Seafloor spreading

Fig. 3.4. Range chart of back-arc basin formation. Solid lines show confined age ranges of the formation of marginal basins by seafloor spreading, and broken lines show rough estimates of the age range. Rhombic marks show the timing of entrapment of the basins (Tamaki and Honza, 1991).

Lister, C.R.B. (1973) Hydrothermal convection at seafloor spreading centers source of power or geophysical nightmare Geol. Soc. Am. Ab.st. Programs, 5, 74. 

Hydrothermal vents are another source of water entering the ocean. These vents are submarine hot-water geysers that are part of seafloor spreading centers. The hydrothermal fluids contain some major ions, such as magnesium and sulfete, in significantly different ratios than foimd in seawater. The importance of hydrothermal venting in determining the chemical composition of seawater is described in Chapters 19 and 21. 

Seafloor spreading eventually pushes oceanic crust into subduction zones where the hydrothermal sediments and rock are recycled back into the mantle. A small fraction of these deposits is uplifted, or obducted, onto land. These rescued deposits are termed ophiolites. Because of their metal enrichments, they serve as major ore bodies and have been mined for various precious metals, such as copper, for thousands of years. 

Because of the relative scarcity of lithogenous particles and fast seafloor spreading rates, metalliferous sediments are common around the East Pacific Rise and very high densities of manganese nodules are present on the abyssal plains, especially in the Southern Hemisphere. In these locations, the weathering products of volcanic detritus, such as montmorillonite, phillipsite, nontronite, and celadonite, are also found in great abimdance. 

Plate tectonics The theory that posits crustal plate movement is caused by seafloor spreading and subduction. 

Von Damm, K.L., Grant, B., Edmond, J.M. 1983. Preliminary report on the chemistry of hydrothermal solutions at 20°N, East Pacific Rise. In Rona, P.A., Bostrom, K., Smith, K.L., Jr. (eds.) Hydrothermal Processes at Seafloor Spreading Centers. Plenum, New York, 369-389. 

Thompson G. (1983a) Basalt-seawater interaction. In Hydrothermal Processes at Seafloor Spreading Centers (eds. P.A. Rona, K. Bostrom, L. Laubjer and K.L. Smith), pp. 225-278. Plenum Press, New York. 

Until the arrival of the theories of plate tectonics and seafloor spreading in the 1960s, the Earth s mantle was generally believed to consist... 

Fleet A. J., Bostrom K., Laubier L., and Smith K. L. (1983) Hydrothermal and hydrogenous ferro-manganese deposits do they form a continuum The rare earth element evidence. In Hydrothermal Processes at Seafloor Spreading Centers (ed. P. A. Rona). Plenum, New York, pp. 535-555. 

The concept of global tectonics (Dietz, 1961 Hess, 1962 Morgan, 1968 Le Pichon et al., 1973) combined the earlier proposals of continental drift and seafloor spreading into a unified theory of terrestrial dynamics. It introduced the notion of continual generation and destruction of oceanic crust and implied similar consequences for other tectonic realms. 

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