Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses
To examine the petrogenesis and sources of basalts from the Kolbeinsey Ridge, one of the shallowest locations along the global ridge system, we present new measurements of Nd, Sr, Hf, and Pb isotopes and U-series disequilibria on 32 axial basalts. Young Kolbeinsey basalts (full-spreading rate = 1.8...
Published in: | Geochimica et Cosmochimica Acta |
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ftoceanrep:oai:oceanrep.geomar.de:12392 2023-05-15T16:57:03+02:00 Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses Elkins, L. J. Sims, K. W. W. Prytulak, J. Elliott, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, Colin Mertz, D. F. Schilling, J.-G. Murrell, M. 2011 text https://oceanrep.geomar.de/id/eprint/12392/ https://oceanrep.geomar.de/id/eprint/12392/1/2011_Elkins__etal_GCA.pdf https://oceanrep.geomar.de/id/eprint/12392/3/Elkins_Suppl.pdf https://doi.org/10.1016/j.gca.2011.08.020 en eng Elsevier https://oceanrep.geomar.de/id/eprint/12392/1/2011_Elkins__etal_GCA.pdf https://oceanrep.geomar.de/id/eprint/12392/3/Elkins_Suppl.pdf Elkins, L. J., Sims, K. W. W., Prytulak, J., Elliott, T., Mattielli, N., Blichert-Toft, J., Blusztajn, J., Dunbar, N., Devey, C. , Mertz, D. F., Schilling, J. G. and Murrell, M. (2011) Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses. Geochimica et Cosmochimica Acta, 75 (21). pp. 6300-6329. DOI 10.1016/j.gca.2011.08.020 <https://doi.org/10.1016/j.gca.2011.08.020>. doi:10.1016/j.gca.2011.08.020 info:eu-repo/semantics/restrictedAccess Article PeerReviewed 2011 ftoceanrep https://doi.org/10.1016/j.gca.2011.08.020 2023-04-07T15:00:48Z To examine the petrogenesis and sources of basalts from the Kolbeinsey Ridge, one of the shallowest locations along the global ridge system, we present new measurements of Nd, Sr, Hf, and Pb isotopes and U-series disequilibria on 32 axial basalts. Young Kolbeinsey basalts (full-spreading rate = 1.8 cm/yr; 67°05′–70°26′N) display (230Th/238U) < 1 and (230Th/238U) > 1 with (230Th/238U) from 0.95 to 1.30 and have low U (11.3–65.6 ppb) and Th (33.0 ppb–2.40 ppm) concentrations. Except for characteristic isotopic enrichment near the Jan Mayen region, the otherwise depleted Kolbeinsey basalts (e.g. 87Sr/86Sr = 0.70272–0.70301, εNd = 8.4–10.5, εHf = 15.4–19.6 (La/Yb)N = 0.28–0.84) encompass a narrow range of (230Th/232Th) (1.20–1.32) over a large range in (238U/232Th) (0.94–1.32), producing a horizontal array on a (230Th/232Th) vs. (238U/232Th) diagram and a large variation in (230Th/238U). However, the (230Th/238U) of the Kolbeinsey Ridge basalts (0.96–1.30) are inversely correlated with (234U/238U) (1.001–1.031). Samples with low (230Th/238U) and elevated (234U/238U) reflect alteration by seawater or seawater-derived materials. The unaltered Kolbeinsey lavas with equilibrium 234U/238U have high (230Th/238U) values (>=1.2), which are consistent with melting in the presence of garnet. This is in keeping with the thick crust and anomalously shallow axial depth for the Kolbeinsey Ridge, which is thought to be the product of large degrees of melting in a long melt column. A time-dependent, dynamic melting scenario involving a long, slowly upwelling melting column that initiates well within the garnet peridotite stability zone can, in general, reproduce the (230Th/238U) and (231Pa/235U) ratios in uncontaminated Kolbeinsey lavas, but low (231Pa/235U) ratios in Eggvin Bank samples suggest eclogite involvement in the source for that ridge segment. Article in Journal/Newspaper Jan Mayen Kolbeinsey OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Jan Mayen Kolbeinsey ENVELOPE(-18.687,-18.687,67.149,67.149) Kolbeinsey Ridge ENVELOPE(-16.917,-16.917,68.833,68.833) Geochimica et Cosmochimica Acta 75 21 6300 6329 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
To examine the petrogenesis and sources of basalts from the Kolbeinsey Ridge, one of the shallowest locations along the global ridge system, we present new measurements of Nd, Sr, Hf, and Pb isotopes and U-series disequilibria on 32 axial basalts. Young Kolbeinsey basalts (full-spreading rate = 1.8 cm/yr; 67°05′–70°26′N) display (230Th/238U) < 1 and (230Th/238U) > 1 with (230Th/238U) from 0.95 to 1.30 and have low U (11.3–65.6 ppb) and Th (33.0 ppb–2.40 ppm) concentrations. Except for characteristic isotopic enrichment near the Jan Mayen region, the otherwise depleted Kolbeinsey basalts (e.g. 87Sr/86Sr = 0.70272–0.70301, εNd = 8.4–10.5, εHf = 15.4–19.6 (La/Yb)N = 0.28–0.84) encompass a narrow range of (230Th/232Th) (1.20–1.32) over a large range in (238U/232Th) (0.94–1.32), producing a horizontal array on a (230Th/232Th) vs. (238U/232Th) diagram and a large variation in (230Th/238U). However, the (230Th/238U) of the Kolbeinsey Ridge basalts (0.96–1.30) are inversely correlated with (234U/238U) (1.001–1.031). Samples with low (230Th/238U) and elevated (234U/238U) reflect alteration by seawater or seawater-derived materials. The unaltered Kolbeinsey lavas with equilibrium 234U/238U have high (230Th/238U) values (>=1.2), which are consistent with melting in the presence of garnet. This is in keeping with the thick crust and anomalously shallow axial depth for the Kolbeinsey Ridge, which is thought to be the product of large degrees of melting in a long melt column. A time-dependent, dynamic melting scenario involving a long, slowly upwelling melting column that initiates well within the garnet peridotite stability zone can, in general, reproduce the (230Th/238U) and (231Pa/235U) ratios in uncontaminated Kolbeinsey lavas, but low (231Pa/235U) ratios in Eggvin Bank samples suggest eclogite involvement in the source for that ridge segment. |
format |
Article in Journal/Newspaper |
author |
Elkins, L. J. Sims, K. W. W. Prytulak, J. Elliott, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, Colin Mertz, D. F. Schilling, J.-G. Murrell, M. |
spellingShingle |
Elkins, L. J. Sims, K. W. W. Prytulak, J. Elliott, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, Colin Mertz, D. F. Schilling, J.-G. Murrell, M. Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
author_facet |
Elkins, L. J. Sims, K. W. W. Prytulak, J. Elliott, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, Colin Mertz, D. F. Schilling, J.-G. Murrell, M. |
author_sort |
Elkins, L. J. |
title |
Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
title_short |
Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
title_full |
Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
title_fullStr |
Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
title_full_unstemmed |
Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses |
title_sort |
understanding melt generation beneath the slow-spreading kolbeinsey ridge using 238u, 230th, and 231pa excesses |
publisher |
Elsevier |
publishDate |
2011 |
url |
https://oceanrep.geomar.de/id/eprint/12392/ https://oceanrep.geomar.de/id/eprint/12392/1/2011_Elkins__etal_GCA.pdf https://oceanrep.geomar.de/id/eprint/12392/3/Elkins_Suppl.pdf https://doi.org/10.1016/j.gca.2011.08.020 |
long_lat |
ENVELOPE(-18.687,-18.687,67.149,67.149) ENVELOPE(-16.917,-16.917,68.833,68.833) |
geographic |
Jan Mayen Kolbeinsey Kolbeinsey Ridge |
geographic_facet |
Jan Mayen Kolbeinsey Kolbeinsey Ridge |
genre |
Jan Mayen Kolbeinsey |
genre_facet |
Jan Mayen Kolbeinsey |
op_relation |
https://oceanrep.geomar.de/id/eprint/12392/1/2011_Elkins__etal_GCA.pdf https://oceanrep.geomar.de/id/eprint/12392/3/Elkins_Suppl.pdf Elkins, L. J., Sims, K. W. W., Prytulak, J., Elliott, T., Mattielli, N., Blichert-Toft, J., Blusztajn, J., Dunbar, N., Devey, C. , Mertz, D. F., Schilling, J. G. and Murrell, M. (2011) Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses. Geochimica et Cosmochimica Acta, 75 (21). pp. 6300-6329. DOI 10.1016/j.gca.2011.08.020 <https://doi.org/10.1016/j.gca.2011.08.020>. doi:10.1016/j.gca.2011.08.020 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.gca.2011.08.020 |
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Geochimica et Cosmochimica Acta |
container_volume |
75 |
container_issue |
21 |
container_start_page |
6300 |
op_container_end_page |
6329 |
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1766048325216239616 |