Geochemical signature of surface water and stream sediments of a mineralized drainage basin at NE Chalkidiki, Greece: A pre-mining survey

The geochemical characteristics of surface water and stream sediments in Asprolakkas drainage basin, an area of Tertiary mineralization within amphibolite, located at NE Chalkidiki peninsula, Greece, were investigated in order to establish the geochemical baseline conditions prior to any type of new mining activities. The area represents the only example of active mining and processing of base metal sulfide ore in Greece and also includes an unmined porphyry Cu–Au ore deposit at Skouries. In a wider context, this research represents a pre-mining baseline geochemical study that can be used as an analog for similar metallogenetic provinces in areas with a Mediterranean type climate.Concentrations of dissolved major ions and trace metals displayed wide variability within the study area. Kokkinolakkas stream, draining the exploited Pb–Zn (±Ag) ore bodies, is strongly influenced by chemical weathering of sulfide minerals and presents elevated levels of SO4 (429–857 mg l−1), Pb (4–64 μg l−1), Zn (290–1350 μg l−1), Mn (1680–7899 μg l−1), Ni (12–50 μg l−1), Cd (2–8 μg l−1), As (8–45 μg l−1) and Sb (9–16 μg l−1). Stream water of unmined areas demonstrated a different chemical composition with elevated values mainly for Pb (up to 45 μg l−1) and As (up to 141 μg l−1). Hydrological conditions highly influence the behavior of major elements and metals. Stream bed sediments from Kokkinolakkas and Tsarkia Lakkos, located at the head waters of Asprolakkas basin, have anomalous values in Pb (1165–3439 mg kg−1), Zn (1368–4538 mg kg−1), As (964–2714 mg kg−1), Sb (30–70 mg kg−1), Cd (3.8–21.6 mg kg−1) and Mn (6811 up to >10,000 mg kg−1). Mobility of selected trace metals was investigated through the application of a 5-step sequential extraction procedure. Results show that, despite the high total metal content, the majority of analyzed elements are mainly bound to relatively immobile operationally defined geochemical phases of amorphous to poorly crystalline Fe and Mn oxides and the residual fraction. Considering the planned mining developments in the area, the results of this study may assist mine planners to set realistic goals for monitoring and remediation programs.

► Geochemical baseline conditions of a mining area, NE Greece.
► Sampling and chemical analyses of stream water and sediment.
► Sequential extraction of stream sediment samples.
► Water and sediment chemistry varies significantly between mined and unmined areas.
► Heavy metals associate mainly with Fe and Mn oxides and residual fraction.