Geochemistry and behavior of REE in stream sediments close to an old Sn-W mine, Ribeira, Northeast Portugal

摘要: Abstract The abandoned Sn-W Ribeira mine, northeast of Portugal, contained quartz veins with cassiterite, wolframite, scheelite, pyrite, arsenopyrite, sphalerite, chalcopyrite, manganocolumbite, bismuthinite, native bismuth, phosphates and carbonates. exploration took place on the northern slope Viveiros stream, which is an affluent Sabor River. waste-rock dumps tailings were deposited hillside, close to mine are nowadays exposed significant weathering erosion, as they not vegetated. eroded material transported by stream toward A seasonal drains tailings. sediments samples collected along in a spring at bottom tailings, River other streams affected workings, following influence (1.2 km away from workings). data show that degree pollution increases especially winter. highest for As, In, W, Sn Bi. drainage main particularly polluted during winter, Bi, In Sn. sedimentary precipitate Cu, Sn, Ta, Zn, Nb, Ag, Sb Ta. significantly W regional streams, have similar REE (NASC normalized) patterns (ΣREE = 131.7–185.9 mg/kg, La N /Lu  = 1.23–1.42 Eu/Eu* = 1.02), while those crossing enriched (ΣREE = 250.3–283.6 mg/kg,  = 1.6–2.09 Eu/Eu* = 0.96). general decrease values increase total Fe 2 O 3 can be explained partitioning HREE solid Fe-oxides phase. coatings, mainly formed Fe-oxy-hydroxides, but also contain jarosite, impoverished all REE. impoverishment release surface occurs due local lowering pH, caused jarosite dissolution. During successive alternate cycles wet dry conditions, takes formation Fe-oxy-hydroxides coatings. subsequent dissolution releases acidity, thus promoting de-sorption mineral phases.