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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 >Subduction and atmospheric escape of Earth's seawater constrained by hydrogen isotopes
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Subduction and atmospheric escape of Earth's seawater constrained by hydrogen isotopes

机译：地球海水的俯冲和大气逃逸受到氢同位素的约束

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The hydrogen isotopic (D/H) ratio reflects the global cycling and evolution of water on Earth as it fractionates through planetary processes. We model the water cycle taking seafloor hydrothermal alteration, chemical alteration of continental crust, slab subduction, hydrogen escape from the early Earth, and degassing at mid-ocean ridges, hot spots, and arcs into account. The differences in D/H ratios between present-day oceans, oceanic and continental crust, and mantle are thought to reflect isotopic fractionation through seafloor alteration, chemical alteration, and slab dehydration. However, if the speed of plate tectonics has been nearly constant throughout Earth's history, the degassing and regassing rates are too small to reach the present-day D/H ratios. We show that (a) hydrogen escape from reduced early atmosphere, (b) secular net regassing, or (c) faster plate tectonics on early Earth is needed to reproduce the present-day D/H ratios of the water reservoirs. The low D/H ratio of Archean seawater at 3.8 Ga has previously been interpreted as a signature of (a) hydrogen escape, but we find it can also be explained either by (b) secular net degassing or by (c) faster plate tectonics on early Earth. The rates of hydrogen escape from early Earth and secular regassing on present-day Earth are constrained to be lower than 2.1 x 10(11) kg/yr and 3.9 x 10(11) kg/yr. Consequently, the volume of water in the present-day mantle could result entirely from the regassing through Earth's history. In that case, the volume of initial oceans could be 2 to 3 times larger than that of current Earth. We suggest that, in addition to the D/H ratio of Archean seawater, identifying the D/H ratios of both seawater and mantle throughout Earth's history would allow to distinguish these evolutionary scenarios. (C) 2018 Elsevier B.V. All rights reserved.
机译：氢同位素（D / H）的比例反映了地球上的全球循环和水的演化，因为它通过行星过程分馏。我们模拟了海底水热改变的水循环，大陆地壳化学改变，平板俯冲，氢气从早期地球逃逸，并在中海脊，热点和弧中脱气。当今海洋，海洋和欧陆地壳之间的D / H比的差异是通过海底改变，化学改变和平板脱水来反映同位素分级。但是，如果板构造的速度在地球历史上几乎恒定，如果脱气和脱气的速率太小而无法达到当前的D / H比率。我们表明（a）氢逃逸从降低的早期气氛，（b）世俗净循环，或（c）早期地球上更快的板构造，以繁殖水库的现状D / H比。 3.8 Ga的Archean海水的低D / H比已被解释为（a）氢逃逸的签名，但我们发现它也可以通过（b）世俗净脱气或由（c）更快的板构造在早期的地球上。从早期地球和现在地球上的早期地球和世俗辐射的氢逃逸的速率受约2.1×10（11）kg / yr和3.9×10（11）kg / yr。因此，本日地幔中的水量可以完全从地球历史上完全导致局部。在这种情况下，初始海洋的体积可能比当前地球大的2至3倍。我们建议，除了Archean海水的D / H比例外，识别海水和地幔的D / H比在地球的历史中允许区分这些进化场景。 （c）2018年elestvier b.v.保留所有权利。

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