Detection of microbial activity at seafloor hydrothermal system by sulfur isotope micro-analysis.

本实验室引进了元素分析仪-连续流动同位素比值质谱仪（EA-IRMS），并对EA-IRMS测量微量硫同位素比值的能力进行了验证。从矿物学和经济地质学的角度对海底热液硫化物-硫酸盐烟囱和硫化物进行了详细的描述，为利用硫同位素比值检测海底热液系统中的微生物活动做准备，发现元素分析仪-连续流同位素比值质谱仪（EA-IRMS）能够分析常见硫化物和硫酸盐矿物的硫同位素组成，如黄铜矿、黄铁矿、闪锌矿和重晶石。测量所需的样品量非常小，与传统的双入口IRMS所使用的量相比是1/100。在样品分析过程中测量参考物质和使用助燃剂使得分析的精度与通过常规方法获得的精度一样准确，尽管在连续测量过程中原始测量的硫同位素比率增加。此外，铌氧化物被发现是一个很好的燃烧促进剂，而不是通常使用的高毒性的钒氧化物。对冲绳海槽Iheya北海底热液系统中活动和死亡的海底热液烟囱进行了详细的矿物学检查，以准备使用其硫同位素比值检测微生物活动。它们主要由黄铜矿、黄铁矿、闪锌矿和重晶石组成。根据这些矿物的产状和结构特征，建立了冲绳海槽海底热液系统的海底烟囱生长模型。

Elemental Analyzer-continuous flow Isotope Ratio Mass Spectrometer (EA-IRMS) was introduced in our laboratory and checked for the ability of the EA-IRMS on micro-scale sulfur isotope ratio measurement. Seafloor hydrothermal sulfide-sulfate chimney and sulfide are were described in detail from the view points of mineralogy and economic geology in order to prepare the detection of the microbial activity at the seafloor hydrothermal system by the sulfur isotopic ratio.Elemental Analyzer-continuous flow Isotope Ratio Mass Spectrometer (EA-IRMS) was found to be capable to analyze sulfur isotopic compositions of common sulfide and sulfate mineral, such as chalcopyrite, pyrite, sphalerite and barite, in seafloor hydrothermal chimney. The required amount of sample for the measurement is very small, which is 1/100 compared to the amount used by conventional double inlet IRMS. Measurement of reference material during sample analyses and the use of combustion improver made the precision of analysis as accurate as those obtained by the conventional method, though the raw measured sulfur isotope ratios increase during consecutive measurements. Furthermore, Niobium oxide was found to be a good combustion improver instead of the commonly used highly toxic Vanadium oxide.Active and dead seafloor hydrothermal chimneys in Iheya North seafloor hydrothermal system, Okinawa Trough, were mineralogically examined in detail to prepare the detection of microbial activity using their sulfur isotopic ratios. They are mainly consisted of chalcopyrite, pyrite, sphalereite and barite. From the occurrences and texture of these minerals, the seafloor chimney growth model in the Okinawa Trough seafloor hydrothermal system was established.