An understanding of the mechanisms of Ti is incorporation into silicate glasses and melts is critical for the field of petrology. Trace-element thermobarometry, high-field-strength element partitioning, and the physical properties of magmas are all be influenced by Ti incorporation into glasses and changes therein in response to changes in composition and temperature. In this study, we combine ²⁹Si solid state NMR and Ti K-edge XAFS spectroscopy to investigate how Ti is incorporated into quenched Na-silicate glasses, and the influence of Ti on the structure of silicate species in these glasses. ²⁹Si NMR shows that in both Ti-bearing Na₂O•4SiO₂ (NS4) and Na₂O•8SiO₂ (NS8) glasses, increasing the amount of Ti in the melt results in a shift of Si Q⁴ peak in the ²⁹Si NMR spectra reflecting Ti nearest neighbors for Si in Q⁴ speciation. The Ti XAFS results from NS8 glass indicate that Ti is primarily incorporated in [5]-fold coordination. At higher Ti content, there is a shift of the XAFS pre-edge feature suggesting mixing of [4]-fold Ti into the spectra. Combined, the ²⁹Si NMR and XAFS pre-edge data are consistent with Ti incorporation as isolated ^[5]Ti atoms and the formation of ^[5]Ti clusters at relatively low Ti concentrations, with no evidence for Ti–Na interactions as suggested by previous studies. As the Ti content increases, the Ti atoms begin to occupy 4-fold coordinated sites interacting primarily with Si in Q⁴ speciation (no significant Na–^[4] Ti bonding). The internal consistency of these two techniques provides a uniquely complete snapshot of the complexity of Ti incorporation in silicate melts and underlies the importance of understanding Ti incorporation mechanisms in natural magmatic systems.

中文翻译：

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29Si固态NMR和Ti K边缘XAFS前边缘光谱显示了Ti在硅酸盐熔体中的复杂行为。

了解Ti的机理是将其掺入硅酸盐玻璃和熔体中对于岩石学领域至关重要。痕量元素热压法，高场强元素分配和岩浆的物理性质都受掺入玻璃中的钛的影响，并随着成分和温度的变化而变化。在这项研究中，我们结合²⁹ Si固态NMR和Ti K边缘XAFS光谱研究了如何将Ti掺入淬火的Na-硅酸盐玻璃中，以及Ti对这些玻璃中硅酸盐种类结构的影响。²⁹ Si NMR表明，在含Ti的Na ₂ O•4SiO ₂（NS4）和Na ₂ O•8SiO _2中（NS8）玻璃，增加熔体中的Ti量会导致²⁹ Si NMR光谱中的Si Q ⁴峰移动，反映了Ti在Q ⁴形态中与Si最接近。来自NS8玻璃的Ti XAFS结果表明，Ti主要以[5]倍配位形式结合。在较高的Ti含量下，XAFS的前边缘特征发生了转变，表明[4]-倍Ti混合到光谱中。结合起来，²⁹ Si NMR和XAFS的前沿数据与孤立的^[5] Ti原子和^[5]的形成与Ti的掺入一致。钛在相对较低的钛浓度下成簇，没有以前的研究表明存在钛-钠相互作用的证据。随着Ti含量的增加，Ti原子开始占据4配位部位，主要在Q ⁴形态中与Si相互作用（无明显的Na– ^[4] Ti键）。这两种技术的内部一致性为硅酸盐熔体中Ti掺入的复杂性提供了唯一完整的快照，并强调了理解天然岩浆系统中Ti掺入机制的重要性。