East Pacific Rise at latitude 21°N: isotopic composition and origin of the hydrothermal sulphur

Sulfur and lead isotopic compositions of massive sulfides from deep-sea hydrothermal systems: Implications for ore genesis and fluid circulation

“…Similar sulfur isotopic disequilibrium has been identified in most investigated seafloor hydrothermal sulfide deposits (e.g., the EPR at 21°N, Arnold and Sheppard, 1981;Styrt et al, 1981;Kerridge et al, 1983;Zierenberg et al, 1984;Woodruff and Shanks, 1988; the Guaymas Basin, Shanks and Niemitz, 1982;Koski et al, 1985 Peter andShanks, 1992; the Red Sea, Bischoff, 1977, 1980; the Axial Seamount, Hannington and Scott, 1988).…”

“…2.5‰, n = 118, Hekinian et al, 1980;Arnold and Sheppard, 1981;Styrt et al, 1981;Kerridge et al, 1983;Zierenberg et al, 1984;Woodruff and Shanks, 1988;Stuart et al, 1994a) (see Table 3; Fig. 3).…”

“…For sedimentstarved MORs, the variation in the sulfur isotopic composition of the sulfides is explained by varying proportions of reduced seawater sulfate and mantle-derived sulfur leached from the underlying igneous rocks (e.g., Arnold and Sheppard, 1981;Herzig et al, 1998a). In contrast, for sediment-associated MORs, negative sulfur isotope values generally occur along with low sulfide-sulfur contents and can be caused by bacterial sulfate reduction (Goldhaber and Kaplan, 1980;Brunner and Bernasconi, 2005).…”

Sulfur Isotope Ratios of Leg 126 Igneous Rocks

“…Determination of the δ 34 S values of rocks recovered from Hole 504B in the Costa Rica Rift (Alt et al, 1989a(Alt et al, , 1989bHubberten, 1983;Kusakabe et al, 1989) (Alt and Chaussidon, 1989). These higher δ 34 S values from the hydrothermally altered rocks are comparable to δ 34 S values from hydrothermal fluids and sulfide deposits from the seafloor of up to about +7 o/ oo (Arnold and Sheppard, 1981;Styrt et al, 1981;Skirrow and Coleman, 1982;Shanks and Seyfried, 1987) and to basalt-seawater experiments yielding pyrite δ 34 S values of about +10 o/ 0 o (Shanks et al, 1981). Thus, the increase in δ 34 S relative to pristine ocean floor basalts is interpreted to arise from the incorporation of sulfide derived from the seawater sulfate reduction.…”

The origin of gypsum in Vertisols in New Caledonia determined by isotopic characteristics of sulphur

“…It is now well realized that data on sulphur composition alone are usually insufficient to define the sulphur source of an ore because large isotopic fractionations are involved in almost all the chemical reactions involved in mineralization (Ohmoto, 1972). Consequently, the accurate estimation of a sulphur source generally requires many additional data (such as pH, jD2, and 2') because oxidation-reduction processes induce large isotopic fractionations between sulphides and coeval dissolved sulphates (Ohmoto, 1972;Arnold and Sheppard, 1981). Similar difficulties occur if bacterial sulphate reducers are involved in near surface marine environments because the isotopic composition of biogenic SH, depends upon nutrient supply, reduction rate, sulphate concentration, and temperature (Harrison and Thode, 1957).…”