Fig. 5: Schematics diagram of Ontong Java Nui volcanism at the explosive subaerial/shallow-marine eruption phase corresponding to CIE(OIB).
From: Brief and intensive volcanic emissions from Ontong Java Nui heralded Oceanic Anoxic Event 1a

The volcanic ash and Os-bearing volatiles originate from a volcanic eruption that formed sg-type OJP and high-Ti-type MP basalts.