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Geodynamic implications for zonal and meridional isotopic patterns across the northern Lau and North Fiji Basins

Price, Allison A.; Jackson, Matthew G.; Blichert-Toft, Janne; Kurz, Mark D.; Gill, Jim; Blusztajn, Jerzy; Jenner, Frances; Brens, Raul and Arculus, Richard (2017). Geodynamic implications for zonal and meridional isotopic patterns across the northern Lau and North Fiji Basins. Geochemistry, Geophysics, Geosystems, 18(3) pp. 1013–1042.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1002/2016GC006651
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Abstract

We present new Sr-Nd-Pb-Hf-He isotopic data for sixty-five volcanic samples from the northern Lau and North Fiji Basin. This includes forty-seven lavas obtained from forty dredge sites spanning an east-west transect across the Lau and North Fiji basins, ten ocean island basalt (OIB)-type lavas collected from seven Fijian islands, and eight OIB lavas sampled on Rotuma. For the first time we are able to map clear north-south and east-west geochemical gradients in 87Sr/86Sr across the northern Lau and North Fiji Basins: lavas with the most geochemically enriched radiogenic isotopic signatures are located in the northeast Lau Basin, while signatures of geochemical enrichment are diminished to the south and west away from the Samoan hotspot. Based on these geochemical patterns and plate reconstructions of the region, these observations are best explained by the addition of Samoa, Rurutu, and Rarotonga hotspot material over the past 4 Ma. We suggest that underplated Samoan material has been advected into the Lau Basin over the past ∼4 Ma. As the slab migrated west (and toward the Samoan plume) via rollback over time, younger and hotter (and therefore less viscous) underplated Samoan plume material was entrained. Thus, entrainment efficiency of underplated plume material was enhanced, and Samoan plume signatures in the Lau Basin became stronger as the trench approached the Samoan hotspot. The addition of subducted volcanoes to the Cook-Austral Volcanic Lineament material, first from the Rarotonga hotspot, then followed by the Rurutu hotspot, contributes to the extreme geochemical signatures observed in the northeast Lau Basin.

Item Type: Journal Item
Copyright Holders: 2017 American Geophysical Union.
ISSN: 1525-2027
Keywords: Lau Basin; geochemistry; Samoa; North Fiji Basin; hotspot; Cook-Austral
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Health and Wellbeing PRA (Priority Research Area)
Item ID: 48702
Depositing User: Frances Jenner
Date Deposited: 01 Mar 2017 16:20
Last Modified: 02 May 2019 05:40
URI: http://oro.open.ac.uk/id/eprint/48702
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