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

Abstract

Sulphur isotope ratio measurements (delta(34)S) of diagenetic pyrite an commonly used to identify S sources and mechanisms of sulphide formation in basinal sediments. This study reports: such data For a diagenetic pyrite nodule from the Brent Group sandstones of the northern North Sea at three sampling 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 ( lt -10 parts per thousand to gt +500 parts per thousand) within the nodule and isotopically heavy S (delta(34)S gt +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 adequate to characterize S isotope variations in this material.