Terrane accretion, contractional deformation, almost continuous magmatism and mineralisation in the New Guinea Orogen

Recent tectonic studies provide a new view of the evolution of the New Guinea Orogen. The Mesozoic–Cenozoic orogen has undergone crustal shortening and thickening with accompanying uplift and almost continuous magmatism since the Early Cretaceous. Ten terranes have been identified in the orogen, with major faults forming the boundaries between these terranes. Terranes display various stages of active collision–accretion. The Australian craton’s deformed northern margin is a complex zone of para-autochthonous and accreted allochthonous terranes. Periods of convergence and compression have occurred within the orogen during sustained westward sinistral movement with intra-plate deformation, microplate formation and large-scale sinistral translations. Major sinistral horizontal dispersals and counterclockwise rotations of terrane fragments have occurred, with blocks of the Owen Stanley terrane and Waria terrane dispersed westward for up to 800 km. Westward dispersal may also account for the 700 km length of the middle–late Miocene Maramuni magmatic arc. The largest allochthonous terrane is the mostly submerged Nakanai terrane, consisting of Lower Cretaceous–Oligocene oceanic crust and island arc rocks along the northern New Guinea mainland and throughout the New Guinea islands and Solomon Islands. Docking of the allochthonous Ontong Java Plateau terrane with the New Guinea Orogen was initiated at 25–20 Ma (Oligocene–Miocene boundary) and is associated with widespread unconformity. Renewed convergence since 4–2 Ma is associated with intra-plate deformation of the Nakanai terrane, including break-up of the terrane into a series of microplates, asymmetric sea-floor spreading in the Manus Basin (3.5 Ma) and Woodlark Basin (6.2 Ma), rotational collision of the South Bismarck microplate with the Owen Stanley terrane (3.7–3.0 Ma), late Miocene (7.0 Ma) deformation of the Aure–Moresby terrane and buckling and formation of a double chain of islands in the Solomon Islands and a series of ridges (Tabar–Lihir–Tanga–Feni arc; Pliocene–Holocene) in the New Ireland region.