Sulfur isotopic exchange between chemosynthetic microbes and sulfur-bearing minerals in seafloor hydrothermal systems

我们进行了研究，探索海底热液网站，海底冷渗漏带，海底天然气水合物，和化石海底热液活动，以阐明地球化学和微生物过程。研究结果表明：（1）西太平洋伊豆小笠原弧水阳海山的硫酸盐矿物和硫化物矿物分别由海水硫酸盐和岩浆硫化物硫形成，尽管热液区附近的沉积物中硫还原菌占优势，但硫化物矿物中没有发现生物成因的特征。（2）北美卡斯卡迪亚海脊间隙水的氢同位素分析表明，甲烷渗漏伴随着天然气水合物分解生成的流体。因此，该地区的高甲烷通量并不一定表明深部甲烷水合物形成的高速率。（3）加拿大西北地区McKenzie三角洲沉积物中黄铁矿的重硫同位素值表明其成因为封闭或半封闭环境下的海水硫酸盐。这个想法与该地区海平面上升和下降的观察相吻合。（4）对东海近海甲烷渗漏细菌基质的有机地球化学分析表明，生物标志物为藻类、好氧细菌和甲烷氧化菌的混合物。（5）黑子存款是中新世日本弧海底热液存款的化石。在黑矿矿床的块状硫化物矿石外围，受热液系统微生物活动的影响，出现了以富含金和银为特征的所谓褐矿石。（6）质谱分析是区分海底热液系统生物活动的最有力的工具。

We conducted research to explore seafloor hydrothermal sites, cold seep zone on seafloor, sub-seafloor gas hydrate, and fossil seafloor hydrothermal activity to elucidate the geochemical and microbiological processes. We obtained following conclusions:(1)Sulfate and sulfide minerals in the Suiyo Seamount, Izu-Bonin Arc, Western Pacific are formed from seawater sulfate and magmatic sulfide sulfur, respectively, and no biogenic signature was identified in the sulfide minerals despite the fact that the sulfur reducing bacteria is dominant in the sediments near the hydrothermal area.(2)Hydrogen isotopic analysis of the interstitial water at the Hydrate Ridge, Cascadia Margin of North America indicate that the methane seep is accompanied with fluid which was derived from decomposition of gas hydrate. Therefore, high methane flux of the area does not necessarily indicate high rate of methane hydrate formation at depth.(3)Heavy sulfur isotopic value of pyrite in sediments from McKenzie Delta, Northwestern Territories, Canada suggests its seawater sulfate origin under closed or semi-closed environment. This idea matches with the observation of sea-level rise and fall in the district.(4)Organic geochemical analysis on bacterial matte at methane seep off Tokai coast indicate that the biomarkers are the mixture of algae, aerobic bacteria, and methane-oxidizing Archaea.(5)Kuroko deposit is the fossil seafloor hydrothermal deposit of Japan Arc in Miocene age. So-called Brown Ore which is characterized by its gold and silver-rich assay occurs on the periphery of the massive sulfide ore of the Kuroko deposits affected by microbial activity of the hydrothermal system.(6)All the results indicate that the mass spectroscopic analysis is the most powerful tool to discriminate the biological activity of the hydrothermal system in the past and present-day seafloor.