Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland
Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field fa...
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Language: | English |
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2010
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Online Access: | https://curis.ku.dk/portal/da/publications/pb-isotopes-during-mingling-and-melting(92bbff10-2118-11df-8ed1-000ea68e967b).html https://doi.org/10.1016/j.lithos.2010.04.012 |
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ftcopenhagenunip:oai:pure.atira.dk:publications/92bbff10-2118-11df-8ed1-000ea68e967b 2023-05-15T16:03:41+02:00 Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland Waight, Tod Earle Lesher, Charles E. 2010 https://curis.ku.dk/portal/da/publications/pb-isotopes-during-mingling-and-melting(92bbff10-2118-11df-8ed1-000ea68e967b).html https://doi.org/10.1016/j.lithos.2010.04.012 eng eng info:eu-repo/semantics/restrictedAccess Waight , T E & Lesher , C E 2010 , ' Pb isotopes during mingling and melting : a precautionary tale from the Miki Fjord macrodike, East Greenland ' , Lithos , vol. 118 , pp. 191-201 . https://doi.org/10.1016/j.lithos.2010.04.012 article 2010 ftcopenhagenunip https://doi.org/10.1016/j.lithos.2010.04.012 2022-02-24T00:03:45Z Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can explain the complex Sr and Nd isotope compositions of the hybrid rocks (Blichert-Toft et al., 1992), cannot fully account for the variability of the Pb isotopic data using the identified crustal end-members. The crustal anatectic end-member, although similar in Sr and Nd isotope composition, has a markedly different Pb isotopic composition than its source gneiss. The differences are consistent with preferential incorporation of radiogenic Pb from accessory phases such as metamict zircon or loosely-bound Pb from grain boundaries during disequilibrium melting of the host rock by the mafic magma. The crustal melt involved in magma interactions was therefore heterogeneous with respect to Pb isotopes on a metre-scale. These results illustrate the difficulties inherent in interpreting isotopic variations in contaminated mafic magmas even when the end-members are well constrained by field relations. We show that the Pb isotopic composition of the crustal contaminants and contamination trajectories for the Miki Fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated lavas of the associated flood basalt province that were contaminated by characteristically unradiogenic Pb and Sr lithologies resembling Lewisian basement not exposed locally. Article in Journal/Newspaper East Greenland Greenland University of Copenhagen: Research Greenland Miki Fjord ENVELOPE(-31.499,-31.499,68.149,68.149) Lithos 118 1-2 191 201 |
institution |
Open Polar |
collection |
University of Copenhagen: Research |
op_collection_id |
ftcopenhagenunip |
language |
English |
description |
Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can explain the complex Sr and Nd isotope compositions of the hybrid rocks (Blichert-Toft et al., 1992), cannot fully account for the variability of the Pb isotopic data using the identified crustal end-members. The crustal anatectic end-member, although similar in Sr and Nd isotope composition, has a markedly different Pb isotopic composition than its source gneiss. The differences are consistent with preferential incorporation of radiogenic Pb from accessory phases such as metamict zircon or loosely-bound Pb from grain boundaries during disequilibrium melting of the host rock by the mafic magma. The crustal melt involved in magma interactions was therefore heterogeneous with respect to Pb isotopes on a metre-scale. These results illustrate the difficulties inherent in interpreting isotopic variations in contaminated mafic magmas even when the end-members are well constrained by field relations. We show that the Pb isotopic composition of the crustal contaminants and contamination trajectories for the Miki Fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated lavas of the associated flood basalt province that were contaminated by characteristically unradiogenic Pb and Sr lithologies resembling Lewisian basement not exposed locally. |
format |
Article in Journal/Newspaper |
author |
Waight, Tod Earle Lesher, Charles E. |
spellingShingle |
Waight, Tod Earle Lesher, Charles E. Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
author_facet |
Waight, Tod Earle Lesher, Charles E. |
author_sort |
Waight, Tod Earle |
title |
Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
title_short |
Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
title_full |
Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
title_fullStr |
Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
title_full_unstemmed |
Pb isotopes during mingling and melting:a precautionary tale from the Miki Fjord macrodike, East Greenland |
title_sort |
pb isotopes during mingling and melting:a precautionary tale from the miki fjord macrodike, east greenland |
publishDate |
2010 |
url |
https://curis.ku.dk/portal/da/publications/pb-isotopes-during-mingling-and-melting(92bbff10-2118-11df-8ed1-000ea68e967b).html https://doi.org/10.1016/j.lithos.2010.04.012 |
long_lat |
ENVELOPE(-31.499,-31.499,68.149,68.149) |
geographic |
Greenland Miki Fjord |
geographic_facet |
Greenland Miki Fjord |
genre |
East Greenland Greenland |
genre_facet |
East Greenland Greenland |
op_source |
Waight , T E & Lesher , C E 2010 , ' Pb isotopes during mingling and melting : a precautionary tale from the Miki Fjord macrodike, East Greenland ' , Lithos , vol. 118 , pp. 191-201 . https://doi.org/10.1016/j.lithos.2010.04.012 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.lithos.2010.04.012 |
container_title |
Lithos |
container_volume |
118 |
container_issue |
1-2 |
container_start_page |
191 |
op_container_end_page |
201 |
_version_ |
1766399381871788032 |