The solubility of molecular hydrogen in silicate melts and the origin of hydrogen in the interiors of terrestrial planets

IF 3 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Contributions to Mineralogy and Petrology Pub Date : 2025-10-08 DOI:10.1007/s00410-025-02272-y

Alok Chaudhari, Matteo Masotta, Svyatoslav Shcheka, Hans Keppler

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Abstract

The solubility of molecular hydrogen (H₂) was measured in haplogranite, andesite, and basalt (MORB) melt. Experiments were carried out with rapid-quench TZM vessels and a piston cylinder apparatus at 0.2 GPa − 4 GPa, 1100 ˚C − 1400 ˚C, and iron-wüstite (Fe-FeO) buffer conditions. H₂ contents in quenched glasses were measured by infrared (FTIR) spectroscopy. For this purpose, the infrared extinction coefficient of the 4120 cm^− 1 band of H₂ in haplogranitic glass was re-calibrated by two independent methods. This yielded a linear molar extinction coefficient of (2.12 ± 0.05) liter mol^− 1cm^− 1, which is about one order of magnitude larger than a coefficient used in previous studies. The new extinction coefficient was used to quantify H₂ solubility in all glass samples of this study. The solubility of molecular hydrogen increases with increasing pressure, being higher in haplogranite than in andesitic or basaltic melt, as expected from ionic porosity considerations. The data at Fe-FeO buffer conditions can all be reproduced by a simple Henry style solubility law c_H2 = a_Henry P, with a_Henry = (206 ± 10) ppm/GPa for basalt, (362 ± 35) ppm/GPa for andesite, and (500 ± 62) ppm/GPa for haplogranite, where ppm is ppm H₂ by weight (µg/g). However, due to the use of an erroneous infrared extinction coefficient, previous studies may have overestimated H₂ solubility in silicate melts by about one order of magnitude. According to the new data presented here, H₂ dissolution in a magma ocean is not a very efficient mechanism for generating elevated hydrogen contents in planetary interiors. Equilibrium thermodynamic modelling shows that in an Earth with chondritic bulk composition, even at an oxygen fugacity six log units below the Fe-FeO buffer, the molar ratio of H₂/H₂O in the magma ocean is still below unity. At a more plausible oxygen fugacity two log units below Fe-FeO, the ratio is 0.06. However, the strong partitioning of hydrogen into the atmosphere under the very reducing conditions of early accretion may have enhanced hydrogen loss due to hydrodynamic escape and impact erosion. Possibly, this was a decisive mechanism for depleting the Earth in volatiles as compared to its chondritic building blocks.

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氢分子在硅酸盐熔体中的溶解度和类地行星内部氢的起源

测定了分子氢（H2）在单倍花岗岩、安山岩和玄武岩（MORB）熔体中的溶解度。实验采用快速淬火TZM容器和活塞缸装置，温度为0.2 GPa ~ 4 GPa, 1100˚C ~ 1400˚C，铁- stite （Fe-FeO）缓冲条件。采用红外光谱法测定了淬火玻璃中H2的含量。为此，用两种独立的方法重新校准了单花岗玻璃中H2的4120 cm−1波段的红外消光系数。这产生了线性摩尔消光系数为（2.12±0.05）l mol−1cm−1，这比以前研究中使用的系数大约大一个数量级。新的消光系数用于量化本研究中所有玻璃样品中的H2溶解度。分子氢的溶解度随着压力的增加而增加，在单倍花岗岩中的溶解度比在安山岩或玄武岩熔体中的溶解度高，这与离子孔隙度的考虑是一致的。Fe-FeO缓冲条件下的数据都可以用简单的Henry溶解度定律cH2 = aHenry P来重现，其中玄武岩的aHenry =(206±10)ppm/GPa，安山岩的aHenry =(362±35)ppm/GPa，单倍花岗岩的aHenry =(500±62)ppm/GPa，其中ppm为ppm H2重量（µg/g）。然而，由于使用了错误的红外消光系数，以前的研究可能高估了H2在硅酸盐熔体中的溶解度，大约高估了一个数量级。根据这里提出的新数据，岩浆海洋中的H2溶解并不是在行星内部产生氢含量升高的非常有效的机制。平衡热力学模型表明，在球粒体组成的地球中，即使氧逸度比Fe-FeO缓冲层低6个log单位，岩浆海洋中H2/H2O的摩尔比仍然低于1。在比Fe-FeO低两个对数单位的更合理的氧逸度下，比值为0.06。然而，在早期吸积的非常还原的条件下，氢向大气的强烈分配可能由于流体动力学逃逸和冲击侵蚀而增加了氢的损失。可能，这是一个决定性的机制，消耗地球的挥发物相比，它的球粒状的基石。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Contributions to Mineralogy and Petrology 地学-地球化学与地球物理

CiteScore

6.50

自引率

5.70%

发文量

审稿时长

1.7 months

期刊介绍： Contributions to Mineralogy and Petrology is an international journal that accepts high quality research papers in the fields of igneous and metamorphic petrology, geochemistry and mineralogy. Topics of interest include: major element, trace element and isotope geochemistry, geochronology, experimental petrology, igneous and metamorphic petrology, mineralogy, major and trace element mineral chemistry and thermodynamic modeling of petrologic and geochemical processes.