Sulfur isotope analyses using the laser microprobe
Since the first studies of sulfur isotope variations in natural materials (Thode, 1949), it has been apparent that there are large and dramatic variations of 34S/32S ratios and that sulfur isotope studies are a powerful tool for interpreting the origins of sulfur-bearing minerals. However, sulfur is such a common element in the Earth's crust (sixteenth most abundant, averaging 0.03 wt %; Mason, 1966), and is involved in so many igneous, hydrothermal, biological, and surficial processes that a simple measurement of δ34S, without constraining geological, biological, and geochemical data, is often unenlightening. In many sedimentary and hydrothermal systems, geologists are confronted with multiple sulfur sources, large fractionations of sulfur isotopes during oxidation-reduction reactions that sometimes produce disequilibrium effects, and strong chemical and physical gradients at the site of mineral deposition. Despite significant advances in the understanding and utilization of sulfur isotopes to characterize ore-forming processes (Ohmoto, 1972; Ohmoto and Rye, 1979; Shanks et al., 1981; Janecky and Shanks, 1988), interpretations may be ambiguous and, in ancient ore deposits, difficult to test. Part of this difficulty has been due to an inability to resolve fine-scale spatial variations in isotopic fractionation between successive zones or between coexisting minerals.
Citation Information
Publication Year | 1997 |
---|---|
Title | Sulfur isotope analyses using the laser microprobe |
Authors | W.C. Pat Shanks, D.E. Crowe, Craig A. Johnson |
Publication Type | Book Chapter |
Publication Subtype | Book Chapter |
Index ID | 70207820 |
Record Source | USGS Publications Warehouse |
USGS Organization | Central Mineral and Environmental Resources Science Center; Geology, Geophysics, and Geochemistry Science Center |