Golowin, Roman, Portnyagin, Maxim , Hoernle, Kaj , Hauff, Folkmar , Gurenko, Andrey, Garbe-Schönberg, Dieter, Werner, Reinhard and Turner, Simon (2017) Boninite-like intraplate magmas from Manihiki Plateau Require Ultra-depleted and Enriched Source Components. Nature Communications, 8 (14322). DOI 10.1038/NCOMMS14322.

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Abstract

The Ontong Java and Manihiki oceanic plateaus are believed to have formed through high-degree melting of a mantle plume head. Boninite-like, low-Ti basement rocks at Manihiki, however, imply a more complex magma genesis compared with Ontong Java basement lavas that can be generated by ∼30% melting of a primitive mantle source. Here we show that the trace element and isotope compositions of low-Ti Manihiki rocks can best be explained by re-melting of an ultra-depleted source (possibly a common mantle component in the Ontong Java and Manihiki plume sources) re-enriched by ≤1% of an ocean-island-basalt-like melt component. Unlike boninites formed via hydrous flux melting of refractory mantle at subduction zones, these boninite-like intraplate rocks formed through adiabatic decompression melting of refractory plume material that has been metasomatized by ocean-island-basalt-like melts. Our results suggest that caution is required before assuming all Archaean boninites were formed in association with subduction processes.

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