Figure F2. Plots of Mg# of minerals (olivine [ol], clinopyroxene [cpx], and orthopyroxene [opx]), basaltic melt, and whole-rock gabbroic samples against liquidus temperatures. The relationships of the composition and liquidus temperatures of olivine and basaltic melts are derived from well-established experimental results and phase equilibrium analyses (e.g., Roeder and Emslie, 1970; Bender et al., 1978; Walker et al., 1979; Langmuir and Hanson, 1981; Nielsen and Dungan, 1983; Weaver and Langmuir, 1990; Grove et al., 1992): Tliquidus (°C) = 1026 e[0.01894MgO (wt%)], or Tliquidus (°C) = 1066 + 12.067 Mg# + 312.3 (Mg#)2. The liquidus temperature of olivine is derived from the second equation, with Mg# calculated from olivine using Mg# (melt) = 1/([1/Fo - 1]/Kd + 1), where Kd = 0.30 ± 0.03. A. The range of Mg# values is calculated to consider the range of Kd values from 0.27 to 0.33. Plotted are whole-rock samples of which olivine analyses are available for calculating the liquidus temperatures. Normal mid-ocean-ridge basalt (N-MORB) samples from the East Pacific Rise (Langmuir et al., 1986; Sinton et al., 1991; Niu and Batiza, 1997; Regelous et al., 1999) and Atlantis II Fracture Zone (AII F.Z.) basalts (Johnson and Dick, 1992) are plotted for comparison. B. Clinopyroxene and orthopyroxene compositions are plotted against liquidus temperatures of the corresponding samples derived from olivine compositions.

Figure F2. Plots of Mg# of minerals (olivine [ol], clinopyroxene [cpx], and orthopyroxene [opx]), basaltic melt, and whole-rock gabbroic samples against liquidus temperatures. The relationships of the composition and liquidus temperatures of olivine and basaltic melts are derived from well-established experimental results and phase equilibrium analyses (e.g., Roeder and Emslie, 1970; Bender et al., 1978; Walker et al., 1979; Langmuir and Hanson, 1981; Nielsen and Dungan, 1983; Weaver and Langmuir, 1990; Grove et al., 1992): T_liquidus (°C) = 1026 e^{[0.01894MgO (wt%)]}, or T_liquidus (°C) = 1066 + 12.067 Mg# + 312.3 (Mg#)². The liquidus temperature of olivine is derived from the second equation, with Mg# calculated from olivine using Mg# (melt) = 1/([1/Fo - 1]/K_d + 1), where K_d = 0.30 ± 0.03. A. The range of Mg# values is calculated to consider the range of K_d values from 0.27 to 0.33. Plotted are whole-rock samples of which olivine analyses are available for calculating the liquidus temperatures. Normal mid-ocean-ridge basalt (N-MORB) samples from the East Pacific Rise (Langmuir et al., 1986; Sinton et al., 1991; Niu and Batiza, 1997; Regelous et al., 1999) and Atlantis II Fracture Zone (AII F.Z.) basalts (Johnson and Dick, 1992) are plotted for comparison. B. Clinopyroxene and orthopyroxene compositions are plotted against liquidus temperatures of the corresponding samples derived from olivine compositions.