Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean)
Abyssal peridotites collected along the highly oblique-spreading Lena Trough north of Greenland and Spitsbergen have mineral compositions that are similar to residual abyssal peridotites, except for high sodium concentrations in clinopyroxene (cpx). Most samples are lherzolites with light rare earth...
Published in: | Earth and Planetary Science Letters |
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ftlouisianastuir:oai:digitalcommons.lsu.edu:geo_pubs-1999 2023-06-11T04:09:49+02:00 Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) Hellebrand, Eric Snow, Jonathan E. 2003-11-30T08:00:00Z https://digitalcommons.lsu.edu/geo_pubs/1000 https://doi.org/10.1016/S0012-821X(03)00508-9 unknown LSU Digital Commons https://digitalcommons.lsu.edu/geo_pubs/1000 doi:10.1016/S0012-821X(03)00508-9 Faculty Publications Abyssal peridotite Melt-rock reaction Metasomatism Partial melting Secondary ion mass spectrometry text 2003 ftlouisianastuir https://doi.org/10.1016/S0012-821X(03)00508-9 2023-05-28T18:17:27Z Abyssal peridotites collected along the highly oblique-spreading Lena Trough north of Greenland and Spitsbergen have mineral compositions that are similar to residual abyssal peridotites, except for high sodium concentrations in clinopyroxene (cpx). Most samples are lherzolites with light rare earth element (REE)-depleted cpx trace element patterns, but significantly fractionated middle to heavy REE ratios at relatively high heavy REE concentrations. Such characteristics can only be explained by initial melting of a garnet peridotite followed by low degrees of melting in the stability field of spinel peridotite. The residual garnet signature requires either a high potential temperature of the upwelling mantle, or elevated solidus-lowering water contents. The limited spinel field melting suggests a deep cessation of melt extraction, possibly because of the presence of a thick lithospheric cap. This is consistent with the extremely low effective spreading rate and the vicinity to a passive continental margin, which allow conductive cooling to reach deeper levels than commonly estimated for faster mid-ocean ridges. High sodium concentrations in cpx are neither explainable by melt refertilization, nor by a simple diffusion mechanism. The efficient fractionation of sodium from the light REE requires post-melting metasomatism, which is typically restricted to the subcontinental lithosphere. This might imply that the Lena Trough peridotites represent unroofed subcontinental mantle, from which no melt was extracted during the opening of the Lena Trough. It is more likely that sodic metasomatism occurred after partial melting underneath the Lena Trough, and that such an enrichment process is responsible for elevated sodium concentrations in abyssal peridotites elsewhere. Sodium in cpx of residual peridotites can therefore not serve as an indicator of partial melting or melt refertilization. © 2003 Elsevier B.V. All rights reserved. Text Arctic Arctic Ocean Greenland Spitsbergen LSU Digital Commons (Louisiana State University) Arctic Arctic Ocean Greenland Earth and Planetary Science Letters 216 3 283 299 |
institution |
Open Polar |
collection |
LSU Digital Commons (Louisiana State University) |
op_collection_id |
ftlouisianastuir |
language |
unknown |
topic |
Abyssal peridotite Melt-rock reaction Metasomatism Partial melting Secondary ion mass spectrometry |
spellingShingle |
Abyssal peridotite Melt-rock reaction Metasomatism Partial melting Secondary ion mass spectrometry Hellebrand, Eric Snow, Jonathan E. Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
topic_facet |
Abyssal peridotite Melt-rock reaction Metasomatism Partial melting Secondary ion mass spectrometry |
description |
Abyssal peridotites collected along the highly oblique-spreading Lena Trough north of Greenland and Spitsbergen have mineral compositions that are similar to residual abyssal peridotites, except for high sodium concentrations in clinopyroxene (cpx). Most samples are lherzolites with light rare earth element (REE)-depleted cpx trace element patterns, but significantly fractionated middle to heavy REE ratios at relatively high heavy REE concentrations. Such characteristics can only be explained by initial melting of a garnet peridotite followed by low degrees of melting in the stability field of spinel peridotite. The residual garnet signature requires either a high potential temperature of the upwelling mantle, or elevated solidus-lowering water contents. The limited spinel field melting suggests a deep cessation of melt extraction, possibly because of the presence of a thick lithospheric cap. This is consistent with the extremely low effective spreading rate and the vicinity to a passive continental margin, which allow conductive cooling to reach deeper levels than commonly estimated for faster mid-ocean ridges. High sodium concentrations in cpx are neither explainable by melt refertilization, nor by a simple diffusion mechanism. The efficient fractionation of sodium from the light REE requires post-melting metasomatism, which is typically restricted to the subcontinental lithosphere. This might imply that the Lena Trough peridotites represent unroofed subcontinental mantle, from which no melt was extracted during the opening of the Lena Trough. It is more likely that sodic metasomatism occurred after partial melting underneath the Lena Trough, and that such an enrichment process is responsible for elevated sodium concentrations in abyssal peridotites elsewhere. Sodium in cpx of residual peridotites can therefore not serve as an indicator of partial melting or melt refertilization. © 2003 Elsevier B.V. All rights reserved. |
format |
Text |
author |
Hellebrand, Eric Snow, Jonathan E. |
author_facet |
Hellebrand, Eric Snow, Jonathan E. |
author_sort |
Hellebrand, Eric |
title |
Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
title_short |
Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
title_full |
Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
title_fullStr |
Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
title_full_unstemmed |
Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean) |
title_sort |
deep melting and sodic metasomatism underneath the highly oblique-spreading lena trough (arctic ocean) |
publisher |
LSU Digital Commons |
publishDate |
2003 |
url |
https://digitalcommons.lsu.edu/geo_pubs/1000 https://doi.org/10.1016/S0012-821X(03)00508-9 |
geographic |
Arctic Arctic Ocean Greenland |
geographic_facet |
Arctic Arctic Ocean Greenland |
genre |
Arctic Arctic Ocean Greenland Spitsbergen |
genre_facet |
Arctic Arctic Ocean Greenland Spitsbergen |
op_source |
Faculty Publications |
op_relation |
https://digitalcommons.lsu.edu/geo_pubs/1000 doi:10.1016/S0012-821X(03)00508-9 |
op_doi |
https://doi.org/10.1016/S0012-821X(03)00508-9 |
container_title |
Earth and Planetary Science Letters |
container_volume |
216 |
container_issue |
3 |
container_start_page |
283 |
op_container_end_page |
299 |
_version_ |
1768383814083543040 |