Abstract

Non-collisional, convergent margin orogens are generally called accretionary orogens, although there may not have been horizontal accretion across the plate boundary. We revive the term non-collisional orogen and use a Gondwanaland perspective to discuss different types. On the northern margin of the Australian Plate, the New Guinea non-collisional, accretionary orogen was formed by large-scale terrane accretion across an advancing plate margin. On the eastern margin, the Southwest Pacific Orogen is a non-collisional and non-accretionary orogen, involving virtually no horizontal transfer of material across its eastward-retreating plate boundary. In the Tasmanides, the Lachlan Orogen, commonly described as an accretionary orogen, is another non-collisional, non-accretionary orogen developed behind the plate margin after major Cambrian rollback, with resultant backarc basins filled mainly by quartz-rich turbidites subsequently recycled. The outboard New England Orogen is a non-collisional but accretionary orogen, marked by the frontal accretion of continental margin arc detritus, subsequently recycled into younger arcs. The Permian to Cretaceous Rangitata Orogen of New Zealand is an ?oblique non-collisional, accretionary orogen in which Permian–Triassic sediments of the accretionary wedge have no link with inboard (near) arc terranes. Late Jurassic to Cretaceous parts were sourced by a combination of first cycle volcanogenic detritus passing through the forearc basin together with recycling of the exhumed parts of the wedge. All non-collisional orogens involve continental growth, but only the New England Orogen and to a lesser extent the New Guinea Orogen involve significant crustal growth.

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