Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor
Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a min...
Published in: | Journal of Geophysical Research: Solid Earth |
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AGU (American Geophysical Union)
1995
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Online Access: | https://oceanrep.geomar.de/id/eprint/52799/ https://oceanrep.geomar.de/id/eprint/52799/1/Pyle%20et%20al.pdf https://doi.org/10.1029/95JB01424 |
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ftoceanrep:oai:oceanrep.geomar.de:52799 2023-05-15T13:50:03+02:00 Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor Pyle, D. G. Christie, D. M. Mahoney, J. J. Duncan, R. A. 1995-11-10 text https://oceanrep.geomar.de/id/eprint/52799/ https://oceanrep.geomar.de/id/eprint/52799/1/Pyle%20et%20al.pdf https://doi.org/10.1029/95JB01424 en eng AGU (American Geophysical Union) Wiley https://oceanrep.geomar.de/id/eprint/52799/1/Pyle%20et%20al.pdf Pyle, D. G., Christie, D. M., Mahoney, J. J. and Duncan, R. A. (1995) Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor. Journal of Geophysical Research: Solid Earth, 100 (B11). pp. 22261-22282. DOI 10.1029/95JB01424 <https://doi.org/10.1029/95JB01424>. doi:10.1029/95JB01424 info:eu-repo/semantics/restrictedAccess Article PeerReviewed 1995 ftoceanrep https://doi.org/10.1029/95JB01424 2023-04-07T15:56:18Z Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a minimum rate of 25 mm/yr since 4 Ma; however, its long-term history remains a matter of speculation. To determine if Pacific-type upper mantle has migrated westward beneath the eastern Indian Ocean basin as Australia and Antarctica drifted apart during the last 70 m.y., we present new Sr-Nd-Pb isotope data, combined with trace element and 40Ar-39Ar radiometric age determinations, for samples from Legs 28 and 29 of the Deep Sea Drilling Project (DSDP). Basaltic basement at these DSDP sites provides a record of their upper mantle source composition and shows regional variations consistent with upper mantle flow in this region. East of the South Tasman Rise, all DSDP basalts have 87Sr/86Sr (0.7025–0.7029) and 206Pb/204Pb (18.80–19.48) ratios typical of Pacific-type MORB indicating that Pacific-type upper mantle existed east of the Australian-Antarctic continental margin and beneath the Tasman Sea during the early stages of seafloor spreading in this region. Basalts from DSDP sites west of the AAD have high 87Sr/86Sr (0.7030–0.7035), low 206Pb/204Pb (17.99–18.10) and trace element characteristics typical of present day Indian-type SEIR MORB. Between these two regions, DSDP basalts recovered along the western margin of the South Tasman Rise have isotopic characteristics that are, in one case consistent with an Indian-type MORB source (Site 280A) and, in the second case, transitional between Pacific-type and Indian-type mantle sources. The occurrence of seafloor basalts with transitional or Indian-type isotopic characteristics well to the east of the present Indian-Pacific MORB isotopic boundary within the AAD strongly implies that Pacific-type upper mantle has migrated westward into the region since the South Tasman Rise ... Article in Journal/Newspaper Antarc* Antarctic Antarctica OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Antarctic Australian-Antarctic Discordance ENVELOPE(124.000,124.000,-49.000,-49.000) Indian Pacific South Tasman Rise ENVELOPE(148.000,148.000,-47.500,-47.500) Southeast Indian Ridge ENVELOPE(110.000,110.000,-50.000,-50.000) Journal of Geophysical Research: Solid Earth 100 B11 22261 22282 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a minimum rate of 25 mm/yr since 4 Ma; however, its long-term history remains a matter of speculation. To determine if Pacific-type upper mantle has migrated westward beneath the eastern Indian Ocean basin as Australia and Antarctica drifted apart during the last 70 m.y., we present new Sr-Nd-Pb isotope data, combined with trace element and 40Ar-39Ar radiometric age determinations, for samples from Legs 28 and 29 of the Deep Sea Drilling Project (DSDP). Basaltic basement at these DSDP sites provides a record of their upper mantle source composition and shows regional variations consistent with upper mantle flow in this region. East of the South Tasman Rise, all DSDP basalts have 87Sr/86Sr (0.7025–0.7029) and 206Pb/204Pb (18.80–19.48) ratios typical of Pacific-type MORB indicating that Pacific-type upper mantle existed east of the Australian-Antarctic continental margin and beneath the Tasman Sea during the early stages of seafloor spreading in this region. Basalts from DSDP sites west of the AAD have high 87Sr/86Sr (0.7030–0.7035), low 206Pb/204Pb (17.99–18.10) and trace element characteristics typical of present day Indian-type SEIR MORB. Between these two regions, DSDP basalts recovered along the western margin of the South Tasman Rise have isotopic characteristics that are, in one case consistent with an Indian-type MORB source (Site 280A) and, in the second case, transitional between Pacific-type and Indian-type mantle sources. The occurrence of seafloor basalts with transitional or Indian-type isotopic characteristics well to the east of the present Indian-Pacific MORB isotopic boundary within the AAD strongly implies that Pacific-type upper mantle has migrated westward into the region since the South Tasman Rise ... |
format |
Article in Journal/Newspaper |
author |
Pyle, D. G. Christie, D. M. Mahoney, J. J. Duncan, R. A. |
spellingShingle |
Pyle, D. G. Christie, D. M. Mahoney, J. J. Duncan, R. A. Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
author_facet |
Pyle, D. G. Christie, D. M. Mahoney, J. J. Duncan, R. A. |
author_sort |
Pyle, D. G. |
title |
Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
title_short |
Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
title_full |
Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
title_fullStr |
Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
title_full_unstemmed |
Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor |
title_sort |
geochemistry and geochronology of ancient southeast indian and southwest pacific seafloor |
publisher |
AGU (American Geophysical Union) |
publishDate |
1995 |
url |
https://oceanrep.geomar.de/id/eprint/52799/ https://oceanrep.geomar.de/id/eprint/52799/1/Pyle%20et%20al.pdf https://doi.org/10.1029/95JB01424 |
long_lat |
ENVELOPE(124.000,124.000,-49.000,-49.000) ENVELOPE(148.000,148.000,-47.500,-47.500) ENVELOPE(110.000,110.000,-50.000,-50.000) |
geographic |
Antarctic Australian-Antarctic Discordance Indian Pacific South Tasman Rise Southeast Indian Ridge |
geographic_facet |
Antarctic Australian-Antarctic Discordance Indian Pacific South Tasman Rise Southeast Indian Ridge |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_relation |
https://oceanrep.geomar.de/id/eprint/52799/1/Pyle%20et%20al.pdf Pyle, D. G., Christie, D. M., Mahoney, J. J. and Duncan, R. A. (1995) Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor. Journal of Geophysical Research: Solid Earth, 100 (B11). pp. 22261-22282. DOI 10.1029/95JB01424 <https://doi.org/10.1029/95JB01424>. doi:10.1029/95JB01424 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1029/95JB01424 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
100 |
container_issue |
B11 |
container_start_page |
22261 |
op_container_end_page |
22282 |
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1766252792267145216 |