Iron isotopic evidence for convective resurfacing of recycled arc-front mantle beneath back-arc basins
Geophysical observations suggest sub‐arc convective flow transports melt‐exhausted and metasomatized wedge mantle into deeper mantle regions. Reciprocally, asthenospheric, fertile mantle may supply back‐arc ridges distal to the trench by shallow, lateral mantle ingress, insinuating initial wedge man...
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| Published in: | Geophysical research letters Vol. 40; no. 22; pp. 5849 - 5853 |
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| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Washington, DC
Blackwell Publishing Ltd
28-11-2013
American Geophysical Union John Wiley & Sons, Inc |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Geophysical observations suggest sub‐arc convective flow transports melt‐exhausted and metasomatized wedge mantle into deeper mantle regions. Reciprocally, asthenospheric, fertile mantle may supply back‐arc ridges distal to the trench by shallow, lateral mantle ingress, insinuating initial wedge mantle depletion in its back‐arc region. Here we show that light Fe isotope compositions of the Central Lau Spreading Centre located in the Lau back‐arc basin on the farside of the Tonga‐Kermadec arc are indicative for derivation from a modified arc‐front mantle with elemental and Nd‐isotopic memory of former slab fluid addition. We propose that this shallow wedge material has been transported from the sub‐arc mantle to the back‐arc either convectively or in a buoyant diapir. This implies that melt‐depleted mantle in subduction zones is, at least in parts, recycled in a resurfacing loop. This can explain the depletion in back‐arc regions, and the progressively depleted nature of island arc sources in maturing arc systems.
Key Points
Fe isotopes can be used as tracers for subduction‐modified mantle
Mantle from the sub‐arc wedge is resurfacing by convection in back‐arc regions
Maturing arc systems will be progressively depleted in incompatible elements |
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| Bibliography: | istex:1A705E66C64DA58E26C1AFD38499DC120E7C2750 Australian Research Council - No. DE120100513; No. DP120104240 ark:/67375/WNG-GGQ35S23-M ArticleID:GRL51099 A: Location map of the Lau Basin showing the spreading centres and rifts (solid lines), contours of present and past subduction zones (dotted lines) and the outreach of active subduction components [Martinez and Taylor, 2002] (dashed line). RR-Rochambeau Rifts, NWLSC-North-West Lau Spreading centre, CLSC-Central Lau Spreading Centre, PR + ETZ-Peggy Ridge and Extensional Transform Fault, FRSC-Fonualei Rift Spreading Centre. The PR marks the plate boundary between the Australian plate and the Niuafou'ou microplates. B) Discrimination diagram [Pearce and Peate, 1995] for MORB-OIB vs. IAB for CLSC, FRSC, and FAMOUS samples in comparison with global MORB [Jenner and O'Neill, 2012];Seafloor bathymetry map and locations of Lau basin CLSC samples analysed in this study.Iron isotope results for the IRMM-014 standard reference material analysed in the analytical sessions during which the data were collectedAnalytical methods used to create the data listed in tables 1, 2 and 3 and a full reference list for all references cited in the auxiliary material.Fe isotope data, iron isotope data for the samples used in this study, the data in this table is displayed in Figure B in the main manuscript.Standard reference material, SRM analysed in the course of this studyHf-Nd isotope data, hafnium-neodymium isotope compositionsMajor element composition, as displayed in figure 2B in the main manuscriptsupporting information ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0094-8276 1944-8007 |
| DOI: | 10.1002/2013GL057976 |