Sulfur isotope data

It is worth elucidating mineral particle behavior in hydrothermal plumes in order to consider the formation mechanism of chimney and massive ores on the seafloor. Using the grain size data on sulfides and sulfates, the density of the fluids and of the minerals, the relationship between vertical settling rate and grain size of sulfides and sulfates can be derived based on the following Stokes equation  

Model for the formation of sulfate-sulfide chimneys and massive deposits on the seafloor 

The above summarized mineralogical and geochemical studies on Kuroko and Mariana chimneys (Shikazono and Kusakabe, 1999), and previous studies on midoceanic ridge chimneys, combined with the studies of mineral particle behaviors in the plumbing system, are used to develop the following plausible model for the growth history of sulfate-sulfide chimneys on the seafloor (Shikazono and Kusakabe, 1999). 

Sulfates (barite and anhydrite) precipitate due to the mixing of discharging hydrothermal solution with cold seawater above the seafloor at an early stage of hydrothermal activity. Ca and Ba in hydrothermal solution react with SO in cold seawater, leading to the precipitations of anhydrite and barite. It is observed that anhydrite precipitated earlier than barite. This may depend on the initial Ca and Ba concentrations of end member hydrothermal solutions, temperature and degree of mixing of hydrothermal solutions and 

As already noted, intense bimodal volcanic activity occurred in the Kuroko mine area at middle Miocene age and dacitic and basaltic rocks suffered hydrothermal alteration. The midoceanic ridges basalt (MORE) is widespread and sometimes hydrothermally altered. Shikazono et al. (1995) compared hydrothermally altered basalt from the Kuroko mine area and MORE and clarified the differences in the characteristics of these basaltic rocks. 

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Sulfur isotopic data of separated pyrite as the commonest sulfide mineral (Kajiwara, 1971 Kajiwara and Date, 1971) show different values for the three sub-types of Horikoshi and Shikazono (1978). The values of pyrite in the C sub-type deposits are higher than the values of pyrite from the Y and B sub-types. The values of pyrite from the Y sub-type seem to be slightly higher than those from the B sub-type. Kajiwara and Date (1971) are of a different opinion the values from the Kosaka district are higher than those in the Hanaoka district, because all sulfur isotopic data from the C sub-type were obtained in the Kosaka district. The sulfur isotopic data on the obtained Uwamuki deposits of the B sub-type in the Hanaoka district indicate systematic decrease in 8 S passing from the yellow ore (4-7%o) to the black siliceous ore (4-5%c) (Bryndzia et al., 1983). Kajiwara and Date s data (1971) include three values of pyrite in the Doyashiki deposit of C sub-type in the Hanaoka district. The main Doyashiki... 

This mechanism as a main cause for epithermal-type Au deposition is supported by sulfur isotopic data on sulfides. Shikazono and Shimazaki (1985) determined sulfur isotopic compositions of sulfide minerals from the Zn-Pb and Au-Ag veins of the Yatani deposits which occur in the Green tuff region. The values for Zn-Pb veins and Au-Ag veins are ca. +0.5%o to -f4.5%o and ca. -l-3%o to - -6%c, respectively (Fig. 1.126). This difference in of Zn-Pb veins and Au-Ag veins is difficult to explain by the equilibrium isotopic fractionation between aqueous reduced sulfur species and oxidized sulfur species at the site of ore deposition. The non-equilibrium rapid mixing of H2S-rich fluid (deep fluid) with SO -rich acid fluid (shallow fluid) is the most likely process for the cause of this difference (Fig. 1.127). This fluids mixing can also explain the higher oxidation state of Au-Ag ore fluid and lower oxidation state of Zn-Pb ore fluid. Deposition of gold occurs by this mechanism but not by oxidation of H2S-rich fluid. 

Figure 1.151. Sulfur isotopic compositions of sulfides in the vein-type and Kuroko deposits. Solid box represents sulfur isotopic data from the ore deposits occurring in basement rocks (Shikazono and Shimizu, 1993).

The sulfur isotopic data are consistent with geologic environments of Hg and Sb deposits Sedimentary rocks are dominant and marine rocks are not present in Sb-Hg mineralization districts. However, a few samples of stibnite and cinnabar from the deposits in Green tuff region display high S S values. In contrast of this interpretation on the origin of sulfur, Ishihara and Sasaki (1994) thought that sulfur came from ilmenite-series granific rocks. However, these rocks are not found in the north Hokkaido. 

A large number of sulfur isotope data on the Besshi-type deposits are available, although the variation in individual deposit has not been studied well (Yamamoto et al., 1968, 1984a,b Kajiwara and Date, 1971 Miyake and Sasaki, 1980) (Fig. 2.52). The sulfur isotopic compositions of sulfides are different in different regions. 

Fig. 2.52. Histograms showing sulfur isotope data for sulfide minerals from the major volcanogenic Cu sulfide deposits within the Jurassic to Cretaceous accretionary terrains in Japan (Sato and Kase, 1996).

Fig. 3. Sulfur isotopic data for the MRG deposit compared to published data for sedimentary rocks and base-metal and gold deposits in the BSC. (BB=Boucher Brook Fm, B=Brunswick Mine area, C=Caribou Mine, data from Tupper 1960 Lentz et al. 1996 Goodfellow McCutcheon 2003).

Calculated sulfate-sulfide temperatures, for conditions of complete isotope equilibrium, are typically between 450 and 600°C and agree well with temperatures estimated from other methods. Thus, the sulfur isotope data and temperatures support the magmatic origin of the snlfnr in porphyry deposits. 

Mass spectrometric investigations of isotopes in coal and coal minerals have also been very limited in scope. Rafter (25) published sulfur isotope data on 27 New Zealand coal samples but did not draw any conclusions from these data. Smith and Batts (26) determined the isotopic composition of sulfur in a number of Australian coals and concluded that, from this type of data, one might deduce the origin of the organically... 

Cavarretta G, Lombardi G (1990) Origin of sulfur in the Quaternary perpotassic melts of Italy evidence from haiiyne sulfur isotope data. Chem Geol 82 15-20 Cavazza W, Wezel FC (2003) The Mediterranean region. A geological primer. Episodes 26 160-168... 

Sulfur Isotope Data Analysis of Crude Oils from the Bolivar Coastal Fields (Venezuela)... 

Sulfur Isotope Data Analysis of Crude Oils... 

The evolution of global cycling of sulfur as exemplified by Equations (19) and (20) above is closely tied to the evolution of atmospheric oxygen. Thus, sulfur geochemistry, particularly sulfur isotope data, has proved to be an important probe into the overall evolution of the Earth atmosphere system (Canfield et al., 2000 Canfield and Raiswell, 1999 Canfield and Teske, 1996 Knoll et al., 1998 Lyons et al., in press Schidlowski, 1979 Schidlowski et al., 1983). 

The reduction is typically limited by the availability of organic carbon and often occurs in shallow waters at continental margins. Thus, global sulfide production would be dependent on the availability of biological productive areas over geological time. Sulfur-isotope data can be used to constrain simple models of the sulfur cycle over geological time and establish the size of the reservoirs as shown in Figure 5(b). 

On the basis of the experimental trends outlined on p. 327, sulfur isotope data have been used in unravelling the sulfur biogeochemistry of springs. The relationships between finely divided iron sulfides in the beds of springs and biogenic sulfide have been determined on isotopic evidence. 

In open flow systems, it is possible that re-oxidation of sulfide may occur far removed from the site of the sulfate reduction. This appears to be the case in Flysch waters in Czechoslovakia. Sulfur isotope data obtained by Smejkal et al. (1971) provided evidence of sequential oxidations and reductions of the form ... 

Sulfur isotope data provide additional evidence that sulfide oxidation is occurring in the aquifer. The sulfur isotopic signature (8 S) of pyrite from the SCH sample was -6.05 (-6.25 replicate) permil. This can be compared to the 5 S of sulfate (-6.48 permil) in ground water to infer origin of the... 

Figure 6. Comparison of ice core record of volcanic eruptions with sulfur isotope data from 2.5 Ga Mt. McRae shale, Western Australia. Range of sulfur isotope anomalies in Mt. McRae shale is 5 times bigger than in snow samples. Note 100-fold difference in depth scale (34, 41).

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