Hydrothermal Processes at Seafloor Spreading Centers: Application of Basalt-Seawater Experimental Results

  • Michael J. Mottl
Part of the NATO Conference Series book series (NATOCS, volume 12)


Both the chemistry of seafloor hot springs and the chemical changes exhibited by basalts during alteration to greenschist facies assemblages have been accurately predicted by laboratory experiments reacting seawater with basalt. Although the experiments were run as an isothermal, closed-system, batch process, they largely succeeded in duplicating the products of the natural open-system, continuous flow process. For the solutions, this resulted mainly from rapid reaction rates at high temperature, relative to flow rates in the natural systems, so that equilibrium with the secondary mineral assemblage represented a significant control on solution composition both in the experiments and in nature. For the rocks, it resulted from a similar alteration history in which largely unreacted seawater reached greenschist facies temperatures before reacting with the basalts, and from element exchanges between rock and solution which were coupled via charge balance constraints so that the batch process in the experiments simulated the incremental process in nature.

The key concept in relating the batch process to the incremental process is the seawater/rock ratio, which because of the nature of the chemical exchanges involved can best be estimated from the uptake of seawater Mg by the altered rock. The experiments predict a systematic change in rock chemistry and mineralogy as alteration proceeds to higher seawater/rock ratios. The prediction is borne out for the fluxes of Mg and Ca, the flux directions of Na, Si, and Mn, and the mineral abundances of chlorite, quartz, and actinolite. It is not borne out for the Fe flux, the magnitude of the Na flux, and the abundances of albite and epidote, because the experiments failed as batch processes to allow for local redistribution of elements via diffusion. This latter process is important in altered rocks from the natural systems for Fe2+, which diffuses into zones where chlorite is forming preferentially due to influx of seawater Mg, and for Na+, which accumulates as albite in zones of lesser Mg influx, in exchange for Ca.


Hydrothermal System Hydrothermal Process Greenschist Facies Altered Rock Alteration History 
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  1. Arnorsson, S. (1975) Application of the silica geothermometer in low temperature hydrothermal areas in Iceland, Am. Jour. Science 275, 763–784. 1Google Scholar
  2. Arnorsson, S., Gronvold, K., and Sigurdsson, S. (1978) Aquifer chemistry of four high-temperature geothermal systems in Iceland, Geochim. Cosmochim. Acta 42, 523–536.Google Scholar
  3. Bischoff, J. L. and Dickson, F. W. (1975) Seawater-basalt interaction at 200°C and 500 bars: implications for origin of sea-floor heavy-metal deposits and regulation of seawater chemistry, Earth Planet. Sci. Lett. 25, 385–397.Google Scholar
  4. Bischoff, J. L. and Seyfried, W. E. (1978) Hydrothermal chemistry of seawater from 25° to 350°C, Am. Jour. Science 278, 838–860.Google Scholar
  5. Bischoff, J. L., Radtke, A. S. and Rosenbauer, R. J. (1981) Hydrothermal alteration of graywacke by brine and seawater: roles of alteration and chloride complexing on metal solubilization at 200°C and 350°C, Econ. Geol. 76, 659–676.Google Scholar
  6. Bjornsson, S., Arnorsson, S. and Tomasson, J. (1972) Economic evaluation of Reykjanes thermal brine area, Iceland, Am. Assoc. Petrol. Geol. Bulletin 56, 2380–2391.Google Scholar
  7. Cann, J. R. (1969) Spilites from the Carlsberg Ridge, Indian Ocean, Jour. Petrol. 10, 1–19.CrossRefGoogle Scholar
  8. Cann, J. R. (1979) Metamorphism in the Ocean Crust: In Talwani, M., Harrison, C. G., and Hayes, D. E. (eds.), Deep Drilling Results in the Atlantic Ocean: Ocean Crust 230–238: Am. Geophys. Union, Washington, D.C., 431 p.Google Scholar
  9. Corliss, J. G., Dymond, J., Gordon, L. I., Edmond, J. M., von Herzen, R. P., Ballard, R. D., Green, K., Williams, D., Bainbridge, A., Crane, K. and van Andel, Tj. H. (1979) Submarine thermal springs on the Galapagos rift, Science 203, 1073–1083.Google Scholar
  10. Craig, H., Welham, J. A., Kim, K., Poreda, R., and Lupton, J. E. (1980) Geochemical studies of the 21°N EPR hydrothermal fluids (abst.), EOS 61, 992.Google Scholar
  11. Crovisier, J. L., Thomassin, J. H., Juteau, T., Eberhart, J. P., Touray, J. C., and Baillif, P. (1983) Experimental seawater-basaltic glass interaction at 50°C: study of early developed phases by electron microscopy and x-ray photoelectron spectrometry, Geochim. Cosmochim. Acta 47, 377–387.Google Scholar
  12. Edmond, J. R., Measures, C., McDuff, R. E., Chan, L. H., Collier, R., Grant, B., Gordon, L. I., and Corliss, J. B. (1979) Ridge crest hydrothermal activity and the balances of major and minor elements in the ocean: the Galapagos data, Earth Planet. Sci. Lett. 46, 1–18.Google Scholar
  13. Edmond, J. R. (1980) The chemistry of the 350°C hot springs at 21°N on the East Pacific Rise (abst.), EOS 61, 992.Google Scholar
  14. Edmond, J. R., Von Damm, K., and McDuff, R. E. (1982) Chemistry of hot springs on the East Pacific Rise and their effluent dispersal, Nature 297, 187–191.Google Scholar
  15. Ellis, A. J. (1970) Quantitative interpretation of chemical characteristics of hydrothermal systems. Geothermics Spec. Issue 2, 516–528.Google Scholar
  16. Furnes, H. (1975) Experimental palagonitization of basaltic glass of varied composition, Contrib. Mineral. Petrol. 50, 105–113.Google Scholar
  17. Hajash, A. (1975) Hydrothermal processes along mid-ocean ridges: an experimental investigation, Contrib. Mineral. Petrol. 53, 205–226.Google Scholar
  18. Hajash, A. and Archer, P. (1980) Experimental seawater/basalt interactions: effects of cooling, Contrib. Mineral, Petrol. 75, 1–13.Google Scholar
  19. Hajash, A., and Chandler, G. W. (1981) An experimental investigation of high-termapture interactions betweenGoogle Scholar
  20. seawater and rhyolite, andesite, basalt and peridotite, Contrib. Mineral. Petrol. 78, 240–254.Google Scholar
  21. Humphris, S. E. and Thompson, G. (1978) Hydrothermal alteration of oceanic basalts by seawater, Geochim. Cosmochim. Acta 42, 107–125.Google Scholar
  22. Janecky, D. R., and Seyfried, W. E., Jr. (1982) The solubility of magnesium hydroxide sulfate hydrate in seawater at elevated temperatures and pressures, submitted to Am. Jour. Science.Google Scholar
  23. Krismannsdottir, H. (1976) Hydrothermal alteration of basaltic rocks in Icelandic geothermal areas, In: Proceedings, Second U.N. Symposium on the Development and Use of Geothermal Resources, v. 1, U. S. Gov’t Printing Off., Wash., DC, p. 441–445.Google Scholar
  24. MacDonald, K. C., Becker, K., Spiess, F. N., and Ballard, R. D. (1980) Hydrothermal heat flux of the “black smoker” vents on the East Pacific Rise, Earth Planet. Science Lett. 48, 1–7.Google Scholar
  25. McDuff, R. E. and Edmond, J. M. (1982) On the fate of sulfate during hydrothermal circulation at mid-ocean ridges, Earth Planet. Sci. Lett. 57, 117–132.CrossRefGoogle Scholar
  26. Menzies, M. and Seyfried, W. E., Jr. (1979) Basalt-seawater interaction: trace element and strontium isotopic variations in experimentally altered glassy basalt. Earth and Plan. Sci. Lett. 44, 463–472.Google Scholar
  27. Moody, J. B., Meyer, D., and Jenkins, J. E. (1983) Experimental characterization of the greenschist/amphibolite boundary in mafic systems. Amer. J. Sci. 283, 48–92.Google Scholar
  28. Mottl, M. J., Corr, R. F. and Holland, H. D. (1975) Trace element content of the Reykjanes and Svartsengi thermal brines, Iceland (abstract). Abstracts with Programs, Geol. Soc. Amer. Ann. Meetings 7, 1206–1207.Google Scholar
  29. Mottl, M. J. and Holland, H. D. (1978) Chemical exchange during hydrothermal alteration of basalt by seawater - I. Experimental results for major and minor components of seawater, Geochim. Cosmochim. Acta 42, 1103–1115.Google Scholar
  30. Mottl, M. J., Holland, H. D., and Corr, R. F. (1979) Chemical exchange during hydrothermal alteration of basalt by seawater - II. Experimental results for Fe, Mn and sulfur species, Geochim. Cosmochim. Acta, 43, 869–884.Google Scholar
  31. Mottl, M. J. and Seyfried, W. E. (1980) Sub-sea-floor hydrothermal systems: rock vs. seawater-dominated, In: Rona, P. A., and Lowell, R. P. (eds.), Seafloor Spreading Centers: Hydrothermal Systems p. 66–82: Dowden, Hutchinson and Ross, Inc., Stroudsburg, Pennsylvania, 424 p.Google Scholar
  32. Mottl, M. J. (1983) Metabasalts, axial hot springs, and the structure of hydrothermal systesm at mid-ocean ridges. Bull. Geol. Soc. Amer. 94, 161–180.Google Scholar
  33. Olafsson, J., and Riley, J. P. (1978) Geochemical studies on the thermal brine from Reykjanes ( Iceland ), Chem. Geol. 21, 219–237.Google Scholar
  34. RISE (1980) East Pacific Rise: hot springs and geophysical experiments, Science 207, 1421–1433.Google Scholar
  35. Seyfried, W. E., Jr. (1977) Seawater-basalt interaction from 25° - 300°C and 1 500 bars: implications for the origin of submarine metal-bearing hydrothermal solutions and regulation of ocean chemistry, Ph.D. thesis, University of Southern California, 242 p.Google Scholar
  36. Seyfried, W. E., and Bischoff, J. L. (1977) Hydrothermal transport of heavy metals by seawater: the role of seawater/basalt ratio, Earth Planet. Sci. Lett. 34, 71–77.Google Scholar
  37. Seyfried, W. E., Jr., and Bischoff, J. L. (1979) Low temperature basalt alteration by seawater: an experimental study at 70°C and 150°C, Geochim. Cosmochim. Acta 43, 1937–1947.Google Scholar
  38. Seyfried, W. E., Jr., and Bischoff, J. L. (1981) Experimental seawater-basalt interaction at 300°C and 500 bars: chemical exchange, secondary mineral formation and implications for the transport of heavy metals, Geochim. et Cosmochim. Acta 45, 135–147.Google Scholar
  39. Seyfried, W. E., Jr., Gordon, P. C., and Dickson, F. W. (1979) A new reaction cell for hydrothermal solution equipment, Amer. Mineralogist 64, 646–649.Google Scholar
  40. Seyfried, W. E., Jr., and Dibble, W. E. Jr. (1980) Seawater-peridotite interaction at 300°C and 500 bars: implications for the origin of oceanic serpentinites, Geochim. Cosmochim. Acta 44, 309–321.CrossRefGoogle Scholar
  41. Seyfried, W. E., Jr. Mottl, M. J., and Bischoff, J. L. (1978) Seawater-basalt ratio effects on the chemistry and mineralogy of spilites from the ocean floor, Nature 275, 211–213.Google Scholar
  42. Seyfried, W. E., Jr. and Mottl, M. J. (1982) Hydrothermal alteration of basalt by seawater under seawater-dominated conditions, Geochim. Cosmochim. Acta 46, 985–1002.Google Scholar
  43. Shanks, W. C. III, Bischoff, J. L., and Rosenbauer, R. J. (1981) Seawater sulfate reduction and sulfur isotope fractionation in basaltic systems: interation of seawater with fayalite and magnetite at 200–350°C, Geochim. Cosmochim. Acta 45, 1977–1995.Google Scholar
  44. Thomassin, J. H. and Touray, J. C. (1979) Etude des premiers stades de l’interaction eau de mer - verre basaltique: doneés de la spectrométrie de photoélectrons (XPS) et de la microscopie électronique à balayage, Bull. Minéral. 102, 594–599.Google Scholar
  45. Thomassin, J. H. and Touray, J. C. (1982) L’hydrotalcite, un hydroxycarbonate transitoire précocément formé lors de l’interaction verre basaltique - eau de mer, Bull. Minéral. 105, 312–319.Google Scholar

Copyright information

© Springer Science+Business Media New York 1983

Authors and Affiliations

  • Michael J. Mottl
    • 1
  1. 1.Department of ChemistryWoods Hole Oceanographic InstitutionWoods HoleUSA

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