b'The Australian continent: A geophysical synthesisFeatureFigure 6.Surface geology of Australia with main geological provinces marked (following Figure 3).well as some mineral data. For felsic samples there was a goodand Southern Australian cratons. Archean model ages are most agreement with estimated or known magmatic age. common in the Archean Pilbara and Yilgarn cratons of West The Sm-Nd data were standardised and used to calculateAustralia, but also occur in both the North and South Australian epsilon Nd (Nd) and two-stage depleted mantle model agescratons. The majority of Australian model ages are Proterozoic (T2 DM ). The map in Figure 8 has been constructed from aroundin age. The youngest model ages are restricted to the Tasman 1500 data points, with the exclusion of samples from S-typeBelt in the east, chiefly within the New England Orogen.magmatism to avoid sediment contamination. Within all the major elements of structure across the Australian continent there are indications of internal isotopic zonation, The estimated model ages range from 4.0 Ga in the Yilgarnincluding regions with relatively sharp changes over narrow and Pilbara cratons of the West Australian Element to ca. 0.3 Gabands or distinct, but diffuse, gradients.in the New England Orogen of the Tasman Element in eastern Australia. Even though the granites may have somewhatMany of the breaks and gradients in the distribution of variable properties with respect to retention of Nd signals, themodel ages across the continent correspond to known model ages generally correlate well with the known geology ofcrustal boundaries or changes in geology, which indicates Australia and the major crustal elements. that Sm-Nd whole rock signatures can be used to identify crustal changes. For example, the strong increase in younger There is a broad eastward trend in decreasing model agesisotopic signatures in the southern half of the Northern across the Australian continent, mirroring the surfaceTerritory suggests processes associated with an accretionary exposures. Younger domains through Central Australiamargin, similar to the patterns observed in the Tasman separate the cratonic zones in West Australia and the Northernorogens.45 PREVIEW APRIL 2019'