Provenance and tectonics of the allochthonous New Guinea terranes: implications for the formation and evolution of regional basins

Papua New Guinea resides in a complex tectonic junction between the Australian continent, the Southwest Pacific, and Southeast Asia. Resolving the plate tectonic evolution of this region has proven difficult to date due to the plethora of contradicting geologic models that stem from a lack of constraining regional datasets. A growing body of geochronologic, geochemical and isotopic data acquired over the past decade, combined with new field observations, has led to a progressive shift from a largely autochthonous terrane model, to one of allochthonous terranes and accretion at the northern Australian continental margin. Findings from a compilation of zircon and biostratigraphic age data throughout the Papuan Peninsula and the New Guinea Fold and Thrust, and Mobile Belts, extending west to the Bird’s Head of West Papua, provide a robust evidence-based provenance model for the origin of these terranes. The evaluation of inherited and detrital zircon age populations indicates that many of the terranes are allochthonous in nature and that existing tectonic reconstructions require major revision. For example, a reconstruction that infers a North Queensland provenance for clastic rocks of the Papuan Peninsula based on closure of the Coral Sea is no longer supported by the available data. Instead, some of the allochthonous terranes are now interpreted to be derived from eastern Australia, with provenance of the Papuan Peninsula more akin to that of New Caledonia than North Queensland. This paradigm shift in our understanding of the regional terrane evolution has important implications for the formation and subsequent evolution of regional basins. For instance, basement rocks of the New Guinea Mobile Belt preserve a record of semi-continuous magmatism throughout the Mesozoic, however, this contradicts the absence of prolonged volcanic input into the Papuan Basin. Recognition of the New Guinea Mobile Belt as an allochthonous terrane resolves this inconsistency. The eastern margin of Australia, however, is now characterized by a convergent margin throughout the Mesozoic. Rifting of the allochthonous terranes and the associated arc from eastern Australia likely did not occur until the Late Cretaceous and is constrained by the maximum depositional age of volcaniclastic basement of the Papuan Peninsula at ca. 100 Ma, together with magmatic rocks identified in eastern Papua New Guinea. Rifting of the allochthonous terranes at this time would have resulted in widespread extension and basin formation, including basement crust of the Papuan and Eastern Plateaus, and sea floor spreading that culminated in formation of the Coral Sea Basin. This is supported by biostratigraphic data from Late Cretaceous synrift sediments deposited in the northern New Guinea marginal basins. Construction of a comprehensive and robust evidence-based tectonic model for the history of New Guinea basins is essential for our geological understanding of the region and to drive successful exploration models