Light oxygen isotopes in mantle-derived magmas reflect assimilation of sub-continental lithospheric mantle material

Oxygen isotope ratios in mantle-derived magmas that differ from typical mantle values are generally attributed to crustal contamination, deeply subducted crustal material in the mantle source or primordial heterogeneities. Here we provide an alternative view for the origin of light oxygen-isotope si...

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Bibliographic Details
Published in:Nature communications 2021-11, Vol.12 (1), p.6295-6295, Article 6295
Main Authors: Xu, Jing-Yao, Giuliani, Andrea, Li, Qiu-Li, Lu, Kai, Melgarejo, Joan Carles, Griffin, William L.
Format: Article
Language:English
Subjects:
140/58
147/135
147/28
704/2151/209
704/2151/431
Ascent
Assimilation
Composition
Contamination
Humanities and Social Sciences
Isotope ratios
Isotopes
Lava
Magma
Mass spectrometry
Mass spectroscopy
multidisciplinary
Olivine
Oxygen
Oxygen isotopes
Science
Science (multidisciplinary)
Secondary ion mass spectrometry
Signatures
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Summary:Oxygen isotope ratios in mantle-derived magmas that differ from typical mantle values are generally attributed to crustal contamination, deeply subducted crustal material in the mantle source or primordial heterogeneities. Here we provide an alternative view for the origin of light oxygen-isotope signatures in mantle-derived magmas using kimberlites, carbonate-rich magmas that assimilate mantle debris during ascent. Olivine grains in kimberlites are commonly zoned between a mantle-derived core and a magmatic rim, thus constraining the compositions of both mantle wall-rocks and melt phase. Secondary ion mass spectrometry (SIMS) analyses of olivine in worldwide kimberlites show a remarkable correlation between mean oxygen-isotope compositions of cores and rims from mantle-like 18 O/ 16 O to lower ‘crustal’ values. This observation indicates that kimberlites entraining low- 18 O/ 16 O olivine xenocrysts are modified by assimilation of low- 18 O/ 16 O sub-continental lithospheric mantle material. Interaction with geochemically-enriched domains of the sub-continental lithospheric mantle can therefore be an important source of apparently ‘crustal’ signatures in mantle-derived magmas. Isotopically light oxygen in mantle derived magmas is generally attributed to the occurrence of deeply subducted crustal material in the mantle. New analyses of olivine in kimberlites worldwide suggest that assimilation of lithospheric mantle during magma ascent is the source of isotopically light oxygen in these, and, potentially other continental magmas.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-021-26668-z