Clay Mineralogy of deep-sea sediments from ODP, Bonins

通过对伊豆-博宁弧前沉积盆地的沉积物进行深部取心，已经恢复了大范围蚀变的孔隙水，其成分不同于以前通过DSDP/ODP法报告的任何孔隙水(第126条船上科学小组，1989；Fujioka等人，1989)。伊豆-博宁弧前盆地以上渐新世玻璃岩和浮质砂岩为主，火山成因沉积堆积速率极高，易发生蚀变。在这里，我们报告了生物成因改变的迹象。对793B孔20个火山岩样品进行了光学显微镜、抛光薄片、透射电子显微镜、X射线粉末衍射仪、傅立叶变换红外光谱仪和X射线光电子能谱的观察。结果表明，火山岩中存在CH、CoO、C-0、C-C基团和石墨，表明火山砂岩中的绿色球形粘土(绿云母粘土)不仅是由…形成的热液蚀变产物较多，还受丝状细菌与有机物之间的微生物相互作用影响。生物材料和碎片似乎影响了绿色球形粘土和石墨的性质。显微镜观察发现，在多孔性火山砂岩的热液流体中，细菌和石墨的存在可以诱导绿色球形粘土的形成。砂岩中含有许多水热蚀变矿物，如沸石、硬石膏、蒙皂石和方石英。根据这些矿物组合，这些产物的条件被估计为海山附近的低温热液场(Tazaki，1991年；Tazaki和Fyfe，1992)。最近的全球海洋通量联合研究讨论了海洋过程在全球生物地球化学循环中的作用，特别关注了CO2的海-气交换。我们的观察表明，海洋热液系统中有大量的细菌，它们肯定是成岩作用期间蚀变物质中后来产生二氧化碳的原因。较少

Extensively altered pore water, with a composition different from that of any previously reported pore water by DSDP/ODP, have been recovered by deep coring of sediments in Izu-Bonin fore-arc sedimentary basin (Leg 126 shipboard scientific party, 1989 ; Fujioka et al., 1989). Upper oligocene vitric and pumiceous sandstone are the dominant products of Izu-Bonin fore-arc basin, where accumulation rates of volcanogenic sediment are extremely high and the sediments are susceptible to alteration. Here we report indications of biogenic alteration. A total of 20 volcanic sandstone samples from Holes 793B were observed by optical microscopy in preparations of polished thin section, transmission electron microscopy, X-ray powder diffraction, Fourier Transform Infrared Spectrometer, and X-ray photoelectron spectrometer.The data show presence of CH, COO, C-0, C-C groups and graphite, suggesting that the green spherical clays (glckuconitic mica clays) in the volcanic sandstone formed not only from … More hydrothermal alteration products, but also by microbiological interaction between filamentous bacteria and organic materials. The biological materials and debris appear to influence the nature of both the green spherical clays and graphite. Microscopical observation has revealed the presence of bacteria and graphite which can induce the formation of green spherical clays in hydrothermal fluids of porous volcanic sandstone. The sandstone contains numerous hydrothermally altered minerals such as zeolites, anhydrite, smectite, and cristobarite. According to these mineralogical assemblage, the conditions of the products were estimated to be below 200 ﾟC as low-temperature hydrothermal fields near seamounts (Tazaki, 1991 ; Tazaki and Fyfe, 1992).Recently the Joint Global Ocean Flux Study addresses the role of ocean processes in global biogeochemical cycles, with special attention is given to air-sea exchanges of C02. Our observations show that bacteria are abundant in marine hydrothermal systems, and they must contribute to later C02 generation in the altered materials during diagenesis. Less