Nitrogen and noble gas isotopic compositions of mantle xenoliths from Far Eastern Russia: Implications for nitrogen isotopic characteristics of mantle wedge fluid
Nitrogen and noble gas isotopic compositions of mantle xenoliths from Far Eastern Russia: Implications for nitrogen isotopic characteristics of mantle wedge fluid
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俄罗斯远东地幔捕虏体的氮和稀有气体同位素组成：对地幔楔流体氮同位素特征的影响
DOI：
10.1016/j.epsl.2020.116109
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发表时间：
2020
影响因子：
5.3
通讯作者：
Prikhod'ko V.S.
中科院分区：
文献类型：
--
作者：
Yamamoto J.;Takahata N.;Sano Y.;Yanagita M.;Arai S.;Prikhod'ko V.S.
为了研究俯冲作用下的氮循环，我们测量了远东俄罗斯地幔包体的氮和惰性气体的同位素组成，该地区的构造环境是中新生代的板块会聚边缘。动力学分馏伴随着从俯冲板块中提取挥发分，导致具有轻同位素组成的流体渗入地幔楔形。δ15N值为−13.26~+0.19‰，有些低于空气(0‰)和上地幔(−5±2‰)。3He/4He和40Ar/36Ar比值分别为0.2-5.6Ra和304-1156，这是东亚地幔包体的普遍特征，是典型的俯冲环境。N2/36Ar为1.5×104~4.5×104，远低于地幔(6.7×106)，与大气(2.5×104)和深层海水(1.1×104)值较为接近。动力学分馏可使δ-15N值降至−-15-‰，而对氮气/36-Ar比值无明显影响。因此，现今捕虏体的低δ15N值可能是流体从俯冲洋板渗入地幔楔体过程中经历分馏的值。
To investigate nitrogen circulation via subduction, we measured isotopic compositions of nitrogen and noble gases of mantle-derived xenoliths from Far Eastern Russia, where the tectonic setting is a plate convergence margin in the Mesozoic to Cenozoic era. Kinetic fractionation accompanies the extraction of volatiles from a subducting plate, engendering the infiltration of fluids with light isotopic compositions into mantle wedge. The δ 15 N values are− 13.26 to+ 0.19‰, some of which are lower than those of air (0‰) and upper mantle (− 5±2‰). The 3 He/4 He and 40 Ar/36 Ar ratios are 0.2–5.6 Ra and 304–1156, respectively, which are common for the mantle xenoliths in eastern Asia, a representative subduction setting. The N 2/36 Ar are 1.5× 10 4–4.5× 10 4, which are much lower than the mantle value (6.7× 10 6) and which are rather more similar to atmospheric (2.5× 10 4) and deep seawater (1.1× 10 4) values. Kinetic fractionation can lower the δ 15 N value to− 15‰ without marked change of the N 2/36 Ar ratio. Therefore, the low δ 15 N values of the present xenoliths might be regarded as values of the fluid experiencing fractionation during infiltration of the fluid from the subducting oceanic plate into the mantle wedge.