Thermodynamic constraints on the geochemistry of low-temperature, continental, serpentinization-generated fluids
Thermodynamic constraints on the geochemistry of low-temperature, continental, serpentinization-generated fluids
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低温大陆蛇纹石化生成流体地球化学的热力学约束
DOI：
10.2475/03.2020.01
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发表时间：
2020
影响因子：
2.9
通讯作者：
E. Shock
中科院分区：
文献类型：
--
作者：
J. Leong;E. Shock
超镁铁岩的含水蚀变，即蛇纹岩化，产生的流体可以为微生物群落提供燃料，并使简单的有机化合物得以合成。蛇纹石化反应甚至可以在大陆含水层中存在的环境低温条件下进行，这引起了关于地球地下深处生命极限的问题。超镁铁岩的含水蚀变，即蛇纹岩化，产生的流体可以为微生物群落提供燃料，并使简单的有机化合物得以合成。蛇纹石化反应甚至可以在大陆含水层中存在的环境低温条件下进行，这引起了关于地球地下深处生命极限的问题。通过热力学计算，我们研究了各种反应，促进转化为减少，超碱性流体在低温蛇纹石化的好氧，微酸性雨水。我们探索了一套因素（温度，主岩成分，流体盐度和各种蛇纹化相关矿物的缓冲能力的变化），通过低温蛇纹化形成的化学环境提供了广泛的见解。计算结果表明，富橄榄石岩性的蚀变将导致流体的纤蛇纹石-水镁石-透辉石平衡组合的约束，接近的pH值从最碱性的超镁铁岩流体托管的测量。大陆蛇纹岩化系统中流体成分的变化可以归因于从与透辉石平衡到与方解石平衡的转变，以及其他反应。计算结果还表明，这将是难以区分的流体与新鲜或蚀变超镁铁岩反应的基础上，单独的pH值，和总溶解的Ca，Mg和Si的含量。我们的模型还考虑到铁纳入到固体解决方案的蛇纹石和水镁石，并表明，全球H2通量大陆蛇纹石化可能会大大低于估计的基础上铁氧化磁铁矿。最后，我们提出了充满活力的景观可供地下微生物通过集中在两个微生物过程中使用H2：甲烷生成和氢氧化。有限但可用的能量（0.2-1.7卡路里/千克液体）可以被产甲烷菌利用，从而使蛇形含水层中的深层群落成为可能。当上涌的深层蛇纹化作用产生的流体与浅层地下水混合时，更多的能量可用于甲烷生成（0.2-6卡路里/千克流体）和氢氧化（0-17卡路里/千克流体）。最终，这项研究中提出的预测提供了一个测试想法的框架，这些想法可以解释地球上超镁铁环境中采样的流体和微生物群落的组成，也许在不久的将来，在我们太阳系的海洋世界中。
The hydrous alteration of ultramafic rocks, known as serpentinization, generates fluids that can fuel microbial communities and enable the synthesis of simple organic compounds. Serpentinization reactions can proceed even at the ambient, low-temperature conditions present in continental aquifers raising questions about the limits of life deep in the Earth's subsurface. The hydrous alteration of ultramafic rocks, known as serpentinization, generates fluids that can fuel microbial communities and enable the synthesis of simple organic compounds. Serpentinization reactions can proceed even at the ambient, low-temperature conditions present in continental aquifers raising questions about the limits of life deep in the Earth's subsurface. Through thermodynamic calculations, we investigate various reactions that facilitate the transformation of oxic, slightly acidic rainwater into reduced, hyperalkaline fluids during low-temperature serpentinization. We explore a suite of factors (variabilities in temperature, host-rock compositions, fluid salinity, and the buffering capacity of various serpentinization-relevant minerals) that offer broad insights into the chemical environments formed through low-temperature serpentinization. Results of calculations show that alteration of olivine-rich lithologies will lead to fluids constrained by the chrysotile-brucite-diopside equilibrium assemblage, close in pH to those measured from the most alkaline fluids hosted in ultramafic rocks. Variabilities in the compositions of fluids hosted by continental serpentinizing systems can be attributed to a shift from being in equilibrium with diopside to calcite, among other reactions. Results of calculations also show that it would be difficult to distinguish fluids reacting with either fresh or altered ultramafic rocks based solely on their pH, and total dissolved Ca, Mg and Si content. Our models also account for Fe incorporation into solid solutions of serpentine and brucite and show that the global H2 flux from continental serpentinization could be considerably lower than estimates based on iron oxidation to magnetite only. Lastly, we present the energetic landscape available to subsurface microorganisms by focusing on two microbial process using H2: methanogenesis and hydrogen oxidation. Limited but available energy (0.2–1.7 calories/kg fluid) can be exploited by methanogens, permitting the possibility of deep communities in serpentinizing aquifers. More energy is available for methanogenesis (0.2–6 calories/kg fluid) and hydrogen oxidation (0–17 calories/kg fluid) when upwelling, deep-seated, serpentinization-generated fluids mix with shallow groundwater. Ultimately, predictions set forth in this study provide a framework for testing ideas that can explain the compositions of fluids and microbial communities sampled at ultramafic environments here on Earth and perhaps in the near future, on ocean worlds in our solar system.
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影响因子：
5.2
作者：
Bach W
通讯作者：
Bach W
影响因子：
2.3
作者：
Athanasios Rizoulis;A. Milodowski;K. Morris;J. Lloyd
通讯作者：
Athanasios Rizoulis;A. Milodowski;K. Morris;J. Lloyd
DOI：
10.1007/978-3-642-28394-9_8
发表时间：
2013
期刊：
--
影响因子：
--
作者：
W. Bach;N. Jöns;F. Klein
通讯作者：
W. Bach;N. Jöns;F. Klein
影响因子：
3.5
作者：
G. Früh-Green;B. Orcutt;S. Rouméjon;M. Lilley;Y. Morono;C. Cotterill;S. Green;J. Escartín;
通讯作者：
G. Früh-Green;B. Orcutt;S. Rouméjon;M. Lilley;Y. Morono;C. Cotterill;S. Green;J. Escartín;
影响因子：
3.5
作者：
J. Warren
通讯作者：
J. Warren