Halogene concentrations and iodine isotopic composition in pore water on Hydrare Ridge, Cascadia continental margin, supplement to: Fehn, Udo; Lu, Zunli; Tomaru, Hitoshi (2006): Data report: 129I/I ratios and halogen concentrations in pore water of Hydrate Ridge and their relevance for the origin of gas hydrates: a progress report. In: Tréhu, A.M., Bohrmann, G., Torres, M.E., Colwell, F.S. (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 204, 1-25(online)


We report iodine and bromine concentrations in a total of 256 pore water samples collected from all nine sites of Ocean Drilling Program Leg 204, Hydrate Ridge. In a subset of these samples, we also determined iodine ages in the fluids using the cosmogenic isotope 129I (T1/2 = 15.7 Ma). The presence of this cosmogenic isotope, combined with the strong association of iodine with methane, allows the identification of the organic source material responsible for iodine and methane in gas hydrates. In all cores, iodine concentrations were found to increase strongly with depth from values close to that of seawater (0.0004 mM) to concentrations >0.5 mM. Several of the cores taken from the northwest flank of the southern summit show a pronounced maximum in iodine concentrations at depths between 100 and 150 meters below seafloor in the layer just above the bottom-simulating reflector. This maximum is especially visible at Site 1245, where concentrations reach values as high as 2.3 mM, but maxima are absent in the cores taken from the slope basin sites (Sites 1251 and 1252). Bromine concentrations follow similar trends, but enrichment factors for Br are only 4-8 times that of seawater (i.e., considerably lower than those for iodine).

DOI http://dx.doi.org/doi:10.1594/PANGAEA.706970
Metadata Access http://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite3&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.706970
Creator Fehn, Udo;Tomaru, Hitoshi;Lu, Zunli
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2006
Rights Creative Commons Attribution 3.0 Unported (CC-BY)
Language English
Resource Type Supplementary Collection of Datasets
Format application/zip
Discipline Earth System Research
Spatial Coverage (45N-45N,125W-125W)
Temporal Point 2002-07-12T11:59:59Z