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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Fluid and chemical fluxes in and out of sediments hosting methane hydrate deposits on Hydrate Ridge, OR, I: Hydrological provinces
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Fluid and chemical fluxes in and out of sediments hosting methane hydrate deposits on Hydrate Ridge, OR, I: Hydrological provinces

机译：水合物岭上的甲烷和水合物沉积物的沉积物中的流体和化学通量，I，水文省份

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摘要

Extensive deposits of methane hydrate characterize Hydrate Ridge in the Cascadia margin accretionary complex. The ridge has a northern peak at a depth of about 600 m, which is covered by extensive carbonate deposits, and an 800 m deep southern peak that is predominantly sediment covered. Samples collected with benthic instrumentation and from Alvin push cores reveal a complex hydrogeological system where fluid and methane fluxes from the seafloor vary by several orders of magnitude at sites separated by distances of only a few meters. We identified three distinct active fluid regimes at Hydrate Ridge. The first province is represented by discrete sites of methane gas ebullition, where the bulk of the flow occurs through channels in which gas velocities reach 1 m s~(-1). At the northern summit of the ridge the gas discharge appears to be driven by pressure changes on a deep gas reservoir, and it is released episodically at a rate of ～6 * 10~4 mol day~(-1) following tidal periodicity. Qualitative observations at the southern peak suggest that the gas discharge there is driven by more localized phenomena, possibly associated with destabilization of massive gas hydrate deposits at the seafloor. The second province is characterized by the presence of extensive bacterial mats that overlay sediments capped with methane hydrate crusts, both at the northern and southern summist. Here fluid typically flows out of the sediments at rates ranging from 30 to 100 cm yr~(-1). The third province is represented by sites colonized by vesicomyid clams, where bottom seawater flows into the sediments for at least some fraction of the time. Away from the active gas release sites, fluid calculated from pore water models are in agreement with estimates using published flowmeter data and numerical model calculations. Methane fluxes out of mat-covered sites range from 30 to 90 mmol m~(-2) day~(-1), whereas at clam sites the methane flux is less than 1 mmol m~(-2) day~(-1).
机译：甲烷水合物的大量沉积物是卡斯卡迪亚边缘增生复合物中的水合物岭的特征。该山脊在约600 m的深度处有一个北峰，被大量的碳酸盐沉积物所覆盖，而在一个深800 m的南峰中，则主要被沉积物所覆盖。用底栖仪器和Alvin推进岩心收集的样本揭示了一个复杂的水文地质系统，其中海底的流体和甲烷通量在相距仅几米的位置处变化了几个数量级。我们在水合物岭发现了三种不同的活性流体形态。第一个省是甲烷散发的离散地点，其中大部分流量通过通道传播，其中气体速度达到1 m s〜（-1）。在山脊的北端，气体排放似乎是由深层气藏中的压力变化驱动的，并且在潮汐周期之后，以〜6 * 10〜4 mol·day〜（-1）的速率释放。在南峰的定性观测表明，那里的气体排放是由更多的局部现象驱动的，这可能与海底大量天然气水合物沉积物的失稳有关。第二个省份的特点是，在北部和南部的萨姆斯地区存在着广泛的细菌垫，覆盖了覆盖有甲烷水合物结壳的沉积物。在这里，流体通常以30至100 cm yr〜（-1）的速率从沉积物中流出。第三省以囊藻蛤c定殖的地点为代表，那里的底部海水至少有一部分时间流入沉积物中。除活性气体释放部位外，根据孔隙水模型计算出的流体与使用公开的流量计数据和数值模型计算得出的估计值一致。甲烷从垫层覆盖部位的通量范围为30至90 mmol m〜（-2）天〜（-1），而在蛤lam部位，甲烷通量小于1 mmol m〜（-2）天〜（-1） ）。

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