Bulk GRAPE density and magnetic susceptibility were measured on whole-round cores at a 2-cm sampling interval on the multisensor track (MST) immediately after the core was brought on deck (Duncan, Larsen, Allan, et al., 1996). P-wave velocities were then measured on split cores at 5-15-cm intervals in the Hamilton Frame velocimeter as soon as possible after the core was split to ensure water saturation and minimum relaxation cracking. In addition, Vp, density, and porosity were measured later in 51 minicores using standard shipboard procedures described by Larsen, Saunders, Clift, et al. (1994).
P- and S-wave velocity, density, and porosity were measured on 14 of the samples by the Norwegian Geotechnical Institute (NGI) (Table 2). Dry and saturated weights were initially measured. Average bulk volume was determined from water-saturated samples by (1) averaging volume estimates from vernier measurements of the average of three diameters and three lengths and (2) measuring the immersed weight of the cores. Bulk and dry densities were calculated from the saturated and dry weights, respectively, divided by the average volume. The porosity was obtained from the difference in bulk and dry density. Velocities were measured on water-saturated cores using contact transducers under atmospheric conditions. A 500-kHz P-wave transducer and a 250-kHz S-wave transducer were used, and transit times were picked manually. Velocities were also measured under 10-200-MPa confining pressure on 13 other minicores collected from the massive basalt interior (Cerney and Carlson, Chap. 3, this volume). The altered samples analyzed in this study were regarded as too fragile to obtain reliable high-pressure velocity measurements. Finally, magnetic properties were measured by Norges Geologiske Unders°kelser (NGU) on ten minicores. Magnetic remanence was measured using a JR5 magnetometer; volume susceptibility, using a Bartington MS2; and Curie temperature, using a horizontal translation balance.
Unpolished thin sections and powder were made from the 18 samples. Eight thin sections from massive minicores were subsequently polished for identification of magnetic minerals. Major element X-ray fluorescence (XRF) and bulk normal and clay-sized (<2 Ám fraction) X-ray diffraction (XRD) analyses were carried out at the University of Oslo using standard procedures. XRD runs on the clay-sized fractions were done on bulk, heat-treated (550░C), and ethylene glycol-treated filtrate. Mineral identification and modal analysis of the diffractograms (Table 2) were done using the MacDiff software (Petschink, 1997).