Figure F6. 208Pb/204Pb vs. 206Pb/204Pb isotopic compositions of altered samples from 11 Leg 187 sites. The Pacific mantle domain has generally more radiogenic Pb isotopic composition than Indian mantle. The analyzed sediment and vein material have the most radiogenic 208Pb/204Pb ratios. A strongly altered part of a Hole 1157A sample has similar isotopic ratios to local sediment, showing that very small amounts of sediment can drastically change the isotopic composition. 208Pb/204Pb ratios are constant at individual sites, while 206Pb/204Pb ratios are more radiogenic in the altered samples reflecting their high 238U/204Pb ratios. Figure from S. Krolikowska-Ciaglo, F. Hauff, and K. Hoernle (pers. comm., 2003). AAD = Australian Antarctic Discordance.

Figure F6. ²⁰⁸Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb isotopic compositions of altered samples from 11 Leg 187 sites. The Pacific mantle domain has generally more radiogenic Pb isotopic composition than Indian mantle. The analyzed sediment and vein material have the most radiogenic ²⁰⁸Pb/²⁰⁴Pb ratios. A strongly altered part of a Hole 1157A sample has similar isotopic ratios to local sediment, showing that very small amounts of sediment can drastically change the isotopic composition. ²⁰⁸Pb/²⁰⁴Pb ratios are constant at individual sites, while ²⁰⁶Pb/²⁰⁴Pb ratios are more radiogenic in the altered samples reflecting their high ²³⁸U/²⁰⁴Pb ratios. Figure from S. Krolikowska-Ciaglo, F. Hauff, and K. Hoernle (pers. comm., 2003). AAD = Australian Antarctic Discordance.