Titanium oxynitrides (Ti(N,O,C)) are abundant in xenolithic corundum aggregates in pyroclastic ejecta of Cretaceous volcanoes on Mount Carmel, northern Israel. Petrographic observations indicate that most of these nitrides existed as melts, immiscible with coexisting silicate and Fe-Ti-C silicide melts; some nitrides may also have crystallized directly from the silicide melts. The TiN phase shows a wide range of solid solution, taking up 0–10 wt% carbon and 1.7–17 wt% oxygen; these have crystallized in the halite (fcc) structure common to synthetic and natural TiN. Nitrides coexisting with silicide melts have higher C/O than those coexisting with silicate melts. Analyses with no carbon fall along the TiN–TiO join in the Ti–N–O phase space, implying that their Ti is a mixture of Ti³⁺ and Ti²⁺, while those with 1–3 at.% C appear to be solid solutions between TiN and Ti_0.75O. Analyses with >10 at% C have higher Ti²⁺/Ti³⁺, reflecting a decrease in fO₂. Oxygen fugacity was 6 to 8 log units below the iron–wüstite buffer, at or below the Ti₂O₃–TiO buffer. These relationships and coexisting silicide phases indicate temperatures of 1400–1100 °C. Ti oxynitrides are probably locally abundant in the upper mantle, especially in the presence of CH₄–H₂ fluids derived from the deeper metal-saturated mantle.

中文翻译：

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超还原条件下的氮：氮氧化钛在来自 Mt Carmel（以色列北部）的捕集刚玉聚集体中熔化

氮氧化钛 (Ti(N,O,C)) 在以色列北部卡梅尔山白垩纪火山的火山碎屑喷出物中的捕集刚玉聚集体中含量丰富。岩相观察表明，这些氮化物大部分以熔体形式存在，与共存的硅酸盐和 Fe-Ti-C 硅化物熔体不混溶；一些氮化物也可能直接从硅化物熔体中结晶出来。TiN 相显示出广泛的固溶体，占据 0-10 wt% 的碳和 1.7-17 wt% 的氧；它们在合成和天然 TiN 常见的岩盐 (fcc) 结构中结晶。与硅化物熔体共存的氮化物比与硅酸盐熔体共存的氮化物具有更高的 C/O。没有碳沿着 TiN-TiO 加入 Ti-N-O 相空间的分析表明它们的 Ti 是 Ti ³⁺和 Ti ²⁺的混合物，而具有 1–3 at.% C 的那些似乎是 TiN 和 Ti _0.75 O之间的固溶体。具有 >10 at% C 的分析具有更高的 Ti ²⁺ /Ti ³⁺，反映了f O ₂的降低。氧逸度为铁-方铁矿缓冲液以下、Ti ₂ O ₃ -TiO 缓冲液以下 6 到 8 个 log 单位。这些关系和共存的硅化物相表明温度为 1400–1100 °C。Ti氧氮化物可能在上地幔局部丰富，特别是在存在源自更深金属饱和地幔的CH ₄ -H ₂流体的情况下。