Stream sediment and soil geochemistry of the largest volcanogenic massive sulfide deposit in Türkiye, Karaburun deposit (Central Pontides)

Abstract

The recently discovered and potentially economic Karaburun deposit stands out as the largest VMS deposit in Türkiye, with a geological resource of ~125 Mt. at 1.16 wt% Cu, 0.25 wt% Zn, and 0.05 wt% Co. The pelitic-mafic type mineralization occurs within the low-grade greenschist facies metamorphic rocks in the Central Pontides Orogenic Belt. It is associated with volcaniclastic, clastic detrital sedimentary, and deep marine sedimentary rocks and cross-cutting submarine mafic dikes and/or sills. This study reports the statistical evaluation of stream sediment and soil geochemistry surveys, providing a well-documented example of preliminary surficial geochemical studies prior to the discovery of the Karaburun mineralization. Statistical analysis of 166 stream sediment samples shows that copper is the most reliable indicator of potential mineralization. Soil sampling was subsequently conducted in the source area of Cu anomalies, and a total of 2306 samples were collected. Both the median-median absolute deviation and the concentration-number (CN) fractal methods yielded reliable results in determining spatial distributions; however, the fractal method provided more robust threshold values. The positive moderate to strong correlations between As–Pb–Zn and Cu–Zn–Bi indicate that these elements can be used to determine potential areas exhibiting anomalies. The distribution of selected elements in the “B” soil horizon is mostly consistent with the gossan formation. Anomalies in Cu, Zn and Co as the best indicator and pathfinder elements suggest weathering processes through pre-existent outcropping mineralized zones. The weathering, oxidation, and possibly erosion in the upper section of pre-existing Pb-enriched mineralization may have caused some Pb enrichments and local anomalies. Bismuth has been highlighted for the first time in soil geochemistry studies in the Central Pontides and could serve as a pathfinder element. However, structural features largely control the spatial distribution of elements and gossan zones; therefore, physical dispersion should also be considered alongside geochemical patterns. Factor analysis was applied to samples from Cu- and Zn-dominant zones identified through anomaly maps. The extracted factors collectively indicate associations with immobile elements during weathering processes, mineralization content, mafic volcanic or volcaniclastic rocks, and absorption onto Fe-oxides or newly formed compounds. Finally, we applied the robust weathering index, which indicates temperate climatic conditions during the weathering processes.