Figure F23. A. Variations in ²⁰⁶Pb/²⁰⁴Pb along the Southeast Indian Ridge (SEIR) between 115°E and 140°E. The present position of the isotope boundary between Indian- and Pacific-type provinces is located at ~126°E. Note the break in the horizontal scale due to the overlap of the AAD and Zone A axes (see Fig. F3). Data are taken from Klein et al. (1988), Pyle et al. (1992), and Pyle et al. (1995). B. Variations of Zr/Ba vs. ²⁰⁶Pb/²⁰⁴Pb showing the data distribution used to determine Indian- and Pacific-type mantle provinces. Data are taken from Klein et al. (1988), Pyle et al. (1992, 1995), Pyle (1994), and D. Pyle and D. Christie (unpubl. data).