ABSTRACT

Sulphide and sulphate minerals mixed with V₂O₅ and SiO₂, were heated in a vacuum at 950°C for 15 minutes. The evolved SO₃ was converted to SO₂ by reaction with metallic Cu for sulphur isotope determinations. This technique yields SO₂ of consistent oxygen isotope composition regardless of whether sulphide or sulphate is converted. The reproducibilities of sulphur conversion and δ³⁴S values were 98 ±5% and ±0.2‰, respectively. The technique is particularly suitable for small samples. Successful isotope determinations have been obtained with natural samples containing less than 1 mg S. In some cases, variations in δ³⁴S of 2‰ have been found for single grains analysed from a small specimen.