Figure 16. A spidergram for a basalt clast from interval 149-899B-27R-1, 33-40 cm, normalized to primitive mantle and the five common basalt provinces for comparison and source determination. This spidergram is not as parallel to the MORB spidergrams as the other basalt clasts, but the less mobile elements are similar in abundance to E-MORB, CFB, or even OIB. The high Nb-Ta values indicate it was not formed in an island-arc environment. The negative Sr peak probably relates to Ca removal during seafloor weathering. The positive U peak suggests it was added during seafloor weathering, and the addition of U and K accentuate an apparent negative Th peak that is actually rather small.