Pleistocene Basaltic Volcanism on the Fly Platform in Papua New Guinea

Papua New Guinea (PNG) remains one of the least studied regions in the Southwest Pacific, and the tectono-magmatic evolution of extensive areas such as the Fly Platform remains poorly constrained. This study presents the first investigation of basaltic volcanism on the Fly Platform based on the discovery of two previously unrecognized volcanic centres, Meahill and Yemsigi, located approximately 13 km apart along a northeast–southwest alignment. Integrated field observations and petrographic studies reveal contrasting eruptive and emplacement histories. Yemsigi is characterized by coherent porphyritic basalts, whereas Meahill comprises highly vesicular porphyritic to micro-porphyritic basalts indicative of explosive volcanism. Mineral chemistry and whole-rock geochemistry indicate that both basalt suites were derived from a common magma source. The K–Ar age of 0.57 ± 0.09 Ma for the Meahill basalts suggests that volcanism on the Fly Platform represents a late-stage magmatic event that post-dates the Maramuni Arc and Central Highlands magmatism on the PNG mainland. These findings provide the first evidence for Middle Pleistocene volcanism on the Fly Platform and place new constraints on the tectono-magmatic evolution of southern PNG.