Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands
The East Scotia Ridge, situated in the South Atlantic, is the back-arc spreading centre to the intra-oceanic South Sandwich arc. Samples from the ridge show a wide diversity in erupted magma compositions. Segment E2, in the northern part of the ridge, has an axial topographic high, which contrasts w...
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Geological Society of London
2003
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ftnerc:oai:nora.nerc.ac.uk:17641 2023-05-15T13:45:12+02:00 Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands Harrison, D. Leat, P.T. Burnard, P.G. Turner, G. Fretzdorff, S. Millar, I. Larter, R.D. Leat, P.T. 2003 http://nora.nerc.ac.uk/id/eprint/17641/ unknown Geological Society of London Harrison, D.; Leat, P.T.; Burnard, P.G.; Turner, G.; Fretzdorff, S.; Millar, I. 2003 Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands. In: Larter, R.D. orcid:0000-0002-8414-7389 Leat, P.T., (eds.) Intra-oceanic subduction systems: tectonic and magmatic processes. London, Geological Society of London, 333-344. (Geological Society Special Publication, 219). Publication - Book Section NonPeerReviewed 2003 ftnerc 2023-02-04T19:31:13Z The East Scotia Ridge, situated in the South Atlantic, is the back-arc spreading centre to the intra-oceanic South Sandwich arc. Samples from the ridge show a wide diversity in erupted magma compositions. Segment E2, in the northern part of the ridge, has an axial topographic high, which contrasts with the rift-like topography common to most of the ridge. Lava compositions in the segment have been modelled by mixing of magmas derived from normal mid-ocean ridge basalt (N-MORB)-like mantle, a mantle plume component similar in composition to that sampled by Bouvet Island and mantle modified by addition of components from the subducting slab. The ‘Bouvet’-like plume signature has higher 87Sr/86Sr, 206Pb/204Pb, Nb/Yb, and lower 143Nd/144Nd and 4He/3He, than the local upper mantle. It can be traced geochemically from the Bouvet Island hot spot to segment E2, via the South American-Antarctic Ridge, which connects the Bouvet triple junction to the South Sandwich subduction system. Four samples dredged from segment E2 have 4He/3He ratios of 85 000–90 200 (8.5–8.0 R/RA, where) R/RA is the 4He/3He ratio normalized to air) and three wax core samples taken from the segment axis have values of 104 300, 101 560 and 176 620 (6.9, 7.1 and 4.1 R/RA). These latter data are similar to values from the South American-Antarctic Ridge which have no discernable plume input. Whilst the dredge samples have a measurably lower 4He/3He ratio than the South American-Antarctic Ridge and samples from the segment axis, these He isotope data contrast with a dominant plume signature recorded by other petrogenetic tracers. This is interpreted to be due to re-melting of an entrained plume component, with an inherent low He concentration, incorporated into the E2 mantle. Helium depletion from the plume component can be seen to be a consequence of mantle processing and does not imply shallow-level degassing prior to entrainment within the upper-mantle-melting zone. As a consequence, He is characterized in the back-arc by values more similar to the ... Book Part Antarc* Antarctic Bouvet Island South Sandwich Islands Natural Environment Research Council: NERC Open Research Archive Antarctic Sandwich Islands South Sandwich Islands Bouvet ENVELOPE(3.358,3.358,-54.422,-54.422) Bouvet Island ENVELOPE(3.358,3.358,-54.422,-54.422) East Scotia Ridge ENVELOPE(-29.250,-29.250,-57.917,-57.917) |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
description |
The East Scotia Ridge, situated in the South Atlantic, is the back-arc spreading centre to the intra-oceanic South Sandwich arc. Samples from the ridge show a wide diversity in erupted magma compositions. Segment E2, in the northern part of the ridge, has an axial topographic high, which contrasts with the rift-like topography common to most of the ridge. Lava compositions in the segment have been modelled by mixing of magmas derived from normal mid-ocean ridge basalt (N-MORB)-like mantle, a mantle plume component similar in composition to that sampled by Bouvet Island and mantle modified by addition of components from the subducting slab. The ‘Bouvet’-like plume signature has higher 87Sr/86Sr, 206Pb/204Pb, Nb/Yb, and lower 143Nd/144Nd and 4He/3He, than the local upper mantle. It can be traced geochemically from the Bouvet Island hot spot to segment E2, via the South American-Antarctic Ridge, which connects the Bouvet triple junction to the South Sandwich subduction system. Four samples dredged from segment E2 have 4He/3He ratios of 85 000–90 200 (8.5–8.0 R/RA, where) R/RA is the 4He/3He ratio normalized to air) and three wax core samples taken from the segment axis have values of 104 300, 101 560 and 176 620 (6.9, 7.1 and 4.1 R/RA). These latter data are similar to values from the South American-Antarctic Ridge which have no discernable plume input. Whilst the dredge samples have a measurably lower 4He/3He ratio than the South American-Antarctic Ridge and samples from the segment axis, these He isotope data contrast with a dominant plume signature recorded by other petrogenetic tracers. This is interpreted to be due to re-melting of an entrained plume component, with an inherent low He concentration, incorporated into the E2 mantle. Helium depletion from the plume component can be seen to be a consequence of mantle processing and does not imply shallow-level degassing prior to entrainment within the upper-mantle-melting zone. As a consequence, He is characterized in the back-arc by values more similar to the ... |
author2 |
Larter, R.D. Leat, P.T. |
format |
Book Part |
author |
Harrison, D. Leat, P.T. Burnard, P.G. Turner, G. Fretzdorff, S. Millar, I. |
spellingShingle |
Harrison, D. Leat, P.T. Burnard, P.G. Turner, G. Fretzdorff, S. Millar, I. Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
author_facet |
Harrison, D. Leat, P.T. Burnard, P.G. Turner, G. Fretzdorff, S. Millar, I. |
author_sort |
Harrison, D. |
title |
Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
title_short |
Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
title_full |
Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
title_fullStr |
Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
title_full_unstemmed |
Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands |
title_sort |
resolving mantle components in oceanic lavas from segment e2 of the east scotia back-arc ridge, south sandwich islands |
publisher |
Geological Society of London |
publishDate |
2003 |
url |
http://nora.nerc.ac.uk/id/eprint/17641/ |
long_lat |
ENVELOPE(3.358,3.358,-54.422,-54.422) ENVELOPE(3.358,3.358,-54.422,-54.422) ENVELOPE(-29.250,-29.250,-57.917,-57.917) |
geographic |
Antarctic Sandwich Islands South Sandwich Islands Bouvet Bouvet Island East Scotia Ridge |
geographic_facet |
Antarctic Sandwich Islands South Sandwich Islands Bouvet Bouvet Island East Scotia Ridge |
genre |
Antarc* Antarctic Bouvet Island South Sandwich Islands |
genre_facet |
Antarc* Antarctic Bouvet Island South Sandwich Islands |
op_relation |
Harrison, D.; Leat, P.T.; Burnard, P.G.; Turner, G.; Fretzdorff, S.; Millar, I. 2003 Resolving mantle components in oceanic lavas from segment E2 of the East Scotia back-arc ridge, South Sandwich Islands. In: Larter, R.D. orcid:0000-0002-8414-7389 Leat, P.T., (eds.) Intra-oceanic subduction systems: tectonic and magmatic processes. London, Geological Society of London, 333-344. (Geological Society Special Publication, 219). |
_version_ |
1766216432487497728 |