Metamorphic evolution of the Great Slave Lake shear zone
Abstract The Palaeoproterozoic Great Slave Lake shear zone (GSLsz) is a crustal‐scale strike‐slip structure, with a total length of >1,000 km and a width of ~25 km, that separates the Archean Rae and Slave cratons. The range of metamorphic rocks now exposed at the surface encompasses granulite fa...
Published in: | Journal of Metamorphic Geology |
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crwiley:10.1111/jmg.12576 2024-09-15T18:08:13+00:00 Metamorphic evolution of the Great Slave Lake shear zone Dyck, Brendan Goddard, Rellie M. Wallis, David Hansen, Lars N. Martel, Edith Natural Environment Research Council Natural Sciences and Engineering Research Council of Canada 2021 http://dx.doi.org/10.1111/jmg.12576 https://onlinelibrary.wiley.com/doi/pdf/10.1111/jmg.12576 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jmg.12576 en eng Wiley http://creativecommons.org/licenses/by/4.0/ Journal of Metamorphic Geology volume 39, issue 5, page 567-590 ISSN 0263-4929 1525-1314 journal-article 2021 crwiley https://doi.org/10.1111/jmg.12576 2024-08-13T04:17:15Z Abstract The Palaeoproterozoic Great Slave Lake shear zone (GSLsz) is a crustal‐scale strike‐slip structure, with a total length of >1,000 km and a width of ~25 km, that separates the Archean Rae and Slave cratons. The range of metamorphic rocks now exposed at the surface encompasses granulite facies mylonite through to lower‐greenschist facies ultramylonite and cataclasite, providing a potential type example of fault‐zone structure in the middle and lower crust. However, the metamorphic evolution of the units remains poorly quantified, hindering detailed structural and tectonic interpretations. Here, we use phase equilibria modelling and thermobarometry to determine the metamorphic conditions recorded by pelitic, mafic and felsic GSLsz mylonites. Samples from the entire range of granulite–greenschist facies units preserve evidence for nested clockwise pressure–temperature paths that are consistent with a single orogenic cycle. Our findings indicate that the northern Rae margin underwent pervasive crustal thickening with peak pressures in metasedimentary rocks reaching ~1.1 GPa. The crustal thermal gradient at the onset of thickening was ~650°C/GPa, whereas the final stages of equilibrium recorded by fine‐grained matrix minerals in all samples collectively define a metamorphic field gradient of ~1,000°C/GPa. Deformation microstructures are consistent with the main phase of dextral shear having been synchronous with or following peak metamorphism. The history of metamorphism and exhumation of the GSLsz is consistent with the Sibson–Scholz model for shear zones, with a narrowing of the deforming zone and the progressive overprinting of higher‐grade assemblages during exhumation through shallower crustal levels. Article in Journal/Newspaper Great Slave Lake Wiley Online Library Journal of Metamorphic Geology 39 5 567 590 |
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Wiley Online Library |
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crwiley |
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English |
description |
Abstract The Palaeoproterozoic Great Slave Lake shear zone (GSLsz) is a crustal‐scale strike‐slip structure, with a total length of >1,000 km and a width of ~25 km, that separates the Archean Rae and Slave cratons. The range of metamorphic rocks now exposed at the surface encompasses granulite facies mylonite through to lower‐greenschist facies ultramylonite and cataclasite, providing a potential type example of fault‐zone structure in the middle and lower crust. However, the metamorphic evolution of the units remains poorly quantified, hindering detailed structural and tectonic interpretations. Here, we use phase equilibria modelling and thermobarometry to determine the metamorphic conditions recorded by pelitic, mafic and felsic GSLsz mylonites. Samples from the entire range of granulite–greenschist facies units preserve evidence for nested clockwise pressure–temperature paths that are consistent with a single orogenic cycle. Our findings indicate that the northern Rae margin underwent pervasive crustal thickening with peak pressures in metasedimentary rocks reaching ~1.1 GPa. The crustal thermal gradient at the onset of thickening was ~650°C/GPa, whereas the final stages of equilibrium recorded by fine‐grained matrix minerals in all samples collectively define a metamorphic field gradient of ~1,000°C/GPa. Deformation microstructures are consistent with the main phase of dextral shear having been synchronous with or following peak metamorphism. The history of metamorphism and exhumation of the GSLsz is consistent with the Sibson–Scholz model for shear zones, with a narrowing of the deforming zone and the progressive overprinting of higher‐grade assemblages during exhumation through shallower crustal levels. |
author2 |
Natural Environment Research Council Natural Sciences and Engineering Research Council of Canada |
format |
Article in Journal/Newspaper |
author |
Dyck, Brendan Goddard, Rellie M. Wallis, David Hansen, Lars N. Martel, Edith |
spellingShingle |
Dyck, Brendan Goddard, Rellie M. Wallis, David Hansen, Lars N. Martel, Edith Metamorphic evolution of the Great Slave Lake shear zone |
author_facet |
Dyck, Brendan Goddard, Rellie M. Wallis, David Hansen, Lars N. Martel, Edith |
author_sort |
Dyck, Brendan |
title |
Metamorphic evolution of the Great Slave Lake shear zone |
title_short |
Metamorphic evolution of the Great Slave Lake shear zone |
title_full |
Metamorphic evolution of the Great Slave Lake shear zone |
title_fullStr |
Metamorphic evolution of the Great Slave Lake shear zone |
title_full_unstemmed |
Metamorphic evolution of the Great Slave Lake shear zone |
title_sort |
metamorphic evolution of the great slave lake shear zone |
publisher |
Wiley |
publishDate |
2021 |
url |
http://dx.doi.org/10.1111/jmg.12576 https://onlinelibrary.wiley.com/doi/pdf/10.1111/jmg.12576 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jmg.12576 |
genre |
Great Slave Lake |
genre_facet |
Great Slave Lake |
op_source |
Journal of Metamorphic Geology volume 39, issue 5, page 567-590 ISSN 0263-4929 1525-1314 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1111/jmg.12576 |
container_title |
Journal of Metamorphic Geology |
container_volume |
39 |
container_issue |
5 |
container_start_page |
567 |
op_container_end_page |
590 |
_version_ |
1810445562034520064 |