Woodlark dyke swarm

Dyke swarms and sill complexes have until now gone unrecognised on Woodlark Island. They are intimately associated with Middle Miocene volcanic and intrusive complexes. The Woodlark dyke swarm (K-Ar age date 14.0±0.2 Ma) is onshore from the Woodlark Basin and the Woodlark Basin Spreading Centre (rifting initiated 6.2 Ma), one of the best studied examples of active seafloor spreading rifting into continental lithosphere. Extension and intrusion of the Woodlark dyke swarm preceded the initiation of rifting in the Woodlark Basin by 7.8 Ma. Contrasting ages of rifting initiation, longevities of rifting histories and directions of extension suggest the Woodlark dyke swarm is failed rift branch of the Woodlark Basin Spreading Centre. The potassic extrusive and intrusive igneous rocks of the failed Woodlark rift zone have historically been a large producer of Au and Ag from multiple centres, e.g. Busai, Kulumadau, Woodlark King (Boniavat), Mweim, The Ben and Wonai.