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doi:10.2204/iodp.proc.337.201.2015

Materials and methods

Most of the pore water samples were collected by the conventional sediment squeezer, whereas four of the samples were collected by the Quicksilver probe (Fig. F1). The Quicksilver water samples were extracted from the formation under in situ pressure and temperature. All pore water samples were recovered and treated under standard IODP protocol (see the “Methods” chapter [Expedition 337 Scientists, 2013b]). Sr concentration was measured on board by inductively coupled plasma–atomic emission spectroscopy (ICP-AES). We used preserved samples for onboard alkalinity titration for our Sr isotopic analyses. All samples were kept below ~4°C before analyses.

For all pore water, 75 µL of sample was loaded onto Eichrom “Sr-spec” chromatographic columns (Horwitz et al., 1992). Four samples from Sections 337-C0020A-11R-5, 13R-2, 13R-8, and 15R-7 were processed through cation columns using Eichrom cation-exchange (AG50 8X) resin (Cohen et al., 1988) prior to Sr isolation to reduce the high concentrations of rubidium (Rb) in these samples. This initial reduction of Rb increased the efficiency of the Sr isolation, thus reducing isobaric interference from ⁸⁷Rb. Pure solutions at 20–30 ppb Sr were then analyzed using the Nu Plasma multicollector inductively coupled plasma–mass spectrometer (MC-ICPMS) in the W.M. Keck Collaboratory for Plasma Spectrometry in the College of Earth, Ocean, and Atmospheric Science at Oregon State University (OSU-CEOAS; USA). Instrument mass bias was corrected using ⁸⁸Sr/⁸⁶Sr of 8.375209, and all data were normalized to an ⁸⁸Sr/⁸⁶Sr value for the NBS987 standard of 0.710245 (2σ = 0.000050, which is 91). Replicate analyses of an in house standard (an EMD Millipore Sr standard solution) defines the long-term 2σ external reproducibility, which was 0.000060 (n = 79). We used the same protocols for sample pretreatment and analyses as Joseph et al. (2013). All data and the associated analytical error can be found in Tables T1 and T2.

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