The local coordination environments of Ti in Cretaceous–Paleogene (K–Pg) from Stevns Klint and Devonian–Carboniferous (D–C) boundary from western part of Cat Co Beach on Cat Ba Island sediments are studied by K-edge X-ray absorption fine structure (XAFS) in order to provide local atomic information by X-ray absorption near edge structure (XANES) and coordination environments by extended X-ray absorption fine structure (EXAFS). Ti K-edge XAFS spectra in bulk part of K–Pg and D–C boundary sediments are compared with those of reference materials such as TiO2 (rutile, anatase and brookite polymorph), CaTiO3, MgTiO3, SrTiO3, PbTiO3, moldavite-brownish, moldavite-green, suevite from Ries crater, impactite, obsidian and Kilauea volcanic glass. The shapes of XANES and EXAFS spectra in K–Pg sediments are similar to those in suevite. Suevite was formed under meteorite impact and its glass component was formed under high temperature and high pressure. Similarities of XANES and EXAFS between K–Pg sediments and suevite indicate that formation process of K–Pg sediments is related to a meteorite impact event. On the other hand, the shape of XANES spectrum in D–C sediments is similar to those in anatase and obsidian. However, the shape of EXAFS spectra in D–C sediments is similar to those in obsidian, rather than anatase. Coordination environments of Ti in D–C sediments suggest that the original glass-like local environments were changed to anatase-like local environments by devitrification. This leads to the conclusion that the analysis of the atomic coordination environments of Ti in boundary sediments can in principle be used as a marker of large meteorite impact, though this Ti local environmental information is actually lost due to the devitrification phenomenon to anatase by quenching process or long-time diagenesis. This may be compensated by the XAFS analysis of Zr because local coordination environments of Zr in same analytical point of K–Pg sediments were not affected by diagenesis (Tobase et al., J Miner Petrol Sci 110:88–91, 2015a).

中文翻译：

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白垩纪-古近纪和泥盆纪-石炭纪边界沉积物中的钛局部配位环境作为大型陨石撞击的可能标志

通过K-edge X射线吸收研究了来自Stevns Klint的白垩纪-古近纪（K-Pg）和来自Cat Co海滩西部的Cat Ba岛沉积物的泥盆纪-石炭纪（D-C）边界的Ti局部配位环境精细结构 (XAFS) 以通过 X 射线吸收近边结构 (XANES) 和扩展 X 射线吸收精细结构 (EXAFS) 提供配位环境提供局部原子信息。将 K-Pg 和 D-C 边界沉积物主体部分的 Ti K-edge XAFS 光谱与参考材料，如 TiO2（金红石、锐钛矿和板钛矿多晶型物）、CaTiO3、MgTiO3、SrTiO3、PbTiO3、陨石-褐色、陨石绿色，来自里斯陨石坑的绒毛岩，撞击岩，黑曜石和基拉韦厄火山玻璃。K-Pg 沉积物中 XANES 和 EXAFS 光谱的形状与绒毛岩中的相似。Suevite是在陨石撞击下形成的，其玻璃成分是在高温高压下形成的。K-Pg 沉积物和 suevite 之间 XANES 和 EXAFS 的相似性表明 K-Pg 沉积物的形成过程与陨石撞击事件有关。另一方面，D-C 沉积物中 XANES 光谱的形状与锐钛矿和黑曜石中的相似。然而，D-C 沉积物中 EXAFS 光谱的形状与黑曜石相似，而不是锐钛矿。D-C沉积物中Ti的配位环境表明，原始的玻璃状局部环境通过反玻璃化作用转变为锐钛矿状局部环境。由此得出结论，对边界沉积物中钛原子配位环境的分析，原则上可以作为大陨石撞击的标志，尽管这种 Ti 局部环境信息实际上由于淬火过程或长时间成岩作用对锐钛矿的反玻璃化现象而丢失。这可能会通过 Zr 的 XAFS 分析得到补偿，因为在 K-Pg 沉积物的同一分析点中 Zr 的局部配位环境不受成岩作用的影响（Tobase 等，J Miner Petrol Sci 110:88-91, 2015a）。