Soil Geochemical Investigation of Cu–Pb–Zn Anomalies in the Örencik Prospect (Geyve, Sakarya, Türkiye)

This study evaluates Cu–Pb–Zn soil-geochemical anomalies in the Örencik prospect, NW Türkiye, using robust thresholding, multivariate statistics and indicator-kriging probability mapping. The dataset comprises 1100 primary B-horizon soil samples collected on a nested grid locally densified from 50 × 100 m to 50 × 50 m and 25 × 25 m. Background–anomaly boundaries for Cu, Pb, Zn and As were defined using the median and normalised median absolute deviation (nMAD) of log10-transformed concentrations. The element-specific M + nMAD thresholds were 54.68 ppm Cu, 19.18 ppm Pb, 81.23 ppm Zn and 13.68 ppm As. At or above these thresholds, 15.64% of Cu, 16.64% of Pb and 12.18% of Zn observations were classified as anomalous; notably, 133 of the 134 anomalous Zn samples remained within the weak anomaly class. Correlation analysis and PCA distinguish a Cu–As association from a Zn–Co–Ni–V association; PC1 and PC2 explain 69.51% of the total variance, while a Pb-dominated PC3 is treated only as an exploratory secondary component. Indicator kriging delineates compact and discontinuous Cu probability zones, a more continuous Pb belt and a broad Zn pattern. Integration of the robust thresholds, multivariate relationships and spatial probability patterns indicates that Zn variability has a stronger lithological contribution, whereas spatially coherent Cu and Pb zones provide the principal exploration targets. These targets require geological verification and are not interpreted as confirmed economic mineralisation.