Hydrothermal Vapor‐Phase Fluids on the Seafloor: Evidence From In Situ Observations

Abstract

Subseafloor phase separation is a common and significant process in hydrothermal systems and may result in a large of fluid composition differences. The temperatures of hydrothermal fluids are generally considered to be below the associated fluid boiling temperature due to mixing with ambient seawater and the phase separation process. However, we report here shimmering water with temperatures up to 383.3°C observed in a hot overturned lake at the Yokosuka site, Okinawa Trough, East China Sea, where in situ Raman spectra suggest the presence of a superheated vapor phase. Hydrothermal vents similar to the low-density hydrothermal system found at the Yokosuka site have also been observed in many other regions. Therefore, much more attention should be given to the impacts of low-density hydrothermal fluid emanations on marine environments and resource distributions.Plain Language Summary Hydrothermal systems characterized by the emanations of supercritical-and vapor-phase fluids associated with igneous activities have been observed on mid-ocean ridges. Here, we report a newly found hydrothermal system dominated by low-density vapor-phase fluids at the Yokosuka site, a hydrothermal field located in a backarc basin spreading center. Multiple methods, including in situ Raman spectroscopy measurements, thermocouple sensor measurements, and gas-tight sampling, were used to investigate this vapor-phase hydrothermal emanation. In situ observations suggest that the highest temperature (383.3°C) of the hydrothermal fluids at the Yokosuka site is above the two-phase boundary of seawater at a depth of 2,180 m (378.1°C) and in situ Raman spectra indicate the fluid of the hot overturned lake features a layered structure. Hydrothermal systems with low-density emanations are likely to be widespread throughout various tectonic settings since similar phenomena have been observed in other hydrothermal fields with conditions close to the phase separation boundary.

深海热液区微生物群落与环境适应性机理

“…其生长温度范围 50-100℃，生长 pH 范围 4-9，生长压力范围为 0.1-70 MPa [27] ；而该菌株 的基因组仅 2.1 Mb，且代谢途径相对简单 [28] ，由此推测该菌株可能通过一种简单却高效 体与海水混合相以及底层的正常海水相 [33] ，这表明高温高压下热液流体中的水经历着复 杂的物理化学过程。此外，高温会扰乱水分子与胞内溶质形成的氢键网络及其他化学键， 而高压可在一定程度上增强氢键网络 [34] 子动力学影响，发现超嗜热菌中的 IPPase 蛋白比中温菌中的蛋白有更快的弛豫动力学特 征 [35] 。Tros 等人使用超快振动光谱和介电弛豫光谱观察活细胞内水分子的随机定向运动， 发现大多数胞内水表现出与纯水相同的随机定向运动，而较小部分(~20-45%)表现出较 慢的定向动力学特征 [36] 。而 Martinez 等使用准弹性中子散射在超嗜热嗜压古菌中观察到 胞内水分子的较慢运动可能与高压适应有关 [37] 。尽管越来越多的物理学检测技术开始被 细胞膜是古菌和细菌最主要的区别，它使细胞能够维持一个相对稳定的内部环境， 帮助微生物在面对极端或波动的外部环境时也能保持胞内环境相对稳定。细胞膜的流动性 和通透性随着温度升高而增加，在高温极限下，膜蛋白聚集，膜蛋白活性降低，溶质通量 降低，阳离子渗透性增加 [38] 。因此，热液环境中的(超)嗜热微生物具有一些特殊的细 胞膜组分，并通过改变膜脂组分来适应高温。例如，嗜热细菌通过增加磷脂分子中饱和脂 肪酸的比例、增加磷脂烷基链的长度和增加异构化支链的比例来增强细胞膜的热稳定性 [39] 。超嗜热古细菌则利用特殊的四醚 (Glycerol dibiphytanyl glycerol tetraethers, GDGT) 形…”

A Piecewise Model for In Situ Raman Measurement of the Chlorinity of Deep-Sea High-Temperature Hydrothermal Fluids

“…The temperature of seawater and hydrothermal fluids in the Jade and Hakurei fields was measured using a K-type Omega thermocouple with an accuracy of 99.25%. 55,56 In situ Raman spectra of seawater and hydrothermal fluids in the Jade and Hakurei fields were collected by the RiP system. As shown in Fig.…”

Direct H2S, HS− and pH Measurements of High‐Temperature Hydrothermal Vent Fluids With In Situ Raman Spectroscopy

“…In situ Raman spectroscopy has been widely used for the detection of deep‐sea hydrothermal fluids since the advent of the Deep‐ocean Raman in situ spectrometer and Raman insertion Probe systems due to their advantages of noncontact, not requiring sample pretreatment, and the ability to simultaneously detect multiple components (Brewer et al., 2004; Zhang et al., 2011, 2017). An in situ detection method based on Raman spectroscopy used to measure gas volatiles (CH 4 , CO 2 and H 2 ) in hydrothermal fluids has been established and successfully applied to the in situ measurement of high‐temperature hydrothermal fluids in the Okinawa Trough (Li et al., 2018a, 2018b, 2020a, 2020b, 2021, 2023). Although Raman spectroscopy cannot directly obtain the pH parameter of a hydrothermal fluid, the ionic equilibrium systems, such as H 2 S‐HS − , CO 2 ‐HCO 3 − and HSO 4 − ‐$${\mathrm{S}{\mathrm{O}}_{4}}^{2-}$$, present in the hydrothermal fluid can be analyzed quantitatively to measure the pH in situ (Peltzer et al., 2016; Xi et al., 2018).…”

“…measure gas volatiles (CH 4 , CO 2 and H 2 ) in hydrothermal fluids has been established and successfully applied to the in situ measurement of high-temperature hydrothermal fluids in the Okinawa Trough (Li et al, 2018a(Li et al, , 2018b(Li et al, , 2020a(Li et al, , 2020b(Li et al, , 2021(Li et al, , 2023. Although Raman spectroscopy cannot directly obtain the pH parameter of a hydrothermal fluid, the ionic equilibrium systems, such as H 2 S-HS − , CO 2 -HCO 3 − and HSO 4 − -𝐴𝐴 SO4 2− , present in the hydrothermal fluid can be analyzed quantitatively to measure the pH in situ (Peltzer et al, 2016;Xi et al, 2018).…”