Boninite-like intraplate magmas from Manihiki Plateau require ultra-depleted and enriched source components.
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.
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.
Roman
R
Golowin
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.|V.I.Vernadsky Institute of Geochemistry and Analytical Chemistry, Kosigin street 19, Moscow 119991, Russia.
Maxim
M
Portnyagin
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.|Christian-Albrechts-University of Kiel, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany.
Kaj
0000-0002-3165-3480
K
Hoernle
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.
Folkmar
F
Hauff
Centre de Recherches Pétrographiques et Géochimiques, UMR 7358, Université de Lorraine, 54501 Vandoeuvre-lès-Nancy, France.
Andrey
A
Gurenko
Christian-Albrechts-University of Kiel, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany.
Dieter
D
Garbe-Schönberg
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.
Reinhard
R
Werner
Department of Earth and Planetary Sciences, Macquarie University, New South Wales 2109, Australia.
Simon
S
Turner