Determination of multiple sulfur isotopes in glasses: A reappraisal of the MORB δ34S

► A new quantitative method, redox specific, for sulfur extraction from glasses has been validated. ► Compared to previous studies, δ34S of MORB are negative, with a mean value of − 0.91 ± 0.50 per mil. ► We confirm that Δ33S and Δ36S are close to zero, indistinguishable from the CDT standard.