Sulfur isotope anomalous

Figure 4. Sulfur isotope anomalous fractionations (see text) plotted v. age in Ga. Sharp change in magnitude of anomalies at 2.5 Ga is found worldwide in rocks from Australia, Canada, India, and South Africa (29, 30, 31, 32, 33, 34, 35)...

In order to determine the origin of sulfur in coals, Hackley and Anderson (18) studied the sulfur isotopic composition of various coals from the western United States. Coals from the Powder River Basin, Wyoming were found to have anomalously low values (-18.7 to 3.9 parts per mil). The unusual values of these coals suggest that original plant material and isotopically light secondary sulfur from bacterial activity were the major contributors to the sulfur content of these coals. 

Convincing evidence of recycling of volatiles to the mantle and their incorporation into diamonds has recently been reported from sulfur isotope studies of sulfide inclusions within diamond (Farquhar et al., 2002). SIMS analysis of sulfide inclusions has revealed anomalous mass-indepen-dently fractionated sulfur isotopic compositions from the Orapa kimberlite, which are explained as a consequence of the recycling of surface sulfur produced through photolytic chemistry in the Archean atmosphere. Such studies need to be extended to other diamond populations and combined with C-N isotope studies on the host diamonds. 

Farquhar J., Wing B. A., McKeegan K. D., Harris J. W., Cartigny P., and Thiemens M. H. (2002) Anomalous sulfur isotope compositions of inclusions from diamonds evidence... 

The discovery of large anomalous fractionations in sulfur isotopes,... 

The magnitude of anomalous fractionations of sulfur isotopes is given by the formula... 

Figure 5. Sulfur isotope compositions of sulfuric acid aerosols in South Pole ice core samples. Aerosols from two eruptions, Pinatubo and AD 1259 that injected SO2 into the stratosphere have anomalously fractionated S- S- S (39).

A growing body of data on Antarctic ice cores shows that the history of volcanic eruptions is resolvable year-by-year (38). The record includes dated explosive events such as Cerro Hudson in 1991, Pinatubo-1991, Agung-1963, Krakatoa-1883, Tambora-1815, and a 1259 AD eruption of unknown location. Analysis of the oxygen and sulfur isotope composition of aerosol particles frozen in the polar refrigerator provides a proxy of atmospheric chemistry applicable to early Earth. Aerosols from Cerro Hudson, the smallest of the explosive eruptions, have normal sulfur isotope compositions with no anomalous fractionation of (39). Cerro Hudson s eruption cloud did not break... 

Again because of its high volatility, sulfur is relatively undepleted from interstellar gas by condensation in interstellar grains, so that its isotopic composition has been pardy measured by radioastronomers, who detect emission lines from the molecule CS in the interstellar medium. By comparing the rotational transitions of 13C/32S with those of 12C/34S the interstellar isotopic ratio has been found for sulfur (see 34S, Anomalous isotopic abundance). 

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