The physical properties of the peridotites and gabbros cored in Holes 1270A, 1270B, 1270C, and 1270D were characterized through a series of measurements on whole-core sections, split-core pieces, and discrete samples as described in "Physical Properties" in the "Explanatory Notes" chapter. We measured NGR activity and magnetic susceptibility on the multisensor track (MST) system and thermal conductivity, compressional wave velocity, density, and porosity. The rock names reported in data tables correspond to the primary lithologies determined by the igneous core description group.
All cores recovered during Leg 209 were measured using the NGR logger on the MST at intervals of 10 cm with a time period of 30 s. Results are output in counts per second. The cores in Holes 1270A, 1270B, 1270C, and 1270D display natural radioactivity in the same range as the background radiation in the core laboratory onboard the JOIDES Resolution. No significant peak was recorded in the NGR data in these cores.
Magnetic susceptibility values were acquired on the MST at 2.5-cm intervals for all recovered cores. All cores from Site 1270 have high magnetic susceptibility (Fig. F105), which is related to the presence of magnetite in the oxide-rich gabbros and serpentinized peridotites. The magnetic susceptibilities of the rocks from Site 1270 are comparable to the susceptibilities of ultramafic rocks and gabbros from Hess Deep (Gillis, Mével, Allan, et al., 1993) or the MARK area (Cannat, Karson, Miller, et al., 1995) (see Fig. F88 in the "Site 1268" chapter), whereas the magnetic susceptibilities of the highly altered gabbros and peridotites recovered at Site 1268 are two orders of magnitude lower than the values for cores recovered during Legs 147 and 153.
Thermal conductivity measurements were made at irregularly spaced intervals along cores from Holes 1270A, 1270B, 1270C, and 1270D (Fig. F106). The data are summarized in Table T5. The thermal conductivities of the ultramafic samples range 2.4–3.1 W/(mˇK) (mean = 2.64 W/[mˇK]). Thermal conductivity in the gabbros ranges 2.0–2.4 W/(mˇK) (mean = 2.24 W/[mˇK]). These values are comparable to the thermal conductivities of gabbros and ultramafic rocks from ODP sites at Atlantis Bank (Robinson, Von Herzen, et al., 1989; Dick, Natland, Miller, et al., 1999), Hess Deep (Gillis, Mével, Allan, et al., 1993), and MARK (Cannat, Karson, Miller, et al., 1995).
As described in "Thermal Conductivity" in "Physical Properties" in the "Explanatory Notes" chapter, measurements were taken in three directions on the cut face of the archive sample half, whenever possible. The purpose of these measurements was to determine the degree of anisotropy. The apparent conductivity anisotropy of peridotites and gabbros measured in samples from Site 1270 ranges 1.1%–10.9%. Apparent thermal conductivity anisotropies measured in samples from Sites 1268 and 1270 are compiled in Figure F107. Anisotropy ranges 0.2%–12.6% (mean = 4.95%) in both gabbros and peridotites.
Thermal conductivity measurements were also made at 10° intervals on a foliated oxide gabbro (interval 209-1270B-1R-1, 120–128 cm). These measurements are shown in Table T6 and Figure F108. There is a clear conductivity minimum in the direction perpendicular to the foliation of this rock (i.e., the needle probe aligned with the foliation). The two measurements at –40° and 40° from the core axis may be biased by the position of the probe, too oblique with respect to the core axis, with the needle tips very close to the curved outer surface of the core and may therefore be underestimated. The apparent maximum at –20° may thus be an artifact.
Bulk density, grain density, and porosity were measured on minicores and chips from Holes 1270A, 1270B, 1270C, and 1270D. P-wave velocity was measured in only three minicores (Table T7). P-wave velocity and wet bulk density were measured in a larger suite of cube samples, as described in "P-Wave Velocity" and "Porosity and Density" both in "Physical Properties" in the "Explanatory Notes" chapter. These data are summarized in Table T8.
The density and velocity data are compared with data from Legs 147 and 153, as well as Site 1268, in Figure F109. Velocities and densities in the peridotite and gabbro samples from Site 1268 are notably lower than the velocities and densities of samples from Legs 147 (Gillis, Mével, Allan, et al., 1993) and 153 (Cannat, Karson, Miller, et al., 1995). The velocities and bulk densities of the peridotite samples from Site 1270 are comparable to the velocities and densities of samples from Site 1268, whereas the velocities and densities of gabbro samples are higher. The velocities in gabbro samples from Site 1270 are comparable to the velocities in similar samples from Hole 923A (Cannat, Karson, Miller, et al., 1995), but the densities are significantly higher, probably because of the higher oxide content of the gabbros sampled at Site 1270.