Hydrostatic pressure exerted by the ocean water column fundamentally influences magmatic and hydrothermal processes in submarine volcanic settings and is therefore an important parameter to know when investigating such processes. Currently, there are few reliable methods for reconstructing past ocean depths for ancient volcanic terranes. Here, we develop and test an empirically calibrated statistical approach for determining paleodepths of eruption from the concentrations of H₂O and CO₂ dissolved in volcanic glasses, utilizing the well-defined pressure-dependent solubility of these volatiles in silicate melts. By comparing newly determined and published glass compositions from the Samail and Troodos ophiolites with sedimentary and fluid inclusion evidence, we propose that the Samail lavas erupted at ocean depths of ∼3.4 km, and the Troodos lavas at ∼4.1 km. These depths are 1–2 km deeper than those assumed in most previous studies of hydrothermal activity in the two ophiolites. These high depths imply high hydrostatic pressures within the underlying oceanic crust. Such pressures may have allowed convecting hydrothermal fluids to attain significantly higher temperatures (e.g., >450°C) than in typical modern ocean ridge hydrothermal systems during metal leaching in the crust and metal precipitation in seafloor sulfide deposits.

中文翻译：

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Samail 和 Troodos 蛇绿岩中海底熔岩的古水深测量：对玻璃中挥发物的洞察和对热液系统的影响

海洋水柱施加的静水压力从根本上影响海底火山环境中的岩浆和热液过程，因此是研究此类过程时需要了解的重要参数。目前，几乎没有可靠的方法来重建古代火山岩体的过去海洋深度。在这里，我们开发并测试了一种根据经验校准的统计方法，用于根据 H ₂ O 和 CO ₂的浓度确定火山喷发的古深度溶解在火山玻璃中，利用这些挥发物在硅酸盐熔体中的明确定义的压力依赖性溶解度。通过将来自 Samail 和 Troodos 蛇绿岩的新确定和发表的玻璃成分与沉积和流体包裹体证据进行比较，我们提出 Samail 熔岩在约 3.4 公里的海洋深处喷发，而 Troodos 熔岩在约 4.1 公里处喷发。这些深度比之前大多数关于两个蛇绿岩中热液活动的研究中假设的深度深 1-2 公里。这些高深度意味着下伏洋壳内的高静水压力。在地壳中的金属浸出和海底硫化物矿床中的金属沉淀期间，这种压力可能允许对流热液流体达到比典型现代洋脊热液系统显着更高的温度（例如，> 450°C）。