Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica
Geochronological data, combined with field and petrological evidence, constrain the timing and rate of near‐isothermal decompression at granulite facies temperatures in rocks from the Lützow‐Holm Complex of East Antarctica. Granulite facies gneisses from Rundvågshetta in Lützow‐Holm Bay experienced...
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crwiley:10.1046/j.1525-1314.2000.00270.x 2024-06-23T07:47:37+00:00 Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica Fraser, G. McDougall, I. Ellis, D. J. Williams, I. S. 2000 http://dx.doi.org/10.1046/j.1525-1314.2000.00270.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1525-1314.2000.00270.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1525-1314.2000.00270.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 18, issue 4, page 441-454 ISSN 0263-4929 1525-1314 journal-article 2000 crwiley https://doi.org/10.1046/j.1525-1314.2000.00270.x 2024-05-31T08:14:41Z Geochronological data, combined with field and petrological evidence, constrain the timing and rate of near‐isothermal decompression at granulite facies temperatures in rocks from the Lützow‐Holm Complex of East Antarctica. Granulite facies gneisses from Rundvågshetta in Lützow‐Holm Bay experienced a peak metamorphic temperature of over 900 °C at c . 11 kbar, as evidenced by primary orthopyroxene–sillimanite‐bearing assemblages, and secondary cordierite–sapphirine‐bearing assemblages in metapelites. Peak metamorphic assemblages show strong preferred mineral orientation, interpreted to have developed synchronously with pervasive ductile deformation. Zircon from a syndeformational leucosome has a U–Pb age of 517±9 Ma, which is interpreted as a melt crystallization age. This age provides the best estimate of the time of peak metamorphic conditions. The post‐peak metamorphic history is characterized by near‐isothermal decompression, recorded by mineral textures in a variety of rock compositions. Field and textural relations indicate that decompression post‐dated pervasive ductile deformation. K/Ar and 40 Ar/ 39 Ar ages from hornblende and biotite represent closure ages during cooling subsequent to decompression, and indicate cooling to temperatures between c . 350 and 300 °C by c . 500 Ma, thus placing a lower time limit on the duration of the high‐temperature isothermal decompression episode. The combination of the zircon age from a syndeformational melt with K/Ar and 40 Ar/ 39 Ar closure ages indicates that near‐isothermal decompression from c . 11 to c . 4 kbar at granulite facies temperatures, followed by cooling to c . 300 °C, took place within a time interval of 20±10 Myr. Simple one‐dimensional models for exhumation‐controlled cooling indicate that these data require exhumation rates of the order of c . 3 km Myr −1 for several million years, then cessation of exhumation followed by relatively isobaric cooling during thermal re‐equilibration. Article in Journal/Newspaper Antarc* Antarctica East Antarctica Wiley Online Library East Antarctica Lützow-Holm Bay ENVELOPE(38.000,38.000,-69.500,-69.500) Journal of Metamorphic Geology 18 4 441 454 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Geochronological data, combined with field and petrological evidence, constrain the timing and rate of near‐isothermal decompression at granulite facies temperatures in rocks from the Lützow‐Holm Complex of East Antarctica. Granulite facies gneisses from Rundvågshetta in Lützow‐Holm Bay experienced a peak metamorphic temperature of over 900 °C at c . 11 kbar, as evidenced by primary orthopyroxene–sillimanite‐bearing assemblages, and secondary cordierite–sapphirine‐bearing assemblages in metapelites. Peak metamorphic assemblages show strong preferred mineral orientation, interpreted to have developed synchronously with pervasive ductile deformation. Zircon from a syndeformational leucosome has a U–Pb age of 517±9 Ma, which is interpreted as a melt crystallization age. This age provides the best estimate of the time of peak metamorphic conditions. The post‐peak metamorphic history is characterized by near‐isothermal decompression, recorded by mineral textures in a variety of rock compositions. Field and textural relations indicate that decompression post‐dated pervasive ductile deformation. K/Ar and 40 Ar/ 39 Ar ages from hornblende and biotite represent closure ages during cooling subsequent to decompression, and indicate cooling to temperatures between c . 350 and 300 °C by c . 500 Ma, thus placing a lower time limit on the duration of the high‐temperature isothermal decompression episode. The combination of the zircon age from a syndeformational melt with K/Ar and 40 Ar/ 39 Ar closure ages indicates that near‐isothermal decompression from c . 11 to c . 4 kbar at granulite facies temperatures, followed by cooling to c . 300 °C, took place within a time interval of 20±10 Myr. Simple one‐dimensional models for exhumation‐controlled cooling indicate that these data require exhumation rates of the order of c . 3 km Myr −1 for several million years, then cessation of exhumation followed by relatively isobaric cooling during thermal re‐equilibration. |
format |
Article in Journal/Newspaper |
author |
Fraser, G. McDougall, I. Ellis, D. J. Williams, I. S. |
spellingShingle |
Fraser, G. McDougall, I. Ellis, D. J. Williams, I. S. Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
author_facet |
Fraser, G. McDougall, I. Ellis, D. J. Williams, I. S. |
author_sort |
Fraser, G. |
title |
Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
title_short |
Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
title_full |
Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
title_fullStr |
Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
title_full_unstemmed |
Timing and rate of isothermal decompression in Pan‐African granulites from Rundvågshetta, East Antarctica |
title_sort |
timing and rate of isothermal decompression in pan‐african granulites from rundvågshetta, east antarctica |
publisher |
Wiley |
publishDate |
2000 |
url |
http://dx.doi.org/10.1046/j.1525-1314.2000.00270.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1525-1314.2000.00270.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1525-1314.2000.00270.x |
long_lat |
ENVELOPE(38.000,38.000,-69.500,-69.500) |
geographic |
East Antarctica Lützow-Holm Bay |
geographic_facet |
East Antarctica Lützow-Holm Bay |
genre |
Antarc* Antarctica East Antarctica |
genre_facet |
Antarc* Antarctica East Antarctica |
op_source |
Journal of Metamorphic Geology volume 18, issue 4, page 441-454 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1046/j.1525-1314.2000.00270.x |
container_title |
Journal of Metamorphic Geology |
container_volume |
18 |
container_issue |
4 |
container_start_page |
441 |
op_container_end_page |
454 |
_version_ |
1802651756198363136 |