fig03.htm

Figure 3. Processes at mid-ocean ridges (after Schubert et al. [[2001]). (a) Movement pattern of partially molten mantle material in mid-ocean ridge and hotspot regions. Broken lines show the matrix motion. Solid lines show the base of the lithosphere and contours of the melting extent. The melt is separated from the partially molten mantle material in ascending flows. The melt in the central part of the flow concentrates in a magma chamber, whereas the peripheral melt solidifies to form the lithosphere material. (b) Melt velocity in the partial melting zone as a function of the melt viscosity and ascending mantle flow velocity at the asthenosphere base. (c) Porosity (in percent) in the partial melting zone. At f<2%, pores are isolated and the porosity coincides with the melting extent. At f>2%, pores form interconnected channels and the porosity is much smaller than the melting extent due to the upward filtration of the melt. The porosity depends in this case on the melt viscosity and ascending mantle flow velocity.


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