https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:11218 Wed 11 Apr 2018 10:32:36 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31472 Hf(t)-in-zircon values (to −40) require an Archean source, which is not proximal to the Terra Australis active margin. Based on similar ɛ_Hf(t) arrays defined by Neoproterozoic granites in Western Australia and detrital zircon populations from the surrounding basins, we suggest that PG zircon grains were derived from the >2000-km-long, late Neoproterozoic Paterson-Petermann orogen, which sutured northern and southern Australia at 550–530 Ma. This Himalayan-style orogen was responsible for amalgamating Southeast Asian terranes into northeast Gondwana, thereby constraining the paleogeography of the northern Gondwanan margin at the Precambrian-Cambrian boundary. Remarkable isotopic similarity of zircon grains with the Lhasa terrane of Tibet suggests that the Paterson-Petermann orogen was the eastern sector of the developing circum-Gondwana subduction system from ca. 700 Ma.]]> Sat 24 Mar 2018 08:44:55 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1222 Sat 24 Mar 2018 08:28:30 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:20789 Sat 24 Mar 2018 08:06:02 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:20406 10 s. One of the most notable deviations occurs along the edge of cratonic Australia, where the Curnamona Province forms a salient into the younger accretionary terrane, here, the fast axis of anisotropy follows the boundary almost exactly, and is virtually coincident with magnetic lineations extracted from aeromagnetic data. To the east of this boundary beneath the Lachlan orogen, a region masked by the Cenozoic Murray Basin, the fast axis of anisotropy becomes strongly curved and traces out a semicircular pattern with a radius of 200-250 km. Farther east, the fast axis of anisotropy returns to a dominantly north-south orientation. These new findings provide strong observational support to recent geodynamic modeling results that demonstrate how large-scale oroclinal structures can become embedded in accretionary mountain belts.]]> Sat 24 Mar 2018 08:00:51 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28826 Sat 24 Mar 2018 07:38:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30080 900 °C). The values contrast with Tzr from alkaline rocks from the Cenozoic U.S. Cordillera, which are typically >800 °C for 65–70 wt% SiO2. Case studies of titanium-in-zircon thermometry from the U.S. Cordillera also suggest that alkaline magma injections into granitic magma chambers are hot, but calc-alkaline magma injections are usually cooler. A model is presented suggesting that silicic Cordilleran magmas form in magmatic arcs where hydrous basaltic magmas solidify in the arc root, producing mafic underplates that exsolve aqueous fluids, which transfer to the crust and promote water-fluxed partial melting at ambient pressure-temperature (∼750–800 °C at 8 kbar) conditions. Subsequent rock-buffered melting reactions modulate the water content of arc magmas. The granitic partial melts are water undersaturated, rise adiabatically as increments, but stall in the middle to upper crust, building cool and hydrous, crystal-rich magma chambers (batholiths). However, injections of hotter magmas are required to drive volcanic eruption. In the backarc, granitic magma chambers are intermittently recharged with hotter, drier alkaline magmas, which are produced mostly by decompression melting during lithospheric extension, not hydrous fluxing. This highlights the control of subduction dynamics on water content and consequently magmatic temperatures in silicic magma systems.]]> Sat 24 Mar 2018 07:31:17 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3207 Sat 24 Mar 2018 07:21:56 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3183 Sat 24 Mar 2018 07:18:09 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3339 Sat 24 Mar 2018 07:18:01 AEDT ]]>