Figure F21. Mantle-normalized (Nb/Ce)_N, (Zr/Ti)_N, and (Nb/Zr)_N vs. (Zr/Y)_N ratio or Zr content (subscript N indicates ratios normalized to primitive mantle abundances of Sun and McDonough, 1989). These ratios are sensitive to the presence of a component from the continental crust. Note that basalts from Site 738, which are thought to contain a continental component, have the lowest Nb/Ce and Nb/Zr and highest Zr/Ti values. Site 1137 basalts have a comparable Zr/Ti range but higher Nb and Zr contents and, consequently, higher Zr/Y, Nb/Ce, and Nb/Zr. In contrast, Site 1136 basalts most closely resemble basalts from Site 749. Data sources are given in the Figure F20 caption.