Delivery of carbon, nitrogen, and sulfur to the silicate Earth by a giant impact
Delivery of carbon, nitrogen, and sulfur to the silicate Earth by a giant impact
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DOI：
10.1126/sciadv.aau3669
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发表时间：
2019-01-01
期刊：
影响因子：
13.6
通讯作者：
Costin, Gelu
中科院分区：
文献类型：
--
作者：
Grewal, Damanveer S.;Dasgupta, Rajdeep;Costin, Gelu
地球作为唯一维持生命的行星的地位是碳（C），氮（N），硫（S）和氢（H）的时间和输送机制的结果。根据其同位素特征，陆地挥发物被认为来自碳质辉长岩，而非挥发性主要和微量元素的同位素组成表明顽火辉石类物质是地球的主要组成部分。然而，散装硅酸盐地球（BSE）的C/N比是supercritical的，这排除了挥发性交付的supercritical晚期单板。此外，如果在地球吸积的主要阶段交付，那么，由于更大的亲铁性（金属爱好）性质的C相对于N，核心的形成应该留下了一个亚南极洲的C/N比在BSE。在这里，我们提出了高压-温度实验，以限制混合C-N-S挥发物在行星胚胎岩浆海洋的核幔分离过程中的命运，并表明，在含N和富S合金中，C的亲铁性大大降低，而N的亲铁性在S的存在下基本上不受影响。使用新的数据和逆蒙特卡罗模拟，我们表明，火星大小的行星的影响，具有最小的贡献，从碳质类陨石物质和月球形成的事件相吻合，可以在BSE的主要挥发物的来源。
Earth's status as the only life-sustaining planet is a result of the timing and delivery mechanism of carbon (C), nitrogen (N), sulfur (S), and hydrogen (H). On the basis of their isotopic signatures, terrestrial volatiles are thought to have derived from carbonaceous chondrites, while the isotopic compositions of nonvolatile major and trace elements suggest that enstatite chondrite-like materials are the primary building blocks of Earth. However, the C/N ratio of the bulk silicate Earth (BSE) is superchondritic, which rules out volatile delivery by a chondritic late veneer. In addition, if delivered during the main phase of Earth's accretion, then, owing to the greater siderophile (metal loving) nature of C relative to N, core formation should have left behind a subchondritic C/N ratio in the BSE. Here, we present high pressure-temperature experiments to constrain the fate of mixed C-N-S volatiles during core-mantle segregation in the planetary embryo magma oceans and show that C becomes much less siderophile in N-bearing and S-rich alloys, while the siderophile character of N remains largely unaffected in the presence of S. Using the new data and inverse Monte Carlo simulations, we show that the impact of a Mars-sized planet, having minimal contributions from carbonaceous chondrite-like material and coinciding with the Moon-forming event, can be the source of major volatiles in the BSE.