Abstract Hydrogen concentrations in minerals of peridotite xenoliths in alkali basaltic rocks from Quaternary volcanoes in northwest Spitsbergen were measured using polarized Fourier transform infrared spectroscopy (FTIR) to trace the effects of geologic processes on hydrogen distribution in the continental lithospheric mantle. The mineral grains show hydrogen profiles with lower concentrations at rims suggesting diffusive hydrogen loss during the entrapment and transport of the xenoliths in magma. However, hydrogen concentrations in the centers of the grains are uniform and appear to represent hydrogen abundances in the Spitsbergen upper mantle. The olivine, orthopyroxene, and clinopyroxene contain 1–10, 130–290, and 350–560 ppm H2O, respectively. Hydrogen abundances away from metasomatic melt conduits recorded by Type 1 xenoliths are correlated with the concentrations of incompatible trace elements, indicating that hydrogen distribution is related to mantle metasomatism. By contrast, hydrogen near the melt conduits, recorded by Type 2 xenoliths, shows no regular correlations with incompatible trace elements (except Nb in clinopyroxene) and may be affected by fractional crystallization of amphibole in the conduits. Hydrogen contents decrease away from the melt conduits and are controlled by the interaction between the depleted host mantle and percolating metasomatic melts. Therefore, the metasomatic melt could have variably hydrated the Spitsbergen upper mantle via different processes. The H2O/Ce ratios of the melt in equilibrium with clinopyroxene near the metasomatic melt conduits range from 93 to 218, i.e., within the oceanic island basalt (OIB) range. This is consistent with that the metasomatic melt could have been derived from OIB-type sources evidenced by the Sr-Nd isotope compositions of the xenoliths.

中文翻译：

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斯匹次卑尔根上地幔交代控制的氢分布

摘要 利用偏振傅里叶变换红外光谱 (FTIR) 测量了斯匹次卑尔根岛西北部第四纪火山中橄榄岩捕虏体矿物中的氢浓度，以追踪地质过程对大陆岩石圈地幔中氢分布的影响。矿物颗粒显示出边缘处浓度较低的氢剖面，这表明在岩浆中捕获和运输捕虏体期间存在扩散性氢损失。然而，颗粒中心的氢浓度是均匀的，似乎代表了斯匹次卑尔根上地幔中的氢丰度。橄榄石、斜方辉石和单斜辉石分别含有 1-10、130-290 和 350-560 ppm H2O。1 型捕虏体记录的远离交代熔体管道的氢丰度与不相容的微量元素浓度相关，表明氢分布与地幔交代有关。相比之下，由 2 型捕虏体记录的熔体管道附近的氢与不相容的微量元素（单斜辉石中的 Nb 除外）没有规律的相关性，并且可能受到管道中角闪石分级结晶的影响。氢含量随着远离熔体管道而减少，并受耗尽的宿主地幔和渗透交代熔体之间的相互作用控制。因此，交代熔体可能通过不同的过程对斯匹次卑尔根上地幔进行了不同程度的水合。在交代熔体管道附近与单斜辉石平衡的熔体的 H2O/Ce 比率范围为 93 至 218，即在大洋岛玄武岩 (OIB) 范围内。这与交代熔体可能源自 OIB 型来源一致，由捕虏体的 Sr-Nd 同位素组成证明。