Sulphur isotope ratios

Variations in the 8 34S values for plants have been summarised by Krouse et al. (1991), these range from -20 to +34%o and are comparable to those reported in sedemintary rocks. It has been found that the sulphur uptake by the plant is mainly from soil sulphate where ambient S02 levels are low. In some cases ambient S02 dominates and the 8 34S values are close to those of the S02. These two uptake mechanisms are a factor in the differing isotope ratios in different parts of an individual plant (Chukhrov et al., 1978). Thus sulphur isotope ratios are helpful in the determination of sulphur sources in the environment. 

Andersson P., Torssander P., and Ingri J. (1992) Sulphur isotope ratios in sulphate and oxygen isotopes in water from a small watershed in central Sweden. Hydrobiologia 235/ 236, 205-217. 

The sulphur isotopic ratios (Fig. 5b) have a wide range, with a sharp 5 S peak around 0%o. As with the Shavi samples, some values are very negative (e.g. — 14.9%o compare Goodwin et al. 1976 Hayes et al. 1983) considering the age of the rock (Habicht Canfield 1996). 

The sulphur isotopic ratio, 34S/32S, expressed as 834S (in parts per thousand, %o, relative to meteoritic sulphur) of ocean water has changed through time, and is reasonably well known for the past 900 Myr (Holser and Kaplan, 1966 Claypool et al., 1980 Strauss, 1997). Accordingly, older marine (and therefore, by default, also some terrestrial) evaporites may be... 

Fig. 7.21 Sulphur isotope ratios (834S) for various sources of sulphur and in atmospheric aerosols for several localities. Mace Head (western Ireland) data, courtesy of Nicola McArdle,...

Sulphur isotopic ratios were measured on two samples from Murgental and Altishofen (Lower Freshwater Molasse). In the pervasive pyrite cements from Murgental, both the edge and the centre of a patch were measured, yielding cdt (Canyon Diablo Troilite) values of -14.4%o and +1.1 %o, respectively. In Altishofen, two spots of mica replacement were measured, yielding 6 S cdt values of-28.1%0 and -22.1%o. 

Several lines of evidence suggest the involvement of TSR. Partially dissolved remnants of early diagenetic anhydrite cement are found embedded in quartz cement (Fig. 12). Fluid inclusion data indicate that nodular quartz cement with anhydrite inclusions (Fig. 15) formed at elevated temperatures, suggesting that anhydrite dissolution may have coincided with high temperature TSR. Post-pyrobitumen carbonate and pyrite cements and nodules are also present in the Norphlet and may represent late diagenetic precipitates associated with TSR. Pyrite cement from the Norphlet has sulphur isotope ratios that are identical to those of the Pine Hill Anhydrite (Table 3) and within the range reported for Jurassic seawater (Hoefs... 

Newman, L., Forrest, J. and Manowitz, B., 1975a. Determining the extent of oxidation of sulphur dioxide in power plant plumes from isotopic ratio measurements. In Isotope Ratios as Pollutant Source and Behaviour Indicators. International Atomic Energy Agency, Vienna, 486 pp. 

Grassineau, N. V., Mattey, D. P. Lowry, D. 2001a. Rapid sulphur isotopic analyses of sulphide and sulphate minerals by continuous flow-isotope ratio mass spectrometry (CF-IRMS) Analytical Chemistry, 1212), 220—225. 

Calhoun, J.A. Bates, T.S. (1989) Sulfur isotope ratios. Tracers of nonsea-salt sulfur in the remote atmosphere. In Saltzman E.S. Cooper W.J. (Eds) Biogenic Sulphur in the Environment. Washington, DC American Chemical Society, pp. 369-379. 

Stable isotope (see Box 1.1) abundances cannot at present be determined with sufficient accuracy to be of use in studies of their natural variations. Mass spectrometers can, however, measure the relative abundances of some isotopes very accurately, resulting in stable isotope ratio measurements, for example oxygen —180/160, carbon — 13C12C and sulphur—3%/32S. Stable isotope ratios are reported in delta notation (8) as parts per thousand (%o per mil) relative to an international standard, i.e. ... 

An alternative means of sulphur isotope fractionation in igneous rocks is by the degassing of SO2 from sub-aerial or shallow submarine lavas. This fractionation is controlled by the sulphate/sulphide ratio of the melt, which in turn is controlled by temperature, pressure, water content and oxygen activity. SO2 outgassed by basic lavas is enriched m relative to die melt because the dominant sulphur species in the melt is sulphide and SO2 is enriched in 5 S relative to sulphide (see Figure 7.26). The process is documented from Kilauea volcano, Hawaii, by Sakai el al (1982) and quantified by 2heng (1990). 

Sulphur isotope studies of hydrothermal ore depodts offer the opportunity to (1) determine the origin of the sulphur present in the orebody as sulphides and sulphates (2) determine the temperature of formation of the sulphides and of the ore-forming fluids (3) determine the water/rock ratio effective during the mineralization (4) determine the degree of equilibrium attained and (5) thus constrain the mechanism of ore deposition. 

Isotopic composition of sulphur S is determined usually by the ratio (4 stable isotopes - S, and - are known). This ratio is most stable in meteorites. That is why as standard is used the sulphur isotopic composition in troilite (FeS) from the meteorite in the Canyon Diablo Troilite (CDT) where the ratio is 1/22.22. 

Bourns (1963) investigated the bromination of anisole-4-sulphonic-2,6- 2 acid. In the presence of 0 0 to 2-Om bromide ions the ratio kgjkjy increases from 1-00 to 1-31. As a competitive reaction bromode-sulphonation takes place, bromine substituting the sulphonic group in the 4-position. Using anisole-4-sulphonic acid containing the natural abundance of the sulphur isotopes. Bourns measured sulphur isotope effects k jk is 1-003, 1-013 and 1-017 for initial bromide ion concentrations of 0-0, 0-05 and 0-50m respectively. This confirms, that bromodesulphonation also follows mechanism (6-2). 

Rees C. E. and Thode H. G. (1974) Sulphur concentrations and isotope ratios in Apollo 16 and 17 samples. Proc. Lunar Sci. Conf. 5th, 1963-1973. 

Distinct variation of isotope ratios of sulphur, oxygen and strontium in the sea water sulphates in time enables their use to determine ... 

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