The changing patterns and episodic nature of diastrophism, sedimentation, and volcanism from Late Ordovician through Early Devonian time in Australia, New Guinea, and New Zealand is presented with the aid of a correlation chart and two paleogeographic-lithofacies maps for late Llandovery and Ludlow-Pridoli times; such analysis proved impractical for the early Llandovery and Wenlock owing to the paucity of preserved sequences, a reflection of significant diastrophism at those times. The criteria for correlation, patterns of paleocommunities, and the applicability of local series’ names are examined; plutonism and the contribution of radiometric dating, particularly with regard to estimates of the age of system boundaries, using Australian sequences, are briefly probed. Graptolites have been used as the primary basis of correlation, supplemented by conodonts, corals, and brachiopods. Marine sediments of definite Llandovery and Wenlock age are known only from the Tasman Mobile Belt of eastern Australia and its extension through New Guinea. Paleontological control is poor for sequences accumulated in basins within the craton. Evaporitic sedimentation was widespread in the South Canning Basin of Western Australia. Continental, predominantly aeolian, sedimentation occurred in the Amadeus Basin of central Australia; minor marine incursions, the paleogeography as presently known, and the pattern of Silurian orogenesis (Rodingan Movement) in central Australia suggest connection intermittently through the South Canning Basin rather than eastward to the Tasman Mobile Belt. Connection between the South Canning sequence and the Ludlow carbonate-evaporite sequences in the Carnarvon Basin of Western Australia was offshore with respect to the present coastline. Following the wane of Late Ordovician volcanism, most of the Tasman Mobile Belt in southeastern Australia underwent a major diastrophic revolution, the Benambran Orogeny. Three phases are discernible stratigraphically: the first in early Llandovery time, the second in middle or early late Llandovery, and the third during the Wenlock, probably not including latest Wenlock time (Quarry Creek phase). Owing to the severity of deformation and perhaps to its continuity in time over most of the area, the first two phases have not been widely distinguished from each other; they are commonly lumped together as the Canberra orogenic phase. A pattern of two longitudinal troughs and two highs, the Cowra Trough and Molong High–Yass Shelf, the Hill End Trough and Capertee High, perhaps initiated earlier, became pronounced in central and southern New South Wales and eastern Victoria following the Benambran events. Platform sequences accumulated on these highs during late Wenlock-Pridoli time; carbonate buildup was particularly prominent during Ludlow time. Relative diastrophic quiescence persisted from latest Wenlock through Ludlow and Pridoli time when southeastern Australia underwent a new cycle of diastrophic events, the Bowning Orogeny. Although formerly regarded as having taken place toward the close of Silurian time and extending into the Early Devonian, recent paleontologic and stratigraphic work indicates an onset not earlier than the Gedinnian. Effects of the Bowning and Benambran Orogenies are less pronounced in the Melbourne Trough of Tasmania and central Victoria than they are in eastern Victoria and in southern and central New South Wales. Contraction of the Melbourne Trough through Late Ordovician into Silurian time seems apparent from the record as preserved. Orogenic events contemporaneous with the Benambran and Bowning events have not been distinguished in northern Queensland or New Guinea, although diastrophic events of Wenlock age have been documented for the former. Volcanism was conspicuously rare or absent during Llandovery time. Acid and andesitic volcanism was widespread in southeastern Australia following the Quarry Creek phase of the Benambran Orogeny, then contracted during Ludlow time to the Canberra and adjacent areas. Predominantly acid volcanism became widespread following the onset of the Bowning Orogeny. The acme of volcanism appreciably postdates the main deformational episodes for both orogenies in eastern Victoria and southern New South Wales.

Abstract The Cadia district of New South Wales contains four alkalic porphyry Au-Cu deposits (Cadia East, Ridgeway, Cadia Hill, and Cadia Quarry) and two Cu-Au-Fe skarn prospects (Big Cadia and Little Cadia), with a total of ~50 Moz Au and ~9.5 Mt Cu (reserves, resources, and past production). The ore deposits are hosted by volcaniclastic rocks of the Weemalla Formation and Forest Reefs Volcanics, which were deposited in a submarine basin on the flanks of the Macquarie Arc during the Middle to Late Ordovician. Alkalic magmatism occurred during the Benambran orogeny in the Late Ordovician to early Silurian, resulting in the emplacement of monzonite intrusive complexes and the formation of porphyry Au-Cu mineralization. Ridgeway formed synchronous with the first compressive peak of deformation and is characterized by an intrusion-centered quartz-magnetite-bornite-chalcopyrite-Au vein stockwork associated with calc-potassic alteration localized around the apex of the pencil-like Ridgeway intrusive complex. The volcanic-hosted giant Cadia East deposit and the intrusion-hosted Cadia Hill and Cadia Quarry deposits formed during a period of relaxation after the first compressive peak of the Benambran orogeny and are characterized by sheeted quartz-sulfide-carbonate vein arrays associated with subtle potassic, calc-potassic, and propylitic alteration halos.

Abstract The Tasmanides of eastern Australia record the break-up of Rodinia, followed by the growth of orogenic belts along the eastern margin of Gondwana. Spatially, the Tasmanides comprise five orogenic belts, with an internal Permian-Triassic rift-foreland basin system. Temporally, the Tasmanides comprise three (super)cycles, each encompassing relatively long periods of sedimentation and igneous activity, terminated by short deformational events. The Neoproterozoic-earliest Ordovician Delamerian cycle began by rifting, followed by convergent margin tectonism and accretion of island-arc forearc crust and ?island arcs in the Middle-Late Cambrian. The Ordovician-Carboniferous convergent margin Lachlan supercycle consists of three separate cycles, each ending in major deformation. The Ordovician Benambran cycle includes convergent (island-arc) and transform margin activity terminated by terrane accretion in the latest Ordovician-earliest Silurian. The Silurian-Middle Devonian Tabberabberan cycle reflects development of a large back-arc basin system, marked by rift basins and granite batholiths, behind intra-oceanic arcs and an Ordovician-Early Devonian terrane that were accreted in the Middle Devonian. The Middle Devonian to Carboniferous Kanimblan cycle began by rifting, followed by continental sedimentation inboard of a major convergent margin system that forms the early part of the Late Devonian-Triassic Hunter-Bowen supercycle. This supercycle comprises a Late Devonian-Carboniferous continental arc, forearc basin and outboard accreted terranes and subduction complexes intruded by the roots of a Permian-Triassic continental margin arc. Complex deformation ended with accretion of an intra-oceanic arc in the Early Triassic. Key features of the Tasmanides are: continuity of cycles across and along its length, precluding growth by simple eastwards accretion; development of a segmented plate margin in the Late Cambrian, reflected by major rollback of the proto-Pacific plate opposite the southern part of the Tasmanides; rifting of parts of the Delamerian margin oceanwards, to form substrate to outboard parts of the Tasmanides; the presence of five major Ordovician terranes in the Lachlan Orogen; and the generation of deformations either by the accretion of arcs, the largely orogen-parallel ‘transpressive’ accretion of Ordovician turbidite terranes (in the Lachlan Orogen), or by changes in plate coupling.