Figure 10: Curves of constant effective resistivity for varying melt fraction and temperature in a two phase system, taken from Shankland \& Waff (1977). The curves were calculated using the upper Hashin-Shtrikman bound, and experimentally determined basaltic melt conductivities. Zero pressure is assumed. The curves are marked with the overall resistivity in . Dashed lines show the basalt solidus and liquidus (Presnall \etal , 1972). The shaded area shows the region bounded by these two temperatures, the upper resistivity value required by the CSEM data, and the lower bound on crustal resistivity from the MT experiment (Heinson \etal, this issue). The melt content of the crustal magma chamber lies in this region.