Microbial carbon isotope fractionation to produce extraordinarily heavy methane in aging hydrothermal plumes over the southwestern Okinawa Trough
Microbial carbon isotope fractionation to produce extraordinarily heavy methane in aging hydrothermal plumes over the southwestern Okinawa Trough
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DOI：
10.2343/geochemj.1.0097
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发表时间：
2010-01-01
影响因子：
0.8
通讯作者：
Sano, Yuji
中科院分区：
文献类型：
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作者：
Gamo, Toshitaka;Tsunogai, Urumu;Sano, Yuji
在与那国穹丘IV热液区产生的中性浮力热液羽流中（24 ° 51' N，122 ° 42' E D = 1370 ~ 1385 m），获得了冲绳海槽弧后盆地西南部溶解态锰（Mn）的剖面，氦同位素（He-3/He-4）甲烷（CH_4）及其稳定碳同位素比值（delta C-13（PDB））在年轻到老的羽流沃茨我们首先通过拖曳一组固定的光学传感器绘制了热液羽流的空间分布图（微型自主式羽流记录器MAPR）然后我们使用CTD进行水柱观测和采样（电导率温度和深度传感器）-Carnival套件，带透射计和Niskin-在距热液活动中心0.6 ~ 6.1km的5个位置上，X射线瓶的光透射和化学示踪物的垂直分布表明三层烟羽的中心位于700-800 m的深度，类似于1 050 m和1 200 m。1 200 m烟羽的CH 4浓度和δ C-13值介于1，026和10 nmol/kg之间，在-22 4和+40 4 ppm之间（迄今为止海洋CH 4的最高Δ C-13值）分别表明活跃的微生物CH 4氧化伴随着残余CH 4的Δ C-13增加。应用Rayleigh蒸馏方程计算了1000 m以上热液柱中甲烷氧化过程的动力学同位素分馏因子为1012
Within neutrally buoyant hydrothermal plumes derived from the Yonaguni Knoll IV hydrothermal field (24 degrees 51' N, 122 degrees 42' E D = 1 370-1 385 m) in the southwestern Okinawa Trough back arc basin we obtained profiles of dissolved manganese (Mn), helium isotopes (He-3/He-4) methane (CH4) and its stable carbon isotope ratio (delta C-13(PDB)) in young to old plume waters We first mapped the spatial distribution of hydrothermal plumes by towing a fixed array of optical sensors (Miniature Autonomous Plume Recorders MAPRs) above the field We then made water column observations and samplings using a CTD (Conductivity Temperature and Depth sensors)-Carousel package with a transmissometer and Niskin-X bottles at five locations with distances between 0 6 and 6 1 km horn the hydrothermally active center so far discovered Vertical profiles of light transmission and chemical tracers indicated triple-layered plumes the centers of which were at depths of 700-800 m similar to 1 050 m and similar to 1 200 m The CH4 concentrations and delta C-13 value for the 1 200-m plume ranged between 1,026 and 10 nmol/kg, and between -22 4 and +40 4 parts per thousand (the highest delta C-13 value yet reported for oceanic CH4) respectively indicating active microbial CH4 oxidation accompanied by the delta C-13 increase for residual CH4 The delta C-13(CH4) was shown to be useful for tracing such a "microbial plume whose CH4 concentration has already fallen to almost the background level By applying the Rayleigh distillation equation for a closed system we estimated the kinetic isotope fractionation factor of 1 012 for the CH4 oxidation process occurring within the hydrothermal plumes deeper than 1 000 m