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| Macquarie Arc | |
|---|---|
| Name | Macquarie Arc |
| Type | Volcanic arc |
| Location | Tasman Sea margin, New South Wales, Australia |
| Age | Permian–Triassic |
| Orogeny | New England Orogen |
Macquarie Arc is a Permian–Triassic volcanic arc complex associated with the convergent margin of eastern Australia. The arc crops out within the New England Orogen region and records subduction-related magmatism, basin development, and mineralization across what is now New South Wales and adjacent areas. Its rocks provide insight into plate interactions that involved the Tasman Sea margin, Gondwana breakup, and Paleotethys-related terrane accretion.
The Macquarie Arc occupies parts of the New England Orogen, extending near exposures linked to the Hunter Region, Narrabri Basin, and Gunnedah Basin. It interrelates with terranes that have affinities to the Lachlan Orogen, Sydney Basin, and Bowen Basin. Key localities include volcanic centers proximate to Tamworth, Armidale, and Glen Innes, and it is spatially associated with mineral provinces noted around Broken Hill and Mount Isa in broader Australian contexts. Studies often reference comparisons to arcs such as the Banda Arc, Kermadec Arc, and Izu-Bonin Arc for subduction dynamics.
The arc formed during convergent margin processes in the Permian and Triassic, contemporaneous with regional deformation recorded in the Hunter and Hunter-Bowen fold-thrust systems. Its development involved accretion of oceanic crust and island-arc terranes similar in setting to the Hikurangi Margin, Aleutian Arc, and Philippine Mobile Belt. Significant structural elements include thrusts and mélanges analogous to those mapped in the Franciscan Complex, Chugach Complex, and the Scandinavian Caledonides. Sedimentary successions that interfinger with volcanic sequences resemble lithologies in the Karoo Basin and Molteno Formation.
Tectonically, the Macquarie Arc evolved as part of east-dipping subduction beneath the eastern margin of Gondwana, a setting comparable to the Tasman Front reconstructions, the Peru–Chile Trench, and the Sunda Trench. Plate reconstructions invoke interactions among the Indo-Australian Plate, Pacific Plate, and intervening microplates such as the Lord Howe Rise microcontinental fragments and the New Caledonia Block. The arc records stages of arc migration, slab rollback, and terrane translation similar to processes inferred for the Tonga-Kermadec system, Scotia Arc, and the Caribbean Arc. Collision and accretion phases tied to the Hunter Geosyncline and Bathurst Basin analogues produced uplift events comparable to those in the Alps and the Apennines.
Volcanism within the arc produced a range of igneous rocks from basaltic andesites to rhyolites, with intrusive suites including diorite, tonalite, and granodiorite reminiscent of plutons in the Sierra Nevada Batholith, Coast Plutonic Complex, and the Lachlan Fold Belt granites. Mafic to intermediate lava flows, pyroclastic deposits, and ignimbrites correlate with eruptive styles seen in the Taupo Volcanic Zone, Mount St. Helens, and Mount Read Volcanics. Geochemical affinities show calc-alkaline signatures comparable to the Andes, Cascades, and Indonesian volcanic arcs, with trace element distributions resembling those of the Kohistan Arc, Talkeetna Arc, and Siletzia terrane.
Stratigraphic relationships comprise volcanic-sedimentary successions, intrusive bodies, and metamorphosed sequences correlated to units named in regional mapping schemes such as the Barnard Volcanics, Dorrigo Volcanics, and Permian–Triassic turbidite assemblages. Correlative sequences are compared to the Ecca Group, Beacon Supergroup, and the Karoo Supergroup in terms of basin fill and volcaniclastic input. Key lithostratigraphic markers are interbedded tuffs, volcaniclastic breccias, and submarine pillow basalts that relate to ophiolitic fragments akin to the Bay of Islands Complex and Cove Pond Complex. Metamorphic grades vary from greenschist to amphibolite facies, paralleling metamorphic belts like the Acadian and Caledonian orogens.
The arc hosts mineralization styles including porphyry copper-gold, epithermal gold-silver, volcanogenic massive sulfide (VMS), and orogenic gold systems, compared with deposits in the Grasberg District, Porgera, and the Bingham Canyon Mine. VMS-style lenses are analogous to the Kidd Creek and Noranda camps, whereas porphyry affinities recall the El Salvador and Chuquicamata deposits. Hydrothermal alteration halos, stockwork veining, and magnetite-chalcopyrite-pyrite assemblages occur in settings similar to the Yerington District, Lachlan Fold Belt porphyries, and the Hishikari Mine. Exploration has targeted structural conduits analogous to those exploited at Kalgoorlie, Olympic Dam, and McArthur River.
Investigation of the arc spans mapping, geochronology, geochemistry, and tectonic synthesis, with notable contributions drawing on methods used in studies of the Izu-Bonin-Mariana system, the Cordilleran orogen, and the Variscan Belt. Key analytical techniques include U-Pb zircon dating comparable to work in the Jack Hills, SHRIMP studies like those on the Lachlan Orogen, and isotopic tracing using Nd-Sr-Pb systems as employed in investigations of the Red Sea margins, North Atlantic Igneous Province, and the Siberian Traps. Influential publications integrate field surveys akin to those by the Geological Survey of New South Wales and comparative research from institutions engaged in studies of the Alpine orogeny, Appalachian terranes, and the Tasmanides.
Category:Geology of New South Wales Category:Volcanic arcs