Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta
At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the uppe...
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1985
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crcansciencepubl:10.1139/e85-104 2023-12-17T10:49:59+01:00 Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta Burwash, R. A. Krupicka, J. Basu, A. R. Wagner, P. A. 1985 http://dx.doi.org/10.1139/e85-104 http://www.nrcresearchpress.com/doi/pdf/10.1139/e85-104 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 22, issue 7, page 992-1000 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1985 crcansciencepubl https://doi.org/10.1139/e85-104 2023-11-19T13:39:09Z At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the upper amphibolite facies. The banding of the mafic granulites is truncated by sharply defined boundaries with the felsic granulites. The felsic granulites contain K-feldspar, the mafic rocks almost none. The mineral assemblages are otherwise identical: plagioclase–hypersthene–quartz–biotite–magnetite.A whole-rock Sm–Nd isochron of one felsic and six mafic granulites gives 2436 ± 44 Ma [Formula: see text]. This time is significantly younger than the Sm–Nd model ages. The same mafic samples give a Rb–Sr age of 1898 ± 5 Ma. These are interpreted as the times of reequilibration and closure of the Rb–Sr isotopic systems within the Mountain Rapids Granulite enclave. From cordierite–garnet barometry the indicated pressure of the younger event is 5.5 ± 0.7 kbar (550 ± 70 MPa). By analogy with hornblende granulite assemblages elsewhere, the older event probably occurred in the intermediate crust (~25–30 km depth). This event apparently effectively reset the Sm–Nd isotopic system; subsequent cooling closed it. Once established this system withstood the later, lower pressure event that reset the Rb–Sr geochronometer on a regional scale. Article in Journal/Newspaper Slave River Canadian Science Publishing (via Crossref) Canadian Journal of Earth Sciences 22 7 992 1000 |
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Open Polar |
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Canadian Science Publishing (via Crossref) |
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crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Burwash, R. A. Krupicka, J. Basu, A. R. Wagner, P. A. Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
topic_facet |
General Earth and Planetary Sciences |
description |
At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the upper amphibolite facies. The banding of the mafic granulites is truncated by sharply defined boundaries with the felsic granulites. The felsic granulites contain K-feldspar, the mafic rocks almost none. The mineral assemblages are otherwise identical: plagioclase–hypersthene–quartz–biotite–magnetite.A whole-rock Sm–Nd isochron of one felsic and six mafic granulites gives 2436 ± 44 Ma [Formula: see text]. This time is significantly younger than the Sm–Nd model ages. The same mafic samples give a Rb–Sr age of 1898 ± 5 Ma. These are interpreted as the times of reequilibration and closure of the Rb–Sr isotopic systems within the Mountain Rapids Granulite enclave. From cordierite–garnet barometry the indicated pressure of the younger event is 5.5 ± 0.7 kbar (550 ± 70 MPa). By analogy with hornblende granulite assemblages elsewhere, the older event probably occurred in the intermediate crust (~25–30 km depth). This event apparently effectively reset the Sm–Nd isotopic system; subsequent cooling closed it. Once established this system withstood the later, lower pressure event that reset the Rb–Sr geochronometer on a regional scale. |
format |
Article in Journal/Newspaper |
author |
Burwash, R. A. Krupicka, J. Basu, A. R. Wagner, P. A. |
author_facet |
Burwash, R. A. Krupicka, J. Basu, A. R. Wagner, P. A. |
author_sort |
Burwash, R. A. |
title |
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
title_short |
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
title_full |
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
title_fullStr |
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
title_full_unstemmed |
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta |
title_sort |
resetting of nd and sr whole-rock isochrons from polymetamorphic granulites, northeastern alberta |
publisher |
Canadian Science Publishing |
publishDate |
1985 |
url |
http://dx.doi.org/10.1139/e85-104 http://www.nrcresearchpress.com/doi/pdf/10.1139/e85-104 |
genre |
Slave River |
genre_facet |
Slave River |
op_source |
Canadian Journal of Earth Sciences volume 22, issue 7, page 992-1000 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e85-104 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
22 |
container_issue |
7 |
container_start_page |
992 |
op_container_end_page |
1000 |
_version_ |
1785574632813756416 |