Vent fluids

The test for critical or non-critical does not apply. These equations apply to single-phase (at inlet) liquids, non-flashing to vapor on venting, fluid viscosity is less than or equal to water [69]. 

Figure 1.158. Rare earth elements in vent fluids from the East Pacific Rise (redrawn from Michard and Albarede, 1986). The Sm values for the 1984 13 N set are thought to be somewhat too high because of contamination from the sampling syringes. Data for basalt from 13°N East Pacific Rise are from Michard et al. (1983) (Scott, 1997).

Fig. 2.45. Hypothetical mineral paragenesis for a sulfide-sulfate-silica chimney. Approximate temperature ranges for different minerals are based on direct measurements of vent fluid temperatures and analyses of fluid inclusions in real chimneys (Hannington et al., 1995).

Butterfield, V.A., McDuff, R.E., Franklin, J. and Wheat, C.G. (1994) Geochemistry of hydrothermal vent fluids from Middle Valley, Juan de Fuca Ridge. In Mottl, M.J., Davis, E.E., Fi.sher, A.T. and Slack, J.F. (eds.). Proceedings of the Ocean Drilling Program. Sci. Proc., 139, 395-410. 

Shanks, W.C. Ill and Seyfried, W.E. Jr. (1987) Stable isotope studies of vent fluids and chimney minerals. SJFR. J. Geophys. Res., 92, 11387-11399. 

During the mixing, concentrations of the Fl2S(aq), CH4(aq), and CH3COO components decrease as the vent fluid is diluted, and the SO4 concentration increases toward that of seawater. FhCaq) in the vent fluid attenuates not only... 

Fig. 22.5. Concentrations of components (sulfate, sulfide, carbonate, methane, and acetate) and species (O2 and H2) that make up redox couples, plotted against temperature, during a model of the mixing of fluid from a hot subsea hydrothermal vent with cold seawater. Model assumes redox couples remain in chemical disequilibrium, except between 02(aq) and H2(aq). As the mixture cools past about 38 °C, the last of the dihydrogen from the vent fluid is consumed by reaction with dioxygen in the seawater. At this point the anoxic mixture becomes oxic as dioxygen begins to accumulate.

Lithium is enriched in high temperature (c. 350°C) vent fluids by a factor of 20-50 relative to seawater (Edmond et al. 1979 Von Damm 1995). The Li isotopic compositions of marine hydrothermal vent fluids ranged from MORB-like to heavier compositions (see... 

Figure 14. Plot of Li isotopic composition vs. concentration of thermal waters from the continents and the oceans (see text for references). Differences between the isotopic range of marine versus non-marine fluids emphasizes the variability in 5 Li of continental rocks compared to oceanic basalt. The dilution of the continental fluids goes along with their lower temperatures vent fluids are the only truly geothermal samples here, with temperatures in excess of 300°C.

Bouman C, Vroon PZ, Elliott TR, Schwieters JB, Hamester M (2002) Determination of lithium isotope compositions by MC-ICPMS (Thermo Finnigan MAT Neptune). Geochim Cosmochim Acta 66 A97 Bray AM (2001) The geochemistry of boron and lithium in mid-ocean ridge hydrothermal vent fluids. PhD thesis. University of New Hampshire, 125 p... 

Foustoukos DI, James RH, Seyfried Jr WE (2003) Lithium isotopic systematics of the Main Endeavor Field vent fluids. Northern Juan de Fuca Ridge. Geochim Cosmochim Acta 67 A101 Franklin KJ, Halliday JD, Plante LM, Symons EA (1986) Measurement of the Li-6 Li-7 isotope ratio for lithium-salts hy FT NMR-spectroscopy. J Magnet Resonance 67 162-165 Fritz SJ (1992) Measuring the ratio of aqueous diliusion coefficients between Li Ck and Li Cf by osmometry. Geochim Cosmochim Acta 56 3781-3789... 

Vapor and brine from the Brandon vent of the East Pacific Rise have identical Fe isotope compositions, implying that phase separation does not produce an isotopic fractionation (Beard et al. 2003a). The role that sulfide precipitation plays in controlling the Fe isotope composition of the fluid remains unknown. The precision of the two sulfide analyses reported by Sharma et al. (2001) was not sufficient to resolve if sulfide precipitation would produce Fe isotope fractionation in the vent fluid. In a detailed study of sulfldes from the Lucky Strike hydrothermal field from the mid Atlantic Ridge, however, Rouxel et al. (2004) found that sulfldes span a range in 5 Fe values from -2.0 to +0.2%o, and that pyrite/marcasite has lower 5 Fe values ( l%o) as compared to chalcopyrite. The variations in mineralogy and isotope composition are inferred to represent open-system equilibrium fractionation of Fe whereby... 

The fate of dissolved Fe from MOR vents has been investigated at the Rainbow plume from the mid-Atlantic Ridge. Plume particles were sampled from the buoyant part of the Rainbow plume, proximal to the vent, as well as particles from neutrally buoyant portions of the plume that were more distal from the vent (Severmann et al. 2003). Particles from the buoyant part of the plume have positive 5 Fe values (up to +1.2%o), whereas in the neutrally buoyant sections of the plume, the particles have a near-constant 8 Fe value of -0.2%o that matches the Fe isotope composition of the vent fluid. The high 5 Fe values of plume particles that were proximal to the vent probably reflect oxidation processes. In the neutrally-buoyant plume, all aqueous Fe(ll) had been oxidized and it appears that there was no net loss in Fe because the neutrally buoyant plume particles have the same isotopic composition as the vent fluid. Moreover, metalliferous sediments sampled below the plume match the isotopic composition of the plume particles. The implication of these data is that for at least one plume, the Fe isotope composition of the vent fluid matches that of the plume particles. The Rainbow vent fluid, however, has an unusually high Fe to S ratio and hence it is uncertain if these results can be extrapolated to other plumes that originated fi om vent fluids that had lower Fe to S ratios. 

Table 19.1 Ranges in Chemical Composition for All Known Vent Fluids. ... 

Theoretical estimates of energy available from hydrothermal vent fluids for various chemosynthesis reactions used by vent microbes. Oxidative reactions are shown as dashed lines and reductive reactions as solid lines. Iron reduction provides too little energy to appear on plot. H2 oxidation was not calculated. Source From Leveille, R. J., and S. K. Juniper (2003). Biogeochemistry of Marine Systems, Blackwell Publications, pp. 238-292. 

Seyfried, W.E., Jr., Seewald, J.S., Berndt, M.E., Ding, K., Foustoukos, D.I. 2003. Chemistry of hydrothermal vent fluids from the Main Endeavor Field, northern Juan de... 

Fig. 1. Water/rock reaction diagramme illustrates fields of mapped high- and low-temperature isotopic alteration (see text) for rhyolites (R) and andesites (A) districts studied (DBL = Doyon-Bousquet-LaRonde). Solid and dashed curves evolution of rock and water, respectively. Multi-phase reaction history of the central Noranda district, shown schematically, generally corresponds to intrusive history. Approximate of modern high-temperature submarine vent fluid and estimated W/R after Shanks et al. (1995) and Bowers Taylor (1985), respectively.

The isotopic composition of present day ocean water is more or less constant with 5-values close to 0%c. The isotopic composition of ancient ocean water is less well constrained, but stiU should not be removed from 0 by more than 1 or 2%c. Many volcanogenic massive sulfide deposits are formed in submarine environments from heated oceanic waters. This concept gains support from the recently observed hydrothermal systems at ocean ridges, where measured isotopic compositions of fluids are only slightly modified relative to 0%c. 8 0 and 5D-values of vent fluids are best understood in terms of sea water interaction with the ocean crust (Shanks 2001). 

Foustoukous D, Seyfried WE (2004) Hydrocarbons in vent fluids the role of chromium catalysts. Science 304 1002-1005... 

Hilton, D. R., McMurty, G. M., Goff, F. (1998) Large variations in vent fluid C02/3He ratios signal rapid changes in magma chemistry at Loihi seamount, Hawaii. Nature, 396, 359-62. 

Toxic heavy metals Cd 2-5 mM, bacteria and archaeans Ni 2.5 mM, Co 20 mM, Zn 12 mM, Cd 2.5mM, Ralstonia eutrophus Algae, e.g., Euglena and Chlorella can grow in Cd, Zn, and Co at mM concentrations Submarine hydrothermal vent fluids and sulfides some high-metal-containing lakes... 

---