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Ocean Ridge Hydrothermal Fluxes

Group Members

M.J. Bickle FRS, H.J. Chapman, J. Maclennan

Previous Group Members

Chen Feng You (Taiwan), A. Davis (Perth)

Collaborations

D.A.H. Teagle (NOCS Southampton), Laurence Coogan (Victoria, British Columbia, Canada)

Hydrothermal circulation at ocean ridges, which passes the mass of the oceans through the ocean crust every ~ 30 Ma, buffers ocean chemistry, transports a significant fraction of the Earth’s heat flow and plays a fundamental role in geochemical fluxes between the solid Earth, oceans and atmosphere. However there are major uncertainties in both the magnitude of the hydrothermal fluxes (see Davis et al., 2003) and the structure of the hydrothermal systems. 

amygeotimes
Pillow lavas, Geotimes locality, Semail Ophiolite, Oman
sheeted-dykes
Sheeted dykes in the Semail ophiolite, Oman

We have been studying the structure of oceanic hydrothermal systems in ophiolites (Troodos and Oman, Teagle & Bickle, 1992; Benyon et al., 1998), modelling hydrothermal fluxes from geochemical alteration of the oceanic crust (Teagle et al., 2003), studying the chronology of oceanic sulphide mounds (You & Bickle, 1999) and modelling the thermal evolution of oceanic spreading ridges (Maclennan). Particularly spectacular are the epsidosite zones in the Semail ophiolite, Oman, which Amy Davis (unpublished Cambridge PhD) showed were related to three or more phases of hydrothermal activity and could be mapped from the top of the gabbros, through the sheeted dykes and into the lavas. Each phase of hydrothermal activity exhibits a distinctive range of 87Sr/86Sr ratios.

plagio-dyke
Plagiogranite with xenoliths of earlier dyke generation cut by epidotised later mafic dyke in hydrothermal 'reaction zone' near top of gabbros. Semail ophiolite, Oman
epdi-dykes
Two generations of sheeted dykes both strongly epidotised. Earlier generation rotated to ~ 30° dipping screens between steeply dipping later generation. Wadi Rajmi, Semail ophiolite, Oman

pillows_wadi_amy
Pillows surrounded by epidosite.
oman6
Cu and Fe sulphides within epidosite sampled from pillow outcrop figured to left

epidosite_zones
Dark epidosite zones mapped within plagiogranite, Wadi Rajmi, Semail ophiolite, Oman

epidosite-zones-wr
Sketch-map of the previous field locality showing higher, ~ 0.705, 87Sr/86Sr ratios of epidosite zones (green) and late phorphyritic dyke (grey) compared with ~ 0.704 values in plagiogranite host rock

sulphide_pit
Mined-out massive sulphide pit in lavas, Semail ophiolite, Oman

Publications From This Work

  1. Davis, A., Bickle, M.J., and Teagle, D.A.H. (2003) Imbalance in the oceanic strontium budget, Earth and Planetary Science Letters 211, 173-187.
  2. Teagle, D.A.H., M.J. Bickle, J.C. Alt (2003) Recharge flux to ocean-ridge black smoker systems: a geochemical estimate from ODP Hole 504B, Earth and Planetary Science Letters 210, 81-89.
  3. Bickle, M.J., Teagle, D.A.H., Beynon, J., Chapman, H. J. (1998) The structure and controls on fluid-rock interactions in ocean ridge hydrothermal systems: constraints from the Troodos ophiolite. Special Publication of the Geological Society of London, 148, 127-152
  4. Bickle, M.J., Alt, J.C., Teagle, D.A.H. (1994) Sulphur transport and sulphur isotope fractionations in ocean floor hydrothermal systems. Mineralogical Magazine, 58A, 88-89
  5. Bickle, M.J., Teagle, D.A.H. (1992) Strontium alteration in the Troodos ophiolite: implications for fluid fluxes and geochemical transport in mid-ocean ridge hydrothermal systems. Earth and Planetary Science Letters, 113, 219-237.
  6. Maclennan, J., T. Hulme, and S. C. Singh, Cooling of the lower oceanic crust, Geology, 33, 357-360, 2005. [online article]
  7. Maclennan, J., T. Hulme, and S. C. Singh, Thermal models of oceanic crustal accretion: Linking geophysical, geological and petrological observations, Geochem. Geophys. Geosyst., 5, Q02F25, doi:10.1029/2003GC000605, 2004. [online article]
  8. Wilson, D.S. and 52 others, Drilling to gabbro in intact ocean crust, Science, 312, 1016-1020, 2006. [online article]
  9. Cannat, M., J. Cann and J. Maclennan, Some hard rock constraints on the supply of heat to mid-ocean ridges, In: Mid-ocean ridges: Hydrothermal Interactions between the Lithosphere and Oceans, edited by C.R. German, J. Lin and L.M Parson, Geophys. Monogr. Ser.,vol. 148, AGU, Washington, D.C., 2004.

 

Last updated on 21-Nov-08 17:12