| _version_ | 1867168552944926720 |
|---|---|
| author | Alt, Jeffrey C Shanks, Wayne C |
| author_facet | Alt, Jeffrey C Shanks, Wayne C |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | The mineralogy, contents, and isotopic compositions of sulfur in oceanic serpentinites reflect variations in temperatures and fluid fluxes. Serpentinization of <1 Ma peridotites at Hess Deep occurred at high temperatures (200°-400°C) and low water/rock ratios. Oxidation of ferrous iron to magnetite maintained low ƒO2 and produced a reduced, low-sulfur assemblage including NiFe alloy. Small amounts of sulfate reduction by thermophilic microbes occurred as the system cooled, producing low-delta34S sulfide (1.5‰ to -23.7‰). In contrast, serpentinization of Iberian Margin peridotites occurred at low temperatures(~20°-200°C) and high water/rock ratios. Complete serpentinization and consumption of ferrous iron allowed evolution to higher ƒO2. Microbial reduction of seawater sulfate resulted in addition of low-delta34S sulfide (~15 to ~43‰) and formation of higher-sulfur assemblages that include valleriite and pyrite. The high SO4/total S ratio of Hess Deep serpentinites (0.89) results in an increase of total sulfur and high delta34S of total sulfur (mean ~8‰). In contrast, Iberian Margin serpentinites gained large amounts of 34S-poor sulfide (mean total S = 3800 ppm), and the high sulfide/total S ratio (0.61) results in a net decrease in delta34S of total sulfur (mean ~ -5‰). Thus serpentinization is a net sink for seawater sulfur, but the amount fixed and its isotopic composition vary significantly. Serpentinization may result in uptake of 0.4-14 * 10**12 g S/yr from the oceans, comparable to isotopic exchange in mafic rocks of seafloor hydrothermal systems and approaching global fluxes of riverine sulfate input and sedimentary sulfide output. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_713718 |
| institution | PANGAEA |
| language | en |
| publishDate | 1998 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Sulfur concentrations and isotopic composition of serpentinized oceanic peridotites Alt, Jeffrey C Shanks, Wayne C 147-895B; 147-895C; 147-895D; 147-895E; 147-895F; 149-897A; 149-897C; 149-897D; DRILL; Drilling/drill rig; Joides Resolution; Leg147; Leg149; North Atlantic Ocean; North Pacific Ocean; Ocean Drilling Program; ODP The mineralogy, contents, and isotopic compositions of sulfur in oceanic serpentinites reflect variations in temperatures and fluid fluxes. Serpentinization of <1 Ma peridotites at Hess Deep occurred at high temperatures (200°-400°C) and low water/rock ratios. Oxidation of ferrous iron to magnetite maintained low ƒO2 and produced a reduced, low-sulfur assemblage including NiFe alloy. Small amounts of sulfate reduction by thermophilic microbes occurred as the system cooled, producing low-delta34S sulfide (1.5‰ to -23.7‰). In contrast, serpentinization of Iberian Margin peridotites occurred at low temperatures(~20°-200°C) and high water/rock ratios. Complete serpentinization and consumption of ferrous iron allowed evolution to higher ƒO2. Microbial reduction of seawater sulfate resulted in addition of low-delta34S sulfide (~15 to ~43‰) and formation of higher-sulfur assemblages that include valleriite and pyrite. The high SO4/total S ratio of Hess Deep serpentinites (0.89) results in an increase of total sulfur and high delta34S of total sulfur (mean ~8‰). In contrast, Iberian Margin serpentinites gained large amounts of 34S-poor sulfide (mean total S = 3800 ppm), and the high sulfide/total S ratio (0.61) results in a net decrease in delta34S of total sulfur (mean ~ -5‰). Thus serpentinization is a net sink for seawater sulfur, but the amount fixed and its isotopic composition vary significantly. Serpentinization may result in uptake of 0.4-14 * 10**12 g S/yr from the oceans, comparable to isotopic exchange in mafic rocks of seafloor hydrothermal systems and approaching global fluxes of riverine sulfate input and sedimentary sulfide output. |
| title | Sulfur concentrations and isotopic composition of serpentinized oceanic peridotites |
| topic | 147-895B; 147-895C; 147-895D; 147-895E; 147-895F; 149-897A; 149-897C; 149-897D; DRILL; Drilling/drill rig; Joides Resolution; Leg147; Leg149; North Atlantic Ocean; North Pacific Ocean; Ocean Drilling Program; ODP |
| url | https://doi.org/10.1594/PANGAEA.713718 |