1968/01/01 by Hitoshi Sakai · 1 citation
Chemistry · Earth and Planetary Sciences · Environmental Science · #Chemical Synthesis and Characterization #Groundwater and Isotope Geochemistry #Radioactive element chemistry and processing
paper · pdf · doi:10.2343/geochemj.2.29
crossref issued 1968/01/01 · crossref published 1968/01/01 · crossref published-print 1968/01/01 · openalex publication_date 1968/01/01 · crossref created 2011/10/11 · crossref deposited 2021/05/20 · openalex created_date 2025/10/10 · crossref indexed 2026/07/29 · openalex updated_date 2026/08/01
The reduced partition function ratio predicts that among sulfide minerals in isotopic equilibria the heavy isotope (34S) is enriched in the following order: galena < chalcopyrite < sphalerite < pyrite. This order also exists among coexisting sulfides in natural deposits. The isotopic composition of pyrite at hydrothermal temperatures is estimated to be very close to that of gaseous hydrogen sulfide. The isotopic property of aqueous sulfide ions is determined by the relative concentrations of the three species H2S, HS-, and S2-, all of which have different reduced partition function ratios. Therefore, the pH of hydrothermal solution is as important a parameter as the temperature in determining the isotopic ratio of a sulfide mineral. δS* of pyrite, for instance, in isotopic equilibrium with a solution at 500°K having a δS of 0.0‰, would be +5.0‰ at pH 9.5, +2.0‰ at pH 8.0, and 0.0‰ at pH 4.0. Some natural examples are discussed which may indicate a change with time in the pH as well as in the isotopic raito of hydrothermal solutions during mineralization. The isotopic exchange reaction between sulfide and sulfate is also discussed.