Abstract Neoarchean rocks of the Tropicana Zone, including granites with subduction-zone affinities, formed in a terrane adjacent to, or on the margin of, the Yilgarn Craton at the commencement of a long-lived, amphibolite to granulite facies event – the 2722–2554 Ma Atlantis Event. Early stages of this event overlap with extensive komatiite emplacement within the Eastern Goldfields Superterrane (Yilgarn Craton), suggestive of a plume-related rift environment, which was followed by 2660–2630 Ma greenschist facies, orogenic gold mineralization. This indicates differences in the tectonic evolution of the Tropicana Zone compared with within the craton, although isotopic data show similarities in crustal sources. At c. 2520 Ma, the Tropicana Zone was retrogressed to greenschist facies as it was thrust onto the Yamarna Terrane (Yilgarn Craton), forming a northwesterly directed fold-and-thrust belt above the flat-lying Plumridge Detachment. This fold-and-thrust belt is host to the c. 2520 Ma, Tropicana gold deposit. The Plumridge Detachment may extend north to the Yamarna greenstone belt, linking to the Yamarna Shear Zone – the boundary between the Burtville and Yamarna Terranes. The fertility of the Tropicana Zone is related to its Neoarchean geodynamic setting within a continental arc environment, implying that deformed margins of Archean cratons may be prospective for Neoarchean Au deposits.

ABSTRACT From the Late Devonian to the Triassic, eastern Australia was part of eastern Gond-wana, where an active, convergent plate margin was influenced by a west-dipping subduction system. This system terminated as the result of global plate reorganization in the Middle to Late Triassic. The southern New England orogen changed from a prowedge (P) mode (terminology of Beaumont et al., 1999 ) in the Devonian-Carboniferous to an uplifted plug (P-U) mode in the Permian to Triassic. In contrast, the northern New England orogen was dominated by the retrowedge (P-U-R) mode in both time periods. This led to the development, in the Permian–Triassic, of a major west-directed retroforeland thrust belt in northern New England, with the formation of a thick foreland-basin phase in the adjacent Bowen Basin to the west. Thick-skinned and thin-skinned processes operated simultaneously. In the orogen, the thrusts are dom-inantly thick-skinned and planar, cutting deep into the crust. The eastern part of the Bowen Basin, however, is dominated by thin-skinned thrusting that, in places, propagated a considerable distance into the basin, with the formation of an imbricate thrust fan. The thick-skinned and thin-skinned thrusts are hard-linked into a single thrust system by a major middle-crust detachment surface. Contractional events at the plate margin associated with the formation of the thrust system were also responsible for the propagation of far-field stresses and the reactivation of older extensional faults as thrusts. These reactivated faults are well inboard of, not physically attached to, and soft-linked to, the retroforeland thrust system. Contraction in the Denison Trough in the western Bowen Basin produced a variety of geometries, including reactivation of Early Permian extensional faults as thrusts and the growth of fault-propagation folds. These inversion structures often house commercial quantities of hydrocarbons.

Abstract The subsurface geometry and tectonic development of the Devonian-Carboniferous Tamworth Belt, a fore-arc basin in the New England Orogen, Eastern Australia, has been examined using seismic reflection, aeromagnetic and gravity data. The Tamworth Belt is bounded to the west by the Moonie Fault, a thrust fault, which exhibits a fault-bend-fold geometry. Two major westward-dipping faults form the main eastern boundary, with a series of eastward-dipping backthrusts located farther to the west. The eastern margin also coincides with a gravity and magnetic ridge, similar to the gravity and magnetic pattern of the serpentinites and iron-enriched rocks that are exposed along the Peel Fault to the south. In the investigated area, the Tamworth Belt is over 50 km wide and has been shortened by at least 10 km across strike. The sedimentary succession is at least 12 km thick and is moderately folded. Within the succession, six seismic sequences were identified, each of which is separated by a major sequence boundary.