The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles
Deep-seated meta-igneous xenoliths brought to the surface by alkali basaltic magmas from the Kerguelen Islands reveal that basaltic magmas have intruded the upper mantle throughout their geological evolution. These xenoliths record volcanic activity associated with their early South East Indian Ridg...
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ftanucanberra:oai:openresearch-repository.anu.edu.au:1885/90560 2024-01-14T10:08:21+01:00 The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles Gregoire, M Jackson, Ian O'Reilly, Suzanne Yvette Cottin, Jean-Yves http://hdl.handle.net/1885/90560 https://openresearch-repository.anu.edu.au/bitstream/1885/90560/5/MigratedxPub20955_RSD_2001.pdf.jpg https://openresearch-repository.anu.edu.au/bitstream/1885/90560/7/01_Gregoire_The_lithospheric_mantle_2001.pdf.jpg unknown Springer 0010-7999 http://hdl.handle.net/1885/90560 https://openresearch-repository.anu.edu.au/bitstream/1885/90560/5/MigratedxPub20955_RSD_2001.pdf.jpg https://openresearch-repository.anu.edu.au/bitstream/1885/90560/7/01_Gregoire_The_lithospheric_mantle_2001.pdf.jpg Contributions to Mineralogy and Petrology Keywords: lithospheric structure mafic rock petrography seismic refraction trace element xenolith Indian Ocean Journal article ftanucanberra 2023-12-15T09:34:27Z Deep-seated meta-igneous xenoliths brought to the surface by alkali basaltic magmas from the Kerguelen Islands reveal that basaltic magmas have intruded the upper mantle throughout their geological evolution. These xenoliths record volcanic activity associated with their early South East Indian Ridge location and subsequent translation to an intraplate setting over the Kerguelen Plume. The meta-igneous xenoliths sample two distinctive geochemical episodes: one is tholeiitic transitional and one is alkali basaltic. Geothermobarometry calculations provide a spatial context for the rock type sequence sampled and for interpreting petrophysical data. The garnet granulites equilibrated over a pressure range of 1.15 to 1.35 GPa and the garnet pyroxenite at 1.8 GPa. Ultrasonic measurements of compressional wave speed Vp have been carried out at pressures up to 1 GPa, and densities measured for representative samples of meta-igneous xenoliths and for a harzburgite that represents the peridotitic mantle. Vp and density have also been calculated using modal proportions of minerals and appropriate elastic properties for the constituent minerals. Calculated and measured Vp agree well for rock types with microstructures not complicated by kelyphitic breakdown of garnet and/or pervasive grain-boundary cracking. Pyroxene granulites have measured and calculated Vp within the range 7.37-7.52 km/s; calculated velocities for the garnet granulites and pyroxenites range from 7.69 to 7.99 km/s, whereas measured and calculated Vp for a mantle harzburgite are 8.45 and 8.29 km/s respectively. The seismic structure observed beneath the Kerguelen Islands can be explained by (1) a mixture of underplated pyroxene granulites and ultramafic rocks responsible for the 2-3 km low velocity transitional zone below the oceanic layer 3, (2) varying proportions of granulites and pyroxenites in different regions within the upper mantle producing the lateral heterogeneities, and (3) intercalation of the granulites and pyroxenites throughout the entire ... Article in Journal/Newspaper Kerguelen Islands Australian National University: ANU Digital Collections Kerguelen Kerguelen Islands Indian |
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Open Polar |
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Australian National University: ANU Digital Collections |
op_collection_id |
ftanucanberra |
language |
unknown |
topic |
Keywords: lithospheric structure mafic rock petrography seismic refraction trace element xenolith Indian Ocean |
spellingShingle |
Keywords: lithospheric structure mafic rock petrography seismic refraction trace element xenolith Indian Ocean Gregoire, M Jackson, Ian O'Reilly, Suzanne Yvette Cottin, Jean-Yves The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
topic_facet |
Keywords: lithospheric structure mafic rock petrography seismic refraction trace element xenolith Indian Ocean |
description |
Deep-seated meta-igneous xenoliths brought to the surface by alkali basaltic magmas from the Kerguelen Islands reveal that basaltic magmas have intruded the upper mantle throughout their geological evolution. These xenoliths record volcanic activity associated with their early South East Indian Ridge location and subsequent translation to an intraplate setting over the Kerguelen Plume. The meta-igneous xenoliths sample two distinctive geochemical episodes: one is tholeiitic transitional and one is alkali basaltic. Geothermobarometry calculations provide a spatial context for the rock type sequence sampled and for interpreting petrophysical data. The garnet granulites equilibrated over a pressure range of 1.15 to 1.35 GPa and the garnet pyroxenite at 1.8 GPa. Ultrasonic measurements of compressional wave speed Vp have been carried out at pressures up to 1 GPa, and densities measured for representative samples of meta-igneous xenoliths and for a harzburgite that represents the peridotitic mantle. Vp and density have also been calculated using modal proportions of minerals and appropriate elastic properties for the constituent minerals. Calculated and measured Vp agree well for rock types with microstructures not complicated by kelyphitic breakdown of garnet and/or pervasive grain-boundary cracking. Pyroxene granulites have measured and calculated Vp within the range 7.37-7.52 km/s; calculated velocities for the garnet granulites and pyroxenites range from 7.69 to 7.99 km/s, whereas measured and calculated Vp for a mantle harzburgite are 8.45 and 8.29 km/s respectively. The seismic structure observed beneath the Kerguelen Islands can be explained by (1) a mixture of underplated pyroxene granulites and ultramafic rocks responsible for the 2-3 km low velocity transitional zone below the oceanic layer 3, (2) varying proportions of granulites and pyroxenites in different regions within the upper mantle producing the lateral heterogeneities, and (3) intercalation of the granulites and pyroxenites throughout the entire ... |
format |
Article in Journal/Newspaper |
author |
Gregoire, M Jackson, Ian O'Reilly, Suzanne Yvette Cottin, Jean-Yves |
author_facet |
Gregoire, M Jackson, Ian O'Reilly, Suzanne Yvette Cottin, Jean-Yves |
author_sort |
Gregoire, M |
title |
The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
title_short |
The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
title_full |
The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
title_fullStr |
The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
title_full_unstemmed |
The lithospheric mantle beneath the Kerguelen Islands (Indian Ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
title_sort |
lithospheric mantle beneath the kerguelen islands (indian ocean): petrological and petrophysical characteristics of mantle mafic rock types and correlation with seismic profiles |
publisher |
Springer |
url |
http://hdl.handle.net/1885/90560 https://openresearch-repository.anu.edu.au/bitstream/1885/90560/5/MigratedxPub20955_RSD_2001.pdf.jpg https://openresearch-repository.anu.edu.au/bitstream/1885/90560/7/01_Gregoire_The_lithospheric_mantle_2001.pdf.jpg |
geographic |
Kerguelen Kerguelen Islands Indian |
geographic_facet |
Kerguelen Kerguelen Islands Indian |
genre |
Kerguelen Islands |
genre_facet |
Kerguelen Islands |
op_source |
Contributions to Mineralogy and Petrology |
op_relation |
0010-7999 http://hdl.handle.net/1885/90560 https://openresearch-repository.anu.edu.au/bitstream/1885/90560/5/MigratedxPub20955_RSD_2001.pdf.jpg https://openresearch-repository.anu.edu.au/bitstream/1885/90560/7/01_Gregoire_The_lithospheric_mantle_2001.pdf.jpg |
_version_ |
1788062774490824704 |