2011 Volume 120 Issue 6 Pages 1026-1034
The mantle beneath the world's largest igneous province, the Cretaceous Ontong Java Plateau in the western Pacific, is accessible via xenoliths from late-stage “kimberlite-like” ultramafic magmas (alnöite) on the Solomon Island of Malaita. The xenoliths can be used to reconstruct the lithospheric stratigraphy (vertical distribution of rock types) beneath the plateau based on geothermobarometry. The results show that the lithosphere forms a genetically unrelated two-layered structure, comprising shallower pre-existing oceanic lithosphere and deeper impinged material regarded as the residual mantle of the Ontong Java Plateau magmatism. This suggests that particular types of Malaitan xenolith represent fragments of mantle plume that possibly originated from the core-mantle boundary.