Sulphur isotope characteristics of remobilised ores from the bleikvassli Zn-Pb-(Cu) deposit, Nordland, Norway

摘要

Sulphur isotope data on ores from the Bleikvassli massive sulphide deposit, Norway, are consistent with formation from hydrothermal fluids in a seafloor exhalative environment. The abundant arsenopyrite and sulphosalt-rich mobilisates, emplaced in the wallrock during the Caledonian regional metamorphism have S-isotope signatures comparable with those of the massive ore. This suggests a closed-system remobilisation in that fluids involved in transport of sulphides to the site of recrystallisation in the wallrock were probably of local origin; no modification of fractionation patterns took place during the remobilisation event. The S-isotope signatures of arsenopyrite and sulphosalt minerals (tennantite, jordanite, seligmannite) are broadly similar to those of coexisting sulphides. No evidence of fractionation ~(34)S in the sulphosalts is recorded. S-isotope data on arsenopyrite or sulphosalts can, thus, be regarded as useful in the interpretation of ore deposits.