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doi:10.2204/iodp.pr.320T.2009 GeochemistryThe geochemical methods and sampling plan have been outlined in "Methods." Here we report the data obtained from the analyses. It should be remembered that the cores from Hole U1330A were taken from a greater depth than those for Hole U1330B (102.5–122.5 meters core depth below seafloor [CSF]-A and 0–92.1 m CSF-B, respectively). Interstitial water samplesA total of 14 interstitial water samples were analyzed for pH, alkalinity, and elemental composition. Figures F9 and F10 show alkalinity and pH, major elements, and minor elements. Only three of the four samples taken for interstitial water pH and alkalinity tests gave reliable results from Hole U1330A. Alkalinity increases downhole in Hole U1330B and appears to slightly decrease with depth in the Hole U1330A interval, whereas pH exhibits a slight decrease downhole in Hole U1330B and is higher and variable in Hole U1330A (Fig. F9; Table T7). In terms of the major elemental abundances (Fig. F10; Table T8), Na and K are quite variable and do not exhibit a consistent trend. Average abundances for Na in Holes U1330A and U1330B are same (462 mM in each hole), whereas Hole U1330B has a slightly higher average K content than Hole U1330A (9.8 versus 9.7 mM). The trends for Ca and Mg are complementary, with Ca increasing downhole in Hole U1330B to Hole U1330A and Mg decreasing. For Ca, Hole U1330A data appear more variable. Whole-rock samplesSix whole-rock samples were analyzed using ICP-AES from Section 320T-U1330A-3R-2 to investigate the nature of the color banding observed in this core (Fig. F11). Data are reported in Table T9. On the basis of these preliminary data, there does not appear to be any correlation between geochemistry and color banding. Headspace gas samplesA total of 14 samples were analyzed for hydrocarbons. The results for methane are presented in Figure F12 and Table T10. Abundances are between 1.5 and 2.0 ppmv methane at the top of Hole U1330B between 3 and 19.1 mbsf. Below this point methane increases to 4.3 ppmv at 47.6 mbsf followed by a decrease to 1.8 ppmv at 66.5 mbsf. Methane abundances in Hole U1330A are higher (6.6–13.9 ppmv), but no systematic variations are apparent in the four data points from this core. Quality assurance/Quality controlNo quality assurance/quality control (QA/QC) data were available to judge the alkalinity and pH data other than the calibration of the electrode prior to the expedition. Normally, the IAPSO seawater standard is tested as an unknown, but this was not done during Expedition 320T. QA/QC data were taken from the ICP-AES analyses through the analysis of standards and the peak heights and shapes of the wavelengths used to quantify each element. However, extracting these data to be able to judge the data quality is a labor-intensive task. Scripts must be written in order to automate this process, but these were not available for Expedition 320T. For the whole-rock analyses, reference materials were analyzed as unknowns and demonstrated a glitch in the Teledyne Leeman Labs data reduction software. All data should be taken as preliminary while these glitches are fixed and the Expedition 320T data are recalibrated. For methane analyses, four standards were analyzed as unknowns on the GC3: |
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