernard Mckenzie, Dan |
author_facet |
Stracke, Andreas Bourdon, Bernard Mckenzie, Dan |
author_sort |
Stracke, Andreas |
title |
Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
title_short |
Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
title_full |
Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
title_fullStr |
Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
title_full_unstemmed |
Melt extraction in the Earth's mantle: Constraints from U–Th–Pa–Ra studies in oceanic basalts |
title_sort |
melt extraction in the earth's mantle: constraints from u–th–pa–ra studies in oceanic basalts |
publisher |
HAL CCSD |
publishDate |
2006 |
url |
https://hal.science/hal-00271233 https://doi.org/10.1016/j.epsl.2006.01.057 |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
ISSN: 0012-821X Earth and Planetary Science Letters https://hal.science/hal-00271233 Earth and Planetary Science Letters, 2006, 244 (1-2), pp.97-112. ⟨10.1016/j.epsl.2006.01.057⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2006.01.057 hal-00271233 https://hal.science/hal-00271233 doi:10.1016/j.epsl.2006.01.057 |
op_doi |
https://doi.org/10.1016/j.epsl.2006.01.057 |
container_title |
Earth and Planetary Science Letters |
container_volume |
244 |
container_issue |
1-2 |
container_start_page |
97 |
op_container_end_page |
112 |
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1810452301577453568 |