Evidence for Middle Pleistocene Intraplate Basaltic Volcanism on Fly Platform in Papua New Guinea

Papua New Guinea is one of the least studied regions in the Southwest Pacific, and large areas of the country, such as the Fly Plat-form, remain poorly understood due to limited exposure and access constraints. This study presents the first documentation of basaltic volcanism on the Fly Platform, based on new field discoveries at Mea-hill and Yemsigi, two areas located approximately 25 km apart. Inte-grated field observations, petrography, mineral chemistry, and whole-rock geochemistry show that both basalt suites were derived from a similar magma source but record contrasting emplacement histories. Meahill basalts, which include welded tuffs and highly ve-sicular basalt units, reflect rapid magma ascent, vigorous degassing, and locally explosive activity. In contrast, the massive, less vesicular porphyritic basalts at Yemsigi preserve a quieter emplacement history, but with more extensive post-magmatic alteration. Geochemical sig-natures from least altered rocks of both suites support an intraplate origin with similarities to Pliocene-Pleistocene lava fields of Northeast Queensland. The origin of the intra-plate basaltic magmatism is enig-matic, but both young volcanic provinces correlate spatially with a lower mantle anomaly that may represent residual slab material and a seated-seated magma source. These findings provide further insight into the tectono-magmatic evolution of the Fly Platform region and highlight the need for continued geological investigation in this underexplored district.