Seawater sulfate

The vast majority of sulfur at any given time is in the lithosphere. The atmosphere, hydrosphere, and biosphere, on the other hand, are where most transfer of sulfur takes place. The role of the biosphere often involves reactions that result in the movement of sulfur from one reservoir to another. The burning of coal by humans (which oxidizes fossilized sulfur to SO2 gas) and the reduction of seawater sulfate by phytoplankton which can lead to the creation of another gas, dimethyl sulfide (CH3SCH3), are examples of such processes. 

Kuroko deposits were reported by Sakai et al. (1970) who indicated that and values of sulfates are very close to but slightly higher than Miocene seawater sulfate value (834s = +2Wco to - -21%o 8 0 = 0%c). 

In contrast to the of hydrothermal solution for the vein, that of pyrite in hydrothermally altered rocks (Shimanto Shale) varies very widely, ranging from —5%o to - -15%o. Based on the microscopic observation, pyrite with low values less than 0%o is usually framboidal in form, suggesting that low 8 S was caused by bacterial reduction of seawater sulfate. There are two possible interpretations of high 8 " S values (+10%o to - -15%o). One is the reduction of seawater sulfate in a relatively closed system. The other one is a contribution of volcanic SO2 gas. As noted already, volcanic SO2 gas interacts with H2O to form H2SO4 and H2S. value of SO formed by... 

There are two possibilities here to explain this correlation. One is that isotopically heavy sulfide sulfur derived from seawater sulfate was fixed in shale because reducing agency of shale with carbonaceous matters is thought to be stronger than that of sandstone. The ore fluids extracted this sulfur. Gold of low NAg precipitated in shale like the Kuryu deposit under more reducing environment than in sandstone like the Saigane deposit. 

Sasaki, A. and Kajiwara, Y. (1971) Evidence of isotopic exchange between seawater sulfate and some syngenetic sulfide ores. Mining Geology Special Issue, 4, 289-294. 

Fig. 2.43. Graphical illustration of sulfur isotope values of HiS (left axis and. solid line) produced during basalt-seawater interaction at various water/rock ratios. Calculations assume that seawater sulfate is mostly removed as anhydrite, that any residual sulfate is reduced by iron oxidation in reacting basalt, and that there is quantitative leaching of basaltic sulfide and homogeneous mixing of both sulfides. Dashed line...

The 8 S data on barites from the Yanahara and Hitachi (Yamamoto et al., 1984b Kase and Yamamoto, 1985) are -f-12%o to - -15%o which is similar to those of Late Paleozoic seawater sulfate, indicating that barite formed by the mixing of seawater and hydrothermal solution as same as Kuroko barite (Kusakabe and Chiba, 1983). 

The ore fluids responsible for epithermal base-metal vein-type deposits were generated predominantly by meteoric water-rock interaction at elevated temperatures (200-350°C). Fossil seawater in marine sediments was also involved in the ore fluids responsible for this type of deposits. Epithermal precious metal ore fluids were generated by meteoric water-rock interaction at 150-250°C. Small amounts of seawater sulfate were involved in the ore fluids responsible for epithermal precious metal vein-type deposits occurring in Green tuff region (submarine volcanic and sedimentary rocks). 

Paytan A, Kastner M, Campbell D, Thiemens MH (1998) Sulfur isotope composition of Cenozoic seawater sulfate. Science 282 1459-1462... 

Unusually low values were reported for seawater sulfate, ranging from +9.7 to 17... 

Figure 1. Transformations in the ocean and overlying atmosphere which lead to the production of sulfate from a marine biogenic source (dark arrows). DMS is produced in the ocean after the uptake of seawater sulfate by phytoplankton and the production and breakdown of DMSP. Sulfate formation occurs after DMS is transferred across the sea-air interface and undergoes atmospheric oxidation. The S S values for the individual sulfur pools are indicated in the boxes and measured or estimated discriminations (D) are indicated above the arrows. Clearly, data for the remote atmosphere are limited.

Although limited, the data suggest that DMS from marine phytoplankton would most likely be enriched in the heavier isotope and would have a 634S value slightly less than seawater sulfate as a result of ASR. Until the 634S values for seawater DMS, remote SO2 and sulfate are actually measured or until the uncertainties which surround the removal pathways for DMS and its atmospheric oxidation are addressed, questions remain as to the i S value of atmospheric sulfate from this source. 

It is already possible to measure the values for seawater sulfate, DMSP, and seawater DMS, but only minimal data exist. Coordinated measurements of these compounds, along with simultaneous 634S measurements of atmospheric DMS, S02, methane sulfonate and non-seasalt sulfate, from atmospheres free of continental influence, are needed. These data will help in the isotopic interpretation of sulfur sources so that their relative contributions to the remote atmosphere can be assessed. 

Source of Sulfur. Most of the sulfur in high-sulfur coal arises from the occasional seawater inundations over the coastal swamp during peat accumulation or from the seawater that flooded the peat swamp and terminated peat accumulation. Seawater sulfate diffused freely into the underlying peat and was reduced by microorganisms to H2S, S°, and polysulfides. 

Shanks W. C., Bischoff J. L., and Rosenbauer R. J. (1981) Seawater sulfate reduction and sulfur isotope fractionation in basaltic systems interaction of seawater with fayaUte and magnetite at 200-300°C. Geochim. Cosmochim. Acta 45, 1977-1995. 

Using and Atmospheric sulfur values are typically in the range of —5%o to - -25%o (Krouse and Mayer, 2000). Seawater sulfate has a value of 4-2 l%o. Atmospheric sulfate derived from marine sources will show values... 

Figure 28 The sulfur isotopic composition of Phanerozoic seawater sulfate based on the analysis of stmcturally substituted sulfate in carbonates (Kampschulte and Sfrauss, in press) and evaporite based 6 data (source Sfrauss,...

Figure 29 Isotopic composition of seawater sulfate during the past 65 Ma (Paytan et al., 1998, 2002) with ages modihed somewhat (sources Pa3dan, personal communication, 2003).

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