Figure 1. Input to and output from "The Subduction Factory."

Figure 2. Perspective map of Izu-Mariana arcs and Leg 185 drilling sites.

Figure 3. Competing models for input-output studies. A. The grass control model indicates that the kind of milk (dark vs. light) is controlled by the kind of grass (dark vs. light) that the cow eats. B. In the cow control model the breed of the cow is the important control in determining the kind of milk produced. Different cows (Guernsey vs. Jersey) eating the same kind of grass may still produce different kinds of milk (dark vs. light). These models are directly analogous to subduction recycling studies, where the grass is the subducted input (sediments and oceanic crust), the milk is the volcanic arc output and the cow is the subduction zone.

Figure 4. Correlation between Ba flux in subducted sediment and Ba enrichment of arc basalts for various arcs (Ant = Northern Antilles, Mar = Mariana, T= Tonga, Mex = Mexico, J = Java, Al = Aleutians, and G = Guatemala) around the world (after Plank and Langmuir, 1993). Open circles = three different sediment flux estimates for the Mariana, based on the three ODP Sites drilled during Leg 129 (800-802) (Plank and Langmuir, 1998). Although there are variations from site to site, the average sediment input to the Mariana is fairly well constrained (± 20%). Note Izu volcanics are lower in Ba/Na than Mariana volcanics by a factor of two. B. Contrasting Pb isotopic composition of Mariana (open circle) and Izu-Bonin (solid circle) arc volcanics. Mariana volcanics form a mixing trend (arrow), almost perfectly coincident with mixtures of ODP Hole 801C sediment (open boxes) and basalt (solid boxes) averages.

Figure 5. Map showing all sites and proximity to magnetic anomaly lineations, basins, and land masses.

Figure 6. Lithologic columns for Hole 801C, Leg 20 sites, and Site 1149. Val-Haut = Valanginian-Hauterivian; Kimm-Barr = Kimmeridgian-Barremian.

Figure 7. Paleogram comparing Sites 801 and 1149.

Figure 8. Seismic profiles that intersect Site 1149.

Figure 9. Cartoon showing drilling strategy chosen to achieve scientific objectives at Hole 801C and Site 1149.

Figure 10. Stratigraphic column showing all of the basement subunits drilled during Legs 129 and 185. The sequences correspond to major lithologic changes but are also related to the presence of breccia zones, hydrothermal deposits, and changes in magma chemistry.

Figure 11. Hole 801C comparison of recovery, resistivity and natural gamma logs, magnetic logs of vertical and horizontal intensity, and the magnetic inclination measured in half-round cores. The major lithologic sequences for the section are also given.

Figure 12. Downhole variation for MgO (A) and Zr (B), demonstrating the magmatic trends of increasing MgO and decreasing Zr toward more primitive liquids upsection. In addition, smaller scale variation is observed within the various core divisions. The alkaline suite in the sequence above the upper hydrothermal unit (upper shaded area) is identified by enrichment in Zr relative to the tholeiites. The Zr/Y diagram demonstrates that the Hole 801C basalts are normal MORB comparable in chemistry to modern East Pacific Rise (EPR) tholeiites (Leg 185). MAR = Mid-Atlantic Ridge.

Figure 13. Section 185-801C-15R-7 showing the extreme alteration types observed. The pale green alteration separates an interflow sediment. The gray-green alteration at the bottom of the core is typical of much of the background alteration in the cores from this site. The proportions of the main secondary minerals are given, as are photomicrographs in which saponite, smectite, and calcite are visible. The two photomicrographs of the pale green alteration show a plagioclase phenocryst, found only rarely in dominantly aphyric lavas.

Figure 14. Summary of the lithostratigraphic section from holes drilled at Site 1149.

Figure 15. Magnetic reversal stratigraphy in the upper 120 m at Site 1149.

Figure 16. Summary of sedimentation rates at Site 1149 calculated from magnetostratigraphy and calcareous nannofossils.

Figure 17. An example of a bacterial population contaminated with fluorescent microspheres.

Figure 18. Summary of the age and nature of stratigraphic units cored at Sites 801 and 1149 during Leg 185.

To 185 Operations Synopsis: Site 801

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