Sr Isotopes data of Kumano mud volcanoes' (Offshore SE Japan) pore waters extracted from cores taken during the SO222 expedition in 2012. A total of 10 acidified fluid samples were analyzed for their strontium isotopic composition. Due to low fluid volume recovery, 5 samples are mixtures of adjacent samples (mixing ratios are given in appendix). Strontium was separated on cation exchange resin using HCl as the eluent and measured on a Micromass Sector 54 multicollector thermal ionization mass spectrometer (TIMS) at SCRIPPS Institute of Oceanography (SIO), following the method described by Solidum (2002). Sr isotopic ratios were measured through dynamic multicollection and fractionation corrected to 86Sr/88Sr = 0.1194. Sr isotopic data are reported relative to NIST SRM 987 with repeated measurements yielding 87Sr/86Sr = 0.710259 ± 0.000017 (2SDmean, n = 19), which is in agreement with the published values analyzed by TIMS [0.710250±0.000034 (2SDmean, n = 1245), GeoRem data base; query July 2017; http://georem.mpch-mainz.gwdg.de.]

Further funding:* FWF Lise Meitner, Award: M3146-N