Soil Salts, Coast of Ross Island

Strontium derived from seawater is even more abundant in soil salts along the coast of Ross Island analyzed by Jones et al. (1983) and Fame and Jones (1989). The Sr/ Sr ratios of these salts in Fig. 16.23 and Appendix 16.8.2 range widely from 0.70344 2 (calcite, Castle Rock, Hut Point Peninsula, elevation 413 m) to 0.70912 3 (thenardite. Trachyte Hill, Cape Bird, elevation 2 m). The calcite on Castle Rock contains strontium of volcanic origin, whereas the strontium in thenardite along the beach at Cape Bird is of marine origin. 

A compilation of all Sr/ Sr ratios of soil salts from Ross Island measured by Jones et al. (1983) and by Faure and Jones (1989) in Fig. 16.23 reveals a strongly bimodal distribution. The salts from the summit of Mt. Erebus have low Sr/ Sr ratios between 0.70339 3 and 0.70353 3, whereas the soil salts along the coast of Ross Island have consistently higher Sr/ Sr ratios that range from 0.70707 to 0.70912. These results support the hypothesis that the soil salts on Ross Island contain strontium of volcanic and marine origin in varying proportions. The salts that are forming in the vicinity of the active volcanic vent on 

This hypothesis was subseqnently confirmed by measurements of the isotopic compositions of sulfur published by Faure and Jones (1989). The isotopic composition of snlfur is expressed by the parameter which is defined as  

The standard is the ratio of sulfnr in troilite (FeS) in meteorites. The 5 S valne of sulfnr in mantle-derived igneous rocks is 0%c because the sulfur in meteorites and the Earth both originated from the 

The abundance of the marine component indicated by this model ranges from about 1% (Fang Ridge, summit of Erebus) to 98% for salt along the beach at Trachyte Hill at Cape Bird. The abundance of the marine component in the salts on the slope of Trachyte Hill decreases with increasing elevation to 81% at 130 m a.s.l. The trend reverses at higher elevations and reaches 97% marine at 390 m a.s.l. At Cape Royds the abundance of the marine component likewise decreases from 92% at 12 m to 75% at 129 m a.s.l with deviations at 60 and 284 m. 

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