Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica
Abstract In the Shackleton Range of East Antarctica, garnet‐bearing ultramafic rocks occur as lenses in supracrustal high‐grade gneisses. In the presence of olivine, garnet is an unmistakable indicator of eclogite facies metamorphic conditions. The eclogite facies assemblages are only present in ult...
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crwiley:10.1111/j.1525-1314.2009.00820.x 2024-06-09T07:40:44+00:00 Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica ROMER, T. MEZGER, K. SCHMÄDICKE, E. 2009 http://dx.doi.org/10.1111/j.1525-1314.2009.00820.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.2009.00820.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2009.00820.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 27, issue 5, page 335-347 ISSN 0263-4929 1525-1314 journal-article 2009 crwiley https://doi.org/10.1111/j.1525-1314.2009.00820.x 2024-05-16T14:26:18Z Abstract In the Shackleton Range of East Antarctica, garnet‐bearing ultramafic rocks occur as lenses in supracrustal high‐grade gneisses. In the presence of olivine, garnet is an unmistakable indicator of eclogite facies metamorphic conditions. The eclogite facies assemblages are only present in ultramafic rocks, particularly in pyroxenites, whereas other lithologies – including metabasites – lack such assemblages. We conclude that under high‐temperature conditions, pyroxenites preserve high‐pressure assemblages better than isofacial metabasites, provided the pressure is high enough to stabilize garnet–olivine assemblages (i.e. ≥18–20 kbar). The Shackleton Range ultramafic rocks experienced a clockwise P–T path and peak conditions of 800–850 °C and 23–25 kbar. These conditions correspond to ∼70 km depth of burial and a metamorphic gradient of 11–12 °C km −1 that is typical of a convergent plate‐margin setting. The age of metamorphism is defined by two garnet–whole‐rock Sm–Nd isochrons that give ages of 525 ± 5 and 520 ± 14 Ma corresponding to the time of the Pan‐African orogeny. These results are evidence of a Pan‐African suture zone within the northern Shackleton Range. This suture marks the site of a palaeo‐subduction zone that likely continues to the Herbert Mountains, where ophiolitic rocks of Neoproterozoic age testify to an ocean basin that was closed during Pan‐African collision. The garnet‐bearing ultramafic rocks in the Shackleton Range are the first known example of eclogite facies metamorphism in Antarctica that is related to the collision of East and West Gondwana and the first example of Pan‐African eclogite facies ultramafic rocks worldwide. Eclogites in the Lanterman Range of the Transantarctic Mountains formed during subduction of the palaeo‐Pacific beneath the East Antarctic craton. Article in Journal/Newspaper Antarc* Antarctic Antarctica East Antarctica Wiley Online Library Antarctic East Antarctica Herbert Mountains ENVELOPE(-25.500,-25.500,-80.333,-80.333) Lanterman Range ENVELOPE(163.167,163.167,-71.667,-71.667) Pacific Shackleton Shackleton Range ENVELOPE(-26.000,-26.000,-80.833,-80.833) Transantarctic Mountains Journal of Metamorphic Geology 27 5 335 347 |
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Open Polar |
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Wiley Online Library |
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crwiley |
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English |
description |
Abstract In the Shackleton Range of East Antarctica, garnet‐bearing ultramafic rocks occur as lenses in supracrustal high‐grade gneisses. In the presence of olivine, garnet is an unmistakable indicator of eclogite facies metamorphic conditions. The eclogite facies assemblages are only present in ultramafic rocks, particularly in pyroxenites, whereas other lithologies – including metabasites – lack such assemblages. We conclude that under high‐temperature conditions, pyroxenites preserve high‐pressure assemblages better than isofacial metabasites, provided the pressure is high enough to stabilize garnet–olivine assemblages (i.e. ≥18–20 kbar). The Shackleton Range ultramafic rocks experienced a clockwise P–T path and peak conditions of 800–850 °C and 23–25 kbar. These conditions correspond to ∼70 km depth of burial and a metamorphic gradient of 11–12 °C km −1 that is typical of a convergent plate‐margin setting. The age of metamorphism is defined by two garnet–whole‐rock Sm–Nd isochrons that give ages of 525 ± 5 and 520 ± 14 Ma corresponding to the time of the Pan‐African orogeny. These results are evidence of a Pan‐African suture zone within the northern Shackleton Range. This suture marks the site of a palaeo‐subduction zone that likely continues to the Herbert Mountains, where ophiolitic rocks of Neoproterozoic age testify to an ocean basin that was closed during Pan‐African collision. The garnet‐bearing ultramafic rocks in the Shackleton Range are the first known example of eclogite facies metamorphism in Antarctica that is related to the collision of East and West Gondwana and the first example of Pan‐African eclogite facies ultramafic rocks worldwide. Eclogites in the Lanterman Range of the Transantarctic Mountains formed during subduction of the palaeo‐Pacific beneath the East Antarctic craton. |
format |
Article in Journal/Newspaper |
author |
ROMER, T. MEZGER, K. SCHMÄDICKE, E. |
spellingShingle |
ROMER, T. MEZGER, K. SCHMÄDICKE, E. Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
author_facet |
ROMER, T. MEZGER, K. SCHMÄDICKE, E. |
author_sort |
ROMER, T. |
title |
Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
title_short |
Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
title_full |
Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
title_fullStr |
Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
title_full_unstemmed |
Pan‐African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica |
title_sort |
pan‐african eclogite facies metamorphism of ultramafic rocks in the shackleton range, antarctica |
publisher |
Wiley |
publishDate |
2009 |
url |
http://dx.doi.org/10.1111/j.1525-1314.2009.00820.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.2009.00820.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2009.00820.x |
long_lat |
ENVELOPE(-25.500,-25.500,-80.333,-80.333) ENVELOPE(163.167,163.167,-71.667,-71.667) ENVELOPE(-26.000,-26.000,-80.833,-80.833) |
geographic |
Antarctic East Antarctica Herbert Mountains Lanterman Range Pacific Shackleton Shackleton Range Transantarctic Mountains |
geographic_facet |
Antarctic East Antarctica Herbert Mountains Lanterman Range Pacific Shackleton Shackleton Range Transantarctic Mountains |
genre |
Antarc* Antarctic Antarctica East Antarctica |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica |
op_source |
Journal of Metamorphic Geology volume 27, issue 5, page 335-347 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1525-1314.2009.00820.x |
container_title |
Journal of Metamorphic Geology |
container_volume |
27 |
container_issue |
5 |
container_start_page |
335 |
op_container_end_page |
347 |
_version_ |
1801369136747511808 |