Figure 24. Mantle-normalized Nb/Ce, Zr/Ti, and Nb/Zr vs. Zr/Y ratio or Zr content. These ratios are sensitive to the presence of a component from the continental crust. Note that b asalts 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. Ratios are normalized using estimat ed primitive mantle abundances of Sun and McDonough (1989). Symbols and data sources as in Fi gure 19. Numbers indicate ODP site numbers.