Papua New Guinea and the Solomon Islands are located in a complex tectonic setting between the converging Ontong Java Plateau on the Pacific plate and the Australian continent. Here we present a Late Neogene to Quaternary plate tectonic reconstruction for this region. The reconstruction was performed using GPlates software and is based on data derived from multiple geological datasets, including seafloor magnetic isochrons, 3D models of subducted slabs, palaeomagnetic data, deformation patterns, and the spatio-temporal distribution of arc magmatism. The reconstruction shows that since ca. 6 Ma, the crustal elements that comprise Papua New Guinea and the Solomon Islands began interacting in advance of the impending collision between the

The Maramuni arc represents the only continuous record of the tectonic evolution of Papua New Guinea during the Miocene, and hence provides an opportunity to gain insight into subduction dynamics, orogenesis and crustal processes that operated throughout this dynamic period. We present an integrated U-Pb geochronology, Hf isotope and geochemical investigation of the Maramuni arc utilizing a suite of intrusive rocks from the Kainantu region of the eastern Papuan Highlands that span the Late Miocene from ca. 12 Ma to 6 Ma. The magmatic rocks formed from ca. 12-9 Ma have compositional affinities of subduction-zone magmas, but record increasing incompatible trace element contents and decreasing εHf with time, which we interpret to reflect a progressive increase in the crustal component of the magmas. Porphyry suites emplaced at 7.5-6 Ma are distinct from the older magmatic rocks by their marked HREE-depletion, which reflects a dramatic shift in arc-mantle dynamics. Based on these results we propose a revised geodynamic model for the tectonic

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