The deep structure of a sea-floor hydrothermal deposit

Zierenberg, Robert A., Fouquet, Yves, Miller, D.J., Bahr, J.M., Baker, P.A., Bjerkgård, T., Brunner, C.A., Duckworth, R.C., Gable, R., Gieskes, J., Goodfellow, W.D., Gröschel-Becker, H.M., Guèrin, G., Ishibashi, J., Iturrino, G., James, R.H., Lackschewitz, K.S., Marquez, L.L., Nehlig, P., Peter, J.M., Rigsby, C.A., Schultheiss, P., Shanks, W.C., Simoneit, B.R.T., Summit, M., Teagle, D.A.H., Urbat, M. and Zuffa, G.G. (1998) The deep structure of a sea-floor hydrothermal deposit. Nature, 392 (6675), 485-488. (doi:10.1038/33126).

Abstract

Hydrothermal circulation at the crests of mid-ocean ridges plays an important role in transferring heat from the interior of the Earth1, 2, 3. A consequence of this hydrothermal circulation is the formation of metallic ore bodies known as volcanic-associated massive sulphide deposits. Such deposits, preserved on land, were important sources of copper for ancient civilizations and continue to provide a significant source of base metals (for example, copper and zinc)4, 5, 6. Here we present results from Ocean Drilling Program Leg 169, which drilled through a massive sulphide deposit on the northern Juan de Fuca spreading centre and penetrated the hydrothermal feeder zone through which the metal-rich fluids reached the sea floor. We found that the style of feeder-zone mineralization changes with depth in response to changes in the pore pressure of the hydrothermal fluids and discovered a stratified zone of high-grade copper-rich replacement mineralization below the massive sulphide deposit. This copper-rich zone represents a type of mineralization not previously observed below sea-floor deposits, and may provide new targets for land-based mineral exploration.

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Contributors

Author: R.H. James

Author: D.A.H. Teagle

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