Geochemistries of methane-derived authigenic carbonates at gas hydrate mounds on Umitaka Spur

Gas hydrate mounds of thermogenic CH4 are located at the central and northern parts of Umitaka Spur in the Sea of Japan (Hiruta et al., 2015). Methane-derived authigenic carbonates (MDACs) were collected from these mounds during UT04 and KY05-08 cruises (Hiruta et al., 2009). Geochemistries of these MDACs are valuable archives of ancient events at the anticline.Subsample preparation procedures and subsequent geochemical analyses followed those described in Hiruta et al. (2014). Powder samples were prepared from cut surfaces of MDACs. d13C and d18O of CaCO3 in MDACs were determined using an isotope ratio mass spectrometer (Finnigan, MAT252). Carbonate mineralogy was determined using an X-ray diffraction instrument (PANalytical, X’ Pert PRO). The d-space of calcite was calculated using 1.54187 Å for Cu radiation wavelength. Mg content was calculated from the d-space following Hiruta and Matsumoto (2022). The d18O is original value (i.e., not calibrated for Mg content). Note that remaining parts of some MDACs were used in Watanabe et al. (2008) with simplified IDs (italic IDs in remarks).Uploaded dataCross section of MDACs (G401_G403)Cross section of MDACs (PC415)Cross section of MDACs (PC502)(with 1 cm interval division)Cross section of MDACs (PC509)(with 1 cm interval division)Cross section of MDACs (PC513)(with 1 cm interval division)Fossil shells (G403)Geochemistries of MDACs (from UT04 cruise)Geochemistries of MDACs (from KY05-08 cruise)Related articlesHiruta, A., Matsumoto, R., 2022. Geochemical comparison of ikaite and methane-derived authigenic carbonates recovered from Echigo Bank in the Sea of Japan. Mar. Geol. 443, 106672. https://doi.org/10.1016/j.margeo.2021.106672.Hiruta, A., Snyder, G.T., Tomaru, H., Matsumoto, R., 2009. Geochemical constraints for the formation and dissociation of gas hydrate in an area of high methane flux, eastern margin of the Japan Sea. Earth Planet. Sci. Lett. 279, 326-339. https://doi.org/10.1016/j.epsl.2009.01.015.Hiruta, A., Wang, L.-C., Ishizaki, O., Matsumoto, R., 2014. Last glacial emplacement of methane-derived authigenic carbonates in the Sea of Japan constrained by diatom assemblage, carbon-14, and carbonate content. Mar. Petrol. Geol. 56, 51-62. https://doi.org/10.1016/j.marpetgeo.2014.04.005.Hiruta, A., Ishizaki, O., Tuchinaga, K., Snyder, G.T., Matsumoto, R., 2015. Influence of the carbon isotopic composition of methane and the proportion of methane-derived bicarbonate on the 13C/12C ratio of dissolved inorganic carbon at the sulfate-methane transition in the Joetsu Basin area, eastern margin of the Sea of Japan. Mar. Petrol. Geol. 67, 468-480. https://doi.org/10.1016/j.marpetgeo.2015.05.004.Watanabe, Y., Nakai, S., Hiruta, A., Matsumoto, R., Yoshida, K., 2008. U–Th dating of carbonate nodules from methane seeps off Joetsu, Eastern Margin of Japan Sea. Earth. Planet. Sci. Lett. 272, 89-96. https://doi.org/10.1016/j.epsl.2008.04.012