Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa 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...
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Scholarship, Research, and Creative Work at Bryn Mawr College
2011
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Online Access: | https://repository.brynmawr.edu/geo_pubs/2 https://doi.org/10.1016/j.gca.2011.08.020 https://repository.brynmawr.edu/context/geo_pubs/article/1003/viewcontent/Elkins_75.21.6300.pdf |
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ftbrynmawrcoll:oai:repository.brynmawr.edu:geo_pubs-1003 2024-06-23T07:54:14+00:00 Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses Elkins, Lynne J Sims, K.W.W. Prytulak, J. Elliot, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, C. Mertz, D. F. Schilling, J. G. Murrell, M. 2011-11-01T07:00:00Z application/pdf https://repository.brynmawr.edu/geo_pubs/2 https://doi.org/10.1016/j.gca.2011.08.020 https://repository.brynmawr.edu/context/geo_pubs/article/1003/viewcontent/Elkins_75.21.6300.pdf unknown Scholarship, Research, and Creative Work at Bryn Mawr College https://repository.brynmawr.edu/geo_pubs/2 doi:10.1016/j.gca.2011.08.020 https://repository.brynmawr.edu/context/geo_pubs/article/1003/viewcontent/Elkins_75.21.6300.pdf Geology Faculty Research and Scholarship Earth Sciences text 2011 ftbrynmawrcoll https://doi.org/10.1016/j.gca.2011.08.020 2024-05-31T03:06:11Z 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 degrees 05'-70 degrees 26'N) display ((230)Th/(238)U) < 1 and ((230)Th/(238)U) > 1 with ((230)Th/(238)U) 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. (87)Sr/(86)Sr = 0.70272-0.70301, epsilon(Nd) = 8.4-10.5, epsilon(Hf) = 15.4-19.6 (La/Yb)(N) = 0.28-0.84) encompass a narrow range of ((230)Th/(232)Th) (1.20-1.32) over a large range in ((238)U/(232)Th) (0.94-1.32), producing a horizontal array on a ((230)Th/(232)Th) vs. ((238)U/(232)Th) diagram and a large variation in ((230)Th/(238)U). However, the ((230)Th/(238)U) of the Kolbeinsey Ridge basalts (0.96-1.30) are inversely correlated with ((234)U/(238)U) (1.001-1.031). Samples with low ((230)Th/(238)U) and elevated ((234)U/(238)U) reflect alteration by seawater or seawater-derived materials. The unaltered Kolbeinsey lavas with equilibrium (234)U/(238)U have high ((230)Th/(238)U) 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 ((230)Th/(238)U) and ((231)Pa/(235)U) ratios in uncontaminated Kolbeinsey lavas, but low ((231)Pa/(235)U) ratios in Eggvin Bank samples suggest eclogite involvement in the source for that ridge segment. Text Jan Mayen Kolbeinsey Bryn Mawr College: Scholarship, Research, and Creative Work 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 |
Bryn Mawr College: Scholarship, Research, and Creative Work |
op_collection_id |
ftbrynmawrcoll |
language |
unknown |
topic |
Earth Sciences |
spellingShingle |
Earth Sciences Elkins, Lynne J Sims, K.W.W. Prytulak, J. Elliot, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, C. Mertz, D. F. Schilling, J. G. Murrell, M. Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
topic_facet |
Earth Sciences |
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 degrees 05'-70 degrees 26'N) display ((230)Th/(238)U) < 1 and ((230)Th/(238)U) > 1 with ((230)Th/(238)U) 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. (87)Sr/(86)Sr = 0.70272-0.70301, epsilon(Nd) = 8.4-10.5, epsilon(Hf) = 15.4-19.6 (La/Yb)(N) = 0.28-0.84) encompass a narrow range of ((230)Th/(232)Th) (1.20-1.32) over a large range in ((238)U/(232)Th) (0.94-1.32), producing a horizontal array on a ((230)Th/(232)Th) vs. ((238)U/(232)Th) diagram and a large variation in ((230)Th/(238)U). However, the ((230)Th/(238)U) of the Kolbeinsey Ridge basalts (0.96-1.30) are inversely correlated with ((234)U/(238)U) (1.001-1.031). Samples with low ((230)Th/(238)U) and elevated ((234)U/(238)U) reflect alteration by seawater or seawater-derived materials. The unaltered Kolbeinsey lavas with equilibrium (234)U/(238)U have high ((230)Th/(238)U) 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 ((230)Th/(238)U) and ((231)Pa/(235)U) ratios in uncontaminated Kolbeinsey lavas, but low ((231)Pa/(235)U) ratios in Eggvin Bank samples suggest eclogite involvement in the source for that ridge segment. |
format |
Text |
author |
Elkins, Lynne J Sims, K.W.W. Prytulak, J. Elliot, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, C. Mertz, D. F. Schilling, J. G. Murrell, M. |
author_facet |
Elkins, Lynne J Sims, K.W.W. Prytulak, J. Elliot, T. Mattielli, N. Blichert-Toft, J. Blusztajn, J. Dunbar, N. Devey, C. Mertz, D. F. Schilling, J. G. Murrell, M. |
author_sort |
Elkins, Lynne J |
title |
Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
title_short |
Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
title_full |
Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
title_fullStr |
Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
title_full_unstemmed |
Understanding Melt Generation Beneath the Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, and (231)Pa Excesses |
title_sort |
understanding melt generation beneath the slow-spreading kolbeinsey ridge using (238)u, (230)th, and (231)pa excesses |
publisher |
Scholarship, Research, and Creative Work at Bryn Mawr College |
publishDate |
2011 |
url |
https://repository.brynmawr.edu/geo_pubs/2 https://doi.org/10.1016/j.gca.2011.08.020 https://repository.brynmawr.edu/context/geo_pubs/article/1003/viewcontent/Elkins_75.21.6300.pdf |
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_source |
Geology Faculty Research and Scholarship |
op_relation |
https://repository.brynmawr.edu/geo_pubs/2 doi:10.1016/j.gca.2011.08.020 https://repository.brynmawr.edu/context/geo_pubs/article/1003/viewcontent/Elkins_75.21.6300.pdf |
op_doi |
https://doi.org/10.1016/j.gca.2011.08.020 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
75 |
container_issue |
21 |
container_start_page |
6300 |
op_container_end_page |
6329 |
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1802646311292370944 |