Figure F12. Downhole variations in (A) MgO and (B) Zr from shipboard XRF data, demonstrating the magmatic trends upsection. Smaller scale variation is observed within the various igneous sequences. The alkaline suite in Sequence I is identified by enriched Zr relative to the tholeiites. Leg 185 basalts are in solid circles and open diamonds (>2 wt%, LOI >1 wt%, K₂O). Leg 129 basalts are in open circles. The Zr/Y diagram (C) demonstrates that Site 801 tholeiites are comparable to modern East Pacific Rise and mid-Atlantic Ridge MORB (Langmuir et al., 1986; Langmuir, 1987).