TARGET: Proterozoic sedimentary phosphate deposits, occurring in an area 40 miles long that is aligned north-south and centered on Orroroo township, were shown by previous geological mapping undertaken by the Zinc Corp. in 1962 (over a large Enterprise Exploration Co. SML application area - the proposed licence was never issued) to be concentrated along two stratigraphic horizons in the Sturtian sequence. However, CRA's recent independent examination of old phosphate workings exposed near Pekina, Tarcowie, Orroroo and Bendleby indicated that there has been secondary redistribution of phosphate due to weathering. This finding implied that higher phosphorus concentrations may exist in possible nearby primary phosphate accumulations. EXPLORATION: Inclined diamond drilling (2 holes, total penetration 582 feet) at two surface-mineralised sites located 0.5 and 2 miles south of Orroroo, to test the phosphate-bearing rocks at depths below the zone of weathering. RESULTS: Both drillholes encountered predominantly limestone and some dolomite, with little sign of any phosphate - bearing shales or siltstones. It is suggested that the shaley surface rocks could have been derived from prolonged weathering of argillaceous carbonate rocks.