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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The δ~(18)O of primary and secondary waters in hydrous volcanic glass
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The δ~(18)O of primary and secondary waters in hydrous volcanic glass

机译：含水火山玻璃中原水和副水的δ〜（18）O

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We present analyses of phyllosilicates, volcanic glass, and a series of experiments and observations on the delta O-18 of water extracted by rapid thermal pyrolysis at 1450 degrees C using the TCEA (Thermal Conversion Elemental Analyzer). The study includes the same hydrous glasses that were previously analyzed for their delta D values of extracted water (Seligman et al., 2016). We utilize natural phyllosilicates (where water is present as OH- only), natural magmatic and experimentally quenched glasses, (in which water occurs as H2Om and OH-), and glasses that underwent low-temperature secondary hydration by meteoric water (almost completely as H2Om). Our study documents that: 1) thermal extraction and simultaneous pyrolysis of H2Ot into CO and H-2 produces little or no exchange (1%.) in delta O-18 between hydrogen-bound and silica-bound oxygen; 2) water extracted from different natural phyllosilicates have 10(3)In alpha(silicate-OH) (similar to delta O-18(silicate)-delta O-18(OH)) values ranging from -3 to 6 parts per thousand, which is in agreement with previous results using partial fluorination, Density-Functional Theory, and the increment method; 3) water extracted from eruptively or experimentally quenched hydrous magmatic glasses have 10(3)In alpha(silicate-H2Or) values that decrease with increasing quench temperature from 10 parts per thousand (900 degrees C) to 3 parts per thousand (1100 degrees C); 4) during progressive volcanic degassing, the delta O-18 of remaining water in glass decrease as the departing H2Om is more positive in delta O-18, especially at lower temperature; this oxygen isotope trend correlates with delta D as the departing H2Om is also more positive in delta D than the remaining magmatic water. 5) the 6180 of water extracted from glass hydrated at low-temperature by secondary water yields isotopically negative delta O-18 values that are closer to the delta O-18 values of local meteoric water than values appropriate for low temperature silicate-water O-18/O-16 equilibrium; this suggests that upon hydration water simply dissolves into glass as H2O; 6) subsequently, secondarily hydrated glasses appear to show an increase in delta O-18 values that trend towards equilibrium with continued secondary hydration, with time, and at higher temperatures. This research demonstrates that the delta O-18 of extracted water, despite its 1-2 per mil- analytical precision, provides an isotopic tool for investigations of first order trends of both magmatic degassing, and of secondary hydration by meteoric waters. The trends described here aids hydrogen isotopic variations in the same processeses and combined use of both O and H isotopic variation of water in glass to help fingerprint sources of meteoric water, extent and stages of alteration of glass, and magmatic degassing. (C) 2019 Elsevier B.V. All rights reserved.
机译：我们介绍了层状硅酸盐，火山玻璃的分析，以及使用TCEA（热转化元素分析仪）在1450摄氏度下通过快速热解法提取的水的O-18增量的一系列实验和观察结果。该研究包括相同的含水玻璃，之前已对它们的提取水的δD值进行了分析（Seligman等，2016）。我们利用天然页硅酸盐（其中水仅以OH-形式存在），天然岩浆和经实验淬火的玻璃（其中水以H2Om和OH-形式出现）以及经过流星水进行低温二次水合处理的玻璃（几乎完全H2Om）。我们的研究文件表明：1）H2Ot的热萃取和同时热解成CO和H-2时，氢键结合的氧与二氧化硅键结合的氧之间的O-18交换几乎没有或没有交换（<1％。）； 2）从不同的天然层状硅酸盐中提取的水的α（硅酸盐-OH）的10（3）In（类似于δO-18（硅酸盐）-δO-18（OH））的值范围是千分之三到六至六与先前使用部分氟化，密度泛函理论和增量方法得出的结果一致； 3）从喷发性或实验性淬火的含水岩浆玻璃中提取的水具有10（3）Inα（硅酸盐-H2Or）值，随着淬火温度的升高，其值从千分之10（900摄氏度）降低至千分之三（1100摄氏度） ）; 4）在逐步进行火山脱气的过程中，玻璃中残留水的δO-18随δO-18中离去的H2Om的增加而减小，尤其是在较低温度下；该氧同位素趋势与δD相关，因为离开的H2Om在δD中也比剩余的岩浆水更正。 5）从二次水在低温下水合的玻璃中提取的水6180的同位素O-18负同位素值比适用于低温硅酸盐-水O-的值更接近局部流水的O-18值。 18 / O-16平衡；这表明水合后，水仅以H2O的形式溶于玻璃中。 6）随后，二次水合玻璃显示出O-18值的增加，随着持续的二次水合，时间和温度的升高，趋于达到平衡。这项研究表明，尽管萃取水的δO-18精度为每密耳1-2，但它提供了一种同位素工具，可用于研究岩浆脱气和陨石水的二次水化的一阶趋势。此处描述的趋势有助于在相同的过程中氢同位素的变化，并结合使用玻璃中水的O和H同位素变化来帮助识别陨石水的指纹来源，玻璃的变化程度和阶段以及岩浆脱气。 （C）2019 Elsevier B.V.保留所有权利。

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