Hydrothermal venting at pressure-temperature conditions above the critical point of seawater, 5°S on the Mid-Atlantic Ridge
Hydrothermal venting at pressure-temperature conditions above the critical point of seawater, 5°S on the Mid-Atlantic Ridge
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DOI：
10.1130/g24726a.1
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发表时间：
2008-08-01
期刊：
影响因子：
5.8
通讯作者：
Strauss, Harald
中科院分区：
文献类型：
--
作者：
Koschinsky, Andrea;Garbe-Schoenberg, Dieter;Strauss, Harald
海洋地壳内的热液循环取决于压力（P）和温度（T）;海水的临界点（CP）为298巴和407摄氏度，是亚临界和超临界条件之间的阈值。在这里，我们提出的数据从第一个热液系统中，采样的流体落在CP和以上。在中大西洋海脊南纬5度发现的喷口系统的特点是，在接近3 000米的水深中，在不同温度下有多种流体喷出。剧烈的汽相鼓泡、407 ℃时超热流体的稳定发散以及盐度的降低表明在一个地点CP以上的条件下发生了相分离。在另一个地点，在20秒间隔内测得的最大温度为464摄氏度，这是迄今为止在海底测得的最热流体，并且福尔斯落入海水的汽相超临界区域。除了这两个具有持续的相分离和极热流体的独立区域外，第三个喷口区域散发出349摄氏度的非相分离流体，并用作参考位置。流体化学表明，超临界流体的演变不同于亚临界流体，使这个通风系统成为一个独特的自然实验室，以研究在高P-T条件下的过程。2002年假定的地震触发事件后，2005年和2006年测量的高温和流体地球化学的稳定性支持这是一个特殊的网站沿着大西洋中脊。
Hydrothermal circulation within oceanic crust depends on pressure (P) and temperature (T); the critical point (CP) of seawater at 298 bar and 407 degrees C represents the threshold between subcritical and supercritical conditions. Here we present data from the first hydrothermal system in which the sampled fluids fall on and above the CP. The vent system discovered at 5 degrees S on the Mid-Atlantic Ridge is characterized by multiple fluid emanations at variable temperatures in water depths of similar to 3000 m. Vigorous vapor phase bubbling, stable emanation of superhot fluid at 407 degrees C, and decreased salinity indicate phase separation at conditions above the CP at one site. At another site the measured maximum T of 464 degrees C during a 20 s interval is by far the hottest fluid ever measured at the seafloor and falls into the vapor-phase supercritical region of seawater. Besides these two separate fields with ongoing phase separation and extremely hot fluids, a third vent field emanates non-phase-separated fluids at 349 degrees C and is used as a reference site. Fluid chemistry shows that supercritical fluids evolve differently than subcritical fluids, making this vent system a unique natural laboratory to investigate processes at high P-T conditions. The stability of the high temperature and fluid geochemistry measured in 2005 and 2006 after the assumed seismic trigger event in 2002 supports this as an exceptional site along the Mid-Atlantic Ridge.