The possible role of thiosulfate in the precipitation of 34S-rich barite in some Mississippi Valley-type deposits

Abstract

Abstract. The precipitation of extremely 34S-rich barite in the late stage of mineralization in the Mississippi Valleytype deposits of the Illinois-Kentucky district (U.S.A.) may be explained by reactions involving thiosulfate ($20~). Inorganic processes are known to concentrate 34S in the sulfonate site of thiosulfate and 32S in the sulfate site. In the mineralizing solution, these inorganic processes may have fractionated sulfur between the two sites by about 40 per rail. At the low temperatures of the late barite stage of mineralization, bacteria are known to metabolize thiosulfate by various reactions. In one of these, dissimilatory reduction, hydrogen sulfide and sulrite are produced. Isotopically light sulfite is preferentially reduced to sulfide by bacteria to leave a residual sulfite enriched in 34S. Part of the residual sulfite may be oxidized to form isotopically heavy sulfate; part may recombine with hydrogen sulfide to form thiosulfate. The recombination also enriches the sulfonate site in 34S and the sulfane site in 32S. Recycling the newly formed thiosulfate through the above steps further enriches sulfite and sulfate from oxidation of sulfite in 34S. During genesis of the ores, the aggregate effect of these reactions may have been the precipitation of extremely 34S-rich barite.The sequence of reactions suggested above requires the presence of organic matter. Previously proposed reactions to account for the precipitation of sulfide minerals and fluorite and for the carbonate paragenesis also require the presence of organic matter. Thus, organic matter in the host rocks may cause the various ore-zone reactions and account for the localization of the ores.

Variability in fluid sources in the fluorite deposits from Asturias (N Spain): Further evidences from REE, radiogenic (Sr, Sm, Nd) and stable (S, C, O) isotope data

“…We can thus envisage a scenario where sulphate, dissolved in a fluid of surficial origin trapped within the sediments, was being bacteriogenically reduced in the presence of organic matter in a closed system. Similar high 8 34 S values were reported by Richardson et al (1988) in late stage barite from the illinois-Kentucky district, U.S.A., and were explained by a combination of inorganic and bacterially catalyzed reduction processes involving thiosulphate in the presence of organic matter (Spirakis, 1991). This hypothesis cannot be discarded as the presence of organic matter associated with fluorite and sulphides (hydrocarbon-bearing fluid inclusions and bitumen) is a common feature in the studied deposits.…”

Barite deposition resulting from phototrophic sulfide-oxidizing bacterial activity

“…Alternatively, barium laden brines may mix with sulfate-containing meteoric water, also resulting in barite formation (Kaiser, 1987;Williams-Jones et al, 1992). Although microbial processes have not been previously shown to be directly involved in sulfide oxidation and resultant barite formation in subsurface systems, stable isotope data has shown that sulfate or thiosulfate reducing bacteria may be involved in formation of sulfide and sulfite, respectively (Kaiser, 1987;Spirakis, 1991). These sulfur compounds can then be oxidized to form sulfate and subsequently barite.…”

Barite encrustation of benthic sulfur‐oxidizing bacteria at a marine cold seep

“…Specific mechanism(s) by which microorganisms mediate barite precipitation vary and are incompletely understood. Potential mechanisms include passive or active biological enrichment of barium (e.g., Goldberg & Arrhenius, ; Bishop, ; Ganeshram et al ., ; Bonny & Jones, ), the generation of sulfate via sulfide oxidation (Spirakis, ; Senko et al ., ; Bonny & Jones, ), and cellular surfaces acting as nucleation sites for crystal precipitation (e.g., Gonzalez‐Muñoz et al ., ; Gonzalez‐Muñoz et al ., ).…”