Mick Dodson

A search for ancient detrital zircons in Zimbabwean sediments

86 detrital zircon grains from Archaean quartzites from the Mweza and Shurugwi greenstone belts have been dated by the ion probe SHRIMP. Nine of these give ages of 3.75–3.80 Ga, older than any Zimbabwean rocks so far satisfactorily dated, and the Tokwe-Zvishavane gneisses are a possible source for these old grains. However, none are comparable in age with the 4.2 Ga zircons discovered in Western Australia. If such old grains exist in the sample it is unlikely (P>0.05) that their abundance could exceed 3%. Ages of the younger grains are broadly consistent with the presumed age of the quartzites sampled, though some high Th/U grains in the Shurugwi sample may be anomalously young.

The Mushandike granite: further evidence for 3.4 Ga magmatism in the Zimbabwe craton

The conflict between independently published ages for the Mushandike Granite, Zimbabwe (2.92 ± 0.17 Ga and 3.45 ± 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 ± 7 and 3368 ± 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 granites 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.

Introducing the longitudinal study of Indigenous children

This chapter outlines the key design and process elements of Footprints in Time: The Longitudinal Study of Indigenous Children (LSIC). The survey collects data on the physical and mental wellbeing of the Study Children: their social and cognitive development; their place in their family and community; their health, work, lifestyle and family and community connectedness; and the services, such as child care, education and health, available in their communities. The objective of LSIC is to provide high value quantitative and qualitative data that can be used to provide a better insight into how a child’s early years affect development and to inform and improve policy responses to the diverse circumstances faced by Aboriginal and Torres Strait Islander children, families and communities.