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The conflict between independently published ages for the Mushandike Granite, Zimbabwe (2.92 [+ or -] 0.17 Ga and 3.45 [+ or -] 0.13 Ga) has been resolved in favour of the older age by SHRIMP U-Pb analyses of zircon. Two samples yield indistinguishable estimates of 3374 [+ or -] 7 and 3368 [+ or -] 11 Ma for the crystallization age of the magma. Together with published data from elsewhere in southern Zimbabwe, the results imply a widespread magmatic event at about 3.35 Ga. A single zircon core giving 3.46 Ga, together with the granite's previously measured Nd model age, suggests that the Mushandike magma could have incorporated remobilized basement similar to the c. 3.5 Ga Tokwe gneisses which crop out 30 km to the west. The published Rb-Sr and Pb-Pb datasets show evidence of late Archaean disturbance of Sr and Pb isotope systematics. In the absence of exposed contacts between the Mushandike granite and the neighbouring Mushandike stromatolitic limestone, the new U-Pb emplacement age suggests that the limestone is unconformable on the granite.

The U-Pb ages of fine-grained zircon separated from 2 dust-dominated soils in the eastern highlands of south-eastern Australia and measured by ion microprobe (SHRIMP) revealed a characteristic age `fingerprint' from which the source of the dust has been determined and by which it will be possible to assess the contribution of dust to other soil profiles. The 2 soils are dominated by zircon 400-600 and 1000-1200 Ma old, derived from Palaeozoic granites and sediments of the Lachlan Fold Belt, but also contain significant components 100-300 Ma old, characteristic of igneous rocks in the New England Fold Belt in northern New South Wales and Queensland. This pattern closely matches that of sediments of the Murray-Darling Basin, especially the Mallee dunefield, suggesting that weathering of rocks in the eastern highlands has contributed large quantities of sediment to the arid and semi-arid inland basins via internally draining rivers of the present and past Murray-Darling River systems, where it has formed a major source of dust subsequently blown eastwards and deposited in the highland soils of eastern Australia. Additional keywords: aeolian dust, dust deposition, dust provenance., Introduction Windblown dust contributes significantly to soil formation in many regions worldwide (Simonson 1995). In south-eastern Australia, dust is carried from the arid and semi-arid interior and deposited in the [...]