Sulphur isotope variations in diagenetic pyrite from core plug to sub-millimetre scales

Sulphur isotope ratio measurements (delta(34)S) of diagenetic pyrite an com monly used to identify S sources and mechanisms of sulphide formation in ba sinal sediments. This study reports: such data For a diagenetic pyrite nodu le from the Brent Group sandstones of the northern North Sea at three sampl ing scales: 50 cm (core subsample), 500 mu m (laser microprobe) and 50 mu m (ion microprobe), Similar delta(34)S variations are found by the laser and ion microprobe techniques. There is a very wide range in delta(34)S (<-10 parts per thousand to >+500 parts per thousand) within the nodule and isoto pically heavy S (delta(34)S>+20 parts per thousand) is common at all scales . The nodule delta(34)S distribution does not fit a Rayleigh fractionation pattern. The laser microprobe sampling at 100-500 mu m scales seems to be a dequate to characterize S isotope variations in this material.