EM1‐Signature in the North Fiji Basin: Evidence for Stagnant Slab‐Derived Mantle Upwelling Beneath the Trench‐Distal Back‐Arc Basin SCIE SCOPUS

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Title
EM1‐Signature in the North Fiji Basin: Evidence for Stagnant Slab‐Derived Mantle Upwelling Beneath the Trench‐Distal Back‐Arc Basin
Author(s)
Oh, Jihye; Lee, Insung; Stuart, Finlay M.; Park, Munjae; Kim, Jonguk
KIOST Author(s)
Oh, Ji Hye(오지혜)Kim, Jonguk(김종욱)
Alternative Author(s)
오지혜; 김종욱
Publication Year
2021-04
Abstract
Basaltic volcanism at the mature back‐arc spreading axis in the North Fiji Basin (NFB) exhibits significant geochemical heterogeneity from depleted mid‐ocean ridge basalt (MORB) to enriched MORB compositions. The volatile and Sr‐Nd‐Pb‐He isotope composition of basaltic glasses from the Central Spreading Ridge (CSR) of the NFB suggests that a second enrichment mantle component is present in addition to the previously observed Samoan mantle plume. The hydrous OIB‐like basalts from the northern CSR have a weak enriched mantle 1 (EM1) isotopic signature and negative correlation between Ba/Th and Zr/Hf ratios, similar to rejuvenated Samoan lavas associated with tectonic driven volcanism. The EM1 signature is distinct from shield‐stage Samoan basalts and back‐arc basin basalts from the Lau Basin by high Ba/La ratio and negative correlation between Ba/Th and Ba/Ta ratios, indicating contributions from dehydrated and altered oceanic crust and sediments. Our new geochemical data suggest that focused melting above the mantle transition zone (MTZ) triggered by dehydration of stagnant slab can be a source of the EM1‐like melts containing both elevated 3He/4He ratios (up to 12.52 RA) and altered oceanic slab components. Given the spatial coincidence of the inferred EM1 basalts with the clustered deep earthquakes, our results support the presence of detached oceanic slabs in the MTZ beneath the northern NFB.
ISSN
2169-9313
URI
https://sciwatch.kiost.ac.kr/handle/2020.kiost/41282
DOI
10.1029/2020jb021017
Bibliographic Citation
Journal of Geophysical Research-solid Earth, v.126, no.4, 2021
Publisher
Blackwell Publishing Ltd
Keywords
EM1; mantle heterogeneity; mantle transition zone; mantle upwelling; North Fiji Basin; stagnant slab
Type
Article
Language
English
Publisher
Blackwell Publishing Ltd
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