Figure F8. A. Data on the seismic velocity of the mantle beneath oceanic crust (depths >7 km) from seismic refraction experiments, as a function of oceanic plate age. Data compiled from Beé and Bibee (1989), Bratt and Purdy (1984), Bratt and Solomon (1984), Canales et al. (1998, 2000, 2003), Cary and Chapman (1988a), Collins et al. (1989, 1995), Collins and Brown (1998), Detrick et al. (1993, 1994, 1998), Detrick and Purdy (1980), Duennebier et al. (1987), Fowler (1976, 1978), Fowler and Keen (1979), Ginzburg et al. (1985), Hooft et al. (2000), Lewis and Garmany (1982), Lewis and Snydsman (1979), McClain and Atallah (1986), Minshull et al. (1991), Mithal and Mutter (1989), Morris et al. (1993), Orcutt et al. (1976), Purdy (1983), Purdy and Detrick (1986), Shearer and Orcutt (1986), Spudich and Orcutt (1980), Vera et al. (1990), Waldron et al. (1990), White (1979), White et al. (1992), Whitmarsh and Calvert (1986), Whitmarsh et al. (1982, 1990). B. Calculated P-wave velocity for polycrystalline dunite and pyroxenite at 25°C as a function of pressure, with 1 s error estimates, from Christensen and Mooney (1995). Based on these estimates, harzburgite with 20% orthopyroxene at the base of oceanic crust would have a P-wave velocity = ~8.2 ± 0.1 km/s at 25°C, or ~ 8.1 km/s at 200°C.