Page 148 - Global Tectonics
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134   CHAPTER 6



              (a)
                   2
                         Volcanics

                         Dikes                         Melt
                   4
                 Depth (km)                            Mush


                         Gabbro
                                         Transition             zone
                   6


                         Moho


                              5                          0                          5




              (b)  2
                                                      Rift valley


                   4
                 Depth (km)  Gabbro


                                      Transition
                   6
                                      zone
                         Moho                                  Mush
                   8


                         10             5              0              5             10
                                                  Distance (km)


           Fig. 6.11  Interpretive models of magma chambers beneath a fast (a) and slow (b) spreading ridge (modified from
           Sinton & Detrick, 1992, by permission of the American Geophysical Union. Copyright © 1992 American Geophysical
           Union).





           been employed which provide complete areal coverage   Studies of the East Pacific Rise have shown that it is
           of oceanic features. These systems have been used to   segmented along its strike by nontransform ridge axis
           reveal variations in the structure of ocean ridges along   discontinuities such as propagating rifts (Section 6.11)
           strike. A review of these developments was provided by   and overlapping spreading centers (OSC), which occur
           Macdonald et al. (1988).                     at local depth maxima, and by smooth variations in the
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