Figure 12. Schematic cross sections (not to scale) illustrating the development of the model shown in Figure 11 (from Whitmarsh and Miles, 1995). A. Just prior to continental breakup; crosses indicate continental crust. The first products of asthenospheric decompressional melting penetrate the upper crust. B. At the point just after continental breakup where the top of the asthenosphere is shallow enough to allow igneous intrusion of the continental crust to occur over a broad zone. Dotted region represents serpentinized peridotite. C. After the point where igneous activity has become sharply focused and steady-state seafloor spreading has been reached, after initially producing an abnormally thin oceanic crust (v symbol).

Figure 12. Schematic cross sections (not to scale) illustrating the development of the model shown in Figure 11 (from Whitmarsh and Miles, 1995). A. Just prior to continental breakup; crosses indicate continental crust. The first products of asthenospheric decompressional melting penetrate the upper crust. B. At the point just after continental breakup where the top of the asthenosphere is shallow enough to allow igneous intrusion of the continental crust to occur over a broad zone. Dotted region represents serpentinized peridotite. C. After the point where igneous activity has become sharply focused and steady-state seafloor spreading has been reached, after initially producing an abnormally thin oceanic crust (v symbol).