Economic stratabound Mississippi Valley-type zinc-lead-silver deposits in Early Cambrian carbonate rocks were the targets of exploration carried out north and west of Reaphook Hill in the central Flinders Ranges. Regional geological mapping (at 1:20,000 scale), stratigraphic sectional prospecting, stream sediment geochemical sampling (822 samples), the inspection of 11 gravel samples for kimberlitic indicator minerals, rock chip and soil sampling, and grid surveying and detailed (1:5,000 scale) geological mapping of the Linda prospect, were followed by drilling both there (20 reverse circulation holes totalling 500 m, plus 2 diamond holes totalling 302.4 m) and at the Third Plain willemite occurrence (2 diamond holes totalling 187.5 m). At the Linda prospect, widespread surface mineralisation occurs in pods containing up to 20% Zn+Pb sulphides, associated with an apparently long-lived biohermal reef complex in the Wilkawillina Limestone. Major facies components include archaeocyathid-rich biohermal limestones, inter-reef calcarenites, and interbedded massive calcarenites and thin calcilutites. The depositional environment variation over time was controlled by basin margin fault movements. Fracturing of the reef complex and deep karstic weathering have produced considerable open space within all of the lithotypes. Base metal mineralisation now seen at the surface occurs as linings to vughs and macrofossil clasts, as stylolytic fracture-fill, and as disseminated blebs in the matrix of sedimentary breccias, over a stratigraphic interval about 400 m thick. 13 of the 20 shallow (to 25 m) RC drillholes first put in at Linda prospect in December 1984 met with such forms of mineralisation, but only hole PLP17 had ore of an economic grade (5 m @ 2% Pb+Zn). The subsequent diamond drillholes put down in this vicinity during May 1985 encountered only sporadic sphalerite mineralisation at depth (best intercept 11 m @ 1.3% Zn below 44 m in inclined hole DLP1, including intervals of 1 m @ 4.4%, 3.9% and 2.8% Zn). The potential existence of primary zinc sulphide mineralisation at depth beneath the Third Plain willemite deposit was not effectively tested by the two diamond drillholes put down there in May-June 1985: scarce and probably secondary mineralisation was seen in hole DTP 2 above 43 m depth (8 m averaging 0.6% Zn, with the last metre assaying 1.44% Zn).