Raman spectroscopy study of C-O-H-N speciation in reduced basaltic glasses: Implications for reduced planetary mantles
Raman spectroscopy study of C-O-H-N speciation in reduced basaltic glasses: Implications for reduced planetary mantles
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DOI：
10.1016/j.gca.2019.08.029
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发表时间：
2019-11-15
影响因子：
5
通讯作者：
Le Losq, Charles
中科院分区：
文献类型：
--
作者：
Dalou, Celia;Hirschmann, Marc M.;Le Losq, Charles
为了更好地理解还原岩浆海洋中挥发性物质的溶解，我们通过拉曼光谱确定了一系列还原玄武岩玻璃中溶解的C-O-H-N挥发性物质的性质。合成过程中的氧逸度（f（O2））从高度减少在两个日志单位以下的铁-浮氏体缓冲（IW-2.1）到中度减少（IW-0.4），跨越了大部分的岩浆f（O2）的条件下，在陆地吸积的后期阶段。从所有还原玻璃的能带归属中推断出H-2、NH-2、NH-3、CH-4、CO、CN-、N-2和OH-物种的拉曼振动模式。玻璃中N-2、CH_4、NH_3和H-2振动的拉曼谱带的积分面积随熔体摩尔体积的增加而增加，而CO的积分面积则随熔体摩尔体积的增加而减小。此外，随着f（O2）的增加，CO带面积增加，而那些N-2减少，这表明这些中性分子的溶解度是不是仅仅由熔体的摩尔体积在还原条件下。与这些中性分子共存的其他物种如CN-、NH 2-和OH-在硅酸盐网络内化学键合。结果表明，在还原条件下，（1）H2-、NH 2-、NH3-、CH 4-、CO-、CN-、N2-和OH-等物种共存于岩浆海硅酸盐液体的硅酸盐玻璃中;（2）它们在岩浆海中溶解的相对丰度取决于熔体成分、f（O2）和H的有效性;（3）这些岩浆挥发组分的金属-硅酸盐配分或脱气反应必然涉及熔体和蒸汽形态的变化，而熔体和蒸汽形态的变化又可能影响同位素分馏。(C)2019爱思唯尔有限公司版权所有。
To better understand the solution of volatile species in a reduced magma ocean, we identify via Raman spectroscopy the nature of C-O-H-N volatile species dissolved in a series of reduced basaltic glasses. The oxygen fugacity (f(O2)) during synthesis varied from highly reduced at two log units below the iron-wustite buffer (IW-2.1) to moderately reduced (IW-0.4), spanning much of the magmatic f(O2) conditions during late stages of terrestrial accretion. Raman vibrational modes for H-2, NH2-, NH3, CH4, CO, CN-, N-2, and OH- species are inferred from band assignments in all reduced glasses. The integrated area of Raman bands assigned to N-2, CH4, NH3 and H-2 vibrations in glasses increases with increasing molar volume of the melt, whereas that of CO decreases. Additionally, with increasing f(O2), CO band areas increase while those of N-2 decrease, suggesting that the solubility of these neutral molecules is not solely determined by the melt molar volume under reduced conditions. Coexisting with these neutral molecules, other species as CN-, NH2- and OH- are chemically bonded within the silicate network. The observations indicate that, under reduced conditions, (1) H-2, NH2-, NH3, CH4, CO, CN-, N-2, and OH- species coexist in silicate glasses representative of silicate liquids in a magma ocean (2) their relative abundances dissolved in a magma ocean depend on melt composition, f(O2) and the availability of H and, (3) metal-silicate partitioning or degassing reactions of those magmatic volatile species must involve changes in melt and vapor speciation, which in turn may influence isotopic fractionation. (C) 2019 Elsevier Ltd. All rights reserved.