MATERIALS AND METHODS

All pore fluids analyzed were obtained by routine shipboard squeezing of whole-round sediment samples almost immediately after retrieval. The sediments were squeezed in titanium squeezers at ambient temperature and pressures of 2000–3000 psi (140–210 kg/cm²). Samples were analyzed on board for a range of constituents (Morris, Villinger, Klaus, et al., 2003) and were supplemented by shore-based analyses summarized in Tables T1 and T2. F and Br (Figs. F1, F2, F3) were analyzed by ion chromatography with a precision of 3%–5% after diluting the pore fluids (typical dilution ratio = 10). Saether's F concentration data were obtained with ion selective electrodes with a detection limit of 0.1 ppm. The error reported is 0.7% and the standard deviation is 3.6%. Rb, Cs, and Ba concentrations in both pore fluids and sediments (Figs. F4, F5, F6, F7) were analyzed by inductively coupled plasma–mass spectroscopy (ICP-MS; ThermoQuest/Finnigan Element 2). The pore fluid samples and standards were diluted with 0.4-N HNO₃ and spiked with a 1.0-ppb In internal standard. Twenty pore fluid samples and a 0.5- and 2.0-ppb standard were analyzed in each batch of analyses. A 1.0-ppb drift standard was analyzed after every four samples. Instrumental drift was corrected online by normalization of the intensity of the analyte with that of the ¹¹⁵In standard. A second drift correction was applied offline using repeated analyses of the 1.0-ppb Ba, Rb, and Cs drift standard made by dilution of the primary stock solution. The accuracy and precision of multiple analyses were determined by repeated analyses of the 1.0- ppb drift standard, as well as the 0.5- and 2.0-ppb standards. The average accuracies for Ba, Rb, and Cs were <1%, <1%, and <2%, respectively, and the average precisions of the Ba, Rb, and Cs analyses were <0.65%, 0.5%, and <2%, respectively. An additional 65 pore fluid samples were analyzed for Ba concentrations by standard addition on a Perkin Elmer Optima 3000 ICP–optical emission spectrometer (OES) (Figs. F6, F7, F8). The average accuracy and precision of the ICP-OES analyses determined by multiple analyses of drift and calibration standards were <4% and <7%, respectively. The results of ICP-MS and ICP-OES determinations agree well (Figs. F6, F7, F8).

The sediment samples were digested by adding 4-N HNO₃ to dissolve the carbonate, 30% hydrogen peroxide to oxidize the organic matter, a 2:1 mixture of concentrated hydrofluoric (HF) and nitric (HNO₃) acids to digest the sample, and then two portions of concentrated nitric acid. The digested samples were diluted with a 2% Optima nitric acid solution. All solutions were spiked with a 1.0-ppb In internal standard. The method of analysis by ICP-MS was identical to that performed on the pore fluid samples outlined above. The precision and accuracy of the sediment digestion protocol were determined by repeated digestions of reference U.S. Geological Survey (USGS) certified rock standards MAG-1 (marine mud) and SCO-1 (Cody shale). The average percent accuracies of multiple determinations of these standards for Ba, Rb, and Cs were <1%, 1.9%, and 3.5%, respectively, and the average percent precisions for Ba, Rb, and Cs were <1%, ~1%, and 1.3%, respectively. The Ba concentration data are from Solomon et al. (this volume). Some shipboard X-ray fluorescence (XRF) data analyzed during Leg 170 are included in Figures F6 and F7. The samples were measured on an ARL 8420 XRF with reported percent accuracy and precision of 2%–3% (Kimura, Silver, Blum, et al., 1997).

Isotopic compositions of pore fluids and bulk solids were determined by thermal ionization mass spectrometry (TIMS) according to the procedures previously described in Paytan et al. (1993) for Sr isotope ratios and You and Chan (1996) and Chan and Kastner (2000) for Li isotope ratios. Sr and Li concentrations were determined on board by ICP-atomic emission spectroscopy (Morris, Villinger, Klaus, et al., 2003). Sr isotope ratios (Fig. F9) were determined at Scripps Institution of Oceanography (SIO; California, USA) and Li isotope ratios (Fig. F10) were determined at Louisiana State University. The 2 errors in Sr isotope ratio run uncertainties are smaller than the external precision of ±0.000024. The modern seawater value (NASS-2) measured at SIO is 0.709175 ± 24. All ratios are normalized to ⁸⁶Sr/⁸⁸Sr = 0.1194. The ⁸⁷Sr/⁸⁶Sr ratio of the National Bureau of Standards (NBS) standard measured at the SIO laboratory is 0.710260 ± 24. Li isotope ratios of pore fluids were determined using Li₃PO₄ as an ion source material. The precision of both methods is ~1%. Li isotope ratios are reported as ⁷Li relative to National Institute of Standards and Testing (NIST) standard LSVEC. The ⁷Li/⁶Li of the standard determined by the phosphate method during the course of the study was 12.0844 ± 0.0088 (2).