Carbonate-silicate melts that originate in Earth's interior are described as transitional melts which possess compositions intermediate between carbonatitic and basaltic end members. The covariation of key oxides between carbonatite and basalt (e.g., 10–35 wt% SiO and 40–10 wt% CO, respectively) is expected to have a strong effect on liquid properties. However, due to their paucity both in the record of terrestrial rocks and as quenched glasses, their molecular structure has remained poorly explored to date. We investigated the atomic structure of a synthetic carbonate-silicate liquid with chemical composition within the CaO-MgO-AlO-SiO-FeO-NaO-ClO-CO oxide system having 18.28 wt% SiO and 22.54 wt% CO using multi-angle energy dispersive X-ray diffraction at pressures (P) and temperatures (T) of 1.4 GPa/1815 °C, 2.6 GPa/1865 °C, 4.3 GPa/1990 °C, 4.4 GPa/1950 °C. The results show that the intermediate range ordering of the structure decreases with an increase of both P and T. Based on this study, the carbonate-silicate magmas at upper mantle P-T conditions are expected to increase their viscosities during their ascent through the mantle as a result of increasing intermediate range ordering upon cooling and decompression. Additionally, spectroscopic measurements were carried out on the quenched glasses at ambient pressure using micro-Raman as well as micro-FTIR in reflection and transmission modes in the mid infrared range. High pressure investigation using micro-FTIR was also conducted. The distribution of Q species obtained by deconvolution of the Raman spectra within the aluminosilicate region confirms the depolymerized nature of the quenched glasses as inferred by the low viscosities of the corresponding liquids; peculiar characteristics of the C vibrations would suggest a distorted environment surrounding the network modifying CO anion. No evidence of molecular CO was detected. Notably, we find evidence of both dissolved molecular CO and CO linked to a metal cation forming carbonyl complexes in the quenched glasses at P-T-o conditions compatible with a hot Archean upper mantle. This suggests a role for carbonate-silicate magmas as carriers of reduced gaseous C-O-H species towards the early atmosphere along with the mobilization of PGE-elements.

中文翻译：

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高压高温下碳酸盐-硅酸盐液体的原子结构的原位研究以及回收的淬火玻璃的光谱表征


起源于地球内部的碳酸盐-硅酸盐熔体被描述为过渡熔体，其成分介于碳酸盐岩和玄武岩端元之间。碳酸岩和玄武岩之间关键氧化物的共变（例如，分别为 10–35 wt% SiO 和 40–10 wt% CO）预计会对液体性质产生强烈影响。然而，由于它们在陆地岩石和淬火玻璃的记录中都很少，迄今为止，它们的分子结构仍然很少被探索。我们使用多角度能量色散研究了化学成分为 CaO-MgO-Al2O-SiO-FeO-NaO-ClO-CO 氧化物体系的合成碳酸盐-硅酸盐液体的原子结构，该体系具有 18.28 wt% SiO 和 22.54 wt% CO X 射线衍射，压力 (P) 和温度 (T) 为 1.4 GPa/1815 °C、2.6 GPa/1865 °C、4.3 GPa/1990 °C、4.4 GPa/1950 °C。结果表明，结构的中程有序性随着 P 和 T 的增加而降低。根据这项研究，上地幔 P-T 条件下的碳酸盐-硅酸盐岩浆预计在上升穿过地幔的过程中其粘度会增加，作为冷却和减压时增加中间范围排序的结果。此外，在环境压力下使用微型拉曼和微型 FTIR 在中红外范围的反射和透射模式下对淬火玻璃进行光谱测量。还使用微型 FTIR 进行了高压研究。 通过拉曼光谱在铝硅酸盐区域内的去卷积获得的 Q 物质的分布证实了根据相应液体的低粘度推断的淬火玻璃的解聚性质； C 振动的特殊特征表明网络周围存在扭曲的环境，从而改变了 CO 阴离子。没有检测到CO分子的证据。值得注意的是，我们发现了在 P-T-o 条件下与热太古代上地幔相容的淬火玻璃中溶解的 CO 分子和与形成羰基络合物的金属阳离子相关的 CO 的证据。这表明碳酸盐-硅酸盐岩浆作为还原气态 C-O-H 物种的载体以及 PGE 元素的移动而向早期大气移动。