Figure F11. Trace element compositions vs. MgO for Holes 1158A, 1158B, and 1158C basalt glass and whole-rock samples compared with Segments As and A3 zero-age basalt glasses. X-ray fluorescence (XRF) and ICP-AES data for splits of a single whole-rock powder are shown on all plots; therefore, two points represent each type of analysis for one sample. Only the average XRF or ICP-AES analyses reported in Table T3 are plotted. PRT = propagating rift tip lavas.