Sediments were analyzed for inorganic carbon and for total hydrogen, nitrogen, carbon, and sulfur. The organic carbon content of the sediments was then calculated by difference. All samples were freeze-dried prior to analysis.
Total inorganic carbon was determined using a Coulometric 5011 coulometer equipped with a System 140 carbonate carbon analyzer. Depending on carbonate content, 15-20 mg of ground and weighed sediment was reacted in a 2-N HCl solution. The liberated CO2 was titrated in a monoethanolamine solution with a colorimetric indicator while monitoring the change in light transmittance with a photodetection cell.
Total hydrogen, nitrogen, carbon, and sulfur were determined using an H/N/C/S analyzer, model NA 1500 from Carlo Erba Instruments. Bulk samples were combusted at 1000°C in an oxygen atmosphere, converting organic and inorganic carbon to CO2 and sulfur to SO2. These gases, along with nitrogen, were then separated by gas chromatography and measured using a thermal conductivity detector.
As required for safety considerations, the concentrations of the hydrocarbons methane (C1), ethane (C2), and propane (C3) were monitored in the sediment cores. Hydrocarbon gases were extracted from bulk sediment using a headspace sampling technique. As soon as the core arrived on deck, a 5-cm3 plug of sediment was taken using a number four cork borer. This sample was placed immediately in a glass vial that was then sealed with a septum and metal crimp seal and heated to 70°C. The gas driven off was drawn into a glass gas-tight syringe and injected into a Hewlett Packard 6890 series gas chromatograph equipped with a flame ionization detector. Where high concentrations of propane were suspected, a second sample was taken by the same method and analyzed for C1 through C6 hydrocarbons using a Hewlett Packard 6890 series natural gas analyzer, a gas chromatograph equipped with Poropak-Q, molecular-sieve, and silicone-oil coated columns and both flame ionization and thermal conductivity detectors. After the headspace gas was analyzed, the actual volume of the sediment sample was measured to the nearest 0.5 cm3 by water displacement.
Samples of suspected gas pockets in the cores were also analyzed using the Hewlett Packard natural gas analyzer. These samples were taken immediately upon recovery of the core by penetrating the transparent plastic core liner with a hollow stainless steel punch equipped with a valve and hypodermic needle. The gases were injected directly into the gas chromatograph using a three-way nylon valve.
During Leg 195, interstitial water was obtained from sediments and unconsolidated serpentine by squeezing whole-round sections of core, 5-15 cm in length. As soon as the core arrived on deck, these samples were cut by slicing the polycarbonate core tube and capping both ends. The samples were then cooled from a typical arrival temperature of 15°-20°C to the appropriate in situ temperature, removed from the core liner, scraped with a stainless steel spatula to remove the outer contaminated layer, and placed in a titanium piston-cylinder squeezer (Manheim and Sayles, 1974). Both the squeezer and the samples were handled only with plastic gloves to avoid contamination. The squeezer was placed in a Carver hydraulic press and squeezed at pressures that were increased slowly up to 40,000 psi. Interstitial water was collected through an on-line 0.45-µm polysulfone filter mounted in a Gelman "acrodisc" disposable filter holder into a 50-mL plastic syringe, from which the various aliquots for analysis were ejected.
The water sampler temperature-pressure (WSTP) tool (Barnes, 1988) was used only once during Leg 195, to collect borehole water from Hole 1200C when it was suspected that formation fluid might be upwelling through the hole. (This was proved not to be the case, as the sample recovered was seawater.) The sampler is lowered on the sand line and locked into an assembly just above the bit so that the sampling probe projects ~20 cm through the bit. A timer-operated valve opens and draws water under negative pressure through a series of screens and filters into a 93-mL stainless steel coil and then into a 1.2-L steel overflow chamber that is initially filled with air and also contains the sample coils and valves. The coil is initially filled with distilled water that is displaced by the sample. After sampling, the overflow chamber contains sampled water diluted by distilled water displaced from the coil. Water from both the sample coil (the WSTP-1 "prime" aliquot) and the overflow chamber (the WSTP-1 "overflow" aliquot) was analyzed.
The waters were analyzed immediately after recovery for pH, alkalinity (±1.5%) by potentiometric Gran titration, and hydrogen sulfide (±4%) by colorimetry using methylene blue.
Aliquots were refrigerated and analyzed within a few days of collection for chlorinity (±0.4%) and calcium (±0.7%) by electrochemical titration, magnesium (total alkaline earths; ±0.5%) by colorimetric titration, sulfate (±1%) and potassium (±2%) by ion chromatography (IC), ammonium (±4%) and phosphate (±4%) by colorimetry, fluoride by ion-specific electrode, and strontium, barium, manganese, iron, boron, aluminum, silicon, and lithium by ICP-AES. Sodium was calculated from charge balance. Chloride (±1%), sodium (±2%), calcium (±2%), and magnesium (±5%) were also determined by IC and the results used to check the accuracy of the more precise techniques noted above; for low concentrations (<3 mM) of calcium and magnesium where the titration results are inaccurate, the IC data were used instead. Except for the electrochemical end point detection used in the chlorinity and calcium titrations, all shipboard analyses were performed using standard ODP techniques, as detailed by Gieskes et al. (1991). International Association for the Physical Sciences of the Ocean standard seawater was the primary standard for determination of calcium, magnesium, potassium, sulfate, and chlorinity and also provided a check on the accuracy of the analyses for alkalinity and fluoride. Borax solutions were used as standards for the alkalinity titration.