Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front
Xenoliths in basanite from Foster Crater in the foothills of the Transantarctic Mountains have been used to construct a model of the subcontinental lithosphere and lithospheric processes in this segment of Antarctica. The mafic and ultramafic xenoliths define two mineralogically, texturally and chem...
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Oxford University Press
1988
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fthighwire:oai:open-archive.highwire.org:petrology:Special_Volume/1/109 2023-05-15T14:02:49+02:00 Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front Gamble, J. A. McGibbon, F. Kyle, P. R. Menzies, M. A. Kirsch, I. 1988-01-01 00:00:00.0 text/html http://petrology.oxfordjournals.org/cgi/content/short/Special_Volume/1/109 https://doi.org/10.1093/petrology/Special_Volume.1.109 en eng Oxford University Press http://petrology.oxfordjournals.org/cgi/content/short/Special_Volume/1/109 http://dx.doi.org/10.1093/petrology/Special_Volume.1.109 Copyright (C) 1988, Oxford University Press Continental Lithosphere: Where does the Crust End and the Mantle Begin? TEXT 1988 fthighwire https://doi.org/10.1093/petrology/Special_Volume.1.109 2013-05-27T18:49:08Z Xenoliths in basanite from Foster Crater in the foothills of the Transantarctic Mountains have been used to construct a model of the subcontinental lithosphere and lithospheric processes in this segment of Antarctica. The mafic and ultramafic xenoliths define two mineralogically, texturally and chemically distinct populations. One group is identical to Group II xenoliths, as defined by Frey & Prinz (1978). These have igneous cumulate textures and include wehrlites, rare websterites, dunite and amphibolite. In these xenoliths, the amphibole is always kaersutite and the (very rare) mica a Ti-rich phlogopite (TiO 2 > 5%). The other xenoliths have complex metamorphic textures ranging from protogranular to porphyroclastic and are dominated by clinopyroxenites (cpx: Mg/(Mg + Fe) = 0·85–0·95; Ca/(Ca + Mg)>0·53) which show varying degrees of replacement by metasomatic phlogopite. Spinel and anorthite are also present. Collectively, these xenoliths are called the High Calcium Pyroxene Suite (HCPS) in deference to their unusual pyroxene compositions. Moreover, their spinel assemblages indicate equilibrium under variable f O2 conditions contrasting with the Group II spinels which equilibrated at relatively constant f O2 . The mineralogy and chemistry of the HCPS xenoliths are unlike meta-igneous rocks and more closely resemble calc-silicate granulites. Thermobarometric calculations on Group II websterite assemblages and comparison with experimental equilibria on granulites and phlogopite stability suggest equilibration temperatures between 850 and 950° at 5 kb pressure, consistent with equilibration at mid to lower crustal depths. A number of processes have acted to modify Group II and HCPS xenoliths including K-metasomatism, dynamic recrystallization, melt generation, melt infiltration and oxidation. The first two are restricted to the HCPS xenoliths whereas the latter affect both groups. The interaction of these processes highlights the differences between Group II and HCPS protolith assemblages and is ... Text Antarc* Antarctica HighWire Press (Stanford University) Transantarctic Mountains Foster Crater ENVELOPE(162.967,162.967,-78.400,-78.400) Journal of Petrology Special_Volume 1 109 138 |
institution |
Open Polar |
collection |
HighWire Press (Stanford University) |
op_collection_id |
fthighwire |
language |
English |
topic |
Continental Lithosphere: Where does the Crust End and the Mantle Begin? |
spellingShingle |
Continental Lithosphere: Where does the Crust End and the Mantle Begin? Gamble, J. A. McGibbon, F. Kyle, P. R. Menzies, M. A. Kirsch, I. Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
topic_facet |
Continental Lithosphere: Where does the Crust End and the Mantle Begin? |
description |
Xenoliths in basanite from Foster Crater in the foothills of the Transantarctic Mountains have been used to construct a model of the subcontinental lithosphere and lithospheric processes in this segment of Antarctica. The mafic and ultramafic xenoliths define two mineralogically, texturally and chemically distinct populations. One group is identical to Group II xenoliths, as defined by Frey & Prinz (1978). These have igneous cumulate textures and include wehrlites, rare websterites, dunite and amphibolite. In these xenoliths, the amphibole is always kaersutite and the (very rare) mica a Ti-rich phlogopite (TiO 2 > 5%). The other xenoliths have complex metamorphic textures ranging from protogranular to porphyroclastic and are dominated by clinopyroxenites (cpx: Mg/(Mg + Fe) = 0·85–0·95; Ca/(Ca + Mg)>0·53) which show varying degrees of replacement by metasomatic phlogopite. Spinel and anorthite are also present. Collectively, these xenoliths are called the High Calcium Pyroxene Suite (HCPS) in deference to their unusual pyroxene compositions. Moreover, their spinel assemblages indicate equilibrium under variable f O2 conditions contrasting with the Group II spinels which equilibrated at relatively constant f O2 . The mineralogy and chemistry of the HCPS xenoliths are unlike meta-igneous rocks and more closely resemble calc-silicate granulites. Thermobarometric calculations on Group II websterite assemblages and comparison with experimental equilibria on granulites and phlogopite stability suggest equilibration temperatures between 850 and 950° at 5 kb pressure, consistent with equilibration at mid to lower crustal depths. A number of processes have acted to modify Group II and HCPS xenoliths including K-metasomatism, dynamic recrystallization, melt generation, melt infiltration and oxidation. The first two are restricted to the HCPS xenoliths whereas the latter affect both groups. The interaction of these processes highlights the differences between Group II and HCPS protolith assemblages and is ... |
format |
Text |
author |
Gamble, J. A. McGibbon, F. Kyle, P. R. Menzies, M. A. Kirsch, I. |
author_facet |
Gamble, J. A. McGibbon, F. Kyle, P. R. Menzies, M. A. Kirsch, I. |
author_sort |
Gamble, J. A. |
title |
Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
title_short |
Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
title_full |
Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
title_fullStr |
Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
title_full_unstemmed |
Metasomatised Xenoliths from Foster Crater, Antarctica: Implications for Lithospheric Structure and Processes beneath the Transantarctic Mountain Front |
title_sort |
metasomatised xenoliths from foster crater, antarctica: implications for lithospheric structure and processes beneath the transantarctic mountain front |
publisher |
Oxford University Press |
publishDate |
1988 |
url |
http://petrology.oxfordjournals.org/cgi/content/short/Special_Volume/1/109 https://doi.org/10.1093/petrology/Special_Volume.1.109 |
long_lat |
ENVELOPE(162.967,162.967,-78.400,-78.400) |
geographic |
Transantarctic Mountains Foster Crater |
geographic_facet |
Transantarctic Mountains Foster Crater |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_relation |
http://petrology.oxfordjournals.org/cgi/content/short/Special_Volume/1/109 http://dx.doi.org/10.1093/petrology/Special_Volume.1.109 |
op_rights |
Copyright (C) 1988, Oxford University Press |
op_doi |
https://doi.org/10.1093/petrology/Special_Volume.1.109 |
container_title |
Journal of Petrology |
container_volume |
Special_Volume |
container_issue |
1 |
container_start_page |
109 |
op_container_end_page |
138 |
_version_ |
1766273232061595648 |