Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex
Magnesian metapelites of probable Archaean age from Forefinger Point, SW Enderby Land, East Antarctica, contain very‐high‐temperature granulite facies mineral assemblages, which include orthopyroxene (8–9.5 wt% Al 2 O 3 )–sillimanite ± garnet ± quartz ± K‐feldspar, that formed at 10 ± 1.5 kbar and 9...
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crwiley:10.1111/j.1525-1314.1990.tb00490.x 2024-09-15T17:45:49+00:00 Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex HARLEY, S. L. HENSEN, B. J. SHERATON, J. W. 1990 http://dx.doi.org/10.1111/j.1525-1314.1990.tb00490.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1990.tb00490.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1990.tb00490.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 8, issue 6, page 591-613 ISSN 0263-4929 1525-1314 journal-article 1990 crwiley https://doi.org/10.1111/j.1525-1314.1990.tb00490.x 2024-07-25T04:23:10Z Magnesian metapelites of probable Archaean age from Forefinger Point, SW Enderby Land, East Antarctica, contain very‐high‐temperature granulite facies mineral assemblages, which include orthopyroxene (8–9.5 wt% Al 2 O 3 )–sillimanite ± garnet ± quartz ± K‐feldspar, that formed at 10 ± 1.5 kbar and 950 ± 50°C. These assemblages are overprinted by symplectite and corona reaction textures involving sapphirine, orthopyroxene (6–7 wt% Al 2 O 3 ), cordierite and sometimes spinel at the expense of porphyroblastic garnet or earlier orthopyroxene–sillimanite. These textures mainly pre‐date the development of coarse biotite at the expense of initial mesoperthite, and the subsequent formation of orthopyroxene (4–6 wt% Al 2 O 3 )–cordierite–plagioclase rinds on late biotite. The early reaction textures indicate a period of near‐isothermal decompression at temperatures above 900°C. Decompression from 10 ± 1.5 kbar to 7–8 kbar was succeeded by biotite formation at significantly lower temperatures (800–850°C) and further decompression to 4.5 ± 1 kbar at 700–800°C. The later parts of this P–T evolution can be ascribed to the overprinting and reworking of the Forefinger Point granulites by the Late‐Proterozoic ( c . 1000 Ma) Rayner Complex metamorphism, but the age and timing of the early high‐temperature decompression is not known. It is speculated that this initial decompression is of Archaean age and therefore records thinning of the crust of the Napier Complex following crustal thickening by tectonic or magmatic mechanisms and preceding the generally wellpreserved post‐deformational near‐isobaric cooling history of this terrain. Article in Journal/Newspaper Antarc* Antarctica East Antarctica Enderby Land Wiley Online Library Journal of Metamorphic Geology 8 6 591 613 |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Magnesian metapelites of probable Archaean age from Forefinger Point, SW Enderby Land, East Antarctica, contain very‐high‐temperature granulite facies mineral assemblages, which include orthopyroxene (8–9.5 wt% Al 2 O 3 )–sillimanite ± garnet ± quartz ± K‐feldspar, that formed at 10 ± 1.5 kbar and 950 ± 50°C. These assemblages are overprinted by symplectite and corona reaction textures involving sapphirine, orthopyroxene (6–7 wt% Al 2 O 3 ), cordierite and sometimes spinel at the expense of porphyroblastic garnet or earlier orthopyroxene–sillimanite. These textures mainly pre‐date the development of coarse biotite at the expense of initial mesoperthite, and the subsequent formation of orthopyroxene (4–6 wt% Al 2 O 3 )–cordierite–plagioclase rinds on late biotite. The early reaction textures indicate a period of near‐isothermal decompression at temperatures above 900°C. Decompression from 10 ± 1.5 kbar to 7–8 kbar was succeeded by biotite formation at significantly lower temperatures (800–850°C) and further decompression to 4.5 ± 1 kbar at 700–800°C. The later parts of this P–T evolution can be ascribed to the overprinting and reworking of the Forefinger Point granulites by the Late‐Proterozoic ( c . 1000 Ma) Rayner Complex metamorphism, but the age and timing of the early high‐temperature decompression is not known. It is speculated that this initial decompression is of Archaean age and therefore records thinning of the crust of the Napier Complex following crustal thickening by tectonic or magmatic mechanisms and preceding the generally wellpreserved post‐deformational near‐isobaric cooling history of this terrain. |
format |
Article in Journal/Newspaper |
author |
HARLEY, S. L. HENSEN, B. J. SHERATON, J. W. |
spellingShingle |
HARLEY, S. L. HENSEN, B. J. SHERATON, J. W. Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
author_facet |
HARLEY, S. L. HENSEN, B. J. SHERATON, J. W. |
author_sort |
HARLEY, S. L. |
title |
Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
title_short |
Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
title_full |
Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
title_fullStr |
Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
title_full_unstemmed |
Two‐stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex |
title_sort |
two‐stage decompression in orthopyroxene–sillimanite granulites from forefinger point, enderby land, antarctica: implications for the evolution of the archaean napier complex |
publisher |
Wiley |
publishDate |
1990 |
url |
http://dx.doi.org/10.1111/j.1525-1314.1990.tb00490.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1990.tb00490.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1990.tb00490.x |
genre |
Antarc* Antarctica East Antarctica Enderby Land |
genre_facet |
Antarc* Antarctica East Antarctica Enderby Land |
op_source |
Journal of Metamorphic Geology volume 8, issue 6, page 591-613 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1525-1314.1990.tb00490.x |
container_title |
Journal of Metamorphic Geology |
container_volume |
8 |
container_issue |
6 |
container_start_page |
591 |
op_container_end_page |
613 |
_version_ |
1810493735741423616 |