We present a quantitative assessment of the input and output of CO₂ and N₂ along the Hikurangi margin based on the chemical and stable isotope composition of sediments and basalts (from IODP 375), previously accreted metasedimentary rocks, and volcanic/hydrothermal gases (together with noble gas data for the latter). We compare these results with 3-D thermo-petrologic models for four lithologic structures, representing different plateau inputs. The model results indicate that 59%–85% of initially subducted C and 5%–12% of N is lost from the slab during metamorphism, with both volatiles being dominantly sourced from altered oceanic crust with some contribution from subducted sediment at the forearc-arc transition (75–90 km depth). The δ¹³C_VPDB and CO₂/³He values for the arc gases range from −8.3 to −1.4‰ and 2 × 10⁹ to 2.7 × 10¹¹, indicating contributions from slab carbonate, organic C, and mantle C of 67%, 30%, and 3%, respectively. The δ¹⁵N_air and N₂/³⁶Ar values of arc gases are −1.0 to +2.3‰ and 1.54 × 10⁴ to 1.9 × 10⁵, indicating slab and mantle contributions of 74% and 26%. The δ¹³C signature of gases requires addition of organic C by tectonic erosion and/or shallow crustal assimilation. These calculations yield whole-margin fluxes of 5.4–7.0 Tg/yr for CO₂ and 0.0022–0.0057 Tg/yr for N_2, corresponding to ∼2.2% and 1%–30% of the global CO₂ and N₂ flux from subaerial volcanoes worldwide (assuming no loss during transit). This unique assessment of volatile cycling could prove useful in refining regional and global estimates of volatile recycling efficiency.

中文翻译：

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新西兰 Hikurangi 俯冲边缘的 CO2 和 N2 循环：综合地质、理论和同位素方法

我们目前的输入和CO的输出的定量评估₂和N ₂沿根据沉积物和玄武岩（来自IODP 375）的化学稳定的同位素组成的希库朗伊余量，先前增生沉积岩，和火山/水热气体（一起后者的惰性气体数据）。我们将这些结果与代表不同高原输入的四种岩性结构的 3-D 热岩石学模型进行比较。模型结果表明，59%~85% 的初始俯冲 C 和 5%~12% N 在变质作用过程中从板片中流失，两种挥发分主要来自蚀变洋壳，部分来自弧前俯冲沉积物。弧形过渡（75-90 公里深度）。δ ¹³ C _VPDB电弧气体的CO ₂ / ³ He 值范围为 -8.3 至 -1.4‰ 和 2 × 10 ⁹至 2.7 × 10 ¹¹，表明板状碳酸盐、有机碳和地幔 C 的贡献分别为 67%、30% 和分别为 3%。电弧气体的δ ¹⁵ N _air和N ₂ / ³⁶ Ar 值为-1.0 至+2.3‰ 和1.54 × 10 ⁴至1.9 × 10 ⁵，表明板片和地幔的贡献分别为74%和26%。气体的 δ ¹³ C 特征需要通过构造侵蚀和/或浅层地壳同化作用添加有机 C。这些计算得出 CO _{2 的}全边际通量为 5.4–7.0 Tg/yrN _{2 的}Tg/yr 为 0.0022–0.0057 _，对应于全球地下火山产生的全球 CO ₂和 N ₂通量的约2.2% 和 1%–30% （假设在运输过程中没有损失）。这种对挥发性循环的独特评估可证明有助于改进对挥发性循环效率的区域和全球估计。