Figure 2. Regional tectonic setting of the PACMANUS site drilled during Leg 193. The Manus Basin occupies a backarc position relative to present-day subduction on the New Britain Trench to its south. Creation of new oceanic crust occurs at the Manus spreading center and at smaller segments to its west. Major transform faults are somewhat oblique to the spreading segments. The eastern Manus rift zone is a pull-apart structure between two of the major transform faults. It is underlain by thinned older Tertiary arc crust, equivalent to exposures on New Ireland to the north and New Britain to the south. This older crust was generated during subduction on the now inactive Manus Trench. Active volcanoes of the Bismarck arc, above the New Britain subduction–Benioff zone are indicated; submarine volcanism in the eastern Manus rifts lies well off the trend of this chain. Yellow boxes = known hydrothermal sites. Thick blue arrows = plate motions. Curved blue arrows = the sense of rotation on microplates as defined by Global Positioning System geodesy (Tregoning et al., 1998) or by the opening and westward propagation of the Woodlark Basin (Taylor et al., 1995).