Physical properties measurements taken on cores recovered from Site 1189 (Roman Ruins hydrothermal site) included magnetic susceptibility, natural gamma radiation, thermal conductivity, compressional wave velocity, and standard index properties. In most cases, measurements were made at least once per lithologic unit. In areas of large-scale heterogeneity and when recovery allowed, sampling density was increased. On the multisensor track (MST), the magnetic susceptibility meter (MSM) and the natural gamma radiation (NGR) device were used on Cores 193-1189A-2R through 12R and 193-1189B-11R through 18R. Because the other cores were particularly fragmented, incomplete, or disturbed, they did not lend themselves to the continuous automated measurements of the MST. Where possible, compressional wave velocity measurements were made on discrete samples in one direction, which is perpendicular to the hole's vertical axis. Thermal conductivity was measured on almost every lithologic unit for both holes, except where recovery was too low or rock pieces were too small (<5 cm) for the measurement procedure. Index properties, also measured in every lithologic unit when recovery allowed, were measured on minicores, rock fragments, or both. Because of these recovery and size considerations, the lower sequence of Hole 1189 (>125 mbsf) received more attention than its upper sequence. Accompanying diagrams that integrate data from both holes at Site 1189 should be examined in the context of the caveats stated above regarding correlations between the holes (see "Hydrothermal Alteration").
Figure F124 shows the downhole profile for magnetic susceptibility in Holes 1189A and 1189B from 0 to 200 mbsf. Magnetic susceptibility varies greatly over the length of recovered core, ranging from -0.2 × 10-5 to 3101.5 × 10-5 SI, with an average of 486 × 10-5 SI. In Hole 1189A, magnetic susceptibility has high values at the top of the core, from ~9 to 20 mbsf, and moderately elevated values from 58 to 88 mbsf. Magnetic lows are found from ~29 to 49 mbsf, at 78, and from 96 to 107 mbsf. With the exception of the peak found in Core 193-1189A-2R, the magnetic susceptibility coincides with magnetite occurrences in the core. Although thin sections from Core 193-1189A-2R do not show significant amounts of magnetite, it is likely that fine-grained magnetically susceptible material exists in the groundmass.
In the lower sequence of Hole 1189B, magnetic susceptibility values are generally high throughout, with intervals of low values from 148 to 165 and from 180 to 200 mbsf. As in Core 193-1189A-2R, only trace amounts of magnetite were found in thin section, although very fine grained magnetically susceptible material may again be present. However, the high magnetic susceptibility close to seafloor at the site likely corresponds to preservation of igneous magnetite, which indicates low amounts of alteration, whereas the high values at deeper levels of the site are likely caused by magnetic materials in veins associated with more intense alteration (see "Structural Geology").
The NGR records are summarized in plots of total counts per second (cps) vs. curated depth (see Fig. F125). The NGR values from Site 1189 cover a much wider range than those at Site 1188 and range from 0 to 64.9 cps, with an average of 20 cps. As with Site 1188, much of the variation found within each hole may be caused by errors in the measurement process (see "Physical Properties" in the "Site 1188" chapter).
Even with the inaccurate data, there are definite peaks in the NGR measurements in Cores 193-1189A-10R (87-88 mbsf) and 193-1189B-17R (185-195 mbsf). Other high values are found in Cores 193-1189A-2R (9-11 mbsf), 6R through 8R (48-69 mbsf), and 193-1189B-16R (156-168 mbsf). These variations in NGR values do not coincide directly with lithologic changes or alteration patterns. However, the high values at this site as compared to Site 1188 can be attributed to the high percentage of K2O (see "Geochemistry") and the presence of potassium feldspar in the core.
Compressional wave velocities and sample descriptions are given in Table T19 and are plotted in Figure F126. Values range from ~3.4 to 5.0 km/s and average 4.4 km/s. Velocity values generally increase with depth. There is also an apparent trend of decreasing velocity as the percentage of vesicles increases. Although there are some deviations from these trends, lithologic variations, amount of alteration, and structural features may account for some of the variance in the velocity values.
Thermal conductivity values from Holes 1189A and 1189B range from 0.99 to 5.13 W/(m·K), as shown in Figure F127. Most of the values from Hole 1189A are between 1.7 and 2.5 W/(m·K), with an average of 2.12 W/(m·K), very similar to those found at Site 1188. The low values in shallow cores correspond to unaltered dacite. The highest value of 5.13 W/(m·K), found at 107 mbsf, comes from a core interval with the highest amount of pyrite (50% combined pyrite and chalcopyrite).
As at Site 1188, thermal conductivity values in Hole 1189A are generally higher in brecciated rocks and lower in fresh and altered dacites. Every brecciated rock, with the exception of one, has a thermal conductivity value >2.1 W/(m·K). The one low-value brecciated rock consists mostly of altered dacite with very few, thin veins running through it. Most of the unbrecciated rocks have thermal conductivity values <1.9 W/(m·K); samples in this group that do not have a low thermal conductivity generally have abundant pyrite in vesicles, which could account for the increased values.
Thermal conductivity values from the lower sequence of Hole 1189B are relatively constant. There is a slight trend for brecciated samples to have thermal conductivity values higher than those of dacites, although this is not as defined as in Hole 1189A. Of the nine unbrecciated samples, two that have values >2.0 W/(m·K) contain pyrite veins. Only three out of eight breccia and pseudobreccia samples have values >2.0 W/(m·K). The majority of the low-valued breccias have a high clay content (up to 85%), which may contribute to the lower thermal conductivity values.
The data for water content, bulk density, dry density, grain density, porosity, and void ratio are displayed in Table T20. Figures F128 and F129 show grain density and porosity values, respectively, for both holes as a combined depth profile. Grain densities of powder samples prepared for ICP-AES analyses are given in Table T21. In cases where index properties were measured on both rock fragments and minicores, values were consistent for both types of sample. Similarly, where grain density was measured on both ICP-AES powders and whole samples, values were consistent as well. Grain density values are relatively constant throughout the cored interval, but range overall from 2.37 to 3.75 g/cm3, with an average of 2.77 g/cm3. The unaltered rocks from the very top of Hole 1189 have an average value close to 2.5 g/cm3. Below 0.2 mbsf, these rocks become altered and grain density values increase. The higher densities of some alteration products, such as pyrite, anhydrite, and magnetite, most likely account for the increased grain density in the altered rocks. For example, semimassive sulfide Sample 193-1189B-1R-1, 0-2 cm, which has the highest grain density, contains 35% pyrite and 20% chalcopyrite.
Porosity values span a wide range, from 15.8% to 67.1%, with an average of 30.2%. The combined data set has a trend of decreasing porosity with depth, as seen at Site 1188, although in this case the trend arises from lower porosity of the lower sequence (>120 mbsf) in Hole 1189B. High porosity values, as in Sample 193-1189B-1R-1, 20-30 cm, are usually coincident with vesicular rocks that have high clay content. As at Site 1188, such high porosity is generally not observed in thin section.