Figure F7. Examples of sediment recycling at the Izu-Bonin-Marianas-Honshu margins. A. Pb isotopic composition of different arcs can be resolved into mixing arrays between composition in the Pacific mid-ocean-ridge basalt (MORB) field, and compositions entirely consistent with local bulk sediment subducting at each trench, based on DSDP and ODP drilling: Honshu arc mixes to DSDP Site 579/581 bulk sediment; Izu arc mixes to ODP Site 1149 bulk sediment; Marianas arc mixes to ODP Site 801 bulk sediment. The shift in the Mariana arc to high 206Pb/204Pb is quantitatively consistent with a shift toward Cretaceous ocean island volcanics (VCL) that litter the seafloor seaward of the Marianas trench, in both the sediment, from pelagic values near loess toward VCL, and the basement, from low 206Pb Pacific MORB toward VCL. Data sources: Honshu arc (Gust et al., 1995); Site 579/581 (Cousens et al., 1994); Izu arc (Taylor and Nesbitt, 1998); Site 1149 (Hauff et al., 2003); Marianas arc (Elliott et al., 1997); Site 801 sediment and VCL (Plank and Langmuir, 1998). B. Th/La and Sm/La systematics also show mixing toward local sediments. Each arc forms a mixing trend between a mantle composition (in the MORB array) and a sedimentary composition, which in each case is nearly identical to the nearby trench sediment (for a global development of this, see Plank, 2005). The western Pacific arcs show systematic regional trends, where arcs mix toward sediment with progressively higher Th/La to the north (Mariana to Honshu) as seafloor enters the westerly wind belt and receives eolian dust with high, continental Th/La (~0.35, see Fig. F5). Arc data are from Elliott et al. (1997), Gust et al. (1995), Taylor and Nesbitt (1998), and Hochstaedter et al. (2000). Bulk sediment compositions are from Plank and Langmuir (1998) for Mariana and Honshu. New ICP-MS data for Site 1149 sediments is from Plank and Kelley (2001).

Figure F7. Examples of sediment recycling at the Izu-Bonin-Marianas-Honshu margins. A. Pb isotopic composition of different arcs can be resolved into mixing arrays between composition in the Pacific mid-ocean-ridge basalt (MORB) field, and compositions entirely consistent with local bulk sediment subducting at each trench, based on DSDP and ODP drilling: Honshu arc mixes to DSDP Site 579/581 bulk sediment; Izu arc mixes to ODP Site 1149 bulk sediment; Marianas arc mixes to ODP Site 801 bulk sediment. The shift in the Mariana arc to high ²⁰⁶Pb/²⁰⁴Pb is quantitatively consistent with a shift toward Cretaceous ocean island volcanics (VCL) that litter the seafloor seaward of the Marianas trench, in both the sediment, from pelagic values near loess toward VCL, and the basement, from low ²⁰⁶Pb Pacific MORB toward VCL. Data sources: Honshu arc (Gust et al., 1995); Site 579/581 (Cousens et al., 1994); Izu arc (Taylor and Nesbitt, 1998); Site 1149 (Hauff et al., 2003); Marianas arc (Elliott et al., 1997); Site 801 sediment and VCL (Plank and Langmuir, 1998). B. Th/La and Sm/La systematics also show mixing toward local sediments. Each arc forms a mixing trend between a mantle composition (in the MORB array) and a sedimentary composition, which in each case is nearly identical to the nearby trench sediment (for a global development of this, see Plank, 2005). The western Pacific arcs show systematic regional trends, where arcs mix toward sediment with progressively higher Th/La to the north (Mariana to Honshu) as seafloor enters the westerly wind belt and receives eolian dust with high, continental Th/La (~0.35, see Fig. F5). Arc data are from Elliott et al. (1997), Gust et al. (1995), Taylor and Nesbitt (1998), and Hochstaedter et al. (2000). Bulk sediment compositions are from Plank and Langmuir (1998) for Mariana and Honshu. New ICP-MS data for Site 1149 sediments is from Plank and Kelley (2001).