Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador
Sr and Nd isotopic data for middle to late Archean polymetamorphic felsic gneisses from localities in the Nuuk area, West Greenland, are compared and contrasted with new isotopic results for early Archean Amîtsoq gneisses and with data for isotopically reworked Kiyuktok gneisses from the Saglek area...
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1989
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crcansciencepubl:10.1139/e89-039 2023-12-17T10:30:56+01:00 Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador Collerson, Kenneth D. McCulloch, Malcolm T. Nutman, Allan P. 1989 http://dx.doi.org/10.1139/e89-039 http://www.nrcresearchpress.com/doi/pdf/10.1139/e89-039 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 26, issue 3, page 446-466 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1989 crcansciencepubl https://doi.org/10.1139/e89-039 2023-11-19T13:38:31Z Sr and Nd isotopic data for middle to late Archean polymetamorphic felsic gneisses from localities in the Nuuk area, West Greenland, are compared and contrasted with new isotopic results for early Archean Amîtsoq gneisses and with data for isotopically reworked Kiyuktok gneisses from the Saglek area, Labrador. Sr isotopic data for individual suites of felsic gneisses record the time-integrated effect of variable Rb–Sr fractionation during prograde and retrograde events as well as the effect of source inhomogeneity.Contrasting petrologic and Sr–Nd isotopic characteristics are the result of differences in level of exposure, caused partially by juxtaposition of terranes of different metamorphic character by movement on ductile shear zones and post-shearing folding deformation. Sm–Nd systematics of felsic gneisses from Nordafar, Ikerasakitsup akornga, Tinissaq, and Kangimut sammisoq – Qasigianguit define a geologically meaningless ca. 3280 Ma Nd "isochron", which is the result of mixing of samples from unrelated suites and the effect of open-system behaviour. Gneisses lying on this pseudoisochron were variably affected by ca. 2800–2900 Ma prograde granulite-facies metamorphism and structurally controlled retrogression under amphibolite- to greenschist-facies conditions.The study shows that Sr–Nd isotope systematics of geologically identifiable units may be modified by open-system behaviour during prograde and retrograde metamorphism. Isotopic data from gneiss complexes metamorphosed under granulite-facies conditions may therefore yield equivocal information concerning isochron interpretation, significance of model ages, and estimates of crustal residence time. Article in Journal/Newspaper Greenland Nuuk Canadian Science Publishing (via Crossref) Greenland Nuuk ENVELOPE(-52.150,-52.150,68.717,68.717) Amîtsoq ENVELOPE(-51.472,-51.472,64.080,64.080) Kangimut Sammisoq ENVELOPE(-51.833,-51.833,66.650,66.650) Sammisoq ENVELOPE(-43.934,-43.934,59.990,59.990) Akornga ENVELOPE(-53.800,-53.800,67.033,67.033) Ikerasakitsup Akornga ENVELOPE(-51.417,-51.417,63.533,63.533) Canadian Journal of Earth Sciences 26 3 446 466 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Collerson, Kenneth D. McCulloch, Malcolm T. Nutman, Allan P. Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
topic_facet |
General Earth and Planetary Sciences |
description |
Sr and Nd isotopic data for middle to late Archean polymetamorphic felsic gneisses from localities in the Nuuk area, West Greenland, are compared and contrasted with new isotopic results for early Archean Amîtsoq gneisses and with data for isotopically reworked Kiyuktok gneisses from the Saglek area, Labrador. Sr isotopic data for individual suites of felsic gneisses record the time-integrated effect of variable Rb–Sr fractionation during prograde and retrograde events as well as the effect of source inhomogeneity.Contrasting petrologic and Sr–Nd isotopic characteristics are the result of differences in level of exposure, caused partially by juxtaposition of terranes of different metamorphic character by movement on ductile shear zones and post-shearing folding deformation. Sm–Nd systematics of felsic gneisses from Nordafar, Ikerasakitsup akornga, Tinissaq, and Kangimut sammisoq – Qasigianguit define a geologically meaningless ca. 3280 Ma Nd "isochron", which is the result of mixing of samples from unrelated suites and the effect of open-system behaviour. Gneisses lying on this pseudoisochron were variably affected by ca. 2800–2900 Ma prograde granulite-facies metamorphism and structurally controlled retrogression under amphibolite- to greenschist-facies conditions.The study shows that Sr–Nd isotope systematics of geologically identifiable units may be modified by open-system behaviour during prograde and retrograde metamorphism. Isotopic data from gneiss complexes metamorphosed under granulite-facies conditions may therefore yield equivocal information concerning isochron interpretation, significance of model ages, and estimates of crustal residence time. |
format |
Article in Journal/Newspaper |
author |
Collerson, Kenneth D. McCulloch, Malcolm T. Nutman, Allan P. |
author_facet |
Collerson, Kenneth D. McCulloch, Malcolm T. Nutman, Allan P. |
author_sort |
Collerson, Kenneth D. |
title |
Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
title_short |
Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
title_full |
Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
title_fullStr |
Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
title_full_unstemmed |
Sr and Nd isotope systematics of polymetamorphic Archean gneisses from southern West Greenland and northern Labrador |
title_sort |
sr and nd isotope systematics of polymetamorphic archean gneisses from southern west greenland and northern labrador |
publisher |
Canadian Science Publishing |
publishDate |
1989 |
url |
http://dx.doi.org/10.1139/e89-039 http://www.nrcresearchpress.com/doi/pdf/10.1139/e89-039 |
long_lat |
ENVELOPE(-52.150,-52.150,68.717,68.717) ENVELOPE(-51.472,-51.472,64.080,64.080) ENVELOPE(-51.833,-51.833,66.650,66.650) ENVELOPE(-43.934,-43.934,59.990,59.990) ENVELOPE(-53.800,-53.800,67.033,67.033) ENVELOPE(-51.417,-51.417,63.533,63.533) |
geographic |
Greenland Nuuk Amîtsoq Kangimut Sammisoq Sammisoq Akornga Ikerasakitsup Akornga |
geographic_facet |
Greenland Nuuk Amîtsoq Kangimut Sammisoq Sammisoq Akornga Ikerasakitsup Akornga |
genre |
Greenland Nuuk |
genre_facet |
Greenland Nuuk |
op_source |
Canadian Journal of Earth Sciences volume 26, issue 3, page 446-466 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e89-039 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
26 |
container_issue |
3 |
container_start_page |
446 |
op_container_end_page |
466 |
_version_ |
1785584047276163072 |