Nitrogen, because of its abundance and variety of carrier phases, is a unique tracer of physico-chemical processes occurring throughout star and planet formations. The refractory organic matter is commonly considered as the main carrier of nitrogen in the most primitive objects of our Solar System. However, nitrogen in the form of ammonium (NH4+) was observed in the Ivuna-type carbonaceous (CI) chondrites Alais in 1834, and Orgueil just after its fall in 1864, as well as more recently on Ceres, comet 67P/Churyumov-Gerasimenko, and possibly on some asteroids. In the present study, we have measured the nitrogen content and isotopic composition in various nitrogen-bearing phases of several samples of the Orgueil meteorite, with different degrees of terrestrial weathering. Water-soluble NH4+ is present in Orgueil at a mean concentration of 0.07 ± 0.01 wt%, with a mean isotopic composition of δ15N = +72 ± 9 ‰ (14N/15N = 254 ± 2), confirming its extra-terrestrial origin. In the most terrestrially altered sample of Orgueil that we analysed, the isotopic composition is δ15N = +50 ± 12 ‰ (14N/15N = 259 ± 3). NH4+ is in species that are thermally stable up to 383 K, possibly ammonium inorganic/organic salts and ammoniated phyllosilicates. We also show that the nitrogen in Orgueil is distributed among the insoluble organic matter (IOM) (35 ± 5 %), ammonium (27 ± 5 %), and other minor water-soluble species (e.g., nitrate, amines etc.: < 6 %). The remaining nitrogen (34 ± 14 %) is mainly in an unidentified organic matter (UOM), which may be IOM lost during its extraction and/or acid hydrolysable functional groups bounded to the IOM and/or organic nitrogen trapped within minerals. The three main carriers of nitrogen in Orgueil have δ15N (and 14N/15N) values of +32 ± 1 ‰ (264 ± 0.3) for IOM, +39 ± 16 ‰ (262 ± 4) for UOM, and +72 ± 9 ‰ (254 ± 2) for NH4+.

中文翻译：

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Orgueil 陨石中的氮：丰富的铵态氮以及其他可变同位素组成的储层


氮由于其丰富的载流态相和多样性，是整个恒星和行星形成过程中发生的物理化学过程的独特示踪剂。难降解有机物通常被认为是我们太阳系最原始物体中氮的主要载体。然而，在 1834 年的 Ivuna 型碳质 （CI） 球粒陨石 Alais 和 1864 年坠落后的 Orgueil 以及最近的谷神星、67P/Churyumov-Gerasimenko 彗星以及可能在一些小行星上观察到铵态氮 （NH4+）。在本研究中，我们测量了不同程度的 Orgueil 陨石样品在不同含氮阶段的氮含量和同位素组成。水溶性 NH4+ 以 0.07 ± 0.01 wt% 的平均浓度存在于 Orgueil 中，平均同位素组成为 δ15N = +72 ± 9 ‰ （14N/15N = 254 ± 2），证实其起源于外星。在我们分析的 Orgueil 陆地变化最严重的样品中，同位素组成为 δ15N = +50 ± 12 ‰ （14N/15N = 259 ± 3）。NH4+ 存在于热稳定性高达 383 K 的物种中，可能是铵无机/有机盐和氨化层状硅酸盐。我们还表明，Orgueil 中的氮分布在不溶性有机物 （IOM） （35 ± 5 %）、铵态氮 （27 ± 5 %） 和其他次要水溶性物质（例如硝酸盐、胺类等：< 6 %）中。剩余的氮（34 ± 14%）主要存在于不明有机物 （UOM） 中，该有机物可能在提取过程中丢失和/或与 IOM 结合的可酸水解官能团和/或矿物中的有机氮。Orgueil 中氮的三个主要载体的 δ15N（和 14N/15N）值为 +32 ± 1 ‰ （264 ± 0。3） 对于 IOM，UOM 为 +39 ± 16 ‰ （262 ± 4），NH4+ 为 +72 ± 9 ‰ （254 ± 2）。