A sulfur isotope study on pyrite deposits of Southern Tuscany, Italy

Hypogene pyrite and pyrrhotite show a narrow range for S 34 /S 32 , with mean value a little higher than for most magmatic hydrothermal deposits, suggesting an origin in the upper crust rather than in the mantle. Anhydrite has a much higher S 34 /S 32 ratio. These differences correspond to differences in ratios for sulfide and sulfate ions in the depositing geothermal fluid, but measured temperatures of solutions depositing a pyrite-anhydrite pair indicate that solid and aqueous phases do not have the same equilibrium constant. No isotope fractionation occurs when supergene alunite forms from pyrite.

Anhydrite

Alunite

Jarosite

Argillic alteration

10.2113/gsecongeo.61.6.1115

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Citations (37)

Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite

Geochimica et Cosmochimica Acta (2021)

Barbara I. Kleine Andri Stefánsson Robert A. Zierenberg Heejin Jeon Martin J. Whitehouse

Anhydrite

δ34S

Sulfide Minerals

10.1016/j.gca.2021.10.016

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Citations (12)

Stable isotopes and fluid inclusion study of anhydrite from the East Pacific Rise at 21.DEG.N.

GEOCHEMICAL JOURNAL (1982)

Minoru Kusakabe Hitoshi Chiba Hiroshi Ohmoto

Six anhydrite samples from the submarine hydrothermal sulphide/sulphate mineral deposits found along the crest of the East Pacific Rise at 21 °N have been examined for filling temperature of fluid inclusions and for 34S/32S and 18O/16O ratios. The anhydrite was precipitated upon mixing of hot (260–350°C), SO42--poor hydrothermal fluids with cold seawater at various proportions, which is reflected in a large variation in the filling temperatures ranging from 180°C to almost the highest exit temperatures. Seawater sulphate origin for anhydrite-sulphur is indicated by the δ34S values that are essentially identical with the present-day seawater sulphate value, whereas the δ18O values are up to 2‰ higher than the seawater sulphate value. The anhydrites are not in oxygen isotopic equilibrium with the mixed solution at measured exit temperatures of 260 to 350°C. However, this enrichment of 18O may be attributed to partial equilibration of fine-grained anhydrite with solutions at lower temperatures after deposition. Absence of anhydrite at dead vents suggests that SO42- slightly enriched in 18O is added to seawater sulphate owing to dissolution of anhydrite after the cessation of a high temperature stage of the hydrothermal activity.

Anhydrite

δ34S

δ18O

10.2343/geochemj.16.89

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Citations (26)

Evidence of sulfur isotope about the sedimentary environment of new type of polyhalite potassium ore in the northeast Sichuan Basin

Carbonates and Evaporites (2021)

Wenjun Shang Yongsheng Zhang Li Kong Enyuan Xing Yuan Peng

δ34S

Anhydrite

10.1007/s13146-021-00725-6

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Citations (3)