Geological prognosis of potential zinc and lead resources for Triassic formations in the Silesian-Cracow region in southern Poland

Geological prognosis of zinc and lead potential resources for Triassic formations was carried out for the Olkusz district in the southeast part of Silesian-Cracow region. Known deposits, typical phenomena in surrounding rocks, and quantitative methods for metallic ores for the perspective region or formation were a basis for the models. Statistical analysis of zinc and lead distributions and their interpretation were used to distinguish between the populations of background, anomalies, and ore bodies. Estimated values of the thresholds in the Triassic formations, i.e., 0.5 (anomalies) and 1.1 (ore bodies) wt. % of Zn, and 0.3 and 0.7 wt. % of Pb, respectively, represent the natural limits of concentration for both metals. Similar values of the thresholds obtained by other authors for other districts indicate regional regularities of zinc and lead concentration in the Triassic formations in the whole Silesian-Cracow region. Using these threshold values, the perspective zones of metals concentration can be proposed in the poorly explored areas of this region. In known deposits, the natural limit of zinc used as a cut-off value increase the reserves by about 30–40%.