Why did not the Ontong Java Plateau form subaerially?

A recent drilling leg on the Ontong Java Plateau and subsequent studies have consolidated the following observation for this gigantic oceanic plateau: The bulk of the plateau was formed at ∼ 120 Ma in a submarine environment. This rapid construction of a massive igneous body below sea level is impossible to explain with the popular plume head hypothesis. Though the bolide impact hypothesis for oceanic plateaus has recently been resurrected to offer an alternative, it is shown here that it fails to explain submarine eruption for exactly the same reason why the plume hypothesis fails. As a more dynamically promising model, the entrainment of dense fertile mantle by rapid seafloor spreading is proposed to account for voluminous magmatism in the submarine environment. It is also suggested that this chemically dense source mantle may naturally explain the anomalous subsidence history of this plateau as well as minor magmatism observed at ∼ 90 Ma. Modeling the dynamics of compositionally heterogeneous mantle and its geochemical consequences remains as a challenging yet rewarding problem in mantle dynamics and igneous petrology.