Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments
Petrogenetic models for the origin of lamproites are evaluated using new major element, trace element, and Sr, Nd, and Pb isotope data for Holocene lamproites from the Gaussberg volcano in the East Antarctic Shield. Gaussberg lamproites exhibit very unusual Pb isotope compositions (Pb-206/Pb-204 = 1...
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Oxford University Press
2002
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ftunivqespace:oai:espace.library.uq.edu.au:UQ:62921 2023-05-15T13:55:31+02:00 Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments Murphy, DT Collerson, KD Kamber, BS M Wilson 2002-01-01 https://espace.library.uq.edu.au/view/UQ:62921 eng eng Oxford University Press doi:10.1093/petrology/43.6.981 issn:0022-3530 Lamproites Pb Isotopes Mantle Transition Zone Subducted Sediment Anomalous Mantle Reservoirs Geochemistry & Geophysics Continental Lithospheric Mantle Trace-elements Isotopic Evidence Age-determinations Pelagic Sediments Western-australia Depleted Mantle Deep Mantle Re-os Magmas 260301 Geochronology and Isotope Geochemistry C1 780104 Earth sciences Journal Article 2002 ftunivqespace https://doi.org/10.1093/petrology/43.6.981 2020-10-26T23:29:11Z Petrogenetic models for the origin of lamproites are evaluated using new major element, trace element, and Sr, Nd, and Pb isotope data for Holocene lamproites from the Gaussberg volcano in the East Antarctic Shield. Gaussberg lamproites exhibit very unusual Pb isotope compositions (Pb-206/Pb-204 = 17.44-17.55 and Pb-207/Pb-204 = 15.56-15.63), which in common Pb isotope space plot above mantle evolution lines and to the left of the meteorite isochron. Combined with very unradiogenic Nd, such compositions are shown to be inconsistent with an origin by melting of sub-continental lithospheric mantle. Instead, a model is proposed in which late Archaean continent-derived sediment is subducted as K-hollandite and other ultra-high-pressure phases and sequestered in the Transition Zone (or lower mantle) where it is effectively isolated for 2-3 Gyr. The high Pb-207/Pb-204 ratio is thus inherited from ancient continent-derived sediment, and the relatively low Pb-206/Pb-204 ratio is the result of a single stage of U/Pb fractionation by subduction-related U loss during slab dehydration. Sr and Nd isotope ratios, and trace element characteristics (e.g. Nb/Ta ratios) are consistent with sediment subduction and dehydration-related fractionation. Similar models that use variable time of isolation of subducted sediment can be derived for all lamproites. Our interpretation of lamproite sources has important implications for ocean island basalt petrogenesis as well as the preservation of geochemically anomalous reservoirs in the mantle. Article in Journal/Newspaper Antarc* Antarctic Antarctica Ocean Island The University of Queensland: UQ eSpace Antarctic Gaussberg ENVELOPE(89.183,89.183,-66.800,-66.800) Journal of Petrology 43 6 981 1001 |
institution |
Open Polar |
collection |
The University of Queensland: UQ eSpace |
op_collection_id |
ftunivqespace |
language |
English |
topic |
Lamproites Pb Isotopes Mantle Transition Zone Subducted Sediment Anomalous Mantle Reservoirs Geochemistry & Geophysics Continental Lithospheric Mantle Trace-elements Isotopic Evidence Age-determinations Pelagic Sediments Western-australia Depleted Mantle Deep Mantle Re-os Magmas 260301 Geochronology and Isotope Geochemistry C1 780104 Earth sciences |
spellingShingle |
Lamproites Pb Isotopes Mantle Transition Zone Subducted Sediment Anomalous Mantle Reservoirs Geochemistry & Geophysics Continental Lithospheric Mantle Trace-elements Isotopic Evidence Age-determinations Pelagic Sediments Western-australia Depleted Mantle Deep Mantle Re-os Magmas 260301 Geochronology and Isotope Geochemistry C1 780104 Earth sciences Murphy, DT Collerson, KD Kamber, BS Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
topic_facet |
Lamproites Pb Isotopes Mantle Transition Zone Subducted Sediment Anomalous Mantle Reservoirs Geochemistry & Geophysics Continental Lithospheric Mantle Trace-elements Isotopic Evidence Age-determinations Pelagic Sediments Western-australia Depleted Mantle Deep Mantle Re-os Magmas 260301 Geochronology and Isotope Geochemistry C1 780104 Earth sciences |
description |
Petrogenetic models for the origin of lamproites are evaluated using new major element, trace element, and Sr, Nd, and Pb isotope data for Holocene lamproites from the Gaussberg volcano in the East Antarctic Shield. Gaussberg lamproites exhibit very unusual Pb isotope compositions (Pb-206/Pb-204 = 17.44-17.55 and Pb-207/Pb-204 = 15.56-15.63), which in common Pb isotope space plot above mantle evolution lines and to the left of the meteorite isochron. Combined with very unradiogenic Nd, such compositions are shown to be inconsistent with an origin by melting of sub-continental lithospheric mantle. Instead, a model is proposed in which late Archaean continent-derived sediment is subducted as K-hollandite and other ultra-high-pressure phases and sequestered in the Transition Zone (or lower mantle) where it is effectively isolated for 2-3 Gyr. The high Pb-207/Pb-204 ratio is thus inherited from ancient continent-derived sediment, and the relatively low Pb-206/Pb-204 ratio is the result of a single stage of U/Pb fractionation by subduction-related U loss during slab dehydration. Sr and Nd isotope ratios, and trace element characteristics (e.g. Nb/Ta ratios) are consistent with sediment subduction and dehydration-related fractionation. Similar models that use variable time of isolation of subducted sediment can be derived for all lamproites. Our interpretation of lamproite sources has important implications for ocean island basalt petrogenesis as well as the preservation of geochemically anomalous reservoirs in the mantle. |
author2 |
M Wilson |
format |
Article in Journal/Newspaper |
author |
Murphy, DT Collerson, KD Kamber, BS |
author_facet |
Murphy, DT Collerson, KD Kamber, BS |
author_sort |
Murphy, DT |
title |
Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
title_short |
Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
title_full |
Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
title_fullStr |
Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
title_full_unstemmed |
Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments |
title_sort |
lamproites from gaussberg, antarctica: possible transition zone melts of archaean subducted sediments |
publisher |
Oxford University Press |
publishDate |
2002 |
url |
https://espace.library.uq.edu.au/view/UQ:62921 |
long_lat |
ENVELOPE(89.183,89.183,-66.800,-66.800) |
geographic |
Antarctic Gaussberg |
geographic_facet |
Antarctic Gaussberg |
genre |
Antarc* Antarctic Antarctica Ocean Island |
genre_facet |
Antarc* Antarctic Antarctica Ocean Island |
op_relation |
doi:10.1093/petrology/43.6.981 issn:0022-3530 |
op_doi |
https://doi.org/10.1093/petrology/43.6.981 |
container_title |
Journal of Petrology |
container_volume |
43 |
container_issue |
6 |
container_start_page |
981 |
op_container_end_page |
1001 |
_version_ |
1766262182705627136 |