Corrected index properties for ODP Leg 127 and 128 sites

During Legs 127 and 128, we found a systematic error in the index property measurements, in that the wet bulk density, grain density, and porosity did not satisfy well-established interrelationships. We have found that an almost constant difference exists between the weight of water lost during drying and the volume of water lost. This discrepancy is independent of volume or water content of the sample. The water losses should be equal because the density of water is close to 1.0 g/cm**3. The pycnometer wet volume measurement has been identified as the source of the systematic error. The wet volume on average is 0.2 cm**3 too low. For the rare cases when the water content is negligible, there is no offset. The source of the wet volume error results from the partial vapor pressure of water in the pycnometer cell. Newly corrected tables of index properties measured during Legs 127 and 128 are included. The corrected index properties are internally consistent. The data are in better agreement with theoretical models that relate the index properties to other physical properties, such as thermal conductivity and acoustic velocity. In future, a standard volume sampler should be used, or the wet volume should be calculated from the dry volume and the water loss by weight.

(Table 1) Oxygen isotoic composition of interstitial watres from ODP Sites 128-798 and 128-799

Oxygen isotope compositions of the interstitial waters have been measured for 21 samples taken from the depth intervals of 1.5 to 398.9 mbsf at Site 798 (Oki Ridge) and 16.5 to 435.6 mbsf at Site 799 (Kita-Yamato Trough) in Japan Sea. The d18O values decrease with depth from -0.49 to -3.38 per mil (SMOW) at Site 798 and from -0.71 to -4.36 per mil (SMOW) at Site 799 corresponding to an average depletion gradient of -0.8 per mil per 100 m. Material balance calculations reveal that the d18O-variations at Sites 798 and 799 were principally controlled by low-temperature alteration of basement basalt and andesite, resulting in negative shifts in pore water d18O values, and by the polymorphic transformations of biogenic opal-A to opal-CT and opal-CT to microquartz, which tend to increase d18O of interstitial waters. Carbonate diagenesis and ash alteration also caused weakly negative shifts in pore water d18O values.

Geochemistry of ODP Hole 128-798B

The capability of determining elemental concentrations through geochemical logging has recently been established. However, the quality of these data obtained in some environments has yet to be quantified. We assess the quality of geochemical logs compared with XRF results from a suite of core samples from Hole 798B. The resulting core/log correlations are only fair, because the tool has been adversely affected by the very high porosity of the formation. The results, however, do fall within the statistical uncertainties predicted by the processing. The recent application of a modified boron sleeve to the Ocean Drilling Program's geochemical logging tool is shown to reduce interference of borehole chlorine on the resultant chemistry.