The CHILDARA 1:250 000 map area is located on the western Gawler Craton, an ancient crystalline shield comprising Archaean, Palaeoproterozoic and Mesoproterozoic metasediments, volcanics and granites that has been tectonically stable since 1450 Ma (Thomson, 1975; Parker, 1993). Basement outcrop is poor and is restricted to scattered, low sheets of granite and inselbergs over much of the area, except for the Gawler Ranges to the east. Brown (1885), during an expedition from Ceduna to Mount Finke, commented on granite inselbergs in north-western CHILDARA. Bennett (1968) produced a preliminary geological map of part of CHILDARA. Blissett and Vitols (1974) carried out a helicopter survey to collect samples and map basement outcrops on the western Gawler Craton. This survey formed the basis for the previously unpublished 1:250 000 geological mapping (Blissett, 1980). Samples were assayed for a range of elements including base metals and gold. Company mineral exploration has been restricted to the more accessible areas along the eastern and south-western sections of the map area. Major mineral exploration interest in the CHILDARA region began after the discovery of the Tunkillia gold prospect in 1996. During 1996, calcrete sampling by Helix Resources NL and Equinox Resources NL delineated gold anomalies at Tunkillia and Nuckulla Hill within the Yarlbrinda Shear Zone (YSZ). The Tunkillia prospect is located at the northern end of the YSZ, where the north-south trending shear zone is re-orientated towards the north-west by the Yerda Shear Zone. Martin (1996) reported that mineralisation is hosted by variably deformed granite, which has been extensively haematite and/or silica-sericite-chlorite altered. Areas 223 and 191 are located within a demagnetised zone, with gold mineralisation associated with steeply dipping high grade veins within an envelope of essentially barren, but highly altered granite. At Area 223, mineralisation occurs over a strike length of 500 m and is between 10-120 m wide, with a high grade zone 10-25 m wide yielding individual 4 m samples containing up to 32.4 g/t (Martin, 1996). Within the central part of the YSZ, Equinox Resources NL delineated gold mineralisation at the Myall, Sheoak and Bimba prospects. Host rock types range from brecciated granite to syenogranite, quartz diorite, adamellite and mylonitic gneisses, which have undergone amphibolite facies metamorphism (Parker, 1996). Post-peak metamorphic sericitisation and quartz veining were followed by calc-silicate ± epidote veining ± chlorite ± adularia ± quartz ± fluorite or calcite (Parker, 1996). Gold grades range from 7 m at 3.1 g/t, including 3 m at 6.2 g/t within drillhole NHAC 26 at Sheoak, to 3 m at 1.67 g/t (NHAC 150) and 5 m at 1.71 g/t (NHAC 152) at the Bimba prospect (Daly et al., 1998). The first geophysical study of the area was carried out by the Bureau of Mineral Resources, Geology and Geophysics (BMR) in 1961 in the search for iron ore deposits using reconnaissance airborne magnetic and radiometric surveys over most of CHILDARA (Quilty, 1962). The BMR also conducted a regional gravity survey by helicopter, which included CHILDARA, during 1970 (Pettifer and Fraser, 1974). High-resolution aeromagnetic data flown by World Geoscience Corporation, Geoterrex and Kevron during 1992-1995 has greatly enhanced the exploration potential of the western Gawler Craton. Major structures have been delineated including the YSZ which extends for ~170 km and trends north-south along the western margin of the Gawler Range Volcanics, but is re-orientated to the north-west where it intersects the Koonibba Fault and the Yerda Shear Zone. Further fieldwork was undertaken by Ferris in the late 1990s and early 2000, including helicopter surveys of more isolated exposures. This work involved regional mapping and sampling, from which much of the geochemical analyses discussed in these notes are derived. Ferris (2001) provides in-depth details for the Proterozoic lithologies and their relationships on CHILDARA.